Determination of the molecular structures of bis(methylsilyl) ether and bis(dimethylsilyl) ether in the gas phase by electron diffraction

Abstract

The molecular structures of the title compounds, O(SiH₂Me)₂ and O(SiHMe₂)₂, in the gas phase, have been determined by electron diffraction. The monomethylsilyl ether has at least two conformers, the major one (64%) having the methyl groups twisted by 124(4) and 58(8)° away from the positions in which the Si–C bonds are trans to O–Si bonds. Other important parameters (r_a) are: r(Si–C) 186.4(3), r(Si–O) 164.2(3) pm; SiOSi 143.0(6) and OSiC 109.7(5)°. In the dimethylsilyl ether the silyl groups are twisted by 101(8) and 41(4)° away from the symmetrical position in which both Si–H bonds are cis to O–Si bonds, so that the dimethylsilyl groups are staggered with respect to each other. Principal parameters (r_a) are: r(Si–C) 186.4(3), r(Si–O) 163.5(2) pm; SiOSi 148.4(9), OSiC 110.1 (6), and CSiC 107.4(17)°.