Sébastien Ferré
email: ferre@irisa.fr

A Proposal for Nested Results in SPARQL

Tables are a common form of query results, notably in SPARQL. However, due to the flat structure of tables, all structure from the RDF graph is lost, and this can lead to duplications in the table contents, and difficulties to interpret the results. We propose an extension of SPARQL 1.1 aggregations to get nested results, i.e. tables where cells may contain embedded tables instead of RDF terms, and so recursively.

Motivation

The SPARQL query language [START_REF]SPARQL 1.1 query language[END_REF] offers a powerful way to extract and compute information from RDF datasets. For SELECT queries, the results are presented in a table. Each column corresponds to a projected variable in the SELECT clause, and each row corresponds to a solution, mapping those variables to RDF terms. Such tables are universally understood, and can be read in two directions, by row or by column. They make a good use of the screen space, compared for instance to graph visualizations, and can therefore display a lot of information at once. They can be dynamically filtered and ordered according to each column. Despite those advantages, tables in general and SPARQL results in particular have drawbacks due to the fact that they are in first normal form (1NF), a notion from relational databases that states that table cells only contain atomic values, here RDF terms. Although it sounds like a reasonable constraint, it has negative consequences on the readability of query results as shown in the following example.

Table 1 shows an excerpt of the results of the following SPARQL query on DBpedia, which retrieves films directed by Danny Boyle, along with their music composers and actors, and also the birth year of actors.

SELECT ?f ?mc ?a ?y WHERE { ?f a dbo:Film ; dbo:director dbr:Danny_Boyle ; dbo:musicComposer ?mc ; dbo:starring ?a . ?a dbo:birthYear ?y . } It can be observed that the table contains a lot of redundancies. For instance, the birth year of an actor is repeated for each music composer. The number of rows for a film is The key contribution of this paper is to allow table cells to contain smaller tables instead of RDF terms. Those nested tables are obtained by allowing variables to map to sets of solution mappings, in addition to RDF terms. Tables can be deeply nested, with tables containing tables that in turn contain tables, and so on. In practice, RDF terms and nested tables are not mixed randomly inside a table. For a given column, either all cells contain an RDF term or all cells contain a nested table. Moreover, all nested tables in a column are defined on the same variables. This means that our nested tables follow a regular schema, although more complex than that of flat tables.

Table 2 is the nested version of Table 1. The main table has a single row per film, and two of its columns, "music composers" and "actors", contain nested tables. The former column contains one-column nested tables that contain the list of music composers of each film. The latter column contains two-columns nested tables that contain the list of actors of each film, along with their birth year. It can be observed that the nested table does not contain redundancies anymore, and that the dependencies between columns is made explicit. Music composers and actors are dependent on the film, but not on each other. The birth year is dependent on the actor.

Related Work

Nested tables were proposed and formalized in relational databases, where nesting is not only used for query results but also for data tables [START_REF] Roth | Extended algebra and calculus for nested relational databases[END_REF]. The motivation was to relax the first normal form (1NF). The authors extend relational algebra with two operators, nest and unnest, that operate on subsets of columns. In this work, as we start from RDF graphs instead of tables, we only need a mechanism to nest the table of results, there is no need for unnesting. We also need to adapt the nest operation to SPARQL algebra and grammar.

A lot of work have proposed various forms of visualization of SPARQL results (e.g., maps, charts) in order to help their understanding [START_REF] Bikakis | Exploration and visualization in the web of big linked data: A survey of the state of the art[END_REF]. They are a valuable complement to the tabular view but that they cannot fully replace it in the general case. A JSONbased query language has been proposed to facilitate the exposition of SPARQL results in APIs [START_REF] Lisena | Easy web API development with SPARQL transformer[END_REF]. In particular it can generate nested tables similar to ours. However, it only covers a fragment of SPARQL graph patterns, and the grouping criteria is limited to a single variable per table. Some extensions of SPARQL have also been proposed. For instance, a new CLUSTER BY clause was proposed to group the rows of the table of results into a hierarchical clustering [START_REF] Lawrynowicz | Query results clustering by extending SPARQL with CLUSTER BY[END_REF]. In contrast, nested tables can be seen as a form of 2D hierarchical clustering because they involve grouping subsets of columns and subsets of rows at the same time.

A New Aggregation Construct

Our proposal is to extend the algebra and grammar of SPARQL 1.1 with a new aggregation construct [START_REF] Kaminski | Semantics and expressive power of subqueries and aggregates in SPARQL 1.1[END_REF] that computes nested tables (i.e. sequences of solution mappings) instead of RDF terms.

In the above example, Table 1 can be seen as the global multiset of solutions, and Table 2 as the expected result after applying aggregations that compute nested tables instead of RDF terms. After grouping by film, the nested tables in column "music composers" are obtained by projecting each solution group on variable "music composer", and by removing duplicates. Similarly for column "actors" by projecting on "actor" and "birth year", by removing duplicates, and by ordering rows by birth year. To sum up, the new aggregations need at least projecting on a subset of variables, removing duplicates, and ordering results. Those computations correspond to the category of solution modifiers, which are formalized as transformations between sequences of solution modifiers, and hence as table-to-table transformations. In addition to solution modifiers, we allow groupings (clause GROUP BY) in the definition of table aggregations, and hence aggregations in the definition of table aggregations. This makes the definition of aggregations recursive, which enables deeply nested tables.

The main impact of the extension is that a variable may now be bound to a nested table in addition to RDF terms. For the sake of simplicity, we consider that those variables can only be used as projection variables, and produce an error when used in other contexts (e.g., in an expression).

We now extend the grammar of SPARQL 1.1 [START_REF]SPARQL 1.1 query language[END_REF] so as to give a concrete syntax to the extended algebra presented above. It simply consists in extending the Aggregate rule with one new production.

Aggregate ::= . . . | '{' SelectClause SolutionModifier '}'

The ellipsis stands for existing constructs like COUNT(DISTINCT ?x). Symbol SelectClause covers projection (SELECT) and removal of duplicates (DISTINCT, REDUCED). Symbol SolutionModifier covers ordering (ORDER BY), top-k results (LIMIT) and offset (OFFSET), grouping (GROUP BY), and filtering as a solution modifier (HAVING). This production is therefore enough to cover all needed features. We add braces to delimit the aggregation construct, and also by analogy with subqueries. Indeed, our table aggregations are syntactically and semantically equivalent to subqueries where the graph pattern (clause WHERE) is implicit.

In the example on films, the query in the extended SPARQL that returns the nested table (Table 2) is the following.

SELECT ?f ({SELECT DISTINCT ?mc} AS ?mcs) ({SELECT DISTINCT ?a ?y ORDER BY ?y} AS ?as) WHERE { ?f a dbo:Film ; dbo:director dbr:Danny_Boyle ; dbo:musicComposer ?mc ; dbo:starring ?a . ?a dbo:birthYear ?y . } GROUP BY ?f Clause GROUP BY ?f defines the groups of solutions over which the two table aggregations are evaluated. Variable ?mcs holds the list of distinct music composers for each film, a one-column nested table. Variable ?as holds the list of distinct actors and their birth year, in increasing order of birth year, a two-column nested table.

Note that nothing forbids to combine term aggregations with table aggregations. For example, in the above query, one could add the term aggregation (COUNT(DISTINCT ?a) AS ?na) in order to add a column giving the number of actors, for each film, in addition to their list. If those lists are too long, they can be bounded in size by adding a LIMIT clause in the table aggregations.

To illustrate deeply nested tables and top-k results, we extend the above query to get the lists of spouses of each actor as tables nested into the actor tables. We also add a LIMIT to get only the three top actors per film.

SELECT ?f ({SELECT DISTINCT ?mc} AS ?mcs) ({SELECT DISTINCT ?a ?y ({SELECT DISTINCT ?sp} AS ?sps) ORDER BY ?y LIMIT 3} AS ?as) WHERE { ?f a dbo:Film ; dbo:director dbr:Danny_Boyle ; dbo:musicComposer ?mc ; dbo:starring ?a . ?a dbo:birthYear ?y ; dbo:spouse ?sp } GROUP BY ?f It can be observed in the above queries that the nesting schema is entirely expressed in the main SELECT clause (table aggregations can also be used in subqueries). This suggests that nested results can be obtained by post-processing the flat results, without actually extending SPARQL. However, it would require to retrieve more answers than the number of desired answers, because of the redundancies induced by flat results.

In the example, 11 answers in the flat results are used to generate 2 answers in the nested results. The relation between the two numbers is hard to predict, and can be of combinatorial nature. Integrating nested tables into SPARQL enables to control the number of returned results, and creates opportunities for optimization in query evaluation by trying to avoid redundancies altogether.

Another advantage of the SPARQL extension is to extend SPARQL's expressivity with a new class of aggregations that would be otherwise very difficult to express. The most interesting one is the combination of grouping and top-k results, like "the three youngest actors of each film" or "the last two mayors of the three most populated cities of each country".

Conclusion

We have proposed an extension of SPARQL 1.1 aggregations that enables nested tables as query results, i.e. tables that can contain tables in their cells, and so recursively. Nested tables improve the readability of results by avoiding redundancies in their contents, and by exhibiting the dependencies and independencies between their columns. The proposed extension is fully backward compatible, and should be relatively easy to implement in existing query engines. Nested results have been integrated into Sparklis [START_REF] Ferré | Sparklis: An expressive query builder for SPARQL endpoints with guidance in natural language[END_REF], a SPARQL query-builder, as a new view on results. This has to be done by post-processing of flat results until implementations of the proposed extension are available.

Table 1 .

 1 Flat table of films by D. Boyle with music composer, actor, and birth year

	film	music composer actor	birth year
	Slumdog millionaire A. R. Rahman Dev Patel	1990
	Slumdog millionaire A. R. Rahman Freida Pinto	1984
	Slumdog millionaire A. R. Rahman Anil Kapoor	1959
	Sunshine	John Murphy	Cilian Murphy 1976
	Sunshine	John Murphy	Chris Evans	1981
	Sunshine	John Murphy	Rose Byrne	1979
	Sunshine	John Murphy	...	...
	Sunshine	Underworld	Cilian Murphy 1976
	Sunshine	Underworld	Chris Evans	1981
	Sunshine	Underworld	Rose Byrne	1979
	Sunshine	Underworld	...	...
	...	...	...	...

Table 2 .

 2 Nested table of films by D.

	Boyle with a list of music composers, and a list

This research is supported by ANR project PEGASE (ANR-16-CE23-0011-08).


Ralucamalacea

Jean-Claude Daran

Rinaldo Poli

Eric Manoury
email: manoury@lcc-toulouse.fr

Combining planar and central chirality in ferrocene thiophosphine-sulfoxides

New chiral ferrocenylthiophosphine-sulfoxide and phosphinesulfoxidederivativespossessing planar chirality for theferrocenemoietyand central chirality at the sulfur atomhave been synthesized. These ligands could be obtained as pure diastereoisomersinboth racemic andenantiomerically pure forms. Complete characterization by XRD analysis has allowed the absolute configuration assignmentineachcase. Preliminarycoordination studies of the phosphine-sulfoxideligandson platinum are also reported. They show chelating complexationbythe phosphorous and sulfur atoms.

1.Introduction

Various chiral bidentate ligands were developed over the past decades, possessing the chiral information on the carbon backbone or on the donor atom. Ligands with variouscombinations of donor atoms (in particular, P-P, P-N, or N-N ligands) have been extensively studied and a fewP-chirogenic compounds such as QuinoxP 1 or dipamp 2 are very effective in a variety of asymmetric catalytic processes. Recently, very efficient systems for asymmetric catalysis using P-S ligands with various backbones, havebeen reported. 3,4 Furthermore, several reports have described the preparation and the coordination chemistry of chiral phosphine sulfoxide ligands possessing the chirality on the sulfur atom, for example αphosphinosulfoxides(PCSO 5 andPNSO 6 ) or β-phosphinosulfoxides 7 (Figure 1). Riera and Verdaguer 8 described ligands with an extra chiral centerin the central carbon atom between P and SO and also camphor derivatives combininga chiral carbon backbone with sulfur chirality. 9 Kagan's methodology based on diastereoselectiveortho-lithiation of ferrocenesulfoxide derivatives was used in order to synthesize phosphine-sulfoxide ligands with additional planar chirality. 10 We have recently developed syntheses of new chiral ferrocenylγ-P,S ligands in both racemic and enantiomerically pure form (RFc or SFcconfiguration), and reported on their coordination chemistry and applications to asymmetric catalysis, namely in asymmetric allylic substitution, alkene methoxycarbonylationand ketone hydrogenation. 11 Here we present the synthesis of new γferrocenyl phosphine sulfoxide ligands (Figure 1)and preliminary studies on their coordination chemistry with platinum.

Figure 1α, β and γ phosphine sulfoxides

Results and Discussion

Starting from the chiral phosphine-thioetherligands already synthesized in our group, we have developed a new class of ferrocenyl phosphine-sulfoxides ligands based on the selective oxidation of the thioether functionality to sulfoxide. Thus, a central chirality on the sulfur atom (RS or SS) is added to the planar chirality of ferrocene (RFc or SFc).The two diastereoisomersthatcana prioribe formed must therefore be subsequently separated.

Afirst potential issue in the synthetic pathway to the thiophosphine-sulfoxides2 fromthiophosphine-thioethers1(see scheme 1) is the possible over-oxidation to the corresponding sulfonesas well as oxidation of the iron atom to ferroceniumor conversion of thethiophosphine to phosphine oxide, as already observed in the oxidation of related (2diphenylthiophosphinoferrocenyl)methanol to the corresponding aldehyde. [START_REF] Mateus | [END_REF] Therefore, the mild method described by Liang Xu 13 using an aqueous solution of H2O2 in the presence of phenol was selected.Under these conditions, the racemic compounds 1a-c (R = Ph, Et, tBu) were transformed into the corresponding thiophosphine-sulfoxides2a-c with total conversion and chemoselectivity (no sulfoneor other by-products were observed). For each thioether, two diastereoisomers (each one as a pair of enantiomers)were obtained in a 1:1 ratio. These reactions are fast (2-3 minutes) andstrongly exothermic. For safety reasons, we therefore limited the thioetheramount (typically 250 mg) transformedineach run. Eachdiastereomercould be isolated in good yields after separation by column chromatography (Scheme 1).

Scheme 1

After diastereomerseparation, the sulfur atomconfigurations were established by single crystal X-ray diffraction analyses. Single crystals of 2a-Dia1, 2a-Dia2, 2b-Dia1, 2c-Dia1 and 2c-Dia2were obtained by slow diffusion of pentane vapors into a dichloromethane solution. Theseproductswere obtained from the racemic thiophosphine-thioethers1a-c (R/SFc) and crystallize as racemates, except for 2c-Dia2 which affords a twin by inversion, therefore also containing both enantiomers (70:30) in the crystal. To the best of our knowledge, these compounds are the first structurally characterized ferrocenylthiophosphine-sulfoxides.Selected geometrical parameters are reported in Table 1. The five compounds have similar structures with the protecting S(1)endo with respect to the Cp ring whereas the sulfido S( 2) is exo (Table 1). The distances and angles within the sulfoxidemoietyare identical within experimental error. The two Cp rings are either nearly eclipsed for 2a-Dia2, 2c-Dia1and 2c-Dia2B and in between eclipsed-staggered for 2a-Dia1,2b-Dia1 and 2c-Dia2A ( values in Table 1).In compound 2c-Dia2, there are two molecules within the asymmetric unit. These molecules have similar configuration as indicated by the molecular fitting shown in Figure 3. The only marked difference is the twist angles observed between the two Cp rings, 12.7(3)° for molecule A and 4.5(3)° for B. As stated above, no diastereoselectivity was observed under theseoxidation conditions. Other achiral oxidants such as meta-chloroperbenzoic acid 14 , tBuOOH/MoO2(acac)2, 15 and also chiral ones such as tBuOOH/diethyltartrate/Ti(OiPr)4 16 and tBuOOH/diethyltartrate/MoO2(acac)2 were then employed. Unfortunately, all of them gave lower conversionsand no significant diastereoselectivity improvement relative to Xu's method. Therefore, our investigations werecontinued using the H2O2/phenol system. The next step was the oxidation ofenantiomerically pure thiophosphine-thioethers (RFc) 1a-c 11a, 12which gave the corresponding thiophosphine-sulfoxides2a-c as a mixture of two diastereomers in enantiomerically pure form (Scheme 2).The results obtained working with optically pure thioethersare quite similar to those obtained using the compounds in racemic form. Thus, we have access to the desiredferrocenylthiophosphine-sulfoxidesin diastereoisomerically and enantiomerically pure form.

Scheme 2

As the thioetheroxidations wereperformed on ferrocene derivatives with thiophosphine group in order to prevent phosphorusoxidation, the next step was the phosphorus deprotectionin order to liberate the free phosphine group and generateferrocenylphosphinesulfoxidesthat can be used as chiral bidentate P-S ligands. This reaction was carried out using tris(dimethylamino)phosphine in refluxing toluene for 3 hours (Scheme 3). 11a Longer reaction time gave partial deoxygenation of the sulfoxide group. Phosphine-sulfoxide compounds3a-cbeing air sensitive, their purification was accomplishedby column chromatography under argon with yields of isolated products from 65 to 93%. Single crystals of (SFc, SS)/(RFc, RS)-3a were obtained by slow diffusion of pentane vapors into a dichloromethane solution, and the XRD structure is presented in Figure 4.The conformation of this unprotected liganddoesnot show significant differencesrelative tothe protected one (SFc, SS)/(RFc, RS)-3a(Table 1). Given that the P,SO ligands could adoptdifferent coordination modes (κ 2 -PS, κ 2 -PO, or κ 1 -P), 17 wecarried out preliminary coordination chemistry investigations with platinum, byreactingthe phosphinesulfoxide ligand 3a (as the racemic diastereoisomericmixture, Dia1/Dia2 = 1/1) with the platinum precursor PtCl2(CH3CN)2. The 31 P{ 1 H} NMRanalysis of the final mixture shows the presence of two signals corresponding to two similar platinum complexes(δ1 = 0.72 ppm, JP-Pt= 3338 Hz and δ2 = 0.47 ppm, JP-Pt = 3444 Hz) in a 1:1 ratio. The 1 JPtPvalue is characteristic of square planar complexes with cischlorine atoms. 18 Crystals of one complex were obtained by diffusion of pentane into a dichloromethane solution, and thus the coordination mode of the sulfoxide group as κ 2 -PSwas determined from the XRD structure (See figure 5). The Pt atom is surrounded by theS2, P1, Cl1 and Cl2donor atoms in square planar coordination geometry. Itdeviatesfrom the least squares plane defined by these four atoms by only -0.0181(7) Å. The C1, C2, C21, S2, Pt1, P1 metallacycledisplays a boat conformation as indicated by the puckering parameters = 302.6(3)° and = 87.9(3). 19 The S2 and O2 atoms are endo with respect to the Cp1 ring by -0.970(9) Å and -2.186(9) Å respectively. The coordination has induced a slight twist of the two Cp rings ( = 14.5(4)°) when compared to the uncoordinated ligand which was roughly eclipsed with a twist angle of 4.7(2)°.

The crystallizedcompound corresponds to the racemic diastereomer with the (RFc,RS)/(SFc,SS)configuration. Given the similarity of the NMR signals, we attribute to the second compound the structure 4a' with the (SFc,RS)/(RFc,SS) configuration (Scheme 4).

Scheme 4

The presence of two complexes in a 1:1 ratio in the product suggests that the two diastereomericferrocenyl phosphine-sulfoxide ligands do nothave significantly different reactivity with the platinum precursor. This might be surprising given that in the case of the correspondingferrocenyl phosphine thioethers, we observed a total discrimination between the two electron pairs for coordination with platinum, palladium 20 or iridium. 21 Our attempts to obtain complex 4a by oxidation of the sulfur atom in the coordination sphere of the corresponding phosphine-thioether platinum precursor (Ph2P-Fc-CH2SPh)PtCl2 20 were unsuccessful (conditions : mCPBA, THF, reflux, 20h). The oxidation reaction did not occur and the starting material was recovered quantitatively.

Conclusion

In conclusion, we have described the synthesis of new ferrocenyl derivatives thiophosphine-sulfoxide2a-c and phosphine-sulfoxide3a-c having aromatic or aliphatic substituents on the sulfur atom. These ligands possess planar chirality for theferrocenemoiety and central chirality at the sulfur atom and could be obtained as pure diastereoisomersin both racemic andenantiomerically pure form. Most of these compounds were fully characterized by XRD analysis allowingthe absolute configuration assignmentfor each stereoisomer.Preliminarycoordination studies of these ligands were carried out with platinum, demonstrating bidentateκ 2 -PScomplexation in this case. Tests of enantiomerically pure ligands in various catalytic asymmetric reactions are in progress in our laboratories and will be presented in due course.

Experimental

General

All reactions were carried out under argon using standardSchlenkline techniques. Solvents were carefully dried by conventionalmethods and distilled under argon before use. The NMR spectra were recorded on a BrukerDRX-500Avanceinstrument with degased solvents.

Elemental analyses were recorded on Perkin Elmer 2400 II. The mass spectrawererecordedon a Nermag R-10-10H spectrometer.

2-thiodiphenylphosphino-(phenyl-sulfoxymethyl)ferrocene, 2a.

In a Schlenktube under argon were introduced 240 mg (0.45 mmol) of racemic thioether (R/SFc)-1a and 500 mg (5.4 mmol) of phenol. The mixture was heated to 35°C, then 0.1 ml of an aqueous solution of H2O2 (30%) were slowly added to the reaction medium. The reaction is highly exothermic and within minutes the solution turned black. After 5 minutes,10 ml of ethyl acetate, then 10 ml of a saturated solution of Na2SO3, and finally 20 ml of an aqueous solution ofNaOH (10%) were added. The phases were separated and the aqueous phase was extracted with three portions (10ml) of ethyl acetate. The combined organic layers were washed with water, dried over MgSO4 and then the solvent was removed by evaporation under reduced pressure.Compound 2awas recovered as an orange solid (yield: 226 mg, 92%).

The two diastereomers were separated by chromatography on silica usinga mixture of ether and dichloromethane (1/1) as eluent to give 100 mg of 2a-Dia1, (RFc,SS)/(SFc,RS)-2a (yield:

2-thiodiphenylphosphino-(ethyl-sulfoxymethyl)-ferrocene 2b

Following the same procedure described abovefor the synthesis of 2a, the reaction was realized starting from 250mg (0.52 mmol) of racemic thioether(R/S)Fc-1b, 500 mg of phenol and 0.10 ml of an aqueous solution of H2O2 (30%). 2bwas recovered as an orange solid (yield: 241 mg, 93%). The two diastereomers were separated by chromatography on silica usinga mixture of ether and dichloromethane (1/1) as eluent to give 114 mg of 2b-Dia1, (RFc,RS)/(SFc,SS)-2b (yield: 44%) and 109 mg of 2b-Dia2, (RFc,SS)/(SFc,RS)-2b (yield:

2-thiodiphenylphosphino-(tert-butyl-sulfoxymethyl)-ferrocene2c

Following the same procedure described abovefor the synthesis of 2a, the reaction was carried outstarting from 250mg (0.496 mmol) of racemic thioether(R/S)Fc-1c, 500 mg of phenol and 0.10 ml of an aqueous solution of H2O2 (30%). 2cwas recovered as an orange solid (yield: 237 mg, 92%). The two diastereomers were separated by chromatography on silica usinga mixture of ether and acetone (5%) as eluent to give 111 mg of 2c-Dia1, (RFc,SS)/(SFc,RS)-2c (yield: In a Schlenktube under argon were introduced 77 mg (0.157mmol) of the racemic sulfoxide(RFc,RS)/(SFc,SS)-2b-Dia1 in 5 ml of toluene and 0.2 ml (0.18 g, 1.1 mmol) of tris(dimethylamino)phosphine. After reflux for 2 h, the solvent was evaporatedunder reduced pressure and the crude reaction productwas purified by column chromatography on silica usingdegased ether/dichloromethane mixture (1/0 -1/1) as eluent. The sulfoxide phosphine product (RFc,RS)/(SFc,SS)-3b-Dia1 was obtained as an orange solid (yield:48mg, 66%).

Figure 2 .

 2 Figure 2.ORTEP views of2a-Dia1, 2a-Dia2, 2b-Dia1, 2c-Dia1 and 2c-Dia2 (* the other enantiomer is present in the crystal structure but not represented in the picture)with the atom labeling scheme. Ellipsoids are drawn at the 50% probability level. H atoms have been omitted for the sake of clarity.

Figure 3 .

 3 Figure 3.Molecular fitting of the two molecules 2c-Dia2A and 2c-Dia2B.

Scheme 3 Figure 4 .

 34 Scheme 3

Figure 5 .

 5 Figure 5.ORTEP view of platinum complex(RFc,RS)-4awith the atom labeling scheme. The other enantiomer (not shown) is also present in the crystal.Ellipsoids are drawn at the 50% probability level. H atoms have been omitted for the sake of clarity.Selected bond lengths (Ǻ): Pt-P: 2,2350(12); Pt-S: 2.2291(12); Pt-Cl1(trans S): 2.2973(12); Pt-Cl2(transP): 2.3312(13); S-O: 1.459.

  41%) and 108 mg of 2a-Dia2, (RFc,RS)/(SFc,SS)-2a (yield: 44%).MS (DCI, NH3):m/z = 541 (M + 1, 20 %); 558(M + NH4, 100%).(RFc,SS)/(SFc,RS)-2a:1 H NMR (δ, 500 MHz, CDCl3):7.86 (2H, m, Ph); 7.65-7.40 (13H, m, Ph); 4.48 (1H, broad s, substCp); 4.44 (5H, s, Cp); 4.35 (1H. broad s, substCp); 4.32 (1H, d(AB), JHH = 13 Hz, CH2Cp); 4.30 (1H, d(AB), JHH = 13 Hz, CH2Cp); 3.87 (1H, broad s, substCp). 13 C{ 1 H} NMR (δ, 125.8 MHz, CDCl3):144.5 (s, quatSPh); 134.8 (d, JCP = 87 Hz, quat PPh2) ; 133.1 (d, JCP = 86 Hz, quat PPh2); 132.5 (d, JCP = 11 Hz, PPh2); 132.3 (d, JCP = 11 Hz, PPh2); 131.96 (s, PPh2); 131.9 (s, PPh2); 131.3 (s, SPh); 129.4 (s, SPh); 128.9 (d, JCP = 13 Hz, PPh2); 128.6 (d, JCP = 13 Hz, PPh2); 124.8 (s, SPh); 83.1 (d, JCP = 12 Hz, quatCp); 75.8 (d, JCP = 95Hz, quatCp); 75.4 (d, JCP = 9 Hz, substCp); 74.6 (d, JCP = 12 Hz, substCp); 71.6 (s, Cp); 70.4 (d, JCP = 10 Hz, substCp); 58.0 (s, CH2Cp). 31 P{ 1 H} NMR (δ, 202.5 MHz. CDCl3):43.5. Elemental analysis:C29H25FePS2O; %C (calcd 64.44, found 62.84), % H (calcd 4.63, found 5.03). (RFc,RS)/(SFc,SS)-2a: 1 H NMR (δ, 500 MHz, CDCl3): 7.89 (2H, m, Ph); 7.87 (2H, m, Ph); 7.6-7.40 (11H, m,Ph); 5.34 (1H, d(AB), JHH = 13 Hz, CH2Cp); 4.85 (1H, m, substCp); 4.49 (1H, m, substCp); 4.30 (5H, s, Cp); 3.87 (1H, m, substCp); 3.61 (1H, d(AB), JHH = 13 Hz, CH2Cp). 13 C{ 1 H} NMR (δ, 125.8 MHz, CDCl3): 134.9 (d, JCP = 87 Hz, quat PPh2); 133.2 (d, JCP = 87 Hz, quat PPh2); 132.7 (d, JCP = 11 Hz, PPh2); 132.4 (d, JCP = 11 Hz, PPh2); 132.1 (d, JCP = 3 Hz, PPh2); 132.0 (d, JCP = 3 Hz, PPh2); 130.9 (s, SPh); 129.5 (s, SPh); 129.4 (s, quatSPh); 128.8 (d, JCP = 13 Hz, PPh2); 128.6 (d, JCP = 13 Hz, PPh2); 123.9 (s, SPh); 83.0 (d, JCP = 12 Hz, quatCp); 76.2 (d, JCP = 9 Hz, substCp); 75.8 (d, JCP = 12 Hz, substCp); 74.8 (d, JCP = 95Hz, quatCp); 71.4 (s, Cp); 71.1 (d, JCP = 10 Hz, substCp); 61.1 (s, CH2Cp). 31 P{ 1 H} NMR (δ, 202.5 MHz, CDCl3):43.9; Elemental analysis: C29H25FePS2O; %C (calcd 64.44, found 64.12), % H (calcd 4.63, found 4.32).

  42%).MS (DCI, NH3):m/z = 493 (M + 1, 45 %); 510 (M + NH4, 100%).(RFc,RS)/(SFc,SS)-2b : 1 H NMR (δ, 500 MHz. CDCl3): 7.85-7.81 (2H, m, PPh2); 7.66-7.47 (6H, m, PPh2); 7.43 (2H, broad s, PPh2); 4.90 (1H, s, subst Cp); 4.47 (1H, s, subst Cp); 4.36 (5H, s, Cp); 4.45-4.28 (2H, m, CH2Cp); 3.87 (1H, s, subst Cp); 2.35 (2H, broad s, CH2CH3); 1.1 (3H, broad s, CH2CH3). 13 C{ 1 H} NMR (δ, 125.8 MHz. CDCl3): 133.9 (d, JCP = 87 Hz, quat PPh2); 132.1 (d, JCP = 86 Hz, quat PPh2); 132.0 (d, JCP = 11 Hz, PPh2); 131.9 (s, PPh2); 131.8 (broad s, PPh2); 128.7 (d, JCP = 12 Hz, PPh2); 128.5 (d, JCP = 12 Hz, PPh2); 82.0 (d, JCP = 12 Hz, quat Cp); 74.8 (s, subst Cp); 74.7 (d, JCP = 12 Hz, subst Cp); 74.0 (d, JCP = 96 Hz, quat Cp); 71.3 (s, Cp); 70.8 (d, JCP = 10 Hz, subst Cp); 50.6 (s, CH2Cp); 44.7 (s, CH2CH3); 7.6 (s, CH2CH3). 31 P{ 1 H} NMR (δ, 202.5 MHz, CDCl3): 41.06. Elemental analysis:C25H25FePS2O; %C (calcd 60.98, found 61.08), % H (calcd 5.08, found 5.17). (RFc,SS)/(SFc,RS)-2b: 1 H NMR (δ, 500 MHz. CDCl3): 7.83-7.79 (2H, m,PPh2); 7.59-7.48 (6H, m, PPh2); 7.41 (2H, broad s, PPh2); 5.26 (1H, d(AB),JHH = 13 Hz, CH2Cp); 4.81 (1H, s, subst Cp); 4.47 (1H, s, subst Cp); 4.32 (5H, s, Cp); 3.82 (1H, s, subst Cp); 3.53 (1H, d(AB), JHH = 13 Hz, CH2Cp); 2.65 (2H, q, JHH = 7 Hz, CH2CH3); 1.5 (3H, broad s, CH2CH3). 13 C{ 1 H} NMR (δ, 125.8 MHz, CDCl3):134.1 (d, JCP = 88 Hz, quat PPh2); 132.3 (d, JCP = 88 Hz, quat PPh2); 132.0 (d, JCP = 11 Hz, PPh2); 131.9 (broad s, PPh2); 128.6 (d, JCP = 12 Hz, PPh2); 128.5 (d, JCP = 13 Hz, PPh2); 82.5 (d, JCP = 10 Hz, quat Cp); 75.8 (d, JCP = 9 Hz, subst Cp); 75.5 (d, JCP = 12 Hz, subst Cp); 73.1 (d, JCP = 95Hz,quat Cp); 71.2 (s, Cp); 71.1 (s, subst Cp); 53.4 (s, CH2Cp); 46.7 (s, CH2CH3); 7.1 (s, CH2CH3). 31 P{ 1 H} NMR (δ, 202.5 MHz, CDCl3):41.6.Elemental analysis: C25H25FePS2O; %C (calcd 60.98, found 60.98), % H (calcd 5.08, found 4.83).

  43%) and 103 mg of 2c-Dia2, (RFc,RS)/(SFc,SS)-2c (yield: 40%).MS (DCI, NH3): m / z = 521 (M + 1, 100 %); 538 (M + NH4, 80%).(RFc,SS)/(SFc,RS)-2c:1 H NMR (δ,500 MHz, CDCl3):7.8 (2H, m, PPh2); m, PPh2); 7.40 (2H, m, PPh2); 5.07 (1H, broad s, subst Cp); 4.47 (1H, broad s, CH2Cp); 4.41(5H, s, Cp) ; 4.41(1H, s, subst Cp); 3.78 (1H, s, subst Cp);3.05 (1H, d(AB), JHH = 14 Hz, CH2Cp); 1.32 (9H, s, C(CH3)3).13 C{ 1 H} NMR (δ,125.8 MHz, CDCl3): 134.6 (d, JCP = 87 Hz, quat PPh2); 132.4 (d, JCP = 86 Hz, quat PPh2); 131.9 (d, JCP = 11 Hz, PPh2); 131.7 (d, JCP = 11 Hz, PPh2); 131.6 (d, JCP = 3 Hz, PPh2); 131.5 (d, JCP = 3 Hz, PPh2); 128.6 (d, JCP = 13 Hz, PPh2); 128.2 (d, JCP = 13 Hz, PPh2); 85.2 (d, JCP = 12 Hz, quat Cp); 74.9 (d, JCP = 96 Hz, quat Cp); 73.8 (d, JCP = 12 Hz, subst Cp); 73.6 (d, JCP = 19 Hz, subst Cp); 71.1 (s, Cp); 70.0 (d, JCP = 9 Hz, subst Cp); 54.2 (broad s, C(CH3)3); 44.9 (s, CH2Cp); 23.1 (s, C(CH3)3). 31 P{ 1 H} NMR (δ,202.5 MHz, CDCl3): 41.8. Elemental analysis: C27H29FePS2O; %C (calcd 62.31, found 62.16), % H (calcd 5.58, found 5.54). (RFc,RS)/(SFc,SS)-2c: 1 H NMR (δ,500 MHz, CDCl3): 7.83 (1H, dd, JHH = 2 Hz, JHP = 14 Hz, m C6H5); 7.82 (1H, dd,JHH = 2 Hz, JHP = 15Hz, m C6H5); 7.66 (1H, dd, JHH = 2 Hz, JHP = 15Hz, m C6H5); 7.65 (1H, dd, JHH = 2 Hz, JHP = 15Hz, m C6H5); 7.58-7.53 (1H, m, p C6H5); 7.52-7.45 (3H, m, p+2o C6H5); 7.42-7.37 (2H, m, 2o C6H5); 5.09 (1H, d(AB). JHH = 13 Hz, CH2Cp); 4.89 (1H, m, subst Cp); 4.43 (1H, m, subst Cp); 4.37 (5H, s, Cp); 3.75 (1H, m, subst Cp); 3.28 (1H, d(AB), JHH = 13 Hz, CH2Cp); 1.04 (9H, s,C(CH3)3). 13 C{ 1 H} NMR (δ,125.8 MHz. CDCl3):134.02 (d, JCP = 87 Hz, quat PPh2); 132.87 (d, JCP = 82 Hz, quat PPh2); 132.53 (d, JCP = 10 Hz, m PPh2); 131.97 (d, JCP = 10 Hz, m PPh2); 131.50 (d, JCP = 3 Hz, pPPh2); 131.45 (d, JCP = 3 Hz, p PPh2); 128.23 (d, JCP = 4 Hz, o PPh2); 128.13 (d. JCP = 4 Hz, o PPh2); 83.50 (d, JCP = 12 Hz, quat Cp); 75.20 (d, JCP = 9 Hz, subst Cp); 75.07 (d, JCP = 13 Hz, subst Cp); 74.47 (d, JCP = 95Hz, quat Cp); 71.04 (s, Cp); 70.41 (d, JCP = 10 Hz, subst Cp); 53.23 (s, C(CH3)3); 47.84 (s, CH2Cp); 22.75 (s, C(CH3)3). 31 P{ 1 H} NMR (δ,202.5 MHz. CDCl3):41.4.Elemental analysis:C27H27FePS2O; %C (calcd 62.31, found 59.81), % H (calcd 5.58, found 5.58).

  The reaction was carried out using enantiomericallypure (RFc)-1afollowing the same procedure described above for the synthesis of racemic 2a. Dia1, (RFc,SS)-2a : [α]D = -100.2;(CHCl3. c=0.49); Dia2, (RFc,RS)-2a : [α]D = +14.2; (CHCl3. c=0.49).The reaction was carried out using enantiomericallypure (RFc)-1bfollowing the same procedure described above for the synthesis of racemic 2b.Dia1, (RFc,RS)-2b: [α]D = -110.The reaction was carried out using enantiomerically pure (RFc)-1cfollowing the same procedure described above for the synthesis of racemic 2c.Dia1, (RFc,SS)-2c:[α]D = -152.In a Schlenktube under argon were introduced 81 mg (0.15 mmol) of racemic sulfoxide(RFc, SS)/(SFc,RS)-2a-Dia1 in 5 ml of toluene and 0.2 ml (0.18 g, 1.1 mmol) of tris(dimethylamino)phosphine. After reflux for 3 h, the solvent wasremoved by evaporation and the crude sulfoxide phosphine (RFc,SS)/(SFc,RS)-3a-Dia1 was obtained as an orange liquid (yield: 71mg, 93%).1 H NMR (δ,500 MHz. CDCl3): 7.64-7.49 (4H, m, Ph); 7.49-7.32 (6H, m, Ph); 7.32-7.12 (5H, m, Ph); 4.43 (1H, dd(ABX), JHH = 13 Hz, JHP = 2 Hz, CH2Cp); 4.42 (1H, broad s, substCp); 4.22 (1H, t, JHH = 2 Hz, substCp); 4.01 (5H, s, Cp); 3.90 (1H, broad s, substCp);3.74 (1H, d(AB), JHH = 13 Hz, CH2Cp). 31 P{1 H} NMR (δ, 202.5 MHz, CDCl3)Following the same procedure described abovefor the desulfurisation of (RFc,SS)/(SFc,RS)-2a-Dia1, the reaction was realized from 92mg (0.17 mmol) of racemic sulfoxide(RFc,RS)/(SFc,SS)-)phosphine. The sulfoxide phosphine product (RFc,RS)/(SFc,SS)-3a-Dia2wasobtained as an orange solid (yield:73 mg,85%).1 H NMR (δ,500 MHz, m, Ph); m, Ph); m, Ph); 4.77 (1H, d, JHH = 1 Hz, substCp); 4.43 (1H, t, JHH = 3 Hz, substCp); 4.17 (1H, dd(ABX), JHH = 13 Hz, JHP = 3 Hz, CH2Cp); 3.99 (5H, s, Cp); 3.85 (1H, t, JHH = 1 Hz, substCp); 3.77 (1H, d(AB), JHH = 13 Hz, CH2Cp). 31 P{ 1 H} NMR (δ, 202.5 MHz, CDCl3):-20.9. 4.10 (RFc,RS)/(SFc,SS)-2-diphenylphosphino-(ethylsulfoxymethyl) ferrocene,3b-Dia1.

4. 11 (

 11 RFc,SS)/(SFc,RS)-2-diphenylphosphino-(ethylsulfoxymethyl) ferrocene,3b-Dia2. Following the same procedure described abovefor the desulfurisation of (RFc,RS)/(SFc,SS)-2b-Dia1, the reaction was realized from 55mg (0.112 mmol) of racemic sulfoxide(RFc,SS)/(SFc,RS)-)phosphine. The crudereaction product waspurified by column chromatography on silica usingdegased ether/methanol mixture (1/0 -95/5) as eluent. The sulfoxide phosphine product (RFc,SS)/(SFc,RS)-3b-Dia2wasobtained as an orange solid (yield: 33 mg, 65%). 1 H NMR (δ,500 MHz, CDCl3):7.62-7.48 (3H, m, Ph); 7.43-7.35 (3H, m, Ph); 7.30-7.13 (4H, m, Ph); 4.72 (1H, d, JHH = 1.5Hz, substCp); 4.41 (1H, t, JHH = 1 Hz, substCp); 4.10 (1H, dd(ABX), JHH = 13 Hz, JHP = 3 Hz, CH2Cp); 4.01 (5H, s, Cp); 3.87 (1H, t, JHH = 1 Hz, substCp); 3.72 (1H, d(AB), JHH = 13 Hz, CH2Cp); 2.45 (1H, dq, JHH = 7.6 Hz, JHP = 3 Hz, CH2CH3); 1.10 (1H, t, JHH = 7.6 Hz, CH2CH3). 31 P{ 1 H} NMR (δ,202.8 MHz, CDCl3):-21.5. Schlenktube under argon wereintroduced 50 mg (0.096mmol) of the sulfoxidecompound (RFc,SS)/(SFc,RS)-2c-Dia1 in 5 ml of toluene and 0.1 ml (90 g, 0.55 mmol) of tris(dimethylamino)phosphine. After reflux for 2 h, the solvent wasremoved and the crudereaction product waspurified by column chromatography on silica usingdegased ether/dichloromethane mixture (1/1) as eluent. the sulfoxide phosphine product (RFc,SS)/(SFc,RS)-3c-Dia1wasobtained as an orange liquid (yield: 36mg, 76%

Table 1 .Selected geometrical parameters for the structures of compounds 2, 3 and 4. 2a-Dia1 2a-Dia2 2b-Dia1 2c-Dia1 2c-Dia2A 2c-Dia2B 3a-Dia2 a 4a b

 1

	110.5(2)	108.1(3)	107.5(3)	110.3(1)	116.2(3)

a :

3a dia2: (SFc, SS)/(RFc, RS)-3a b : 4a: (RFc,RS)/(SFc,SS)-4a

Table 2 .

 2 Crystal data and structure refinement parameters.

	Identification code	2a-Dia1	2a-Dia2	2b-Dia1
	Empirical formula	C29H25FeOPS2	C29H25FeOPS2	C25H25FeOPS2
	Formula weight	540.43	540.43	492.39
	Temperature, K	180(2)	180(2)	180(2)
	Wavelength, Å	0.71073	0.71073	0.71073
	Crystal system	Monoclinic	Monoclinic	Orthorhombic
	Space group	Cc	P 21/a	Pcab
	a, Å	14.5928(10)	12.812(2)	8.1197(6)
	b, Å	18.4079(11)	9.4172(16)	16.9489(11)
	c, Å	9.4244(6)	21.896(4)	33.823(2)
	, °	90.0	90.0	90.0
	, °	93.858(5)	104.832(16)	90.0
	, °	90.0	90.0	90.0
	Volume, Å 3	2525.9(3)	2553.8(8)	4654.7(5)
	Z	4	4	8
	Density (calcd), Mg/m 3	1.421	1.322	1.405
	Absorption coefficient, mm -1	0.847	0.754	0.911
	F(000)	1120	1056	2048
	Crystal size, mm 3	0.45x0.42x0.2	0.16 x 0.10 x 0.05 0.52x 0.39 x 0.12
	Theta range, °	3.56 to 27.81	2.71 to 26.03	3.32 to 26.37
	Reflections collected	9974	18130	33297
	Independent reflections [R(int)]	4487 (0.0242)	5055 (0.1527)	4751 (0.0634)
	Completeness, %,	99.7	99.7	99.8
	Absorption correction	Multiscan	Multi-scan	Multi-scan
	Max. , min. transmission	0.8415 and 0.6881 1.0500 and 0.8078 0.8230 and 0.6750
	Refinement method	F 2	F 2	F 2
	Data / restraints / parameters	4487 / 2 / 308	5055 / 0 / 307	4751 / 0 / 272
	Goodness-of-fit on F 2	1.055	0.892	1.081
	Final R indices [I>2sigma(I)]	0.0278, 0.0642	0.0662, 0.1564	0.0514, 0.1035
	R indices (all data)	0.0305, 0.0656	0.1713, 0.2309	0.0704, 0.1118
	Absolute structure parameter	0.019(14)
	Largest diff. peak and hole, e.Å -3 0.326 and -0.219	0.711 and -0.865	0.417 and -0.367

Table 1 .

 1 Crystal data and structure refinement(Contd.).

	Identification code	2c-Dia1	2c-Dia2	3a-Dia2
	Empirical formula	C27H29FeOPS2	C27H29FeOPS2	C29H25FeOPS
	Formula weight	520.44	520.44	508.37
	Temperature, K	180(2)	180(2)	180(2)
	Wavelength, Å	0.71073	0.71073	0.70930
	Crystal system	Monoclinic	Monoclinic	Triclinic
	Space group	Cc	P21	P -1
	a, Å	11.8130(12)	14.7673(14)	7.8035(8)
	b, Å	14.8503(12)	10.1912(7)	9.3075(9)
	c, Å	13.9653(16)	17.0533(18)	17.5040(15)
	, °	90.0	90.0	79.331(7)
	, °	91.394(13)	98.030(12)	87.727(7)
	, °	90.0	90.0	77.299(8)
	Volume, Å 3	2449.2(4)	2541.3(4)	1218.8(2)
	Z	4	4	2
	Density (calcd), Mg/m 3	1.411	1.360	1.385
	Absorption coefficient, mm -1	0.870	0.838	0.790
	F(000)	1088	1088	528
	Crystal size, mm 3	0.76 x 0.22 x 0.2 0.56 x 0.52 x 0.02 0.35 x 0.32 x 0.2
	Theta range, °	2.62 to 26.04	2.33 to 26.08	3.47 to 28.22
	Reflections collected	11892	21668	10784
	Independent reflections [R(int)]	4769 (0.0442)	9539 (0.0730)	6009 (0.0237)
	Completeness, %,	98.8	97.7	99.1
	Absorption correction	Multi-scan	Multi-scan	Multi-scan
	Max. , min. transmission	0.943 and 0.610 0.8058 and 0.7391 0.7521 and 0.6862
	Refinement method	F 2	F 2	F 2
	Data / restraints / parameters	4769 / 2 / 292	9539 / 1 / 584	6009 / 0 / 298
	Goodness-of-fit on F 2	1.025	0.843	0.991
	Final R indices [I>2sigma(I)]	0.0302, 0.0778	0.0379, 0.0611	0.0389, 0.1012
	R indices (all data)	0.0314, 0.0785	0.0716, 0.0685	0.0507, 0.1067
	Absolute structure parameter	-0.004(11)	0.284(14)
	Largest diff. peak and hole, e.Å -3 0.318 and -0.384 0.328 and -0.425	1.418 and -0.385

Table 1 .

 1 Crystal data and structure refinement(Contd.).

	Identification code	4a
	Empirical formula	C29H25Cl2FeOPPt S
	Formula weight	774.36
	Temperature, K	180(2)
	Wavelength, Å	0.71073
	Crystal system	Monoclinic
	Space group	P21/n
	a, Å	18.6057(14)
	b, Å	7.5780(7)
	c, Å	19.3027(14)
	, °	90.0
	, °	107.659(8)
	, °	90.0
	Volume, Å 3	2593.3(4)
	Z	4
	Density (calcd), Mg/m 3	1.983
	Absorption coefficient, mm -1	6.319
	F(000)	1504
	Crystal size, mm 3	0.18 x 0.08 x 0.08
	Theta range, °	2.21 to 26.06
	Reflections collected	24800
	Independent reflections [R(int)]	5081 (0.0562)
	Completeness, %,	99.0
	Absorption correction	Multi-scan
	Max. , min. transmission	0.5281 and 0.4506
	Refinement method	F 2
	Data / restraints / parameters	5081 / 0 / 325
	Goodness-of-fit on F 2	0.981
	Final R indices [I>2sigma(I)]	0.0289, 0.0585
	R indices (all data)	0.0445, 0.0624
	Absolute structure parameter
	Largest diff. peak and hole, e.Å -3 0.907 and -0.927

7. 18-7.05 (2H, m, Ph); 4.79 (1H, s broad, substCp); 4.34 (1H, t, JHH = 1 Hz, substCp); 4.08 (5H,s,Cp); 3.82 (1H,t, JHH = 1 Hz, substCp); 3.73 (1H, dd(ABX), JHH = 12 Hz, JHP = 2 Hz, CH2Cp); 3.30 (1H, d(AB), JHH = 12 Hz, CH2Cp); 1.2 (9H, s, C(CH3)3). 31 P{ 1 H} NMR (δ,202.8 MHz,CDCl3):-20.6. wasobtained as an orange solid (yield: 57 mg, 86%).

X-ray analyses

A single crystal of each compound was mounted under inert perfluoropolyether at the tip of a glass fibre and cooled in the cryostream of either an Oxford-Diffraction XCALIBUR CCD diffractometer for 2a-Dia1, 2a-Dia2, 2b-Dia1 and3a-Dia2ora Stoe IPDS diffractometer for 2c-Dia1, 2c-Dia2 and 4a. Data were collected using the monochromatic MoK radiation (= 0.71073).

The structures were solved by direct methods (SIR97 21 ) and refined by least-squares procedures on F 2 using SHELXL-97. 22 All H atoms attached to carbon were introduced in calculation in idealised positions and treated as riding models. The drawing of the molecules was realised with the help of ORTEP32. 24 Crystal data and refinement parameters are shown in Table 2.