Reversible Decarbonylation of a Metal Phosphaketene.

The synthesis of a metalated phosphastannene by reaction of the known cobalt(I) phosphaketene complex Co(DippPDI)(PCO) (DippPDI = 1,1'-(pyridine-2,6-diyl)bis(N-(2,6-diisopropylphenyl)ethan-1-imine) with Sn[CH(SiMe3)2]2 is described. The resulting compound, Co(DippPDI)(CO){P═Sn[CH(SiMe3)2]2}, contains a localized P═Sn double bond, yet reacts like a phosphaketene transfer reagent, suggesting that, in solution, Co(DippPDI)(CO){P═Sn[CH(SiMe3)2]2} appears to exist in equilibrium with Co(DippPDI)(PCO) and Sn[CH(SiMe3)2]2. This is facilitated by the fact that, on decarbonylation with Sn[CH(SiMe3)2]2, the carbon monoxide extruded from the phosphaketene precursor Co(DippPDI)(PCO) remains in the coordination sphere of cobalt. The novel phosphaketene compounds (IDipp)Au(PCO) (IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) and (DippNacNac)Zn(PCO) (DippNacnac = HC[C(Me)N(Dipp)]2; Dipp = 2,6-iPr2C6H3) can be synthesized by reaction of Co(DippPDI)(CO){P═Sn[CH(SiMe3)2]2} with Au(IDipp)Cl or (DippNacNac)ZnCl·LiCl(OEt2)2, respectively. In the case of the former, the released stannylene Sn[CH(SiMe3)2]2 ultimately inserts into the Au─PCO bond, affording the tin(IV) complex (IDipp)AuSn(PCO)[CH(SiMe3)2]2.