Determination of the molecular structures and conformations of methylbis(methylsilyl)amine and bis(dimethylsilyl)methylamine in the gas phase by electron diffraction

The molecular structures of methylbis(methylsilyl)amine, NMe(SiH2Me)2, and bis(dimethylsilyl)-methylamine, NMe(SiHMe2)2, in the gas phase have been determined by electron diffraction. In both molecules the NCSi2 skeleton is planar. Principal parameters (ra) for NMe(SiH2Me)2 are: r(Si–N) 171.8(3), r(Si–C) 186.4(5), r(C–N) 149.2(12) pm; Si–N–Si 125.6(10) and N–Si–C 113.5(18)° and for NMe(SiHMe2)2 are: r(Si–N) 172.7(4), r(Si–C) 187.2(3), r(C–N) 148.3(7) pm; Si–N–Si 126.1 (5), N–Si–C 110.8(5), and C–Si–C 115.5(10)°. In NMe(SiH2Me)2 the SiH2Me groups are twisted about 60 and 120° from the positions in which the Si–C bonds eclipse the N–C bond, so that the methyl groups are mutually trans when viewed along the Si⋯Si axis. In NMe-(SiHMe2)2 the SiHMe2 groups are twisted 20 and 120° from positions in which the Si–H bonds are trans to the N–C bond.