Isopropyldisilylamine and disilyl-t-butylamine: preparation, spectroscopic properties, and molecular structure in the gas phase, determined by electron diffraction

Abstract

The compounds NPrⁱ(SiH₃)₂ and NBu^t(SiH₃)₂have been prepared by the gas-phase reactions of SiH₃Cl and the appropriate primary amines, and characterised by i.r. and n.m.r. spectroscopy. The molecular structures of both compounds in the gas phase have been determined by electron diffraction. In each case the bonds to nitrogen are coplanar. The most important parameters (r_a) for NPrⁱ(SiH₃)₂ are Si–N 172.7(1), C–N 148.7(5), and C–C155.0(6) pm, and angles SiNSi 121.6(2), NCC 111.4(9), and CCC 107.6(15)°. The isopropyl group is twisted so that the unique C–H bond almost eclipses one of the Si–N bonds, and the asymmetry thereby introduced leads to non-equivalence of the SiNC angles, which are 121.9(5)° on the more crowded side and 116.5(5)° on the other side of the molecule. Principal parameters for NBu^t(SiH₃)₂ are Si–N 173.5(1), C–N 147.9(8), and C–C 154.6(4) pm, SiNSi 118.4(4) and NCC 109.2(6)°. In this case the butyl group has greatly compressed the SiNSi angle.