Synthesis and Structure of Solvent-Free Hexameric Magnesium Tri(tert-butyl)silylphosphandiide.

Geminal dimetalated amines, phosphanes, and arsanes gained increasing attention due to the expectation of a high reactivity and unique solid-state structures. Power et al.1 reported the molecular structure of a hexameric ether complex of a magnesium imide. The aryl substituent at the nitrogen atom has been a phenyl1 or a naphthyl group.2 Furthermore, the high reactivity allows the synthesis of a wide variety of derivatives.2 Dilithiated phosphanes and arsanes are already published;3 however, they are centered by an oxygen-centered lithium octahedron. The tmeda complex of magnesium bis(phenylphosphanide) has been known since 1987.4 Solvent-free magnesium bis[bis(trimethylsilyl)phosphanide] is trimeric in the solid state, but monomeric and dimeric species are present in the gaseous phase and in solution.5 This equilibrium explains the high reactivity for example toward multiple bonds such as of nitriles and alkynes.6 The ether adducts are monomeric in solution and the solid state.7 Here, we report a solvent-free magnesium phosphandiide.