Heterobinuclear Vinyl, Allyl, and Related Complexes of Rhodium/Osmium from Terminal Alkynes and Allenes, Vinyl to Carbene Transformations, and the Structures of [RhOs(C(CH₃)CH₂)(CO)₃(Ph₂PCH₂PPh₂)₂] and [RhOs(C(CH₃)C(CH₃)₂)(CH₃)(CO)₃(Ph₂PCH₂PPh₂)₂][CF₃SO₃]

Abstract

This paper reports the synthesis and characterization of a series of vinyl, vinyl−hydride, vinyl−alkyl, and related heterobimetallic complexes of Rh and Os. Reductive elimination reactions of the vinyl−hydride products and the transformations of vinyl groups to carbenes are also reported. Reaction of [RhOs(H)(CO)3(dppm)2] (1, dppm = Ph2PCH2PPh2) with propyne yields [RhOs(C(CH3)CH2)(CO)3(dppm)2] (3), and reaction with (CH3)2CCCH2 yields [RhOs(C(CH3)C(CH3)2)(CO)3(dppm)2] (5). Reaction of 1 with allene yields 3 as the major product, together with small amounts of [RhOs(η3-C3H5)(CO)3(dppm)2] (4). Compound 4 can be independently synthesized via reaction of (CH2CHCH2)2Mg with [RhOs(CO)4(dppm)2][BF4] (2). Compound 3 reacts with CO to form the isopropenoyl complex [RhOs(C(O)C(CH3)CH2)(CO)3(dppm)2] (6). Both vinyl complexes 3 and 5 react with CH3SO3CF3 to form [RhOs(C(CH3)CR2)(CH3)(CO)3(dppm)2][CF3SO3] (7a,b R = H; 8a,b R = CH3) and with HBF4·Me2O to form [RhOs(C(CH3)CR2)(H)(CO)3(dppm)2][BF4] (9a,b R = H; 10a,b R = CH3). The isopropenoyl complex 6 reacts with HBF4·Me2O to form [RhOs(C(O)C(CH3)CH2)(μ-H)(CO)3(dppm)2] [BF4] (11). The vinyl−hydride compounds 9 and 10 rearrange under a CO atmosphere to form hydride-bridged isomers [RhOs(C(CH3)CR2)(μ-H)(CO)3(dppm)2][BF4] (12a,b R = H; 13a,b R = CH3), which subsequently reductively eliminate the alkene. Protonation of [RhOs(C(CH3)CH2)(CH3)(CO)3(dppm)2][CF3SO3] (7) or [RhOs(C(CH3)CH2)(H)(CO)3(dppm)2][BF4] (9) at low temperature results in formation of the carbene complexes [RhOs(C(CH3)2)(R)(CO)3(dppm)2][X][Y] (14 R = H, X = Y = BF4; 15 R = CH3, X = BF4, Y = CF3SO3) in which the carbene is terminally bound to Rh. Protonation of [RhOs(C(O)C(CH3)CH2)(μ-H)(CO)3(dppm)2][BF4] (11) yields the carbene complex [RhOs(C(OH)C(CH3)CH2)(μ-H)(CO)3(dppm)2][BF4]2 (16). The structures of 3 and 8 have been established by X-ray crystallography. In compound 3, the isopropenyl group is terminally bound to Rh and three carbonyls are bound to Os, with one of them forming a semibridging interaction with Rh. The trimethylvinyl group in compound 8 is also bound terminally to Rh, while three carbonyls and the methyl group are on Os. Two of the carbonyls form semibridging interactions with Rh.