title: Unusual chalcogen-boron ring compounds: the gas-phase structures of 1,4-B4S2(NMe2)4 and related molecules.
abstract: The structure of 1,4-B4S2(NMe2)4 has been determined by gas-phase electron diffraction and quantum chemical calculations and is compared with the known solid-state structure. While these structures are similar, with a twisted ring geometry [the dihedral angle S-B-B-S from electron diffraction is 75.4(16) degrees], they are strikingly different to the solid-state structure of 1,4-B4O2(OH)4, which is planar. Using quantum chemical calculations, the combinations of O or S in the ring and OH or NMe2 as the substituent have been studied and it has been shown that there are two separate causes of the twisted ring. Since the calculated (and observed) structure of 1,4-B4O2(OH)4 is planar but that of 1,4-B4S2(OH)4 is twisted, it is concluded that the inclusion of sulfur in the ring twists the structure by approximately 40 degrees. By comparing the structures of 1,4-B4S2(OH)4 and 1,4-B4S2(NMe2)4 it has been determined that the twist caused by the NMe2 groups is around 30 degrees.
authors.affiliation: School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh, UK EH9 3JJ.
authors.forename: Derek A
authors.initials: DA
authors.lastname: Wann
authors.forename: Heather E
authors.initials: HE
authors.lastname: Robertson
authors.forename: George
authors.initials: G
authors.lastname: Bramham
authors.forename: Andrew E A
authors.initials: AE
authors.lastname: Bull
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Norman
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Russell
authors.forename: David W H
authors.initials: DW
authors.lastname: Rankin