Formation and Reactivity of a Transient Cationic Alkyl Phosphinidene Complex

Reaction of the chloroisopropylphosphido complex [Cp*Mo(CO)3{P(Cl)i-Pr}] (1) with AlCl3 generates the transient cationic alkylphosphinidene complex [Cp*Mo(CO)3{P(i-Pr)}][AlCl4] (2). If it is generated in the presence of diphenylacetylene, 2 undergoes a (1 + 2) cycloaddition to form the phosphirene complex [Cp*Mo(CO)3{P(i-Pr)C(Ph)C(Ph)}][AlCl4] (3). Reaction of 2 with PPh3 forms the phosphine-coordinated phosphinidene complex [Cp*Mo(CO)3{P(PPh3)(i-Pr)}][AlCl4] (4). Compound 2 reacts with Ph2SiH2 to insert the phosphinidene phosphorus atom into the Si–H bond, forming the secondary silylphosphine complex [Cp*Mo(CO)3{P(H)(SiHPh2)(i-Pr)}][AlCl4] (5). Similarly, 2 reacts with ferrocene to activate a C–H bond, resulting in the formation of [Cp*Mo(CO)3{P(H)(i-Pr)(C5H4FeC5H5)}][AlCl4] (6).