Dr Alexey N Bilyachenko
email: bilyachenko@ineos.ac.ru

Marina S Dronova

Dr.M.S.D Alexey I Yalymov

Frédéric Lamaty
email: frederic.lamaty@univ-montp2.fr

Xavier Bantreil

Jean Martinez

Christelle Bizet

Lidia S Shul'pina
email: shulpin@chph.ras.ru

Alexander A Korlyukov

Dmitry E Arkhipov

Frødøric Lamaty

Jeanm Artinez

Mikhail M Levitsky
email: levitsk@ineos.ac.ru

Prof L S S A A Hul'pina

D E A Korlyukov

Dr M M L Rkhipov

Evitsky

Rof E S Shubina

Dr F L Amaty

Dr X B Antreil

Prof C J Martinez

Bizet

Prof A A Korlyukov Pirogov

Dr A M K Irillov

Prof G B Shul'pin Semenov

Cage-like Copper(II) Silsesquioxanes: Transmetalation Reactions and Structural

Keywords:

come

Introduction

Cage-like metallasilsesquioxanes (CLMSs) represent an unusual class of compounds that simultaneously exhibit properties of both organosilicon derivatives and nanoscale metal clusters; thus attracting significant interestf rom scientific teams worldwide. [1] Au nique feature of CLMSs is ac ombination of s-a nd coordination-bonded compounds, which help to explain the huge variety of molecular architectures of CLMSs. [1a,f] The most abundant representatives of CLMSs are compounds based on the cubane-shaped silsesquioxane polyhedron, which have been discussed in detail in several reviews. [1b,c,e,g,h] The application of CLMSs, for example, as catalysts in different reactions, is therefore mostly limited to the use of cubane-like compounds, [1c, 2] although the catalytic properties of CLMSs of non-cubane types have been described in as mall number of publications. [3] Recently,w ep resented an ovel approacht oward noncubane CLMSs, containing coppera nd sodium ions, incorporated in silsesquioxane matrixes of dramatically varied shapes. [4] These compounds were revealed to be capable of effectively catalyzing the oxygenation of hydrocarbons and alcohols. [4] The oxidation of hydrocarbons, alcohols, and other CÀH compounds with peroxides in the presence of metal complexes represents an importantf ield of contemporary metalcomplex catalysis. [5] In particular,g iven the presence of copper ions in the active sites of variouso xidizing enzymes, [6] ah igh diversity of biomimetic or bioinspired copper-based catalytic systemsh aveb een developed for the oxidation of CÀHb onds by peroxides. [7] Different copper derivatives also catalyzet he oxidation reactions of alcohols [8] and aromatic compounds. [9] Bearing this in mind, we were interested in studying these new types of copper-containing cage silsesquioxanes as catalysts in oxidation reactions. Because our prior studies were devoted to the investigation of bi-and tetranuclear copper cage silsesquioxane compounds, [4] it seemed particularly interesting to evaluate the activity of biggerc lusters and to discusst he possible influence of nuclearity on catalytic activity.

Also, ruthenium- [10] and rhodium-catalyzed [11] direct oxidation of alcohols and amines into the corresponding amides has attracted much attention, and some methodologies involving cheap transition metals (Mn, Zn, Cu, and Fe) and tert-butylhydroperoxide as at erminal oxidanth ave recently been developed. [12] However,C LMSs containing such cheap transition-metal ions have never been evaluated as catalysts in these amidation reactions. This paper is devoted to ac omprehensive study of several types of cage-like copper silsesquioxanes, including their synthesis, structural and topological analysis, and quantum chemical studies. Some of these compounds were also evaluated as catalysts foramide production, as well as in oxidation reactions of benzene and alcohols with peroxides.

To wer" (1), "Globule" (2), and "Sandwich" (3)), [4a,b] which show significant differences in molecular architecture and composition. Ac ommon feature of all of these compounds is the presence of silanolate (RSiÀOÀNa) fragments, which seem to be suitable sites for transmetalation reactions due to their high reactivity.T op robe the possibility of such ap rocedure,w ea ttempted to replaces odium ions in the "initial" cages 1-3 with coppero nes. The treatment of copper-sodium silsesquioxanes 1-3 with copper chloride led to an ew family of hexanuclear products 4-6 with cylinder-like structures (Figure 1). Complexes 4-6 (Figures 234) contain three six-membered cycles: two siloxanolate cycles and one metal oxide ring lying between them.T he cylinder-like form of the products is different from the shape of the initial cages, which is especially clear in cases of the transformation of the decasilsesquioxane skeleton of compound 1 [4a] and dodecasilsesquioxane skeleton of compound 2 [4b] into two six-membered silsesquioxane units of products 4-6.D eep structural reorganization, whicha ccompanies transmetalation, could not be denied, even in the case of reactions involving 3.F ormally,o rganosilicon components of this compound (two six-membered siloxanolate cycles)a re the same as those observed in cylinder-like products 4-6.H owever,t he copper-containing core of compound 3 (two metal oxide Cu 2 O 2 cycles in an eclipsed conformation with respectt o each other [4b] )i sd ifferent from the almostp lanar configuration of metal oxide Cu 6 O 6 cycles in 4-6.I ns ummary,i tm ight be said that all transmetalation reactions reflect the phenomenon of significant rearrangemento fc ages. Nevertheless, all products of transmetalation are characterized by ac ommon set of important parameters:c ompounds 4-6 are hexanuclear, whereas the atomic ratio of silicon/copper is equal to 2/1 (this ratio is equal to 5/1 and 3/1 forcompounds 1 and 2-3,respectively).T he type of product nuclearity was independentn ot only of structuralv ariety of the initial compounds, but also of the solvent system of the reaction( see the Experimental Section).

It seems that the observed formation of hexanuclear cylinder-likep roducts is not exclusive. One of us reported the first instanceo ft he formation of similarh exanuclear compounds (containing Cu II ,M n II ,a nd Co II ions). [14] This report described an alternative synthetic approach and,w hat now seems to us to be very important,d escribed the use of other solvents ystems than those reported herein. It might be concluded that the formation of hexanuclear products is characteristic of synthetic conditions under which sodium ions of the silanolate fragments are completely replaced by copper(II) ions, even if such replacement is accompanied by the deep rearrangement of the silsesquioxane skeletons.

It is important to note that the use of as mall amounto f water during the synthesiso f6(see the Experimental Section) allowed us to obtain an unusual, cage-like, copper-containing compound that encapsulated ac hloride anion.C learly,t he presence of extra water in the reaction mediump revented the complete removal of side product (NaCl) and led to the first instance of anion encapsulation in copper silsesquioxane cage compounds. This provoked significant contraction of the skeleton of cage 6 through the additional coordination of copper ions with the m 6 -Cl À ligand.Am ore detailed discussion of this fact (as well as the early unknown phenomenon of the structurals ensitivity of hexacopper dodecasilsesquioxane cages toward the solvating ligand system as the whole) is provided below.

Structural considerations

The structures of 4-6 were determined by single-crystal XRD (Table 1). The most interesting feature of these compounds is significant structural susceptibility of the cylindrical shape of the coppers ilsesquioxane cage, as governed by the solvates, surrounding the metallasilsesquioxane skeleton of the complex. The influence of coordinated solvent molecules can be studied by considering the distances between opposite copper atoms (distances d 1•••4 ,s ee Figure 5f or details). In the case of structure 4,t hese distances are equal to 5.760,5 .573, and 5.755 , which correspond to almosta nu ndistorted cylindrical shape of the hexacopperd odecaphenylsilsesquioxane moiety (Figure 2). [15] Distortion of the cage moiety becomes prominenti nt he case of complex 5 (Figure 3), in which d 1•••4 are equal to 5.915, 5.547, and 5.679 . The reasonf or such ap ronouncedd istortion of the cylindrical shape is probably related to the replacement of solvent molecules (from those almost equal in their donor ability, nBuOHa nd EtOH in 4,t oP hCN, MeOH, and 1,4dioxanei n5 ). It should be emphasized that compound 5 is the first example of the successful use of ab enzonitrile ligand for the stabilization of am etallasilsesquioxane cage. Nevertheless, the structure of 6 (Figure 4) is even more remarkable because it allows us to discusst he influence of anion (Cl À )e ncapsulation in coppers ilsesquioxane cage compounds. First, the presence of Cl À in 6 leads to an oticeable contraction of the inner void of the cage (d 1•••4 distances are equal to 5.582, 5.458, and 5.631 ). Interestingly,t he position of the chloride anion is not exactly at the inversion centero ft he cage structure. The chloride anion is shifted toward the Cu1 atom (the Cu1•••Cl1 distance is 2.669 ). Hence, there is ap ronounced alteration of distances between vicinal coppera toms (

d 1•••2 ). The shortest d 1•••2 is Cu1•••Cu6 (2.714 ), whereas the longest one is Cu3•••Cu4 (2.809 ).
Charge neutrality of the entirety of compound 6 is maintained by an externals odium cation,w hich is coordinated by the siloxanolate cycle.

Topological analysis

To gain af urther insight into the structural features of copper silsesquioxane derivatives 1-6 with various clusterm otifs, we performed at opological classification. It should be mentioned that the topological classification of silsesquioxane cage-like compounds has not been reported previously.C ompounds 1, 2,a nd 3 reveal 2C1, (1,2M4-1) 2 ,a nd 2M6-1 topology, respectively (for details, see the Supporting Information), and the analysis of new derivatives 4-6 is described below.

For the sake of topological classification of the discrete 0D Cu 6 clusters in 4 and 5,w eh ave applied am ethod developed for the topological analysis of highn uclearity coordination clusters. [16] As ar epresentative example, the analysis of 5 is described in detail. Thus, its simplified structure (Figure 6a)w as generated by removing all non-metal atoms, except for the oxygen bridges betweent he copper centers. Then, ag raph representation of the Cu 6 skeleton (Figure 6b)w as obtained after transforminga ll of the m 2 -O atoms (Cu-O-Cu) into CuÀCu edges.T opological analysiso ft he resulting 2-connected 0D net reveals the 2M6-1 topology. [16a] This topology is described by the NDk-m classification, wherein N is as et of coordination numberso ft he topologically nonequivalentn odes (N = 2f or 2-connected nodes), Di sd imensionality (D = Mf or discrete 0D molecular clusters), k is the number of metal atoms in the cluster (k = 6), and m is ac lassification number to distinguish topologicallyd istinct clusters with equal NDk parameters. [16b, 17] Compound 4 possessest he same 2M6-1 topology and thus is not discussed further.

An interesting feature of 5 consists of the extension of discrete 0D Cu 6 units into a2 Dh ydrogen-bonded network through intermolecular O15ÀH15•••O16 and O16ÀH16•••O2 hydrogen bonds between the MeOH ligand (O15) and solvent (O16) molecules (forming ad imeric MeOH cluster) and the O2 atom of the silsesquioxane moiety.T ob etter understand the structure of the resulting 2D hydrogen-bonded layer,w ec arried out its topological analysis [16a] by following the concept of the simplified underlying net. [17,18] Ad ifferent structure simplification strategy was applied. [16a, 18b,c] The terminal cyanobenzene ligands were eliminated and the bridging silsesquioxane and (MeOH) 2 moieties were contracted to their centroids;t husg iving an underlying network (Figure 6c)c omposed of the 3-connected Cu3 and 4connected silsesquioxane nodes, as well as 2-connected Cu1, Cu2, and (MeOH) 2 linkers. Its topological analysis discloses ab inodal 3,4-connected net with the 3,4L27 topology and the point symbol of (3.8 2 )(3 2 .4.8 2 .9), wherein the (3.8 2 )a nd (3 2 .4.8 2 .9) notationsa re those of the Cu3 and silsesquioxane nodes, respectively.An umber of 3,4L27 topological networks driven by copper nodes have been reported. [19] It is noteworthy to mention that the present net can be simplified further by treatingthe Cu 6 (silsesquioxane) 2 blocks as 4-connected cluster nodes, which, along with the (MeOH) 2 linkers, give rise to au ninodal 4-connected network with the skl (Shubnikov tetragonal plane net) topology described by the point symbol of (4 4 .6 2 ).

In contrast to 4 and 5,t he structural core of 0D Cu 6 coordination cluster 6 is more complex due to the presence of the "central" m 6 -Cl moiety (Figure 7a). Following the above-mentioned procedure, [16a,b] we also obtained agraph representation of the Cu 6 skeleton (Figure 7b), namely,b yt ransforming the m 2 -O atoms (Cu-O-Cu) into CuÀCu edges and contracting the m 6 -Cl atom into Cu nodes to retain the clusterc onnectivity. [16a,b] The resulting skeleton has been topologically classified as a uninodal 5-connected net with the 5M6-1 topology (NDk-m classification). No topologically relevant hydrogen-bonding interactions were observed in 6.

In summary,t he performed analysisr esulted in the topological classification of copper-containing silsesquioxane cages and their extended networks in compounds 1-6,w hich allowed the identification of diverse topological motifs. We believe that these resultsc an contribute to the prediction of novel metal silsesquioxane cages and facilitate their design and synthesis. [16b,c, 17, 18]

Quantum chemical calculations

To the best of our knowledge,q uantum chemical calculation on CLMSs is the rarest type of such modeling. [20] Possibly,t he realization of such calculations was constrained by the huge size of such clusters. In turn, quantum chemical calculations may be useful to reveal the electronic structure of these compounds. Unfortunately,adirect comparison for cage compounds, as discussed herein, is possible only for binuclear silsesquioxane 1,i nw hicht he spin-coupling constant can be calculated by the broken symmetry approach as the difference between triplet and singlet states.

To study the features of the electron structure of 1 (Figure 8) and the cylinder compound (Figure 5), quantum chemical calculations in the framework of DFT theory were carried out. The optimization of 1 startedfrom experimental coordinates. [4a] Initial coordinates fort he optimization of different formsoft he cylinder( with or without an encapsulated chloride anion)w ere taken from the resultso fX -ray structure determinations of compounds 6 and 5,r espectively.T he main structural parameters, spin populations, and charges of atoms are presented in Ta bles 2-4.

The optimization of atomicp ositions of 1 was carriedo ut for singlet and triplet states. Analogously,t he cylinder-like [4a] are also given. The numbering of atoms is shown in Figure 8. compound was optimizedi nt he singlet (S = 0), triplet = 1), quartet (S = 2), and quintet states (S = 3).

Experimental valuesS inglet

The structuralp arameters of 1 in the singlet state are different from those of the triplet state. Remarkably,t he value of d 1•••2 in the triplet state is 0.2 l arger than that in the singlet state. TheC u-O-Cu angles in the triplet and singlet states are 89.9 and 98.6 8 on average. At the same time, the lengths of the CuÀOb onds in the singlet and triplet states differ by less than 0.02 . Thus, the optimized structure of 1 in the triplet state is closer to the experimental one than the structure of the singlet state. To analyze the spin population of atoms, we used the method based on Hirschfield partitioning of electron density.T he spin populations of copper atoms are 0.62 e, whereas their atomicc harges are equal to 0.

Catalytic oxidation of benzylic alcohols intoa mides

Some of us recently reported copper-catalyzed benzamide formation directly from alcohols and amine hydrochlorides. [12e] Herein, we present the first example of the evaluation of CLMSs under these amidation conditions. Such ar eaction was originally performedw ith 2mol %o fC uO in the presence of tert-butylhydroperoxide (TBHP) in acetonitrile at reflux. To take advantage of the good solubility of cage coppersilsesquioxanes in organic solvents, stock solutions of the catalysts were prepared in acetonitrile, which allowed us to work with av ery low catalyst loading. It is important to note that CLMSs act as the precatalyst and that the structure might be partly changed under the reaction conditions. Optimization of the reaction conditions was performed with compound 1.W hen the reaction was carriedo ut under the reported conditions starting from benzyla lcohol( 7a)a nd (a)-methyl benzylamine hydrochloride( 8a) , [12e] but with only 100 ppm of copperi na cetonitrile at reflux for 24 h, product 9aa was isolated in 99 %y ield (Table 5, entry 1). Because av ery low catalyst loading in copper was used, metallic impurities contained in the inorganic base would be able to performand enhance the amidation reaction. Indeed, in the presence of CaCO 3 (99.995 %p ure), amide 9aa was isolated in 72 %y ield, which provedt hat traces of metal were present in the first batch of base used (Table 5, entry 2). In view of these latest results, 99.995 %p ure CaCO 3 was used in the rest of the study.C ontrol experiments showedt hat base and copperw ere indispensable for this reaction( Ta ble 5, entries 3a nd 4). Diminishing the catalyst loading to 50 ppm of copperg ave 58 %y ield, which indicated that 100 ppm might be the bottom limit fort his reaction (Table 5, entry 5). To obtain an even higher yield of 9aa with only 100 ppm of coppera st he catalyst, the stoichiometry of 7a was increased to 2e quivalents. Gratifyingly,a mide 9aa was isolated in 83 % yield (Table 5, entry 6). Ar emarkable point was that amide 9aa could be obtained in similar yield whether 1mol %o r1 00 ppm of copperw as used (Table 5, entry 7);t hus proving that using 83 [e] 346 7 1 1C aCO 3 84 [e] 21 8 [f] CuO 2C aCO 3 [c] 87 11

[a] Reactionc onditions: 8a (0.5 mmol), 7a (0.75 mmol), CaCO 3 (99.995 % pure;0 .5 mmol), TBHP (5.5 m in nonane, 5equiv,2 .5 mmol), CH 3 CN (1 mL), 80 8C, 24 h. [b] Turnover frequency (TOF) = (mmol of product)/ [(mmol of Cu)(reaction time)]. [ c] CaCO 3 99 %p ure was used. [d] Not relevant. [e] Twoe quivalents of 7a were used. [ f] Result taken from the literature. [12e] such al ow catalyst loading did not influence the outcomeo the reaction. In addition, compared with the originalr eport with CuO (Table 5, entry 8), our new set of conditions was superior in terms of turnover number (TON;8 300 vs. 44) and TOF (346 vs. 11 h À 1 ).

To ensure that such al ow catalyst loading would be generally efficient and to compare the various CLMSs, as af irst approach,w ec hose three of the six catalysts containing two, four,a nd six copper centers, namely,c ompounds 1, 2, 5,a nd performed tests by varying the amine. Primary amines, with varying steric hindrance, and secondary amines were tested (Table 6). Compared with the original report involving CuO (2 mol %), amides 9aa-9af were isolated in at least similar yields when only 100 ppm of Cu was used. Benzamides 9aa, 9ab,a nd 9ac,f eaturing primary (a)-methylbenzylamine, cyclohexylamine, and n-butylamine, respectively,w ere isolated in yields of up to 94 %( Ta ble 6, entries 1-12). Dibenzylamine, piperidine, and morpholinew ere efficientlyc onverted into the corresponding amides 9ad, 9ae,a nd 9af,w ith yields from 64 to 93 %( Ta ble 6, entries 13-24). According to these results, it is apparent that workingw ith CLMSs at very low catalyst loading gives outstanding results. Nevertheless, if CLMSs 1, 2,a nd 5 were efficient in the amidation reaction, catalyst 2,w hich featured four copper centers, was slightly superior to its congeners (Table 6, entries 2, 14, 18, and 22). These good results, combined with av ery lowc atalystl oading, translated directly into the TON andT OF values obtained. Indeed, excellent TON and TOF values, reaching 9400 and 392 h À1 ,r espectively,w ere calculated for this amidation reaction.

Catalytic oxidations of benzene and alcohols

We tested compounds 5 and 6 as catalysts in the oxidation of benzene, hydroquinone, and 1-phenylethanol with aqueous hydrogen peroxide. Herein, we report the first results of this study.

Benzene was oxidized to produce phenol, which at high concentrations of the catalysts is further nonselectively transformed into overoxidation products, including p-quinone (Figure 9). The reactionr equired the presence of as mall amount of an acid promoter (Figure 9a,c urve 1,a nd Figure 9b,c urve 1). Thus, nitric acid added to the reaction solution substantially improved the reaction catalyzed by 6 (Figure 9b). However,t he use of nitric acid resulted in the degradation of catalyst 5,w hich slowly precipitateda sapale-blue solid during the course of the reaction. Fortunately,t his was not the case with TFAa nd the reactiona fforded 0.05 m of phenol after 2.5 h( Figure 9a). Several experiments with varying initial concentrations of benzene, hydrogen peroxide, and nitric acid were carriedo ut.Al inear dependence of the initial reactionr ate, W 0 ,o nt he initial concentration of benzene hasb een found for benzene concentrationsi n the interval [benzene] 0 = 0-0.3 m (Figure S1, curve 1, in the Supporting Information). At higher benzene concentrations the curve approaches ap lateau.A dditionally,t he dependence of W 0 on the initial concentration of hydrogen peroxide (containing 65 %o f water) has the shape of ap arabola (Figure S1, curve 2,i nt he Supporting Information). The initial reaction rate at [HNO 3 ] > 0.03 m was independento f the concentration of added nitric acid (Figure S2, curve 1,i nt he Supporting Information). Finally,t he addition of water slightly decreases the initial oxidation rate (Figure S2, curve 2,i nt he Supporting Information).

All of these observations showed that the kinetic behavior of the copper-based systems described above resembled the features of benzene oxidation with the vanadate anion/pyrazine-2-carboxylic acid Table 6. Variation of the amine at low catalystloading. [a] Entry Product CatalystC u[ mol %] Yield [%] TON/TOF [b,c] 1 1 0.01 83 8300/346 2 0.01 94 9400/392 2 5 0.01 71 7100/296 4C uO [d] 28 74 4/11 5 1 0.01 83 8300/346 6 2 0.01 83 8300/346 7 5 0.01 87 8700/363 8C uO [d] 28 04 0/ CuO [d] 28 74 4/11 CuO [d] 26 23 1/8

[a] Reactionc onditions: amine•HCl (0.5 mmol), 7a (1.0 mmol), CaCO 3 (99.995 %p ure; 0.5 mmol), TBHP (5.5 m in nonane, 5equiv, 2.5 mmol), CH 3 CN (1 mL), 80 8C, 4h for 1mol %C u, 24 hf or 0.01 mol %C u. Yields of products isolateda re given.

[b] TON = (mmol of product)/(mmol of Cu).

[c] TOF = TON/(reaction time);g iven in h À1 . [d] Calculated from data in the literature. [12e] (PCA)/H 2 O 2 reagent in acetonitrile. [21] Analogously,t he ing mechanism for benzene oxidation catalyzed by copper cages could be proposed. Ac opper(II) compound reacts first with am olecule of H 2 O 2 to produce ac opper(I) derivative (Cu II + H 2 O 2 !Cu I + HOOC + H + ), which generates hydroxyl radicals that interact with as econd hydrogen peroxide molecule (Cu I + H 2 O 2 !Cu II + HOC + HO À ). [START_REF] Shilov | Activation and Catalytic Reactions of Saturated Hydrocarbons in the Presence of Metal Complexes[END_REF] Phenoli sf urther formed in this process throughasequence of stages that do not limit the oxidation rate Compounds 5 and 6 were also tested as catalysts in the oxidation of hydroquinone at 20 8C. Compound 5 (Figure S3, curve 1, in the Supporting Information) oxidized hydroquinone to p-quinonel ess rapidlyt han compound 6 (Figure S3, curve 2, in the Supporting Information), although the yield of quinone (56 %a fter 4.5 h) in the case of 5 was higher.A so bserved above in the oxidation of benzene, neither reaction was efficient in the absence of TFA( Figure S3,c urves 1a and 2a, in the Supporting Information). In the case of catalysts 5 or 6,t he formation of p-quinone was followed by its nonselective overoxidation to afford ac omplex mixture of unidentified compounds. As ar esult, the kinetic curves displayed maxima. Controle xperiments showed that hydroquinone could not be oxidizedi nt he presence of only TFAi nt he absence of ac opperc atalyst (the concentration of quinone was 0.0013 m after 2h)a nd especially in the absence of both TFAa nd ac opper catalyst( in the presence of only hydrogen peroxide, the concentration of quinone was lower than 0.0001 m after 2h).

Hydrogen peroxide turned out to be inefficient in the oxidation of 1-phenylethanol. In contrast, TBHP exhibited excellent activity.T he reactiond oes not require the presence of any acid. Figure S4 in the Supporting Information demonstrates the accumulation of acetophenone over the course of the oxidation of 1-phenylethanol in the presence of TBHP catalyzed by 6 at 60 8C( 95 %y ield after 5h). It is interesting to note that, in contrast, compound 5 was unable to catalyze the oxidation of 1-phenylethanol with TBHP.U nder the reaction conditions, compound 5 immediately precipitated as ap ale-blue solid when TBHP was added.

Conclusion

Transmetalation of various copper-sodium phenylsilsesquioxanes (1-3)g ave af amily of three novel hexanuclear cage-like copper(II) silsesquioxanes (4-6), which exhibited noticeable structuralf lexibility as ac onsequence of different solvating systemsu sed in the synthesis and crystallization. The most outstanding case among the hexanuclear products was compound 6,w hich unusually trapped the chloride anion. The inclusion of Cl À into the inner void of the copper silsesquioxane fragment led to ad ecrease of its volume owing to the presence of multiple Cu•••Cl coordination bonds.

The current study also opens up the application of topological analysis methods for the classification of underlying networks in silsesquioxane derivatives. At opological analysis of the newly synthesized discrete Cu 6 coordination clusters revealed the uninodal 2-or 5-connected 0D skeletons with 2M6-1( 4 ,5 )o r5 M6-1 (6)t opology,r espectively.F or comparison, compounds 1-3 were topologically classified. Thus, the same 2M6-1 topology was detected in complex 3 with the Cu 4 Na 2 motif, whereas the compounds with the Cu 2 Na 2 cores featured the 2C1 (1)a nd (1,2M4-1) 2 (2)t opology.F urthermore, an oteworthy feature of 5 consists of the extension of its discrete units into the binodal 3,4-connected 2D hydrogen-bonded layer with 3,4L27 topology,w hich is similart ot hat identified in the metal-organic layer of 3.T he silsesquioxanes thusa ppear to be versatile building blocks fort he construction of various multicopper(II) or copper-sodium cages. The structures of 1 and cylinder compounds weres imulated by quantum chemical modeling;t his is the first example of DFT calculations of cage-like coppers ilsesquioxanes. According to results of the calculations, the structure of 1 corresponded to the triplet state, so the spin density wasd istributed between coppera toms and bridged oxygen atoms. In turn, the geometry of the quartet and quintet states of the cylinder compound was in better agreement with the experimental one than states with low spin. Also, quantum modeling reproduced the contraction of the inner cavity of 6 upon inclusion of achloride anion.

Compounds 1, 2,a nd 5 were evaluated in the direct oxidation of alcohols and amines into corresponding amides. All of these copper(II)-containing cages showed exceptional catalytic results, which allowed for an efficient reaction, even at copper loadings down to 100 ppm. Such behavior permitted TOF values to be obtained that ranged from 267 to 392 h À1 ,w hich were much highert han the one reported so far in the literaturef or this type of reactionconditions (TOF < 34 h À1 ).

Compound 6 turned out to be av ery good catalyst for benzene oxidation with hydrogen peroxide in the presence of certain acids (nitric or trifluoroacetic). The oxidation of 1-phenylethanol with TBHP in the absence of acids was very effective to give an acetophenone yield close to 100 %. Compound 5, which does not contain any chloride anion connecting copper ions, is noticeably less stable and much less efficient as ac atalyst. Further exploration of silsesquioxanes towardt he design of copper-organic materials with intricate topologies and diversefunctional properties is currently in progress.

Experimental Section

General procedures

All solvents were distilled prior to use according to standard procedures. Compounds 1-3 were obtained by following earlier published procedures. [4a,b] Elemental analyses were performed by the microanalytical service of the Nesmeyanov Institute of Organoelement Compounds RAS. IR studies on the dried solid samples were carried out as Nujol mulls on aN icolet 6700 FTIR spectrometer in the 4000-600 cm À1 range. For initial and obtained copper(II)containing silsesquioxanes, au sual set of signals (1120 (n PhÀSi ), 940-1100 (n as SiÀO , n as Si-O-Si ), 900 (n as SiÀO in the Si-O-M fragment), 720-680 cm À1 (s CÀH of monosubstituted phenyl group)) was observed. [4a,b] Synthesis of 4 Compound 4a:C ompound 1 (0.5 g, 0.33 mmol) was dissolved in toluene (25 mL). Then anhydrous CuCl 2 (0.044 g, 0.33 mmol) in am ixture of n-butanol (25 mL) and ethanol (15 mL) was added at once. The mixture was heated under reflux for 2.5 h, then cooled to room temperature, and filtered into an evaporation flask. The flask was equipped with as eptum with needle to allow solvents to evaporate under as low current of nitrogen. Immediately after blue-colored crystals began to form, the flask was transferred to the fridge and stored there until the crystal fraction growth (3-4weeks) ceased, as visually determined. Af ew selected single crystals were used for the X-ray study (for details, see below). Yield: 0.16 g, 28 %; elemental analysis calcd (%) for [(PhSiO 1.5 ) 12 (CuO) 6 ]: Cu 18.80, Si 16.62;f ound (in av acuum-dried sample): Cu 18.59, Si 16.37.

Compound 4b:C ompound 2 (0.5 g, 0.25 mmol) was dissolved in toluene (25 mL). Then anhydrous CuCl 2 (0.068 g, 0.5 mmol) in amixture of n-butanol (25 mL) and ethanol (15 mL) was added at once. The mixture was heated under reflux for 2.5 h, then cooled to room temperature and filtered into an evaporation flask. The flask was equipped with aseptum and needle to allow solvents to evaporate under as low current of nitrogen. Immediately after blue-colored crystals began to form, the flask was transferred to the fridge and stored there until the crystal fraction growth (3-4 weeks) ceased, as visually determined. Af ew selected single crystals were used for the X-ray study (cell parameters equaled those of the product, as described for 4a). Yield:0.35 g, 69 %; elemental analysis calcd (%) for [(PhSiO 1.5 ) 12 (CuO) 6 ]: Cu 18.80, Si 16.62;f ound (in avacuum-dried sample): Cu 18.62, Si 16.34.

Compound 4c:T he same procedure as that described for 4b was used for the synthesis with compound 3 as an initial reagent. Yield:0 .37 g, 73 %; elemental analysis calcd (%) for [(PhSiO 1.5 ) 12 (CuO)

Synthesis of 5

Compound 5a:C ompound 1 (0.5 g, 0.33 mmol) was dissolved in am ixture of toluene (20 mL) and 1,4-dioxane (30 mL). The reaction mixture was brought to reflux and anhydrous CuCl 2 (0.044 g, 0.33 mmol) in methanol (20 mL) was added dropwise, along with simultaneous partial distillation of the solution. As 10 mL of solvents were distilled off, the rest of reaction mixture was down to room temperature and filtered into an evaporation flask containing benzonitrile (7 mL). The flask was equipped with as eptum and needle to allow solvents to evaporate under as low current of nitrogen. Immediately after blue-colored crystals began to form, the flask was transferred to the fridge and stored there until the crystal fraction growth (3-4 weeks) ceased, as visually determined. Af ew selected single crystals were used for the X-ray study (for details, see below). Yield:0 .14 g, 25 %; elemental analysis calcd (%) for [(PhSiO 1.5 ) 12 (CuO) 6 ]: Cu 18.80, Si 16.62;f ound (in av acuum-dried sample): Cu 18.59, Si 16.27.

Compound 5b:C ompound 2 (0.5 g, 0.25 mmol) was dissolved in am ixture of toluene (20 mL) and 1,4-dioxane (30 mL). The reaction mixture was brought to reflux and anhydrous CuCl 2 (0.068 g, 0.5 mmol) in methanol (20 mL) was added dropwise, along with simultaneous partial distillation of the solution. As 10 mL of solvents were distilled off, the rest of reaction mixture was cooled to room temperature and filtered into an evaporation flask containing benzonitrile (7 mL). The flask was equipped with as eptum and needle to allow solvents to evaporate under as low current of nitrogen. Immediately after blue-colored crystals began to form, the flask was transferred to the fridge and stored there until the crystal fraction growth (3-4 weeks) ceased, as visually determined. Af ew selected single crystals were used for the X-ray study (cell parameters equaled those of the product, as described for 5a). Yield:0 .37 g, 72 %; elemental analysis calcd (%) for [(PhSiO 1.5 ) 12 (CuO) 6 ]: Cu 18.80, Si 16.62;f ound (in avacuum-dried sample): Cu 18.69, Si 16.35.

Compound 5c:T he same procedure as that described in 5b was used for the synthesis with compound 3 was an initial reagent. Yield:0 .40 g, 79 %; elemental analysis calcd (%) for [(PhSiO 1.5 ) 12 (CuO) 6 ]: Cu 18.80, Si 16.62;f ound (in av acuum-dried sample): Cu 18.70, Si 16.54.

Synthesis of 6

Compound 6a:C ompound 1 (0.5 g, 0.33 mmol) was in am ixture of toluene (20 mL) and 1,4-dioxane (30 mL). The reaction mixture was brought to reflux and anhydrous CuCl 2 (0.068 g, 0.5 mmol) in methanol (10 mL) was added dropwise, along with simultaneous distillation of the solution to completely remove methanol from reaction mixture. When 10 mL of distillate was collected, water (2 mL) was added to the rest of reaction mixture, then the mixture was cooled to room temperature, and filtered into an evaporation flask. The flask was equipped with as eptum and needle to allow solvents to evaporate under as low current of nitrogen. Immediately after blue-colored crystals began to form, the flask was transferred to the fridge and stored there until the crystal fraction growth (3-4weeks) ceased, as visually determined. Af ew selected monocrystals were used for the X-ray study (for details, see below). Yield:0 .11g,2 0%;e lemental analysis calcd (%) for [(PhSiO Compound 6b:C ompound 2 (0.5 g, 0.25 mmol) was dissolved in the mixture of toluene (20 mL) and 1,4-dioxane (30 mL). The reaction mixture was brought to reflux and anhydrous CuCl 2 (0.068 g, 0.5 mmol) in methanol (10 mL) was added dropwise, along with simultaneous distillation of the solution to completely remove methanol from the reaction mixture. When 10 mL of distillate was collected, water (2 mL) was added to the rest of reaction mixture, then mixture was cooled to room temperature, and filtered into an evaporation flask. The flask was equipped with as eptum and needle to allow solvents to evaporate under as low current of nitrogen. Immediately after blue-colored crystals began to form, the flask was transferred to the fridge and stored there until the crystal fraction growth (3-4 weeks) ceased, as visually determined. Af ew selected monocrystals were used for the X-ray study (cell parameters equaled those of the product, as described for 6a). Yield:0 .35 g, 66 %; elemental analysis calcd (%) for [(PhSiO 1.5 ) 12 (CuO) 6 (NaCl)]: Cl 1.70, Cu 18.28, Na 1.10, Si 16.16;f ound (in avacuum-dried sample): Cl 1.67, Cu 18.20, Na 1.07, Si 16. 10.

Compound 6c:T he same procedure as that described in 6b was used for the synthesis with compound 3 was an initial reagent. Yield:0 .40 g, 75 %; elemental analysis calcd (%) for [(PhSiO 1.5 ) 12 (CuO) 6 (NaCl)]: Cl 1.70, Cu 18.28, Na 1.10, Si 16.16;f ound (in avacuum-dried sample): Cl 1.66, Cu 18.18, Na 1.07, Si 16.09.

XRD studies

All measurements were carried out with Bruker Smart APEX II and Bruker APEX II DUO diffractometers. Collected reflections were integrated and corrected for absorption by using the SADABS pro-gram. [START_REF] Blessing | [END_REF] Crystal data and the parameters of refinement are shown in Ta ble 7. The structures of 4-6 were solved by ad irect method and refined in anisotropic approximation for most non-hydrogen atoms against F 2 .T he Ha toms were calculated from the geometrical point of view and refined with constrained CÀHa nd OÀHb ond length and displacement parameters. Most of the Ph groups and solvated molecules of dioxane, EtOH, and BuOH were disordered. The atoms of these moieties were split over two positions and then refined by using the rigid-body approximation. The value of occupation for several non-coordinated molecules was less than one, as revealed by analysis of their displacement factors. All calculations were carried out by using the SHELXTL PLUS [24] and OLEX II [25] software.

Quantum chemical calculations

Pure exchange-correlation functional PBE and two L1 lambda basis sets (relativistic and nonrelativistic) were chosen for the optimization.

Catalytic oxidation of benzene and alcohols

Catalysts 5 and 6 and the acids (cocatalysts HNO 3 or TFA) were used as stock solutions in acetonitrile. Aliquots of these solutions were added to the reaction mixtures. The reactions were typically carried out in air in thermostated Pyrex cylindrical vessels with vigorous stirring;t he total volume of the reaction solution was 5mL. (CAUTION! The combination of air or molecular oxygen and H 2 O 2 with organic compounds at elevated temperatures may be explosive!) Samples of the reaction mixture were taken after certain time intervals, and concentrations of the products were measured by using the 1 HNMR spectroscopy method ([D 6 ]acetone was used as ac omponent of the solvent and 1,4-dinitrobenzene as as tandard;" Bruker AMX-400" instrument, 400 MHz).

Figure 2 .

 2 Figure 2. Copper silsesquioxane structure 4.A toms are drawn by ADP ellipsoids at 50 %p robability.P henylg roups and the carbon atoms of EtOHa nd nBuOH are schematically shown by wireframe and stick representations. For ar epresentation in color see the SupportingInformation.

Figure 1 .

 1 Figure 1. General scheme for the synthesis of the initial (1-3)a nd resulting (4-6)c opper phenylsilsesquioxanes.

Figure 3 .

 3 Figure 3. Copper silsesquioxane structure 5.A toms of copper silsesquioxane are drawn by atomic displacement parameter (ADP) ellipsoids at 50 %probability.Phenyl groups and 1,4-dioxane moieties are schematically shownby aw ireframe representation. For ar epresentation in color see the Supporting Information.

Figure 4 .

 4 Figure 4. Copper silsesquioxane structure 5.A toms of copper silsesquioxane are drawn by ADP ellipsoids at 50 %p robability.P henylg roups and 1,4dioxanemoieties are schematically shown by awireframe representation. For arepresentation in color see the Supporting Information.

Figure 6 .

 6 Figure 6. To pological fragments of 5:a )adiscrete Cu 6 coordination cluster and b) its simplified graphicalrepresentation, showing auninodal 2-connected motif with the 2M6-1 topology;c )anunderlying binodal 3,4-connected 2D hydrogen-bonded net with the 3,4L27 topology and point symbol of (3.8 2 )(3 2 .4.8 2 .9). Color codes:a )Cuc enters (green), m 2 -O atoms (red); b) 2-connected Cu nodes (green); c) 2-connected Cu1/Cu2 linkers and 3-connected Cu3 nodes (green), centroids of 4-connected silsesquioxane nodes (yellow), and centroids of 2-connected (MeOH) 2 linkers (red).

Figure 7 .

 7 Figure 7. To pological fragments of 6:a )adiscrete Cu 6 coordination cluster and b) its simplified graph representation showing auninodal 5-connected motif with the 5M6-1 topology.C olor codes:a )Cuc enters (green), m 2 -O atoms (red), m 6 -Cl atom (yellow); b) 5-connected Cu nodes (green).

Figure 8 .

 8 Figure 8. Schematic representation of the structure of 1.

  24 e. The rest of the spin density is distributed over bridge oxygen atoms O 1 and terminal oxygen atoms O 2 (the values of the spin population are 0.15 and 0.09 e). The structuralp arameters of variouss pin states of the cylinderc ompound are also noticeably different.T he most prominentf eature of the structure of the singlet state is the alteration of the d 1•••2 distances. The short d 1•••2 contacts alternate to long d 1•••2 ones (2.70 and 2.95 , on average).In the structure of the triplet state there is no visible change to the above distances;h owever,t he d 1•••2 contacts varied over ar ather wide range (2.741-2.795). The states with higher multiplicity (S = 2 and 3) are characterizedb yt he absence of alteration of the d 1•••2 distances (the variations do not exceed 0.02 ). Thus, the geometry of the quartet and quintet states is in better agreement with that determined experimentally than states with low spin (S = 0a nd 1). Regardless of the spin state, the atomic spin population of the coppera tom is about 0.6 e, whereas the spin population of bridge oxygen atom O1 is 0.15 e. The spin populations of the restofa toms are negligible.The inclusion of ac hloride anion into the inner cavity of the cylinderc ompound (in the case of product 6)l eads to the absence of changes to the d 1•••2 distances in the singlet state observed in the case of the chloride-less analogue. Indeed, the chloridea nion in the optimized geometry is located at the center of inversion, regardless of the spin state, so all Cu•••Cl distances are equal. The increase in the total multiplicity of the chloride-containingf orm of the cylinder lead to ad ecrease in the value of d 1•••2 ,s ot he value for the quintet state differs from that of the singlet state by 0.06 . Additionally,q uantum chemicalc alculations reproduced the contraction of the inner cavity upon inclusion of the chloride anion. The values of the d 1•••4 distances in the calculated structures of the quartet states are very close to those obtained experimentally.A nalysis of the spin density distribution showed that the population at the Cl atom was very small (0.02 e), whereas the values for copper and bridge oxygen atoms are the same (0.63 and 0.15 e, respectively) as those in the cylinder compounds without inclusion of achloride anion.

  Nevertheless, compound 6 (in the presence of nitric acid) catalyzed the oxidation noticeably more efficientlyt og ive phenol in ac oncentration of 0.08 m after 1h(yield of 18 %b ased on starting benzene;T OF = 160 h À1 ;F igure 9b,c urve 5). It is interesting to note that the initial oxidation rate, W 0 ,l inearly depends on the concentration of 6 in the interval of its concentrations (0-3) 10 À4 m (Figure9c). In the absence of TFAo r HNO 3 ,o xidation is not efficient (Figure9a,curve 1, and Figure 9b,c urve 1).

Figure 9 .

 9 Figure 9. Oxidationofb enzene to form phenol, as catalyzedbyc ompounds 5 and 6 in acetonitrile at 50 8C. a) Kinetic curves of phenol accumulation in the oxidation of benzene (0.45 m)with H 2 O 2 (2.6 m;3 5% aqueous) catalyzed by 5 at 210 À4 (curves 1 and 3)a nd 110 À4 m (curve 2). b) Kinetic curves of phenol accumulation in the oxidation of benzene (0.45 m)w ith H 2 O 2 (2.6 m; 35 %a queous) in the presence of HNO 3 (0.04 m,6 5%)c atalyzed by 6 at 0.5 10 À4 (curve 2), 110 À4 (curve 3), 210 À4 (curve 4;t he analogous reaction in the absence of HNO 3 is shownbyc urve 1), and 510 À4 m (curve 5). At [6] 0 = 0.5 10 À4 m (curve 2)a fter 13 h, TON was 1510, TOF = 116h À 1 .T he initial rates, W 0 ,w ere determined from the slope of the tangent (in certain examples shownasd otted straight lines 3a and 4a)t othe kinetic curve of oxygenate accumulation.c )Dependence of the initial reaction rate, W 0 ,o n the initial concentrationo f6(for conditionso fthe experiments presented in b).

  1.5 ) 12 (CuO) 6 (NaCl)]: Cl 1.70, Cu 18.28, Na 1.10, Si 16.16;f ound (in avacuum-dried sample): Cl 1.66, Cu 18.19, Na 1.06, Si 16.09.

Table 1 .

 1 Average values of selected structural parameters of 4-6 (numbering is showninF igure 5).

	Structural parameter	456
	CuÀO 1	2.005	2.006	1.990
	SiÀO 1	1.608	1.613	1.613
	SiÀO 2	1.622	1.629	1.631
	d 1•••2	2.822	2.858	2.756
	d 1•••4	5.696	5.714	5.557
	Cu-O-Cu	88.1	86.7	88.3

Table 2 .

 2 Mean valueso fb ond lengths []a nd angles [8]f or the calculated structure of binuclear silsesquioxane 1.T he experimental values from the literature

Table 3 .

 3 Selectedp arameters for the calculated structure of the cylindrical compound(then umbering of atoms is shown in Figure5).

	Triplet

Table 4 .

 4 Selectedp arametersf or the calculated structure of the cylinder compound with an encapsulated chloride anion (numberingo fa toms is shown in Figure5).

		Singlet	Triplet	Quartet	Quintet
	bond length and angles []
	CuÀO1	1.987	1.990	1.990	1.991
	SiÀO1	1.668	1.664	1.664	1.663
	SiÀO2	1.664	1.661	1.661	1.661
	Cu•••Cl	2.824	2.754	2.752	2.748
	d 1•••2	2.822	2.756	2.752	2.748
	d 1•••4	5.652	5.508	5.503	5.495
	Cu-O-Cu	90.5	87.68 7.5	87.3
	spin population [e]
	Cu		0.610 .63
	O1		0.150 .15
	Cl		0.005	0.0110 .016
	atomic charges [e]
	Cu	0.21	0.230 .23	0.23
	O1	À0.23	À0.24	À0.24	À0.25
	O2	À0.25	À0.25	À0.25	À0.25
	Cl	À0.18	À0.14	À0.14	À0.14

Table 5 .

 5 Optimization of the reaction conditions.[a]

	Entry	Catalyst	Cu [mol %]	Base	Yield [%]	TOF [h À1 ] [b]
	1	1	0.01C aCO 3 [c]	99	413
	2	1	0.01C aCO 3	72	300
	3	1	0.01-35	146
	4-	-C aCO 3	24	-[d]
	5	1	0.005	CaCO 3	58	483
	6	1	0.01C aCO 3

  6 ]: Cu 18.80, Si 16.62;f ound (in av acuum-dried sample): Cu 18.54, Si 16.64.

Table 7 .

 7 Crystal data for structures 4-6. 45 6 formula C 92 H 112 Cu 6 O 32 Si 12 C 106 H 118 Cu 6 N 2 O 36 Si 12 C 120 H 159.17 ClCu 6 NaO 50 Si 12 À3 ](1 min /1 max )2 .391/À1.042 0.812/À0.872 1.894/À1.930

	M r	2448.2	2714.34	3178.40
	T [K]	100	100	100
	space group	P2 1 /nP 2 1 / nC 2/c
	Z	22	4
	a []	17.8223(9)	18.2846(6)	35.9078(14)
	b []	18.7138(8)	19.0135(6)	17.6366(6)
	c []1 8.9674(9)	18.9820(6)	28.1259(11)
	a [8]9 0.00	90.00	90.00
	b [8]1 13.152(2)	116.0450(10)	121.6620(10)
	g [8]9 0.00	90.00	90.00
	V [ 3 ]5 816.6(5)	5929.0(3)	15160.8(10)
	1 calcd [g cm À3 ]1 .398	1.520	1.391
	m [cm À1 ]2 9.75	12.58	10.21
	F(000)	4048	2796	6596.7
	2q max [8]5 66 16 1.5
	reflns collected	52917	620452 04989
	independent reflns	10183	180334 6597
	independent reflns (I > 2s(I))	7918	135433 1958
	parameters4 57	732	1161
	R 1 (I > 2s(I))	0.0987	0.0361	0.0843
	wR 2	0.2294	0.1021	0.2857
	GOF	1.047	1.041	1.018
	residual electron density [e

015 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim

Chem. Eur.J.2015, 21,8758 -8770 www.chemeurj.org 2 015 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim

Acknowledgements

This work was supported by the Russian Foundation for Basic (grants 12-03-00084-a, 14-03-00713,a nd 14-03-31772), Council of the Presidento ft he Russian Federation (grant MD-3589.2014.3), the "Science without BordersProgram, Brazil-Russia", CAPES (grant A017-2013), the UniversitØ Montpellier 2, and the Centre National de la Recherche Scientifique (CNRS), throught he Groupe de Recherche International (GDRI) Homogenous catalysis for sustainable development (CH2D), the French Embassy in Moscow,P rogramme AndrØ Mazon, the Foundation for Science and Technology (FCT), Portugal( PTDC/ QUI-QUI/121526/2010).

Keywords: amidation • cage compounds • density functional calculations • metallacycles • oxidation