Roberto Cantoni

Sébastien Chailleux

Philippe Zittoun

Claudia Foltyn

Reiner Keller

Nature Matthias S Klaes

The regime of invisibility in closed spaces of debate: how and why shale gas was perceived as a non

Keywords: shale gas, invisibility, France, public problems, agenda-setting

Our empirical study tackles the definition of shale gas within the Administration and gas companies before social mobilization erupted in France in 2011. We analyze how and why shale gas was neither considered problematic, nor perceived as part of the political agenda, even though it was the object of policymaking. We argue that shale gas was caught up in a regime of invisibility shaped by the actors in charge of dealing with license requests. Constituting a closed space of debate, the department in charge of the licenses imposed its own definition of shale gas licenses, and when the topic circulated outside the department, it was always under a business-as-usual scenario. Invisibility was made possible because of the cadastral organization of the Administration, which considered that this department had exclusive expertise over the granting of licenses, but also because of the department's marginal position within the Administration, rendering shale gas proponents invisible to their own hierarchy. This regime of invisibility helped to define shale gas as a non-problem.

Introduction

On March 1, 2010, the French Minister of Ecology granted three shale gas exploration licenses in South Eastern France to the companies Total and Schuepbach, without raising any particular reaction from the media or from environmental Non-Governmental Organizations (NGOs). These were in addition to a dozen other licenses targeting unconventional oil and gas since the early 2000s which had gone unnoticed even by the Minister who had signed them: when the contestations began, the Minister admitted that he had been unaware of the actual implications of what he was signing then and he regretted a hasty and uninformed decision. In late December 2010, the first reactions began and swift mobilization was initiated, leading to a ban on hydraulic fracturing in July 2011 [START_REF] Chailleux | Unconventional Oil and Gas in France: From Popular Distrust to Politicization of the Underground[END_REF]. To explain the initial absence of reaction, the leaders of the social movement underlined that the government had intentionally hidden the granting of those licenses. The denunciation of "intentional invisibilization" was a core argument in the discourse of opponents protesting against shale gas and contributed to the success of the mobilization. Rather than investigating this unsubstantiated claim, we aim to underline the structural mechanisms producing invisibilization during this pre-controversial stage and to show how administrative and professional routines and organizations generated and maintained a regime of invisibility, preventing certain issues from reaching the public and governmental agendas [START_REF] Cobb | The Politics of Agenda-Building: An Alternative Perspective for Modern Democratic Theory[END_REF] 1 . We argue that such regimes of invisibility are commonplace in consensual spaces of debate that we refer to as "atriums", which are closed spaces dominated by owners who enforce 1 Cobb and Elder made a distinction between two types of agenda; the systemic or public agenda refers to an abstract range of legitimate concerns for the polity, while the institutional or governmental agenda denotes a set of concrete items scheduled for consideration by policy-makers (Cobb and Elder 1971: 906).

Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni, Claudia Foltyn, Reiner Keller, and Matthias S. Klaes, Nature & Culture, 18 (1) 3 a special argumentative regime. We also argue that, while such spaces gain autonomy in regulating specific issues, which increases their invisibility, they may be marginalized within their organization, producing not only invisibility, but also inattention, from their hierarchy, and preventing support when contested.

The literature about public problems is particularly focused on agenda-setting (e.g. Zahariadis 2016b), i.e., on phenomena seeking to catch the attention of actors on a given issue and contributing to setting it on the media and institutional agendas. However, it is less telling about the phenomena of invisibilization which constitutes the dark side of the same process. Most articles on shale gas acknowledge that the pre-controversial stage is "business-as-usual" and is tied to an economic opportunity discourse [START_REF] Cotton | Shale Gas Policy in the United Kingdom: An Argumentative Discourse Analysis[END_REF]Weible et al. 2016;[START_REF] Dodge | Hydraulic Fracturing as an Interpretive Policy Problem: Lessons on Energy Controversies in Europe and the U.S.A[END_REF][START_REF] Metze | Fracking the Debate: Frame Shifts and Boundary Work in Dutch Decision Making on Shale Gas[END_REF][START_REF] Lis | Framing Shale Gas for Policy-Making in Poland[END_REF][START_REF] Evensen | Yet More "Fracking" Social Science: An Overview of Unconventional Hydrocarbon Development Globally[END_REF]. Policy conflicts over hydraulic fracturing and shale gas crop up when another coalition emerges and propagates an environmental discourse that contests the economic opportunity [START_REF] Goussev | Shale Gas U-Turns in Bulgaria and Romania: The Turbulent Politics of Energy and Protest[END_REF][START_REF] Heikkila | Understanding a Period of Policy Change: The Case of Hydraulic Fracturing Disclosure Policy in Colorado[END_REF][START_REF] Mcgowan | Regulating Innovation: European Responses to Shale Gas Development[END_REF]Weible et al. 2016;[START_REF] Dodge | Framing Dynamics and Political Gridlock: The Curious Case of Hydraulic Fracturing in New York[END_REF][START_REF] Metze | Fracking the Debate: Frame Shifts and Boundary Work in Dutch Decision Making on Shale Gas[END_REF][START_REF] Cantoni | Shale Tales: Politics of Knowledge and Promises in Europe's Shale Gas Discourses[END_REF][START_REF] Witt | Industry and Government Responses to Unconventional Gas Development in Australia[END_REF]. The "business-as-usual" coalition then engages in intense strategies to impose its narratives [START_REF] Cantoni | Shale Tales: Politics of Knowledge and Promises in Europe's Shale Gas Discourses[END_REF], to criticize those of their opponents [START_REF] Lis | Framing Shale Gas for Policy-Making in Poland[END_REF], and even to conceal detrimental data and potential side-effects [START_REF] Fisk | The Right to Know? State Politics of Fracking Disclosure[END_REF][START_REF] Wylie | Fractivism: Corporate Bodies and Chemical Bonds[END_REF]. Despite providing interesting findings about policy change or stability, these works generally argue that the inattention to hydraulic fracturing often results from intentional actions. The shale gas issue in France provides an interesting case study because it shows how inattention may also be the outcome of an unintentional systemic regime of invisibility, based on monopoly over expertise and cadastral2 organizationenabling dominant actors in a field to use argumentative practices to discredit opponentsbut also on the marginal position of proponents which prevents them from being visible outside the spaces where they dominate. There is one major advantage to analyzing the case of shale gas in France: it is a new topic because, before the controversy started, nobody had heard of it; this enables us to identify better how actors shifted from inattention to attention. This article is based on 52 interviews with administrative actors from the Ministry of Ecology and the Prime Ministerial cabinets, political actors from the Ministry of Ecology, the Parliament and local governments, and reporters, activists, and industrial actors (Total, Schuepbach, GDF-Suez, Vermilion, Toreador, EGL, UFIP). We also used administrative documents about the granting of licenses and we had access to the archives of the Prime Minister. Lastly, using data from Europresse, we undertook a media analysis with the following keywords (in French): "shale gas", "hydraulic fracturing", and "unconventional gas". We analyzed 548 articles between January 2008 and April 2011 in the French daily newspapers.

First, we will present our theoretical perspective based on a state-of-the-art review of the processes of attention and inattention in policymaking. We will then develop the main features of the shale gas regime of invisibility. (1) A "cadastral" bureaucratic organization fragmented the topic into manageable proportions, but also granted great autonomy to the dedicated administrative department. (2) An expert regime of feasibility helped define shale gas as business-as-usual and as an opportunity. (3) The asymmetrical relations between shale gas proponents and their hierarchy Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni,Claudia Foltyn,Reiner Keller,and Matthias S. Klaes,Nature & Culture,18 (1) 5 contributed to marginalize the former. Lastly, we will analyze how the unproblematic statement from supporters resisted initial criticism.

Table 1

Agenda-setting and the invisibilization of issues

The phenomenon of invisibilization was questioned quite early in the literature on public problems [START_REF] Fuller | Some Aspects of a Theory of Social Problems[END_REF]Myers 1941a, 1941b;[START_REF] Dewey | Le public et ses problèmes[END_REF]. This phenomenon became clear in the 1960s, when it was perceived as essential to reveal the mechanisms behind the sorting out and the selection of problems in the decision-making process. Rejecting the opposition between objective conditions and subjective definitions of problems, sociologists from the Chicago School showed that the absence of collective definition and mobilization generated the inexistence of an issue and therefore its invisibility [START_REF] Blumer | Social Problems as Collective Behavior[END_REF][START_REF] Spector | Social Problems: A Re-Formulation[END_REF]. Political scientists also showed that most of society's "wants" remained invisible to the political system. To be considered in the political system, those "wants" had to be transformed into "demands" through the designation of a public authority in charge of them and through the establishment of collective support for the demand [START_REF] Easton | A Framework for Political Analysis[END_REF]. [START_REF] Schattschneider | Semisovereign People: A Realist's View of Democracy in America[END_REF] highlighted this phenomenon when he suggested looking to the predecisional phase to explain better the role of interest groups in controlling access to the political agenda. He stressed that not only did a conflict have to expand to become important, but also that political power lay first and foremost in mastering this expansion and in limiting participation to policymaking. He invited scholars to study less visible conflicts and to examine those that did not provide access to visibility. Using the concept of bias, he underlined processes of strategic, cultural and political mobilization, limiting the expansion of conflicts and precluding them from becoming visible on the political and democratic scene.

Continuing these works, Bachrach and Baratz developed the concept of non-decision to shed light on the practices that hinder issues from accessing the decision arena, thereby making them invisible to policymakers [START_REF] Bachrach | Two Faces of Power[END_REF]Baratz 1962, 1963). They showed how powerful groups acted upstream of the decisional phase to stop issues from becoming visible public problems that the government should solve. Cobb and Elder used the famous concept of "agenda" to explain the mechanisms of the sorting out and selecting of issues in this pre-decisional phase [START_REF] Cobb | The Politics of Agenda-Building: An Alternative Perspective for Modern Democratic Theory[END_REF]. They differentiated the systemic agenda from the institutional agenda to show the filters operating to select problems. Each of these filters acted as a barrier: gaining access to the systemic agenda did not ensure that the problem would be set on the institutional agenda.

However, since the 1970s, the attention of scholars has focused more on the conditions of access to the institutional agenda than on failures, and invisibilization processes. This period has been marked by the development of policy process approaches suggesting that the pre-decisional phase be integrated into a larger process [START_REF] Lowi | Decision Making vs. Policy Making: Toward an Antidote for Technocracy[END_REF]. This has pushed scholars to examine the problems that succeed in accessing the agenda, leading to policy decisions and implementation.

Studies investigating the definition of problems [START_REF] Kingdon | Agendas, Alternatives, and Public Policies[END_REF]Rochefort and Cobb 1994), their framing [START_REF] Gusfield | The Culture of Public Problems. Drinking, Driving and the Symbolic Order[END_REF], and the attention of governments [START_REF] Baumgartner | Agendas and Instability in American Politics[END_REF][START_REF] Jones | The Politics of Attention -How Government Prioritizes Problems[END_REF] have cast aside the question of inattention and invisibility. Nevertheless, some authors have underlined the importance of scrutinizing "quiet politics" [START_REF] Culpepper | Quiet Politics and Business Power: Corporate Control in Europe and Japan[END_REF] better to understand who benefits from the distribution of costs and advantages regulated by public policies.

Regime of invisibility and the confinement of demands into a hermetic atrium

Recent research in science and technology studies on the production of strategic ignorance [START_REF] Mcgoey | The Logic of Strategic Ignorance: The Logic of Strategic Ignorance[END_REF] and agnotology [START_REF] Proctor | Agnotology: The Making and Unmaking of Ignorance[END_REF] have renewed interest in these phenomena. These studies mostly insisted on intentional deception from powerful actors [START_REF] Oreskes | Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming[END_REF][START_REF] Kirsch | Mining Capitalism: The Relationship between Corporations and Their Critics[END_REF], but the agenda is set to question the various processes contributing to reducing attention and to confining problems before they emerge [START_REF] Paul | Beyond Evidence versus Truthiness: Toward a Symmetrical Approach to Knowledge and Ignorance in Policy Studies[END_REF]. We suggest developing further the mechanisms of the regime of imperceptibility/invisibility [START_REF] Murphy | Sick Building Syndrome and the Problem of Uncertainty: Environmental Politics, Technoscience, and Women Workers[END_REF][START_REF] Henry | Ignorance Scientifique et Inaction Publique: Les Politiques de Santé Au Travail[END_REF][START_REF] Wylie | Fractivism: Corporate Bodies and Chemical Bonds[END_REF] through the investigation of the development of the regime for shale gas in France. Our study addresses the question of why policy issues do not reach the political and public agenda, and we suggest the role of a structural regime of invisibility in rendering potential problems invisible. We explain the inattention of policymakers and wider publics over shale gas through this regime of invisibility, describing the business-as-usual management of oil and gas licenses in France.

To develop this argument, we need first to evoke some key elements of the framework that we used: the pragmatic constructivism framework (PCF) [START_REF] Zittoun | The Politics of Meaning Struggles: Shale Gas Policy Under Pressure in France[END_REF][START_REF] Zittoun | The Politics of Meaning Struggles: Shale Gas Policy Under Pressure in France[END_REF]. Based on a constructivist approach, PCF considers how policymakers define the reality around them and build agreement through their interactions to define collectively a problem or a policy [START_REF] Berger | The Social Construction of Reality: A Treatise in the Sociology of Knowledge[END_REF][START_REF] Rochefort | Agenda Setting, Problem Definition, and Their Contributions to a Political Policy Analysis[END_REF]. PCF differs from the relativism and structuralism frameworks [START_REF] Baudrillard | Simulacres et simulation[END_REF][START_REF] Bourdieu | Langage et pouvoir symbolique[END_REF] importance of the actors' experience, the unexpected consequences of their practices, and the conflictual dimension of their interactions [START_REF] Ansell | Pragmatist Democracy: Evolutionary Learning as Public Philosophy[END_REF][START_REF] Zittoun | The Political Process of Policymaking: A Pragmatic Approach to Public Policy[END_REF][START_REF] Chateauraynaud | Pragmatique Des Transformations et Sociologie Des Controverses[END_REF][START_REF] Dunn | Pragmatism and the Origins of the Policy Sciences: Rediscovering Lasswell and the Chicago School[END_REF]). As Boltanski noted, while structured "reality" is built and ordered through discourse, the enigmatic outside "world" regularly explodes into this social "reality" through unexpected events [START_REF] Boltanski | Rendre La Réalité Inacceptable[END_REF](Boltanski , 2009)).

The first element to consider is the discursive interaction between policymakers and other actors to build a coalition around a "problem statement" and/or a "policy statement" [START_REF] Zittoun | The Political Process of Policymaking: A Pragmatic Approach to Public Policy[END_REF]. If the concept of "policy statement" was initially used by Anderson to evoke the "formal expressions or articulations of public policy" (Anderson 1975: 5), we borrowed from Foucault's concept 3 to describe the definitional coupling between different elements, its stabilization through repetition, and its capacity to cement a "statement coalition" 4 [START_REF] Foucault | L'ordre Du Discours[END_REF]Zittoun 2016). We differentiate problem statementswhich chain together a problem, its victims, a dramatic future, culprits, and responsible authoritiesfrom policy statementswhich chain together a solution and its beneficiaries, a bright future, and a legitimate authority able to restore social order. In this article, we will focus primarily on how interactions between actors shaped a policy statement coalition favorable to shale gas in the shadows of the Administration 5 and of gas companies.

The second element is to analyze the multiple disputes in which these statement coalitions engage so as to impose their own statement in the policy process. We underline the considerable 3 "Enoncé" in French. 4 Statement coalitions differ from discourse coalitions because they need to be observe "in action ", that is they are performed in actual spaces, and they differ from advocacy coalitions because they are not based on share values but on a shared definition of a problem or a policy. 5 We refer to the Administration as encompassing all the State authorities and bureaucracy. uncertainty in the policy process as the power of each coalition, which would like to impose its own definition of a problem or a solution, is tested in multiple events in more or less open spaces.

In this article, we insist on the asymmetrical position of actors in these disputes and on their relative power to build a strong statement coalition in some spaces, but a weak one in other spaces.

The third dimension to consider is the spaces of debates where these discursive practices take place empirically. Rather than consider some very large "policy subsystem" or "policy stream" (Weible and Jenkins-Smith 2016; Zahariadis 2016a) structured by unique rules and modes of regulation, we will observe the multiple locations where the actors argue so as to understand better the multiple rules and regimes of regulation that take place during policy formulation. Specifically, we will distinguish public forums that are open, conflictual, and without any particular regime of discursive regulation, from closed and discrete spaces that could be either conflictual and with a low level of regulation (the arenas), or dominated by a set of actors. In this article, we focus on this last type of space, which we refer to as an atrium. An atrium is a space of debate characterized by an asymmetric position of actors with a dominant group of experts who occupy a strategic position in the policy formulation process and who mobilize arguments to disqualify and discredit any problem statement. Following Gusfield's concept of ownership [START_REF] Gusfield | The Culture of Public Problems. Drinking, Driving and the Symbolic Order[END_REF](Gusfield ,1989;;[START_REF] Zittoun | The Political Formulation of Policy Solutions: Arguments, Arenas and Coalitions[END_REF], we refer to the dominant actors as the owners of the atrium.

We argue that an atrium tends to produce regimes of invisibility shaped by intentional and unintentional features. Our argument is, on the one hand, that an atrium is based on the monopoly of expertise and on a cadastral organizationwhich are two features of our regime of invisibility enabling its owners to impose a dominant definition of a policy statement within the range of their monopoly and to prevent other actors from setting any alternative problem statement on the Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni, Claudia Foltyn, Reiner Keller, and Matthias S. Klaes, Nature & Culture, 18 (1) 10 agenda. We specifically show how actors from the oil and gas atrium maintain the "business-asusual" frame to render any problems tied to shale gas invisible to policymakers outside the atrium.

On the other hand, we argue that the ability of an atrium's owners to impose their definition of a policy statement sometimes comes at the cost of themselves being made invisiblethis is the third feature of our regime of invisibility. Specifically, we show that the oil and gas atrium is marginal in France and, while this marginality favored its autonomy in the pre-controversial stage, granting it the full management of licenses without supervision of its hierarchy, it became a liability when the support of the hierarchy was needed to circumvent the growing criticism.

Invisibility through bureaucratic cadastral organization: how shale gas licenses requests were confined within the bureaucratic atrium

Traditionally, the administration is structured through a division of tasks between departments and offices, which contributes to fragmenting and confining issues [START_REF] Blau | Bureaucracy in Modern Society[END_REF][START_REF] Crozier | L'acteur et Le Système[END_REF][START_REF] Weber | Economie et Société[END_REF][START_REF] Selznick | Leadership in Administration: A Sociological Interpretation[END_REF]). This bureaucratic division of tasks contributes to designing a cadastral map where each office manages its own demands and issues, making these offices atriums as they possess exclusive expertise and the ability to define ordinary items that lie out of the scope of other offices, departments, and ministries.

In the case of France, the division of tasks leads all requests for an oil and gas license to the Department of Energy and, more specifically, to one of its offices, i.e., the Bureau of Exploration and Production of Hydrocarbons (BEPH) (Table 2). The minister's final signature constitutes a formal step in a procedure managed exclusively by one office. Despite the fact that the requests pass through various departments, BEPH imposes its expertise and its ownership over their acceptance or rejection. A request must follow four phases defined in a codified procedure and reflecting the fragmentation of tasks (Table 3). The request is first received and validated by BEPH which then sends it to the regional level for a legal notice.

However, given that this regional authority was integrated into the procedure only in 2008 and has almost no expertise in hydrocarbons, it follows BEPH's suggestions. The request is then sent back to BEPH, which provides a report on its feasibility. Using a self-defined regime of truth, the bureau proceeds to the validation of its technical, economic and financial feasibility. Finally, the request is sent to a technical body for an additional legal notice, but the civil servants from the Corps des Mines generally validate the expertise provided by BEPH. Therefore, despite its circulation, BEPH maintains total domination over the regime of truth and the conditions of validity, to the extent of making it invisible to the other departments that handle the request.

Table 3 Another feature of invisibility relates to the cadastral organization and the division of tasks. The French procedure is structured with a gap between licenses and work authorizations, which fragments the management of the requests. Licenses grant access to the land but drilling activities require work authorizations which are granted by a different office. Managing licenses, BEPH does not have to take a stance on drilling techniques, including on hydraulic fracturing. BEPH only assesses the competences of the company and its financial capabilities. Once the licenses are granted, techniques are assessed in a second procedure by another office from the General Directorate of Risk Prevention (direction générale de la prévention des risques: DGPR) (Table 2).

We deal with the land. We grant land titles. (...) We are in charge of granting mining rights [and] we manage the licenses. As far as work authorizations are concerned, that's something else; it is a different procedure. (BEPH interviewee) However, when the social movement against shale gas started in late 2010, licenses had been granted but no work authorization had been delivered, meaning that the drilling techniques, and particularly hydraulic fracturing, had not been assessed by the Administration.

The BEPH agents managed the license requests autonomously in their own atrium. They never alerted their hierarchies of any issues relating to drilling techniques and even when the minister had to sign the licenses, he or she followed the advice from the office.

The minister's delegation was total, I never saw a minister look at a file, never, they were not interested. (Interview with a member of BEPH)

The cadastral organization makes BEPH the unique owner of the oil and gas licenses and also separates the administrative management of licenses from work authorization, contributing to rendering oil and gas license requests invisible to actors outside this atrium, or at least to giving the BEPH agents the ability to be the key players in shaping the demands. Indeed, this cadastral organization must be connected to the dominating framework about shale gas within the BEPH atrium, which was the narrative about "business-as-usual" demands. Invisibility through the definition of shale gas as a business-as-usual situation: how BEPH agents framed the requests as policy solutions rather than as problems BEPH agents and exploration companies were the first actors to give meaning to shale gas requests.

Within the hermetic space of the atrium, they defined shale gas as "business-as-usual", based on a specific regime of technical and legal feasibility.

To understand better how BEPH agents understood shale gas requests, we must first explain the larger and the historical narratives that they developed and institutionalized concerning their activity of granting licenses. In the 1990s, BEPH experienced a major decline in its activity with a sharp drop in requests. The agents adopted a mission of "saving" the exploration of the French subsurface and the discourse of decline led to a narrative of promoting the French mining domain.

BEPH agents became representatives and promoters of abandoned licenses and deposits.

At the beginning of the 1990s, the policy was to promote the mining sector. From 1995 onward, I participated in the promotion of the French mining sector in international conventions such as the AAPG [American Association of Petroleum Geologists] up until 2006. (BEPH interviewee) Therefore, rather than defining unconventional oil and gas as a new problem to address, BEPH considered them as the solution to its decline. The agents declared that the new licenses were "in continuity" with past exploration: coalbed methane exploration from Enron in the 1990s and from European Gas Limited in the 2000s; tight gas exploration from Conoco/Encana in 2006; and even shale oil exploration from Toreador and Seven Petroleum in 2007. Similarly, hydraulic fracturing was understood by these actors as a classic, old, well-known, and mastered technique. For them, it Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni, Claudia Foltyn, Reiner Keller, and Matthias S. Klaes, Nature & Culture, 18 (1) 14 had neither specificity nor particularity that could be defined as a problem: "Hydraulic fracturing is used to enhance oil recovery. It's a technique mastered since the 1970s. That has always been used." (BEPH interviewee). Based on geology and engineering knowledge and on mining regulation, the agents defined shale gas and hydraulic fracturing as technically feasible, businessas-usual, and unproblematic. They chained shale gas to their own problem of decline and made it an opportunity for renewal, further erasing any problematic aspects.

Most requests are considered as "business-as-usual" demands because they fulfill a set of norms and expectations that make those demands ordinary demands for BEPH agents. We can highlight two main expectations about the "seriousness" and the "business-as-usual" features of the requests: the identity of the requester as a petroleum geologist, and the co-construction of the demand with BEPH agents. The requests from Schuepbach in 2008 followed the ordinary procedure bound by the Mining Code. BEPH agents saw no problem with this request, but it was crucial for the requester to be a "petroleum geologist". Indeed, all BEPH agents are petroleum geologists trained at the French School of Petroleum, and during the interviews, they identified themselves with this "world" by repeatedly saying "we, the geologists" (rather than "we, the administration"). This was the door opener that would determine if one was serious and whether one would act as a guarantee of the request's quality: Moreover, if requesters made an effort to work with the department and followed their recommendations to submit a request compliant with the department's regulations, then all the conditions were fulfilled. When Total requested a license for the same area targeted by Schuepbach but without making an effort to work with BEPH, the latter gave precedence to the junior American company rather than the major French firm, exemplifying the importance of co-construction.

Emmanuel Mousset is the president [of
We almost rejected them, Total, I almost rejected them. They came on the last day because they were late, that's all. They were caught in a rush. They made their application but it had to be written in a nice way and it took them a long time. (BEPH interviewee) Schuepbach was granted two licenses and Total only one. Total tried to bypass the BEPH decision and went to the Director of Energy who let his deputy director deal with the case. However, even outside the atrium, the deputy director finally trusted his department and followed its advice.

Outside this issue of competition, no other issue emerged from the atrium and the BEPH's policy statement remained the dominant one: shale gas licenses were not an issue.

Having monopoly over expertise and being the unique owners of oil and gas licenses, BEPH agents produced their own definition of shale gas license requests and exported this definition outside the atrium. When the shale gas policy statement circulated during the two-year procedure, it was always under the BEPH frame that the requests were considered as business-as-usual and as unproblematic. The invisibility of, and inattention given to, shale gas management was not only the result of the division of tasks between offices but also of the marginal position of the agent within the department and ministry. Indeed, in 2010, BEPH had hierarchical and symbolically weak positions: its agents did not interest their hierarchy and they had no access to their organization's agenda. In 2010, shale gas was invisible not only because it was confined within the BEPH atrium and only circulated outside under the frame of "business-as-usual" narratives, but also because the actors dealing with the demands were themselves invisible. This disinterest arose from the decline of extraction in France since the 1970s [START_REF] Chailleux | Unconventional Oil and Gas in France: From Popular Distrust to Politicization of the Underground[END_REF] which led the Corps des Mines to manage other activities such as nuclear energy. It was also visible in the absence of interest from the direct hierarchy. We have already stressed how the atrium was granted autonomy with total delegation, but this autonomy also meant inattention. Deputy directors showed no interest in this self-organized department:

The marginal positions of the owners of gas: how BEPH was also invisible

So each time I had a new deputy director, it took him a few months to understand the main goals of the department, to see that we were on an activity that was working, that was going smoothly. He was less involved in monitoring. We were completely entrusted with this task and this role of proposition. (BEPH interviewee)

The Director of Energy, before the mobilization, explained that he paid no attention to oil and gas requests (interview with the Director of Energy). BEPH was therefore a department in the shadow of the bureaucratic system, whose concerns rarely became those of its hierarchy. This type of asymmetry also existed between exploration companies and their professional union.

France has always had marginal oil and gas extraction (less than 3% of its consumption) which peaked in the 1970s. While major companies (Total and Shell) left France in the 1990s when exploitation became less profitable, they were replaced by smaller companies (Vermilion, Toreador) which made profits from smaller deposits and which invested in exploration. The Union of Oil and Gas Companies (Union Française de l'Industrie Pétrolière or UFIP) is an illustration of this shift. In 2010, major companies, which had no interest in exploration, dominated the union's agenda. The dedicated union in charge of exploration within UFIP was an ad hoc department in the 2000s:

When I began to take charge of this union chamber in the mid-2000s, we simplified the structures. We were engaged in a logic of decline and we forecast the end of the exploitation and production activity in the long term. (UFIP interviewee)

When exploration companies such as Toreador (which owned exploration licenses for shale oil in the Paris basin) came to seek support from their union in the late 2000s, they were met with skepticism:

When Toreador started to talk about it, it made a lot of people laugh, especially the foreign companies who thought that it was what had happened with Elf, sniffer planes, a swindle. (Interview with Toreador)

Even when the major companies, Total and GDF-Suez, came looking for shale gas, it was marginal teams within these big groups that led the project, without the support of top managers. At that time, shale gas was not high on the list. It was clearly not a priority at Total, and even more so in France, where opinions on the potential were very divided within the company. (Interview with a senior Total manager) Contrary to the two previous features of the regime of invisibility, the marginal position of shale gas supporters in France was endured by actors rather than activated to promote exploration. Shale gas was thus an invisible issue in 2010 because it had been confined within the BEPH atrium which imposed its "business-as-usual" framework, rendering any problematic features invisible. It was also an invisible topic because its supporters were themselves invisible, both in their organization and to the general public.

Preventing criticism by mobilizing the regime of feasibility: how BEPH tried to invisibilize the first problem statement

BEPH domination over shale gas was put to the test in late 2010 when the issue was constructed as a public problem [START_REF] Zittoun | The Politics of Meaning Struggles: Shale Gas Policy Under Pressure in France[END_REF]. When a new problem statement emerged, BEPH agents mobilized their expert legitimacy to criticize the definition of shale gas as a problem and to disqualify their opponents. This resistance only worked for a couple of weeks, but it exemplified, on the one hand, how these agents used both the cadastral organization and the monopoly over expertise to disqualify their opponents, and on the other hand, how they suffered from their marginalization.

In 2010, a problem statement about shale gas emerged in other countries (Dodge and investigation, a reporter developed a problem statement associating shale gas with environmental problems such as air and water pollution, water consumption, and landscape degradation. 6 A few other isolated articles followed from April to September in other newspapers, but without leading to the mobilization of actors. Even with a media visibility, the problem statement did not really circulate. The situation changed in late December 2010 when a handful of people organized the first public meeting which marked the beginning of the problem agenda setting from January onward [START_REF] Zittoun | The Politics of Meaning Struggles: Shale Gas Policy Under Pressure in France[END_REF]. The problem was threefold: hydraulic fracturing led to pollution; shale gas disrupted the local socioeconomic organization; the licenses had been granted "on the sly". Therefore, opponents called a halt to all licenses.

While the objective of this article is not to analyze the construction and success of the problem statement, we would like to observe how the problem statement made its way to the atrium and came back. The problem statement accessed the media agenda in late December, but the first governmental reaction only appeared at the end of January. The problem statement entered governmental and administrative spaces through the deputy director of the cabinet of the Ministry of Ecology7 , who was alerted through emails and press articles. His reaction was to ask for an explanation from the Director of Energy who himself demanded a memo from BEPH. The problem statement arrived in the atrium where the agents disqualified the problem by explaining that shale gas and hydraulic fracking were not problems. They argued that France was not the US, where the problem statement came from, and that French standards guaranteed proper drilling. They also disqualified the statement's spokespeople, explaining how they were not experts and spoke falsehoods. Moreover, they mobilized an argument of legal feasibility to explain how halting the licenses was legally impossible.

These arguments came back to the Minister of Ecology who made a speech before Parliament on January 26, 2011 to state the position of the government. This meant that the atrium disqualified the problem statement and persuaded the Director of Energy, the cabinet, and the Minister herself that their policy statement was the most relevant one and that the problem statement was not legitimate. Mobilizing the power of the atrium, they shaped the governmental position and excluded the problem statement from the government agenda. Unfortunately for them, the public forum worked under different rules and other modes of regulation, and the position of the Minister was highly criticized, pushing the Minister to change her position and announce the licenses' suspension and the launch of an expert mission only four days later. Calling upon new experts, the Minister distanced herself from an office that was labelled as "too legalistic" by its hierarchy (interview with the Director of Energy). Criticized outside the atrium, these experts suffered from their marginal position which deprived them from any hierarchical or political support.

Conclusion

The case of shale gas in France allows us to put under the spotlight the issue of invisibility in agenda-setting and the selection of public problems. While shale gas has been analyzed under different perspectives over the last decade, few studies have questioned what happens in the discreet spaces of the administration and the industry. In this article, we explained why shale gas Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni,Claudia Foltyn,Reiner Keller,and Matthias S. Klaes,Nature & Culture,18 (1) 22 was invisible in the French agenda before the end of 2010 and how the topic was shaped within the closed space of the BEPH atrium. The topic was confined in an atrium which developed a regime of invisibility, preventing shale gas from circulating outside it and when it did, it was always defined under the scenario of business-as-usual and economic opportunity.

We have shown how the structures of the atrium shed light on the dynamics suffocating potential public issues. The cadastral organization and the monopoly over expertise enabled BEPH to be the main owner of oil and gas licenses and to impose its definition about shale gas under the "businessas-usual" framework. These two features of the regime of invisibility provided resources for BEPH to define a policy statement making shale gas unproblematic. However, a third feature worked both ways because the marginal position of shale gas supporters within their organization gave them autonomy, but also rendered them invisible to their own hierarchy. Before the end of 2010, shale gas was therefore invisible for most actors, both as a problem and as a policy statement. When confronted with a potential social mobilization, the supporters of shale gas did not resist for long because they suffered from their marginal position and because their particular argumentative regime did not enable them to adapt to the rules of the public forum.

At the center of these mechanisms are the definition of collective statements and the configuration of the space of dispute in which statements circulate. Our article contributes to the literature about interpretive policy analysis by showing the importance of a comprehensive analysis of the production of statements, the actors and the coalition creating and propagating them, and the spaces of debate where these statements are produced. The objective of this article is not to explain why shale gas development failed in France. Rather, it aims to shed light on the pre-controversial stage Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni,Claudia Foltyn,Reiner Keller,and Matthias S. Klaes,Nature & Culture,18 (1) 23 when initial statements were produced in order to provide further details on their features and on the rules governing the spaces where they were shaped.

  BEPH agents were in the shadow of a powerful administration which took no account of their concerns. Part of the Directorate of Energy, BEPH was attached to the Ministry of Industry and to the Corps des Mines before 2007. The Corps des Mines is one of the grands corps d'Etat in charge of the French top Administration. Composed of high-ranking civil servants educated in specific schools, such as the French Polytechnique, the Corps des Mines is historically in charge of all the topics regarding mines and energy. In the French bureaucratic system, a "corps" has the ability to monopolize every key position within a Directorate of the Central Administration. In the Directorate of Energy, the director, all deputies and the majority of office managers are from the Corps des Mines and always have been. Young engineers usually use each position to build their career; one generally occupies a position for a maximum of four years before moving on to the next level. The Corps des Mines is historically a powerful body as it has been behind the development of nuclear energy and has crushed all forms of contestation over the past 50 years. This depiction of the French administration in general, and of the Directorate of Energy in particular, sheds light on the particularities of BEPH. The office manager was a petroleum geologist and did not belong to the Corps des Mines. She worked at BEPH from 1998 to 2011, i.e., far longer Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni, Claudia Foltyn, Reiner Keller, and Matthias S. Klaes, Nature & Culture, 18 (1) 17 than the classical career length. The policy officer in charge of shale gas licenses had the same training and had been working at BEPH since 1990. Far from being a simple matter of specialization, the lack of engineers from the Corps des Mines revealed the general lack of interest of young engineers BEPH. There is no doubt that the agents from BEPH were aware of the administrative rules: I have always said we worked for the Secret Service because as long as it was going well, no one was interested. (...) Before the office manager came from the Corps des Mines, he was not a contractual geologist [like me]. Let's say they focused on other topics. (BEPH interviewee)

  Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni, Claudia Foltyn, Reiner Keller, and Matthias S. Klaes, Nature & Culture, 18 (1) 4

  Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni, Claudia Foltyn, Reiner Keller, and Matthias S. Klaes, Nature & Culture, 18 (1) 6

the

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  by seriously taking into account the Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni, Claudia Foltyn, Reiner Keller, and Matthias S. Klaes, Nature & Culture, 18 (1) 8

  Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni, Claudia Foltyn, Reiner Keller, and Matthias S. Klaes, Nature & Culture, 18 (1) 9

  Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni, Claudia Foltyn, Reiner Keller, and Matthias S. Klaes, Nature & Culture, 18 (1) 11

Table 2

 2

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  Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni, Claudia Foltyn, Reiner Keller, and Matthias S. Klaes, Nature & Culture, 18 (1) 13

  Toreador], he is a geologist. And Schuepbach, Martin, he's a doctor in geology too. He was in my office, there was no problem. They are people with a lot of experience about the subsurface and oil. (BEPH interviewee) Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni, Claudia Foltyn, Reiner Keller, and Matthias S. Klaes, Nature & Culture, 18 (1) 15

  Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni, Claudia Foltyn, Reiner Keller, and Matthias S. Klaes, Nature & Culture, 18 (1) 16

  Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni, Claudia Foltyn, Reiner Keller, and Matthias S. Klaes, Nature & Culture, 18 (1) 18

  Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni, Claudia Foltyn, Reiner Keller, and Matthias S. Klaes, Nature & Culture, 18 (1) 19

  Lee 2017; Chailleux 2020), as well as in France, through newspaper articles. In France, the first article was published in March 2010 in Le Monde. Inspired by what happened in the U.S., but also by his own Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni, Claudia Foltyn, Reiner Keller, and Matthias S. Klaes, Nature & Culture, 18 (1) 20

  Pre Print. For citation, use the final version. The article is included in the special issue: "What is Fracking a Case of? Theoretical Lessons from European Case Studies". Guest Editors: Roberto Cantoni, Claudia Foltyn, Reiner Keller, and Matthias S. Klaes, Nature & Culture, 18 (1) 21

The « cadastre » is used in the French legal system to refer to mapping the division of land based on ownership. A cadastral organization therefore refers to the division of tasks between organizations, departments and actors, giving them ownership over specific items.

Hervé Kempf, « Le casse-tête gazier » (The gas puzzle), Le Monde, March 22 2010

All the main actors we interviewed confirmed that they paid attention to the problem statement because of this deputy director.


Stutee Mohapatra

Sourav Gayen

Ranjit Bag

Arpita Das

Rongala Ramalakshmi

Marie Cor- Dier #

Sundargopal Ghosh
email: sghosh@iitm.ac.in

Structures and Bonding of Early Transition Metallaborane Clusters

Structures and bonding of various homo and heterometallic metallaborane clusters are described which are stabilized in the coordination sphere of early transition metals. For example, the bimetallic triborane species, [{Cp*Mo(CO)}2{µη 3 :η 3 -B3H7}], 2 has been synthesized from the pyrolysis of an in situ generated intermediate, produced from the reaction of [Cp*Mo(CO)3Me], 1 and [LiBH4•THF], with an excess amount of [BH3•THF]. Superficially cluster 2 is isostructural but not isoelectronic with [(Cp*MoCl)2B3H7] (I). Both clusters 2 and I contain a bimetallic template bridged by {B3H7} moiety. Cluster 2 is denoted as a unique saturated and unsubstituted closo bimetallic B3H7 cluster. Theoretical output implies that saturation in such clusters brings thermodynamic stability. Further, we have developed a new strategy for the synthesis of various heterometallic metal-rich metallaborane clusters. For example, pyrolysis of an intermediate, obtained from the reaction of [Cp*MoCl4], 4 and [LiBH4•THF], with cobalt and iron carbonyl compounds yielded triply bridging hydrido(hydroborylene), [{Cp*Mo(CO)2}2Co(CO)3BH(μ-H)], 5, tetrametallic μ4-boride, [{Cp*Mo(CO)2}2(μ4-B)(μ-H){Co2(CO)5}], 6, triple decker complex, [(Cp*Mo)2{µ-η 6 :η 6 -B4H4Co2(CO)5}(μ-H)2], 7, metal-rich dimolybdaborane cluster, [(Cp*Mo)2Co2(CO)3(μ-CO)3B3H3(μ-H)2], 8 and mixed-metal cluster, [(Cp*Mo)2B4H8Fe(CO)3], 9. All the molecules have been characterized by 1 H, 11 B{ 1 H}, and 13 C{ 1 H} NMR spectroscopy; mass spectrometry; infrared (IR) spectroscopy and single-crystal X-ray diffraction studies for clusters 2 and 5-9. The electron counting rules and density functional theory (DFT) calculations provided further insight into the bonding and electronic structures of these clusters.

INTRODUCTION

Due to the unique nature of bonding, the lower borane species have been utilized outwardly in many organic syntheses, for example, catalytic diboration, hydroboration and borylation reactions. 1 However, the right-hand neighbours of boron show different properties and one of them is catenation property that led to the formation of consecutive C-C bonds or Si-Si bonds in chemistry of polysilanes. In contrast, due to the electron deficiency, boron favors to oligomerize through non-classical three centered two electron bonding instead of classical electron precise two centered two electron bond unless stabilized by electron donating substituents. [START_REF] Osorio | Analysis of Why Boron Avoids sp 2 Hybridization and Classical Structures in the BnHn+2 Series[END_REF] For example, as shown in Chart 1 [START_REF] Hayashi | Syntheses and properties of triborane(5)s possessing bulky diamino substituents on terminal boron atoms[END_REF][4][5][START_REF] Gaines | Low-Temperature Crystal and Molecular Structure of Tetracarbonyl [2-bromoheptahydrotriborato (1 -)] manganese, (CO)4MnB3H7Br, and a 1 H NMR Study of the Kinetics of Its Intramolecular Hydrogen Exchange in Solution[END_REF][START_REF] Kar | Metal Coordinated Tri-and Tetraborane Analogues[END_REF] , linear catenated triborane(5), A [START_REF] Hayashi | Syntheses and properties of triborane(5)s possessing bulky diamino substituents on terminal boron atoms[END_REF] has been stabilized by bulky diamino substituents on terminal boron atom. However, with increasing number of boron atoms, they lean towards cluster formation, in which the triborane or tetraborane typically prefer cyclic form 8 . Interestingly, Braunschweig et al. reported the hydroboration of diborenes that generated unique bis(NHC)-stabilized triborane B. 4a Successively they have synthesized electron precise sp [START_REF] Hayashi | Syntheses and properties of triborane(5)s possessing bulky diamino substituents on terminal boron atoms[END_REF] -sp 2 -sp [START_REF] Hayashi | Syntheses and properties of triborane(5)s possessing bulky diamino substituents on terminal boron atoms[END_REF] triborane C from ferrocene-bridged diborene. 4b

Chart 1. Various types of triborane species (A-F). M= Pd or Pt, E =SePh.

The triborane moiety is the simplest polyborane in which distinct bonding modes with metal counterparts have been observed. 9 Triborane D, 5 shown in Chart 1, represents a πborallyl triborane ligand, which is coordinated to metal with pseudo square-planar environment. In 1980, Gaines and coworkers isolated and structurally characterized a fascinating butterfly cluster [(CO)4MnB3H8Br], [START_REF] Gaines | Low-Temperature Crystal and Molecular Structure of Tetracarbonyl [2-bromoheptahydrotriborato (1 -)] manganese, (CO)4MnB3H7Br, and a 1 H NMR Study of the Kinetics of Its Intramolecular Hydrogen Exchange in Solution[END_REF] E, in which the bidentate B3 ring is ligated to Mn(CO)4 moiety. To the best of our knowledge, the numbers of linear triboranes are very limited except some structurally characterized B3H8-metal clusters. To isolate such kind of species, transition metal coordination sphere is considered to be one of the key ACCEPTED MANUSCRIPT / CLEAN COPY templates that can stabilize the unstable reactive motifs. [START_REF] Kar | Metal Coordinated Tri-and Tetraborane Analogues[END_REF]10 For example, recently we have isolated a classical [B2H5] - ion stabilized by binuclear tantalum template. 10a Subsequently, we have isolated a triborane analogue {B3H6SePh} which is also stabilized in the coordination sphere of {Cp*Ta}2. [START_REF] Kar | Metal Coordinated Tri-and Tetraborane Analogues[END_REF] Further, a bimetallic diborane(4) species, [{Cp*Mo(CO)2}2{µ-η 2 :η 2 -B2H4}] 10b was isolated which is stabilized by {Cp*Mo}2 fragment. Note that isolobal analogy [START_REF] Hoffmann | Building Bridges Between Inorganic and Organic Chemistry (Nobel Lecture)[END_REF] and electron counting 12 rules play a major role in designing and synthesizing these species, which are stabilized by early transition metal template.

Therefore, with an objective to isolate such metal coordinated lower borane species, we explored the reaction of an

RESULTS AND DISCUSSION

Low temperature reaction of [Cp*Mo(CO)3Me], 1, with [LiBH4•THF] followed by mild pyrolysis with [BH3•THF] resulted in the formation of an air and moisture sensitive green solid 2 (Scheme 1). The reaction also yielded arachno-[Cp*Mo(CO)2B3H8] 10c , 3 and [(Cp*Mo)2B5H9] along with other unstable as well as moisture sensitive compounds, which we were unsuccessful in isolating in pure form. Compound 2 was characterized by 1 H, 11 B, [START_REF] Andersen | Ferraborane B3H7Fe2(CO)6, a Diiron Analogue of Pentaborane(9)[END_REF] C NMR, IR, mass spectrometry and single crystal X-ray diffraction study. The 11 B{ 1 H} NMR spectrum of 2 shows two resonances at δ = 12.9 and -3.7 ppm ~2:1 ratio. Alongside peaks at δ = 3.01 ppm and 1.57 ppm for the B-H terminal protons, the 1 H NMR spectrum shows two distinct Cp* proton peaks at δ = 2.02 and 1.90 ppm. Additionally, a broad up-field resonance at δ = -13.08 ppm has been detected. The IR spectrum of 2 featured bands at 1638 and 2475 cm -1 corresponding to carbonyl and terminal B-H ligands, respectively. Later, the [START_REF] Andersen | Ferraborane B3H7Fe2(CO)6, a Diiron Analogue of Pentaborane(9)[END_REF] along with all other the spectroscopic data provided some tips about nature of the molecule 2, the core geometry was established when the single crystal X-ray diffraction analysis was carried out.

The X-ray analysis of 2 revealed a linear triborane [B3H7], stabilized in the coordination sphere of two Mo atoms that depicted a trigonal bipyramidal [Mo2B3] core geometry (Figure 1). One of the boron atoms (B2) and two metals (Mo1, Mo2) occupy the equatorial positions of the trigonal bipyramid, while other two boron atoms (B1 and B3) are placed at the axial positions. The avg. B-B bond distance in the triborane chain of 2 (1.736 Å) is shorter as compared to the avg. B-B bond distance of [B3H7Fe2(CO)6] (1.778 Å) [START_REF] Andersen | Ferraborane B3H7Fe2(CO)6, a Diiron Analogue of Pentaborane(9)[END_REF] and [1,2-(Cp*Ru)2B3H7(μ-H)2] (1.920 Å) [START_REF] Lei | anes Derived from the Reaction of [Cp*MCl2]2 with Monoboranes (M = Ru, Rh; Cp* = η 5 -C5Me5)[END_REF] . The Mo-Mo bond distance of 3.0326 (6) Å is analogous to that of [{Cp(CO)2Mo}2{µ-η 2 :η 2 -P2}] (3.036(2) Å) [START_REF] Gregoriades | Self-Assemblies Based on [Cp2Mo2(CO)4(μ,η 2 -P2)]-Solid-State Structure and Dynamic Behaviour in Solution[END_REF] , however, it is shorter than that of [CpMo(CO 6), Mo1-B1 2.354(5), Mo1-B2 2.207(5), Mo1-B3 2.351(6), B1-Mo2 2.319(5), B2-Mo2 2.253(5), B3-Mo2 2.338(5), B1-B2 1.715(8), B2-B3 1.757 (7); Mo1-B1-Mo2 80.93( 16), Mo1-B2-Mo2 85.67 (17), B1-B2-B3 127.5(4).

In an effort to isolate the key molybdaborane intermediates during the formation of [(Cp*Mo)2B5H9] 19 , Fehlner and co-workers isolated electronically unsaturated 1). [START_REF] Andersen | Ferraborane B3H7Fe2(CO)6, a Diiron Analogue of Pentaborane(9)[END_REF][START_REF] Lei | anes Derived from the Reaction of [Cp*MCl2]2 with Monoboranes (M = Ru, Rh; Cp* = η 5 -C5Me5)[END_REF]18,[START_REF] Nishihara | Synthesis of Cobaltaborane Clusters from [Cp*CoCl]2 and Monoboranes. New Structures and Mechanistic Implications[END_REF] Apart from 2 and I, all other [M2B3] clusters are manifested as nido-square pyramid geometry consisting 7 SEP. However, metals are located at different vertices in all these nido-[M2B3] clusters. For instance, [2,3-(Cp*Rh)2B3H7] 14 exhibited as 7 SEP nido-square pyramid geometry comprised of M-M bond but [2,3-(Cp*Co)2B3H7] [START_REF] Nishihara | Synthesis of Cobaltaborane Clusters from [Cp*CoCl]2 and Monoboranes. New Structures and Mechanistic Implications[END_REF] reflected the same geometry without any M-M bond. This may be because of more feasibility in overlap between metal d-orbitals when coming down the group in periodic table . To sum up, we can propose that compound 2 is the first reported closo, saturated and unsubstituted dimetallic triborane species. Although 2 and I show structural resemblances, they display different 11 B{ 1 H} chemical shifts. The 11 B{ 1 H} chemical shifts of 2, appeared at δ = 12.9 and -3.7 ppm in ~2:1 ratio, are significantly upfield shifted as compared to the corresponding 11 B{ 1 H} chemical shifts for I that appeared at δ = 105.5 and 34.2 ppm. 18 Cluster 2 rather exhibits similar kind of upfield 11 B resonances like other [M2B3] clusters listed in Table 1. [START_REF] Andersen | Ferraborane B3H7Fe2(CO)6, a Diiron Analogue of Pentaborane(9)[END_REF][START_REF] Lei | anes Derived from the Reaction of [Cp*MCl2]2 with Monoboranes (M = Ru, Rh; Cp* = η 5 -C5Me5)[END_REF]18,[START_REF] Nishihara | Synthesis of Cobaltaborane Clusters from [Cp*CoCl]2 and Monoboranes. New Structures and Mechanistic Implications[END_REF] Therefore, in order to assign the 11 B chemical shifts of 2 and I, we have carried out the 11 B NMR calculations using gauge invariant atomic orbital (GIAO) method that corroborate well with the experimental [START_REF] Hoffmann | Building Bridges Between Inorganic and Organic Chemistry (Nobel Lecture)[END_REF] B chemical shift values (Table S2).

In order to investigate the electronic and steric effect, we have carried out DFT calculation of I and 2 using b3lyp/def2-tzvp level of theory. All the structural parameters are quite comparable with that of solid-state X-ray structures. The MO analysis suggests that the additional pair of electrons of 2 is accommodated in one of the unoccupied orbitals of unsaturated cluster I and gets stabilized. In addition to that, the HOMO-LUMO gap is also remarkably ACCEPTED MANUSCRIPT / CLEAN COPY lower for I (2.439 eV) than 2 (3.370 eV). Moreover, the HOMO-8 of 2 sketched a substantial bonding overlap between the boron p and metal d orbitals extended throughout the cluster (Figure 2(a)). This type of extended orbital interaction was absent in I. These phenomena may demonstrate the fact that saturation in such clusters provides a greater stability. Further, the NBO charge analysis shows that the oxidation state of molybdenum decreased as the ancillary ligand Cl has been replaced by CO. This eventually increases the natural charge of the boron atoms of 2 (Table S1). Thus, the above results support the upfield [START_REF] Hoffmann | Building Bridges Between Inorganic and Organic Chemistry (Nobel Lecture)[END_REF] S1) values suggested the B-B bonding interaction to be more prominent in II, the destabilization of HOMO may be defined by the presence of higher energy 5d orbitals localized on tungsten atom (II) in place of 4d orbital of Mo atom (2). These phenomena indirectly suggest a reduced kinetic stability for II than 2, which may be the reason for nonexistence of the triborane analogue of tungsten.

Reactivity of [Cp*MoCl4] with Co2(CO)8. As part of our effort to synthesize metal-rich metallaborane starting from transition metal stabilized tris-boranes, we tried the reactivity of 2 with different metal carbonyl fragments. These reactions led to the formation of various air-sensitive compounds with poor yield, which we were unable to isolate in pure form. As a result, in search for a different and efficient synthetic strategy from smaller metallaboranes to metal rich metallaborane we investigated the reactivity of metal carbonyls with in-situ generated intermediate, produced from the reaction of [Cp*MoCl4] and [LiBH4•THF]. Thermolysis of the intermediate with Co2(CO)8 led to the formation of hydrido(hydroborylene) 5, μ4-boride 6, triple-decker sandwich complex 7 and bimolybdenametallaborane 8 (Scheme 2). Preparative thin-layer chromatography was used to separate all products for further spectroscopic and structural characterization. Detailed spectroscopic and structural characterization of these species are described below.

Triply-bridging hydrido(hydroborylene), 5. Compound 5 was isolated as green solid in moderate yield. The 11 B NMR spectrum reveals a broad downfield resonance peak at δ = 69.7 ppm. In addition to that, the presence of a peak at δ = 1.86 ppm in 1 H NMR confirmed one Cp* environment. Further, there is a peak at m/z 731.9764 in mass spectrum that corresponds to [C29H31O9Mo2CoB] + . These data indicate that the structural framework contains two Cp*Mo unit. Apart from one up field chemical shift at δ = -11.31 ppm, the 1 H NMR also revealed a downfield broad peak at δ = 10.41 ppm. This could result from the existence of B-Ht. [START_REF] Nishihara | Synthesis of Cobaltaborane Clusters from [Cp*CoCl]2 and Monoboranes. New Structures and Mechanistic Implications[END_REF][START_REF] Sharmila | Synthesis, characterization and crystal structure analysis of cobaltaborane and cobaltaheteroborane clusters[END_REF] The broadened nature of the 11 B peak and the 1 H chemical for shifts due to terminal B-H protons support the existence of borylene moiety in 5. All these spectral information was abstruse to get a proper view on complete structure. Thus, the X-ray diffraction study explicitly guided us to understand the structural framework. To get some insight into the borylene character as well as bonding scenario, we have performed the DFT calculation on b3lyp/def2-tzvp level of theory. Although, the MO analysis shows a head to head overlap between the d orbital of Co and the p orbital of B, the Co-B separation of (2.133 Å) in the optimized structure of 5 is significantly longer in comparison to its solid-state structure (2.04(2) Å). This σ bonding interaction was further supported by WBI value of 0.413. In addition, there is one 3c-2e bonding interaction along Co-H-B (Figure 4(a)). The NBO studies also supported a greater contribution of B (31.83%) than Co (26.63%) in the Co-H-B banana bond. Further, from the topological analysis, we have noticed a shift of BCP towards H atom along the Co-H bond path. This clearly signifies that the bond is more polarized towards hydridic hydrogen than Co-center. Based on all these theoretical outputs, it is apparent that the B-H interaction is more prominent than Co-H within the Co-H-B 3c-2e bonding scenario.

Tetrametallic μ4-Boride, 6. Beside the triply bridging hydrido(hydroborylene) species, another moderately air stable black solid was also yielded in 11% yield. The mass spectrum shows an intense ion peak at m/z 844.8936 that corresponds to [C27H32BO7Mo2Co2] + . The 1 H NMR spectrum displays single peak at δ =1.93 ppm in Cp* region along with one upfield region shift at δ =-3.27 ppm. The presence of CO and Cp* ligand was further confirmed from [START_REF] Andersen | Ferraborane B3H7Fe2(CO)6, a Diiron Analogue of Pentaborane(9)[END_REF] C NMR and IR spectroscopic data. Further, a downfield single resonance shift was recorded at δ = 129.5 ppm in room temperature [START_REF] Hoffmann | Building Bridges Between Inorganic and Organic Chemistry (Nobel Lecture)[END_REF] B NMR, which demonstrates the presence of metal rich environment around boron. The observed 11 B chemical shift is in agreement with some of the structurally characterized boride clusters. 26,28 Along with the spectroscopic details, the X-ray structure analysis also led us to the confirmation about the solid-state structure. As shown in Figure 5, the crystal structure of 6 can be described as heterometallic boride cluster having a boron atom placed at semi-interstitial position of butterfly M2M'2 core (M= Mo, M' = Co). The observed Mo-B (2.41Å) and Co-B (2.05Å) bond distances are consistent with the known molybdaboranes, cobaltaboranes and other reported μ4-boride clusters. 27,18b,29 The boron atom is situated at semi-interstitial position in quite bent fashion because of ACCEPTED MANUSCRIPT / CLEAN COPY Mo1-B1-Mo2 angle of 163.7°. Cluster 6 comprises of 62-CVE. And it is isostructural as well as isoelectronic to recently reported [{Cp*W(CO)2}2{Co2(CO)5}(μ4-B)(μ2-H)]. 29a To investigate the stability of this boride cluster, we have carried out molecular orbital analysis. As shown in Figure 4(c), the HOMO-18 showed an extended overlap between the d orbitals of metal centers and p orbital of semi-interstitial boron atom. In addition, the presence of 3c-2e bonding scenario has also been observed along the Mo-H-B. Interestingly, unlike 5, there was no shift of BCP observed along the Mo-H bond.

In addition to the formation of these species, the reaction also yielded a triple-decker species 7 29b , which was reported recently based on spectroscopic data. Thus, in an attempt to get the X-ray structure, we have carried out the XRD analysis of 7. The solid-state X-ray structure of 7 represented as [(Cp*Mo)2{µ-η 6 :η 6 -Co2(CO)5B4H4}(μ-H)2] possessing two {Cp*Mo} fragments sandwiched hexagonal planar [Co2(CO)5B4H4] middle deck (sum of internal angles = 720°) {Figure 6(left)}. The μ2-bridged carbonyl connected to two cobalt center is inclined towards Mo2 atom. The eclipsed alignment of terminal CO in Co2(CO)5 has also been found in 7. In comparison to some reported dimolybdenaboranes, the Mo-Mo bond distance of 2.790 Å is smaller as compared to, which is also supported by higher WBI values (Table S1).

Metal-rich dimolybdaborane cluster, 8. Along with metal-rich metallaborane clusters 5, 6 and triple decker sandwich complex, 7, the reaction also yielded compound 8 as a brown solid in 12% yield. In the ESI-MS of 8, a molecular ion peak has been recorded at m/z = 786.9598. The 11 B{ 1 H} NMR spectrum of 8 showed three signals at δ = 102.5, 100.0 and 30.3 ppm in ~1:1:1 ratio signifying the existence of three distinct boron environments. The 1 H NMR spectrum revealed one kind of Cp* ligand at δ = 2.00 ppm in addition to the resonance peak for B-Ht protons at δ = 6.89 ppm. The presence of an up-field chemical shift at δ = -13.44 ppm in the 1 H NMR may be due to the presence of Mo-H-B protons. The 13 C NMR and IR spectrum further confirmed the existence of both bridging and terminal CO ligands. However, a definite inference eluded us until the cluster core has been revealed by single-crystal X-ray analysis.

As shown in Figure 6 In a similar fashion, the reaction of Fe2(CO)9 with the insitu generated intermediate, produced from [Cp*MoCl4] with LiBH4 reaction, at 60 ˚C led to the formation of an air and moisture sensitive product 9. 31 Note that, compound 9 and known [(Cp*Mo)2B5H9] couldn't be separated by chromatographic methods. Hence, they were isolated as inseparable solids and crystallized from a CH2Cl2/hexane solution at -5 °C. Two different types of crystals were obtained; crystals of 9 is black and [(Cp*Mo)2B5H9] is orange. The X-ray ACCEPTED MANUSCRIPT / CLEAN COPY diffraction analysis suggested that the structural formulae for 9 can be defined as [(Cp*Mo)2B4H8Fe(CO)3]. As shown in Figure 6(right), 9 can be represented as bicapped trigonal bipyramidal geometry. Two Mo atoms and B4 are placed at equatorial position of the trigonal bipyramid and the axial B1 and B2 atoms capped the {Mo1Fe1Mo2} and {Mo1B3Mo2} triangular faces, respectively. Interestingly, 9 is isostructural with [(Cp*W)2B4H8Fe(CO)3] 32 in which two Mo atoms occupied the same position as that of W. Cluster 9 follows the electron counting rule with total cluster valance electron of 56 (6 SEP). The Mo-Mo bond distance of 2.7969(18) Å is also comparable to other reported dimolybdenaborane containing 6 SEP.

Further, all the spectroscopy data of 9 corroborated well with X-ray structure. For example, four intense boron resonances of 9 appeared at δ = 93.0, 83.1, 38.9, and 34.5 ppm signify the presence of four boron atoms having different environments. The 1 H NMR spectrum showed a peak at δ = 2.07 ppm due to the presence of single Cp* environment. In addition, two upfield region peaks at δ = -5.96 and -12.36 ppm in the 1 H NMR correspond to bridging Mo-H-B hydrogens. Further, the IR spectrum of 9 revealed the presence of terminal CO ligand at ν = 1988, and 1918 cm -1 . The mass spectrum showed molecular ion peak at m/z = 655.0757 which correspond to [M+H] + .

CONCLUSION

In this article, we have explained the isolation and structural characterization of a linear triborane species stabilized in the coordination sphere of two molybdenum atoms. Structural insight obtained from X-ray diffraction analysis, revealed that a B3H7 unit is ligated in η 3 -fashion to both of the metal centre. Cluster [{Cp*Mo(CO)}2{µ-η 3 :η 3 -B3H7}], 2 is an unique addition to the series of linear triborane species which show distinct electronic as well as structural features. Despite of having structural resemblances with [(Cp*MoCl)2B3H7], 2 is considered novel due to its electronic saturation. Additionally, theoretical studies demonstrated the plausible explanation for the stability. Further, we have demonstrated a different and efficient approach to synthesize metal-rich heterometallic metallaborane clusters that led to the formation of triply bridging trimetallic hydrido(hydroborylene), 5 and tetrametallic μ4-boride, 6. NMR studies and a detailed theoretical investigation explicitly explained a lower borylene character of 5 compared as compared to other reported hydrido(borylenes) species.

EXPERIMENTAL SECTION

General Procedures and Instrumentation. All reactions and experiments were performed under an inert atmosphere or in vacuo using standard Schlenk line techniques and glove box. THF, toluene and hexane were among the solvents those were first dried utilising appropriate drying agents (sodium/benzophenone) and then distilled under argon environment. Three cycles of freezepump-thaw degassed CDCl3, which was then reserved over molecular sieves. [Cp*Mo(CO)3Me] 33 and [Cp*MoCl4] 34 were synthesized following the literature methods. Meanwhile, other chemicals like [LiBH4•THF], [Co2(CO)8] and [Fe2(CO)9] were obtained from commercial source (Aldrich) and used exactly as it was given without further purification. Preparative thin layer chromatography was performed for the separation of products (20 x 20 cm). It was made of Merck 105554 TLC silica gel 60 F254 layer, having thickness of 250 μm on aluminium sheets. NMR spectra were recorded on 400 and 500 MHz Bruker FT-NMR spectrometers. The residual solvent protons functioned as reference (, ppm, d6-benzene, 7.16; CDCl3, 7.26). 1 H decoupled 11 B spectra were processed with a backward linear prediction algorithm to remove the broad 11 B background signal of the NMR tube. The infrared spectra were recorded on a Nicolet iS10 spectrometer. Agilent 6545 Q-TOF LC/MS instrument recorded Electrospray mass (ESI-MS) spectra.

Synthesis of 2. In a flame-dried Schlenk tube, [Cp*Mo(CO)3Me], (0.1 g, 0.30 mmol) dissolved in 15 mL of toluene was reacted with 1.2 equiv. (2.4 mL) of [LiBH4•THF] at -78 °C and allowed to stir for 1 h at room temperature and then by addition of [BH3•THF] (1 mL, 10 mmol) it was left to stir for additional 24 h. The volatile components were evaporated using vacuo and then hexane/dcm was added into the residue to dissolve as much as possible. It was then extracted through Celite using a frit. The extracted filtrate was then dried and put through a chromatographic work-up utilising TLC plates made of silica gel. Elution with full hexane mixture afforded the compound in order of elution: green 2 (0.010 g, 12%) 11.8 (s, C5Me5), 11.7 ppm (s, C5Me5); IR (CH2Cl2, cm -1 ): 2475 (w, BHt), 1638 (CO).

Synthesis of 5-8: At first, [Cp*MoCl4], (0.1 g, 0.27 mmol) was weighed in a flame-dried Schlenk tube and dissolved in 10 mL of toulene. Five-fold excess of [LiBH4•THF] (0.7 mL) was slowly added dropwise into it at -78 °C and the mixture was then stirred at room temperature for 1 h. The volatile components were evaporated using vacuo and then hexane was added into the residue to dissolve as much as possible. It was then extracted through Celite using a frit. After drying hexane, we got the brownish-green coloured extract. Later, 10 mL of THF solution of [Co2(CO)8] (0.03 g) was transferred to extracted mixture using argon flow. The thermolysis of whole mixture was carried out for 16 h at 60 °C. The solvent was eliminated using vacuum, and the residue was then extracted into hexane/dcm which was passed through Celite. The extracted filtrate was then dried and put through a chromatographic work-up utilising TLC plates made of silica gel. Elution with a hexane/CH2Cl2 (70:30 v/v) mixture yielded, well separated greenish brown 5 (0.007 g, 7%), black 6 (0.012 g, 11%), brown 7 (0.014 g, 15%), brown 8 (0.013 g, 12%) along with [(Cp*Mo)2B5H9] 19 (0.017 g, 24%). (22 °C, 125 MHz, CDCl3): δ = 103.9 (C5Me5), 10.8 ppm (C5Me5); IR (CH2Cl2, cm -1 ): 2023, 1988 (w, BHt), 1793, 1752 (CO).

8: MS (ESI+): m/z calculated for [M+H] + 786.9601, found 786.9598; 11 B{ 1 H} NMR (160 MHz, CDCl3, 22 °C): δ = 102.5 (s, 1B), 100.0 ppm (s, 1B), 30.3 (s, 1B); 1 H NMR (500 MHz, CDCl3, 22 °C): δ = 6.89 (br, 3H, B-Ht), 2.00 (s, 30H, C5Me5), -13.44 ppm (br, 2H, Mo-H-B); 13 C{ 1 H} NMR (22 °C, 125 MHz, CDCl3): δ = 110.1 (C5Me5), 12.2 (C5Me5); IR (CH2Cl2, cm -1 ): 2490, 2450 (w, BHt), 2012, 1992, 1829, 1639 (CO).

Synthesis of 9: At first, [Cp*MoCl4], (0.1 g, 0.27 mmol) was weighed in a flame-dried Schlenk tube and dissolved in 10 mL of toulene. Five-fold excess of [LiBH4•THF] (0.7 mL) was slowly added

  in situ generated intermediate, made from the reaction of [Cp*Mo(CO)3Me] and [LiBH4•THF], with an excess of [BH3•THF]. The reaction yielded linear triborane species, confined in metal templates. In this article, we described the details of their structure, bonding and spectroscopic characterization. In addition, we have further explored the reactivity of Co2(CO)8 and Fe2(CO)9 with another in situ generated intermediate, generated from the reaction of [Cp*MoCl4] and [LiBH4•THF], that yielded novel metal-rich metallaborane clusters.

  Scheme 1. Synthesis of [{Cp*Mo(CO)}2{µ-η 3 :η 3 -B3H7}] (Mo-Mo bonds are not shown for clearness).

  )3]2 (3.235 Å) 16 , [Mo2(CO)10] 2- (3.123(7) Å) 17 and [(Cp*MoCl)2B3H7], I (3.095(12) Å) 18 . In addition to Cp* ligand, both the Mo centers are ligated to one CO ligand. Interestingly, unlike [(Cp*MCO)2B4H4(μ-H)2] (M = Cr, Mo), the CO ligands are positioned trans to each other in 2, which is reflected in torsional angle of 172.79˚(C-Mo-Mo-C). As a result, Cp* coordinated to Mo2, inclined towards the open face of B3H7 to minimize steric hindrance. This resulted two different Cp* environments, which was also evidential from 1 H and 13 C NMR spectra. This trans orientation of both CO and Cp* ring is quite unique; which was not observed in analogous [(Cp*MoCl)2B3H7], I 18 .

Figure 1 .

 1 Figure 1. Molecular structure and labeling diagram of 2. Selected bond lengths (Å) and angles ( ο ): Mo1-Mo2 3.0326(6), Mo1-B1 2.354(5), Mo1-B2 2.207(5), Mo1-B3 2.351(6), B1-Mo2 2.319(5), B2-Mo2 2.253(5), B3-Mo2 2.338(5), B1-B2 1.715(8), B2-B3 1.757(7); Mo1-B1-Mo2 80.93(16), Mo1-B2-Mo2 85.67(17), B1-B2-B3 127.5(4).

  B{ 1 H} chemical shift of 2. On the other hand, the Laplacian plot of electron density along the B1-B2-B3 plane displayed bond critical points (BCPs) and bond path connecting all these boron centers that represent the strong bonding along the triborane unit {Figure 2(b)}, which was further supported by WBI values of particular bonds. Again, a region of charge concentration has been detected along the B1-B2 and B2-B3 bonds. It shows high covalent character which is also reflected by the average electron density [ρr] value of 0.132 and a negative the energy density [H(r)] of -0.092.

Figure 2 .

 2 Figure 2. (a) HOMO-8 of 2 and (b) contour line diagram along the B1-B2-B3 plane obtained from Laplacian of electron density of 2. [Charge concentration (∇ 2 ρ(r) < 0) regions have been represented by solid red lines, while the areas of charge depletion (∇ 2 ρ(r) > 0) are shown as dashed black lines. Blue dots and bold dark-brown lines depict BCPs and the bond path respectively]. Subsequently, in search for a probable existence of the tungsten analogue of saturated 2, we have optimized [{Cp*W(CO)}2{µ-η 3 :η 3 -B3H7}] II. The B-B bond distance is marginally lower in II compared to 2 and it shows a significant decrease in ΔEHOMO-LUMO by 0.517 eV from Mo analogue 2, which occurred mainly due to the notable destabilization of HOMO. The HOMOs of both 2 and II are localized on the B-B bonds and the d-orbitals of the metal centers. As WBI (TableS1) values suggested the B-B bonding interaction to be more prominent in II, the destabilization of HOMO may be defined by the presence of higher energy 5d orbitals localized on tungsten atom (II) in place of 4d orbital of Mo atom(2). These phenomena indirectly suggest a reduced kinetic stability for II than 2, which may be the reason for nonexistence of the triborane analogue of tungsten.

Figure 3 .

 3 Figure 3. Molecular structure and labeling diagram of 5. The bridging H-atom is not located. Selected bond lengths (Å) and angles ( ο ): B1-Co1 2.04(2), B1-Mo2 2.23(3), B1-Mo1 2.25(3), Mo1-Mo2 3.058(8). Co1-B1-Mo2 80.5(8), Co1-B1-Mo1 81.2(10), Mo2-B1-Mo1 86.2(9), B1-Co1-Mo2 52.7(10).

Scheme 2 .

 2 Scheme 2. Synthetic route to metal rich metallaborane. (Carbonyls and Mo-Mo bonds are not shown for clarity in 7 and 8).

  26a

Figure 4 .

 4 Figure 4. (a) 3c-2e bonding interaction of Co-H-B in 5; (c) HOMO-18 of 6, showing extended bonding overlap over molecular framework; (b) and (d) represent contour line diagram along the M-H-B planes of 5 and 6 respectively, obtained from Laplacian of electron density.

Figure 5 .

 5 Figure 5. Molecular structure and labeling diagram of 6. The bridging H-atom is not located. Selected bond lengths (Å) and angles ( ο ):Mo1-B1 2.180(5), Mo1-Co3 2.8839(8), Mo1-Co4 2.7023(8), Mo2-Co3 2.967(5), Mo2-B1 2.125(5), Co3-B1 2.022(5), Co4-B1 2.076(5). B1-Mo1-Co4 48.92(14), Co4-Mo1-Co3 52.00(2), Mo2-B1-Mo1 163.7(3), Co4-B1-Co3 73.57(17).

  (middle), the molecular structure of 8 can be defined as [(Cp*Mo)2Co2(CO)3(μ-CO)3B3H3(μ-H)2]. It is consistent with the spectroscopic output and structurally and electronically analogous to ditungstenaborane, 29b recently reported by us. The structure can be portrayed as a nido hexagonal bipyramid with atoms Co1, Co2, B1, B2 and B3 constituting the open and flattened base. Mo1 and Mo2 capped above and below of the base respectively. Applying classical skeletal electron counting formalism 12 , using 8vertex oblato-closo hexagonal bipyramid as starting point, cluster 8 can be represented as electron deficient 6-SEP oblato-nido-species. Although the avg. Mo-B-Mo bond angle in 8 is shorter as compared to [{Cp*Mo(CO)}2{µ-η 3 :η 3 -B3H7}], 1, it is larger compared to [(Cp*Mo)2{µ-η 6 :η 6 -Co2(CO)5B4H4}(μ-H)2], 7. Further, the Mo-Mo separation of (2.8489(9) Å) is shorter as compared

Figure 6 .

 6 Figure 6. Molecular structure and labeling diagram of 7 (left), 8 (middle) and 9 (right). Selected bond lengths (Å) and angles ( ο ) of 7: Mo1-Mo2 2.7900(4), Mo1-B1 2.329(3), Mo1-B2 2.181(3), B1-Mo2 2.273(3), B2-Mo2 2.205(3), Co1-Co2 2.5110(6), Co1-Mo1 2.7958(4), B1-Co1 2.112(3), B1-B2 1.715(8); Mo1-B1-Mo2 74.63(9), Mo1-B2-Mo2 79.01(9). Selected bond lengths (Å) and angles ( ο ) of 8: Mo1-Mo2 2.8489(9), Mo1-B1 2.247(8), Mo1-B2 2.186(8), Mo1-B3 2.285(8), Co1-Co2 2.4341(13), Co1-Mo1 2.7032(12), B1-Co1 2.022(8); Mo1-B1-Mo2 78.8(3), Mo1-B2-Mo2 81.4(3), Mo1-B3-Mo2 76.8(3). Selected bond lengths (Å) and angles ( ο ) of 9: Mo1-Mo2 2.7965(18), Mo1-B1 2.41(2), Mo1-B2 2.25(2), Mo1-B3 2.170(18), Mo1-B4 2.22(2), Mo1-Fe1 2.668(3), Fe1-B1 2.12(2), Fe1-B4 2.05(2); Mo2-B1-Mo1 70.9(5), Mo2-B4-Mo1 78.4(6). to [(Cp*Mo)2(CO)(μ-Cl)W(CO)4B3H4], 20 however, it is longer as found in [(Cp*Mo)2Se2(SeCH2Ph)B4H3] and [(Cp*Mo)2Te2B4H4] 30 . In a similar fashion, the reaction of Fe2(CO)9 with the insitu generated intermediate, produced from [Cp*MoCl4] with LiBH4 reaction, at 60 ˚C led to the formation of an air

5 : 6 :

 56 MS (ESI+): m/z calculated for [M+H] + 731.9777, found 731.9764; 11 B{ 1 H} NMR (160 MHz, CDCl3, 22 °C): δ = 69.7 (s, 1B); 1 H NMR (500 MHz, CDCl3, 22 °C): δ = 10.41 (br, 1H, B-Ht), 1.86 (s, 30H, C5Me5), -11.31 (br, 1H, Mo-H-B); 13 C{ 1 H} NMR (22 °C, 125 MHz, CDCl3): δ = 101.8 (C5Me5), 9.6 ppm (C5Me5); IR (CH2Cl2, cm -1 ): 2446 (w, BHt), 2020, 1959 (CO). MS (ESI+): m/z calculated for [M+H] + 844.8938, found 844.8936; 11 B{ 1 H} NMR (160 MHz, CDCl3, 22 °C): δ = 129.5 (s, 1B); 1 H NMR (500 MHz, CDCl3, 22 °C): δ = 1.93 (s, 30H, C5Me5), -3.27 (br, 1H, Mo-H-B); 13 C{ 1 H} NMR

Table 1 . Important geometrical and spectroscopical parameters of some transition metal triborane complexes.

 1

	M2B3 clusters	Geometry, SEP	Structural Parameter	Spectroscopic data	Ref.
	ACCEPTED MANUSCRIPT / CLEAN COPY

(SEP) count of 2 became of interest. According to Wade skeleton electron counting rule, the SEP count required for the trigonal bipyramid [M2B3] core is six (CVE = 42). Thus, cluster 2 is electronically saturated with 42 CVE and 6 SEP.

  Mo-H-B);[START_REF] Andersen | Ferraborane B3H7Fe2(CO)6, a Diiron Analogue of Pentaborane(9)[END_REF] C{ 1 H} NMR(22 °C, 125 MHz, CDCl3): δ = 236.5 (s, CO), 233.7 (s, CO), 103.7 (s, C5Me5), 103.3 (s, C5Me5),

	along with arachno-[Cp*Mo(CO)2B3H8] 10c (0.022 g, 23%) and
	[(Cp*Mo)2B5H9] 19 (0.016 g, 21%).
	2: MS (ESI + ): m/z calculated for [M+H] + 558.1217, found
	558.1215; 11 B{ 1 H} NMR (160 MHz, CDCl3, 22 °C): δ = 12.9 (s, 2B), -
	3.7 ppm (s, 1B); 1 H NMR (500 MHz, CDCl3, 22 °C): δ = 3.01 (br, 2H,
	BHt), 1.57 (br, 1H, BHt) 2.02 (s, 15H, C5Me5), 1.90 (s, 15H, C5Me5), -
	13.08 ppm (br, 4H,

A rare saturated closo bimetallic triborane cluster, stabilized by early transition metal frameworks, has been isolated and structurally characterized. This triborane cluster containing 42 cluster valence electrons (CVE) is the newest addition to the series triborane species.ACCEPTED MANUSCRIPT / CLEAN COPY

ACKNOWLEDGMENT

This work was supported by SERB, (grant no. CRG/2019/001280) and the Centre of Excellence on Molecular Materials and Functions under the Institution of Eminence scheme of IIT Madras. S.M. acknowledges IIT Madras and S.G. thank CSIR for fellowships. We acknowledge the discussions and X-ray structure studies provided by Dr. V. Ramkumar, Dr. P.K.S. Antharjanam and Dr. B. Varghese. IIT Madras' computational facility is gratefully acknowledged.

dropwise into it at -78 °C and the mixture was then stirred at room temperature for 1 h. The volatile components were evaporated using vacuo and then hexane was added into the residue to dissolve as much as possible. It was then extracted through Celite using a frit. After drying hexane, we got the brownish-green coloured extract. Later, 10 mL of THF solution of [Co2(CO)8] (0.03 g) was transfered to the extracted mixture using argon flow. The thermolysis of whole mixture was carried out for 16 h at 60 °C. The solvent was eliminated using vacuum, and the residue was then extracted into hexane/dcm which was passed through Celite. The extracted filtrate was then dried and put through a chromatographic work-up utilising TLC plates made of silica gel. Elution with a hexane/CH2Cl2 (70:30 v/v) mixture yielded black 9 (0.009 g, 11%) along with the known [(Cp*Mo)2B5H9] 19 (0.017 g, 24%). 9: MS (ESI+): m/z calculated for 9 655.0757, found 655.0763; 11 B{ 1 H} NMR (160 MHz, CDCl3, 22 °C): δ = 93.0 (s, 1B), 83.1 ppm (s, 1B), 38.9 (s, 1B), 34.5 ppm (s, 1B); 1 H NMR (500 MHz, CDCl3, 22 °C): δ = 4.46 (br, 2H, B-Ht), 6.54 (q, 2H, B-Ht) 2.07 (s, 30H, C5Me5), -5.96 ppm (br, 2H, Mo-H-B), -12.36 ppm (br, 2H, Mo-H-B); [START_REF] Andersen | Ferraborane B3H7Fe2(CO)6, a Diiron Analogue of Pentaborane(9)[END_REF] C{ 1 H} NMR (22 °C, 125 MHz, CDCl3): δ = 107.2 (C5Me5), 12.0 (C5Me5) ; IR (CH2Cl2, cm -1 ): 2458 (w, BHt), 1988, 1918 (CO).

X-ray Analysis Details. Slow diffusion of a hexane-CH2Cl2 solution of 2, 5-9 compound was applied to grow quality crystals which are suitable for XRD analysis. The crystal data collection of 2, 6 and 7 was done in Bruker AXS Kappa APEXII CCD diffractometer. For 5 and 8, collection and integration of crystal data were performed using a D8 VENTURE Bruker AXS diffractometer with graphite monochromated Mo-Kα (λ = 0.71073 Å) radiation at 150(2) K. Bruker Kappa APEXIII was used to collect as well as integrate the crystal data of 9. In order to solve the structures, dual-space algorithm using SHELXT program [START_REF] Sheldrick | SHELXT -Crystal structure refinement with SHELXL[END_REF] was used and refinement was achieved utilizing full-matrix least-squares methods based on F2 (SHELXL program) [START_REF] Sheldrick | SHELXT -Crystal structure refinement with SHELXL[END_REF] . The molecular structures were drawn using Olex2. [START_REF] Dolomanov | OLEX2: a complete structure solution, refinement and analysis program[END_REF] Whereas, anisotropic displacement parameters assisted for refinement of the non-hydrogen atoms, the hydrogen atoms except bridging hydrogen were introduced through Fourier difference maps analysis. H atoms were finally included in their calculated positions and treated as riding on their parent atom with constrained thermal parameters. Crystallographic data have been deposited with the Cambridge Crystallographic Data Center as supplementary publication no CCDC-1019009 (2), CCDC-2183897 (5), CCDC-2183896 (6), CCDC-2183898 (7), CCDC-2183894 (8), and CCDC-2183895 (9). These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.www.ccdc.cam.ac.uk/data_request/cif.

Crystal data for 2: C22H37B3O2Mo2, Mr = 557.83, Triclinic space group P-1, a = 8.9262(10) Å, b = 9.7089(12) Å, c = 15.7243(18) Å, α = 72.239(4)°, β = 79.130(5)°, γ = 76.193(5)°, V = 1250.4(3) Å 3 , Z = 2, ρcalcd = 1.482 g/cm 3 , μ = 1.017 mm -1 , F(000) = 568, R1 = 0.0554, wR2 = 0.1750, 9322 independent reflections [2θ≤49.20°] and 297 parameters.

Crystal data for 5: C27H31BO7Mo2Co, Mr = 729.14, Orthorhombic space group Pbca, a = 10.800(2) Å, b = 17.380(4) Å, c = 30.260( 6) Å, α = 90°, β = 90°, γ = 90°, V = 5680(2) Å 3 , Z = 8, ρcalcd = 1.705 g/cm [START_REF] Hayashi | Syntheses and properties of triborane(5)s possessing bulky diamino substituents on terminal boron atoms[END_REF] , μ = 1.489 mm -1 , F(000) = 2920, R1= 0.0960, wR2 = 0.2556, 4572 independent reflections [2θ≤49.99°] and 394 parameters.

Crystal data for 6: C29H30BO9Mo2Co2, Mr = 843.08, Monoclinic space group P21/n, a = 9.0234(3) Å, b = 16.8366(4)Å, c = 21.9213 (7) Å, α = 90°, β = 101.8121( 14)°, γ = 90°, V = 3259.83(17) Å 3 , Z = 4, ρcalcd = 1.718 g/cm 3 , μ = 1.800 mm -1 , F(000) = 1676, R1 = 0.0410, wR2 = 0.0907, 5739 independent reflections [2θ≤49.99°] and 398 parameters.

Crystal data for 7: C25H34B4O5Mo2Co2, Mr = 767.50, Orthorhombic, space group Pnma, a = 16.8001(3) Å, b = 15.2353(3) Å, c = 11.5143(2) Å, α = 90°, β = 90°, γ = 90°, V = 2947.14(9) Å 3 , Z = 4, ρcalcd = 1.730 g/cm 3 , μ = 1.970 mm -1 , F(000) = 1528, R1 = 0.0196, wR2 = 0.0533, 2696 independent reflections [2θ≤50.00°] and 198 parameters.

Crystal data for 8: C26H35B3O6Mo2Co2, Mr = 785.77, Triclinic, space group P-1, a = 11.7113(17) Å, b = 16.662(2) Å, c = 16.920(3) Å, α = 114.781(6)°, β = 90.041 (7)°, γ = 99.541 (7)°, V = 2947.1(8) Å 3 , Z = 4, ρcalcd = 1.771 g/cm 3 , μ = 1.976 mm -1 , F(000) = 1568, R1 = 0.0531, wR2 = 0.1315, 11161 independent reflections [2θ≤51.36°] and 755 parameters.

Crystal data for 9: C23H30O3B4Mo2Fe, Mr = 645.44, Monoclinic, space group P21, a = 10.5118(13) Å, b = 16.3058(18) Å, c = 16.700(2) Å, α = 90°, β = 102.664(5)°, γ = 90°, V = 2792.8(6) Å 3 , Z = 4, ρcalcd = 1.535 g/cm 3 , μ = 1.418 mm -1 , F(000) = 1288, R1 = 0.0540, wR2 = 0.1487, 9788 independent reflections [2θ≤50.00°] and 596 parameters.

ASSOCIATED CONTENT Supporting Information

On the ACS publication page at DOI: xxx, the supporting information is freely accessible. It includes comprehensive synthesis instructions, 1 H, 11 B{ 1 H}, [START_REF] Andersen | Ferraborane B3H7Fe2(CO)6, a Diiron Analogue of Pentaborane(9)[END_REF] C{ 1 H} NMR and mass spectra, as well as X-ray analysis details. DFT outputs for 2-9 and other computational details are also provided. This material can be accessed through the internet without any charge at http://pubs.acs.org

AUTHOR INFORMATION

Corresponding Author *E-mail: sghosh@iitm.ac.in. Tel: +91-44-22574230. Fax: +91 44-22574202

Notes

The authors declare no competing financial interest.