Insertions of Cyclic and Acyclic Germanium and Tin Heterocarbenoids into Phosphorus–Chlorine Bonds: Syntheses, Structures, and Reactivities

Abstract

Chloro(organo)phosphines are important precursors to diphosphenes and cyclic oligophosphines. Although chloro(organo)phosphines are commonly reduced with bulk metals (e.g., Na, Mg, and Zn), these reactions are much more selective when done homogeneously. To test whether group 14 heterocarbenoid reductions yield isolable insertion products, the mono- and dichloro(organo)phosphines PhPCl2 (A), Ph2PCl (B), tBuPCl2 (C), tBu2PCl (D), and bis(dichlorophosphino)methane (PCl2)2CH2 (E) were treated with the cyclic Me2Si(μ-NtBu)2El (El = Ge (1), Sn (2)) and the acyclic [(Me3Si)2N]2El (El = Ge (3), Sn (4)) heterocarbenoids. The sterically least-encumbered phosphines were more reactive, while the cyclic stannylene 2 was the most reactive and the acyclic germylene 3 was the least reactive. All but one of the products were either mono- or diinsertion compounds, the lone exception being a distannane derived from 2. Semikinetic and structural data suggest that the tetravalent group 14 compounds are formed via an insertion mechanism whose rate depends on the steric bulk of the reaction partners and the nature of the group 14 elements.