ic034832k_si_005.cif (26.18 kB)

Reactions of the Tetrahedral Clusters [MCo3(CO)12]- (M = Ru, Fe) with Functional Mono- and Diynes

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posted on 12.01.2004, 00:00 by Aldjia Choualeb, Pierre Braunstein, Jacky Rosé, Richard Welter
The tetrahedral cluster [RuCo3(CO)12]- reacts with various alkynes, including the new PhC⋮CC(O)NHCH2C⋮CH (L1), to afford the butterfly clusters [RuCo3(CO)1042-RC2R‘)]- (1, R = R‘ = C(O)OMe; 2, R = H, R‘ = Ph; 3, R = H, R‘ = MeCCH2; 4, R = H, R‘ = CH2OCH2C⋮CH; 5, R = H, R‘ = CH2NHC(O)C⋮CPh), in which the ruthenium atom occupies a hinge position and the alkyne is coordinated in a μ42 fashion. Reaction of the anions 13 with [Cu(NCMe)4]BF4 led to selective loss of the 12e fragment Co(CO)- to form [RuCo2(CO)932-RC2R‘)] (6, R = R‘ = C(O)OMe; 7, R = H, R‘ = Ph; 8, R = H, R‘ = MeCCH2). To prepare functionalized RuCo3 or FeCo3 clusters that could be subsequently condensed with a silica matrix via the sol−gel method, we reacted [MCo3(CO)12]- (M = Ru, Fe) with the alkyne PhC⋮CC(O)NH(CH2)3Si(OMe)3(L2) and obtained the butterfly clusters [MCo3(CO)1042-PhC2C(O)NH(CH2)3Si(OMe)3)]- 9 and 10, respectively. Air-stable [RuCo3(CO)1042-Me3SiC2C⋮CSiMe3)]- (11) was obtained from 1,4-bis(trimethylsilyl)butadiyne and reacted with [Cu(NCMe)4]BF4 to give [RuCo2(CO)932-HC2C⋮CSiMe3)] (12), owing to partial ligand proto-desilylation, and not the expected [RuCo2(CO)932-Me3SiC2C⋮CSiMe3)]. Reaction of 11 with [NO]BF4 afforded, in addition to 12, [RuCo3(CO)9(NO)(μ42-Me3SiC2C⋮CSiMe3)] (13) owing to selective CO substitution on a wing-tip cobalt atom with NO. The thermal reaction of 11 with [AuCl(PPh3)] led to replacement of a CO on Ru by the PPh3 originating from [AuCl(PPh3)] and afforded [RuCo3(CO)9(PPh3)(μ42-Me3SiC2C⋮CSiMe3)]- (14), also obtained directly by reaction of 11 with one equivalent of PPh3. Proto-desilylation of 11 using TBAF/THF−H2O afforded [RuCo3(CO)1042-Me3SiC2C⋮CH)]- (15) which, by Sonogashira coupling with 1,4-diiodobenzene, yielded the dicluster complex [{[RuCo3(CO)1042-Me3SiC2C⋮C)]}2C6H4]2- (16). The crystal structures of NEt4·3a, NEt4·4a, 6, NEt4·11b, NEt4·14, and [N(n-Bu)415a have been determined by X-ray diffraction. Preliminary results indicate the potential of silica-tethered alkyne mixed-metal clusters, obtained by the sol−gel method, as precursors to bimetallic particles.