Synthesis and Reactivity of the Osmate(0) Complexes M[Os(CO)₂(η-C₅R₅)] (M = Li, Na; R = H, Me): Versatile Synthons for Synthesis of Organoosmium Complexes

The anionic osmium complex Li[Os(CO₂)(η-C₅Me₅)] (2a) was synthesized by the reaction of the hydrido complex (η-C₅Me₅Os(CO₂)H (3a) with n-BuLi. The unsubstituted cyclopentadienyl derivatives M[Os(CO)₂(η-C₅H₅)] (2b,M = Li; 2c, M = Na) were also prepared by an identical method or by two-electron reduction of (η-C₅H₅Os(CO)₂I with sodium naphthalenide. Reactions of 2a with various electrophiles (CH₃I, D₂O, Me₃SiCl, ^tBuSiH₂Cl, Me₃SiSiMe₂Cl, Me₂SiCl₂, and Me₃GeCl) afforded the nucleophilic substitution products (η-C₅Me₅)Os(CO)₂R (R = CH₃, D, SiMe₃, SiH₂^tBu, SiMe₂SiMe₃, SiClMe₂, and GeMe₃) in good to excellent yields. Analogous products were also obtained by the reaction of 2b with ^tBuSiH₂Cl and by the reactions of 2c with ^tBuSiH₂Cl and ^tBuSiHCl₂.