Tetra(o-phenyldiazo-p-methylphenoxy)silane – A silicon complex with a fourfold capped-tetrahedral [4+4] coordination sphere

2-Hydroxy-5-methylazobenzene (HO–C6H3-p-Me-o-Ndouble bond; length as m-dashN–C6H5, 1) reacts with SiCl4 in the presence of triethylamine to yield the [4+4]-coordinate silicon complex 2 [Si(O–C6H3-p-Me-o-Ndouble bond; length as m-dashN–C6H5)4]. Its molecular structure has been determined by X-ray crystallography, and 2 represents the first structurally characterized Si-complex bearing o-diazophenoxy ligands. 29Si NMR data suggest that the capped tetrahedral coordination sphere of the Si-atom is retained in solution. Even the difluorocompound 3 [F2Si(O–C6H3-p-Me-o-Ndouble bond; length as m-dashN–C6H5)2] still exhibits a tetracoordinate Si-atom, whereas 4 [F2B(O–C6H3-p-Me-o-Ndouble bond; length as m-dashN–C6H5)], the byproduct of the formation of 3 from 2, bears a bidentate chelating o-phenyldiazo-p-methylphenoxy ligand.