Hydride−Carbyne to Carbene Transformation in a Cyclopentadienyl−Osmium Complex: An Alternative to the Single Hydride−CαMigration

Abstract

Complexes OsH(η5-C5H5)(C⋮CPh)(EPh3)(PiPr3) [E = Si (1), Ge (2)] react with 2.0 equiv of HBF4·OEt2 to give [OsH(η5-C5H5)(⋮C−CH2Ph)(PiPr3)]BF4 (3). Treatment of 3 with KOH affords OsH(η5-C5H5)(CCHPh)(PiPr3) (5) in equilibrium with the metalated species (7) (ΔH° = −3.6 ± 0.2 kcal mol-1 and ΔS° = −10.8 ± 1.9 cal K-1 mol -1 for the formation of 7). The addition of P(OMe)3 to the solution of the isomeric mixture leads to Os(η5-C5H5){(E)-CHCHPh}{P(OMe)3}(PiPr3) (8), which reacts with HBF4·OEt2 to give [Os(η5-C5H5)(CHCH2Ph){P(OMe)3}(PiPr3)]BF4 (4).