Determination by electron diffraction of the molecular structure of bromotris(methoxydimethylsilyl)methane in the gas phase

Abstract

The molecular structure of bromotris(methoxydimethylsilyl)methane in the gas phase has been determined by electron diffraction. The molecules have C₃ symmetry, adopting a conformation in which the Si–O bonds are gauche with respect to the C–Br bond, and the O–C bonds are anti with respect to the inner Si–C bonds. This arrangement avoids conflict between the sterically demanding methoxydimethylsilyl groups and minimises interactions between lone pairs of electrons on the methoxy groups, which are widely separated from each other, on the periphery of the molecule. The Br–C–Si–O and C_inner–Si–O–C dihedral angles are 38.5(5) and 169.9(28)° respectively. Other principal parameters (r_a) are r(C–Br) 196.0(21) pm, r(Si–C_inner) 190.6(10) pm, r(Si–C_outer) 188.3(4) pm, r(Si–O) 167.4(4) pm, r(O–C) 141.9(5) pm, and angles Br–C–Si 106.2(6)°, C_inner–Si–C_outer 114.7(5)°, C_inner–Si–O 107.3(9)°, C_outer–Si–O 106.4(8)° and Si–O–C 121.4(13)°.