The first structurally characterised oligosilylmagnesium compound

The crystalline magnesium compounds Mg[Si(SiMe3)3]2(thf)2 (1) and MgBr[Si(SiMe3)3](thf)2 (2) are obtained in high yield from MgBr2 and the Li or K sisyl in appropriate stoichiometry in Et2O or thf; NMR spectra and X-ray crystal data for 1 and 2 confirm their structures; for 1: MgSi 2.682(2) Å, SiMgSi′ 131.19(15)°.