Si−H Bond Activation by Electrophilic Phosphinidene Complexes

The terminal electrophilic phosphinidene complex [CpFe(CO)₂{PN-i-Pr₂}][AlCl₄] (2), generated via chloride abstraction from [CpFe(CO)₂{P(Cl)N-i-Pr₂}] (1), reacts with primary, secondary, and tertiary silanes to form the silyl phosphine complexes [CpFe(CO)₂{P(H)(SiR₃)N-i-Pr₂}][AlCl₄] (3, SiR₃ = SiPhH₂; 4, SiR₃ = SiPh₂H; 5, SiR₃ = SiEt₃), in which the phosphinidene has inserted into the Si−H bond. A computational study shows that the insertion is concerted and has a triangular transition state. The silyl phosphine complexes 3, 4, and 5 are very susceptible to nucleophilic attack, which leads to P−Si bond cleavage and formation of the bridging phosphido complex [{CpFe(CO)}₂(μ-CO){μ-P(H)N-i-Pr₂}][AlCl₄] (6).