O,O-Monochelate complexes of silicon and germanium halides: The derivatives of l-mandelic N,N-dimethylamide

Reactions of O-trimethylsilyl-l-mandelic N,N-dimethylamide (1) with tetrachlorosilane and tetrachlorogermane lead to O,O-monochelate complexes, [1-(dimethylcarbamoyl)-1-phenylmethoxy]trichlorosilane (2) and [1-(dimethylcarbamoyl)-1-phenylmethoxy]trichlorogermane (3). Pentacoordination of silicon and germanium in these complexes was confirmed by X-ray studies. X-ray data show that the Si and Ge atoms in 2 and 3 have TBP environments where the ether oxygen and two halogens are equatorial while the third halogen and the amide oxygen occupy axial positions. The axial O–M and Cl–M (M = Si, Ge) distances are somewhat longer than those in similar compounds of tetracoordinate silicon and germanium. Intramolecular coordination in compounds 1–3 and relative stabilities of different conformations of their molecules were studied by quantum-chemical calculations.