Molecular structures of silacyclohexane and silacyclopentane as determined by gas phase electron diffraction

Molecular structure of 1,1-dimethylsilacyclopentene-3,4-oxide from gas-phase electron diffraction

“…The geometries of cyclopentene oxide, silacyclopentane, silacyclopent-3-ene, and 1,1-dimethylsilacyclopentene-3,4-0xide are compared in Table V. "Silacyclopentane [14]. b 1,1-Dimethylsilacyclopentene-3,4-oxide, this work.…”

“…The difference between C--C bonds (AI(C--C) = 0. [14], and it is the same as that in 1-silacyclopent-3-ene (rg = 1.903(3) ~,) [16]. These Si--C bond lengths are in agreement with the finding of a thorough study of Si--C bond length variations in a series of free molecules, which pointed to the role of the hybridization state of the carbon atom involved, as well as of steric effects in crowded and cyclic molecules and of the differences in ligand electronegativities [17].…”

“…The C2--C3--C4 bond angle of the five-membered ring portion of the title molecule is markedly different from that of silacyclopentane [14] and is comparable to that of silacyclopentene [ 16].…”

“…Most of the differences and the starting values were taken from previous electron diffraction analyses and spectroscopic calculations on silacyclopentane [14] and cyclopentene oxide [4a,c], respectively.…”

The rotational spectrum of silacyclohexane

“…The microwave (MW) spectrum is available for the asymmetrically substituted deuterated species [3]. Studies of the structure and conformations of several ring-mono-substituted hetero-derivatives have been performed by ED and/or MW spectroscopy: tetrahydropiran [4,5], tetrahydrothian [6], piperidine [7], silacyclohexane [8], and germacyclohexane [9]. All of them have been observed predominantly in the chair form.…”