The molecular structure of p-bis(trimethylsilyl)-benzene from gas phase electron diffraction

Abstract

Nearly regular tetrahedral silicon bond configuration and a considerably distorted ring characterize the p-bis(trimethylsilyl)benzene molecular geometry according to an electron diffraction study. The SiCmethyl bond is longer than the SiCphenyl bond, in agreement with expectation but contrary to an X-ray diffraction determination. The extent of ring deformation is consistent with the electropositive character of the trimethylsilyl substituent and with the structural variations in other para-disubstituted benzene derivatives. The electron diffraction data are consistent with either free rotation around the SiCphenyl bonds or with a rotamer deviating by about 15° from the eclipsed form. The following bond lengths (rg, pm) and bond angles (°) have been determined with parenthesized estimated total errors: (CC)mean 140.8(3), (Cipso)(CorthoCmeta) 1.6(7), (SiC)mean 188.0(4), (SiCmethyl)(SiCphenyl) 3.3(7), (CH)methyl 111.3(3), CCipsoC 115.7(6), and CphenylSiCmethyl 109.2(4).