title: Gas-phase structures of sterically crowded disilanes studied by electron diffraction and quantum chemical methods: 1,1,2,2-tetrakis(trimethylsilyl)disilane and 1,1,2,2-tetrakis(trimethylsilyl)dimethyldisilane.
abstract: The gas-phase structures of the disilanes 1,1,2,2-tetrakis(trimethylsilyl)disilane [(Me3Si)2HSiSiH(SiMe3)2] (1) and 1,1,2,2-tetrakis(trimethylsilyl)dimethyldisilane [(Me3Si)2MeSiSiMe(SiMe3)2] (2) have been determined by density functional theoretical calculations and by gas electron diffraction (GED) employing the SARACEN method. For each of 1 and 2 DFT calculations revealed four C2-symmetric conformers occupying minima on the respective potential-energy surfaces; three conformers were estimated to be present in sufficient quantities to be taken into account when fitting the GED data. For (Me3Si)2RSiSiR(SiMe3)2 [R = H (1), CH3 (2)] the lowest energy conformers were found by GED to have RSiSiR dihedral angles of 87.7(17)° for 1 and -47.0(6)° for 2. For each of 1 and 2 the presence of bulky and flexible trimethylsilyl groups dictates many aspects of the geometric structures in the gas phase, with the molecules often adopting structures that reduce steric strain.
authors.affiliation: Fakultät für Chemie, Anorganische Chemie und Strukturchemie, Universitätsstr. 25, 33615 Bielefeld, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Schwabedissen
authors.forename: Paul D
authors.initials: PD
authors.lastname: Lane
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Masters
authors.forename: Karl
authors.initials: K
authors.lastname: Hassler
authors.forename: Derek A
authors.initials: DA
authors.lastname: Wann