Si−H Bond Activation by Electrophilic Phosphinidene Complexes

The terminal electrophilic phosphinidene complex [CpFe(CO)<sub>2</sub>{PN-<i>i</i>-Pr<sub>2</sub>}][AlCl<sub>4</sub>] (<b>2</b>), generated via chloride abstraction from [CpFe(CO)<sub>2</sub>{P(Cl)N-<i>i</i>-Pr<sub>2</sub>}] (<b>1</b>), reacts with primary, secondary, and tertiary silanes to form the silyl phosphine complexes [CpFe(CO)<sub>2</sub>{P(H)(SiR<sub>3</sub>)N-<i>i</i>-Pr<sub>2</sub>}][AlCl<sub>4</sub>] (<b>3</b>, SiR<sub>3</sub> = SiPhH<sub>2</sub>; <b>4</b>, SiR<sub>3</sub> = SiPh<sub>2</sub>H; <b>5</b>, SiR<sub>3</sub> = SiEt<sub>3</sub>), 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 <b>3</b>, <b>4</b>, and <b>5</b> are very susceptible to nucleophilic attack, which leads to P−Si bond cleavage and formation of the bridging phosphido complex [{CpFe(CO)}<sub>2</sub>(μ-CO){μ-P(H)N<i>-i-</i>Pr<sub>2</sub>}][AlCl<sub>4</sub>] (<b>6</b>).