Metal–metal bond fission and the formation of triosmium–alkene complexes via the reaction of [Os3(µ-H){µ3-η2-CF3CC(H)CF3}(CO)10] with nucleophiles; a complete model for the catalytic reduction of an alkyne to an alkene by a cluster
Abstract
The reaction of [Os3H2(CO)10] with hexafluorobut-2-yne gives the complex [Os3(µ-H){µ3-η2-CF3CC(H)CF3}(CO)10] in 88% yield. The reactions of this complex with a variety of nucleophiles have been investigated and have led to the preparation of a series of stable fluoro-alkene complexes [Os3{CF3(H)CC(H)CF3}(CO)10Y](Y = PEt3, CO, Cl–, Br–, I–, or H–). For Y = PEt3 and CO both the cis- and trans-fluoro-alkene complexes are formed in approximately equimolar proportions, but the other nucleophiles give only a single fluoro-alkene complex which, for Y = Br–, is the trans product. The major product of the reaction with Y = PEt3 results from metal–metal bond cleavage to give the complex [Os3H{µ-η2-CF3CC(H)CF3}(CO)10(PEt3)] which contains a bent chain of Os atoms and a terminal Os–H ligand. The reactions of [Os3(µ-H){µ3-η2-CF3CC(H)CF3}(CO)10] with nucleophiles are compared with those of the unsubstituted vinyl complex [Os3(µ-H)(µ-η2-CHCH2)-(CO)10], and a model is proposed for the catalytic reduction of an alkyne to an alkene by a trinuclear osmium cluster.