The gas-phase structure of octaphenyloctasilsesquioxane Si8O12Ph8 and the crystal structures of Si8O12(p-tolyl)8 and Si8O12(p-ClCH2C6H4)8.
The equilibrium molecular structure of octaphenyloctasilsesquioxane Si(8)O(12)Ph(8) in the gas phase has been determined by electron diffraction. It was found to have D(4) point-group symmetry, with Si-O bond lengths of 1.634(15)-1.645(19) A, and a narrow range [147.5(45)-149.8(24) degrees] of Si-O-Si angles. The structures of Si(8)O(12)(p-tolyl)(8) and Si(8)O(12)(p-ClCH(2)C(6)H(4))(8) have been determined by X-ray diffraction and are found to have Si(8)O(12) cages significantly distorted from the symmetry found for Si(8)O(12)Ph(8) in the gas phase. Thus, Si-O-Si angles range between 144.2(2)-151.64(16) degrees for Si(8)O(12)(p-tolyl)(8), and between 138.8(2)-164.2(2) degrees for Si(8)O(12)(p-ClCH(2)C(6)H(4))(8). These three structures show how much a Si(8)O(12) cage may be distorted away from an ideal structure, free from intermolecular forces, by packing forces in a crystalline lattice.
Zakharov
Alexander V
AV
Department of Physics, Ivanovo State University of Chemistry and Technology, Engelsa 7, Ivanovo, 153000, Russian Federation. a_zakharov@isuct.ru
Masters
Sarah L
SL
Wann
Derek A
DA
Shlykov
Sergei A
SA
Girichev
Georgiy V
GV
Arrowsmith
Sophie
S
Cordes
David B
DB
Lickiss
Paul D
PD
White
Andrew J P
AJ
D018360:Crystallography, X-Ray; D005740:Gases / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D017646:Organosilicon Compounds / Q000138:chemical synthesis / Q000737:chemistry*
D005740:Gases; D017646:Organosilicon Compounds