Metal Control of the Reaction Site in Reactions of [{(η 5-C5H3)2(SiMe2)2}M2(CO)4(μ-H)]+ (M = Fe, Ru, Os) with Nucleophilic Amines

Complexes [{(η 5-C5H3)2(SiMe2)2}M2(CO)4(μ-H)]+BF4 - (M = Fe, Ru, Os; 1a−cH+BF4 -), which feature a protonated metal−metal bond, were synthesized. While the Fe and Os complexes react with nucleophilic amines (ammonia, MeNH2, Me2NH, Et3N, morpholine) to give the deprotonated complexes {(η 5-C5H3)2(SiMe2)2}M2(CO)4, the Ru complex reacts with amines by undergoing attack at a CO ligand. These differences in reactivity can be understood by considering the CO ligands in the Ru complex to be more electrophilic than those in the analogous Fe and Os complexes, as indicated by the ν(CO) values. Molecular structures of 1a−cH+BF4 -, as determined by X-ray diffraction studies, and [{(η 5-C5H3)2(SiMe2)2}Ru2(CO)4(μ-H)]+OTf- (1bD+TfO-), as determined by a neutron diffraction study, show that the bridging hydride ligand is sterically concealed and therefore slow to undergo deprotonation upon reaction with bases.