title: The gas-phase structure of octaphenyloctasilsesquioxane Si8O12Ph8 and the crystal structures of Si8O12(p-tolyl)8 and Si8O12(p-ClCH2C6H4)8.
abstract: 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.
authors.affiliation: Department of Physics, Ivanovo State University of Chemistry and Technology, Engelsa 7, Ivanovo, 153000, Russian Federation. a_zakharov@isuct.ru
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Zakharov
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Masters
authors.forename: Derek A
authors.initials: DA
authors.lastname: Wann
authors.forename: Sergei A
authors.initials: SA
authors.lastname: Shlykov
authors.forename: Georgiy V
authors.initials: GV
authors.lastname: Girichev
authors.forename: Sophie
authors.initials: S
authors.lastname: Arrowsmith
authors.forename: David B
authors.initials: DB
authors.lastname: Cordes
authors.forename: Paul D
authors.initials: PD
authors.lastname: Lickiss
authors.forename: Andrew J P
authors.initials: AJ
authors.lastname: White
mesh_terms: D018360:Crystallography, X-Ray; D005740:Gases / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D017646:Organosilicon Compounds / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D005740:Gases; D017646:Organosilicon Compounds