title: Molecular structure of Hf(BH4)4 investigated by quantum mechanical calculations and gas-phase electron diffraction.
abstract: The structure of the gaseous hafnium tetrakis(tetrahydroborate) molecule, Hf(BH4)4, has been investigated by detailed quantum mechanical calculations and by analysis of its gas electron-diffraction (GED) pattern. The ground-state geometry possesses T symmetry with all of the triply-bridged BH4 groups twisted equally about the Hf...B-H axes. Salient structural parameters (ra distances, r angles) deduced from the GED pattern by the SARACEN method were: r(Hf...B) 231.4(2), r(Hf-Hb) 221.5(7), r(B-Hb) 127.6(5), r(B-Ht) 121(1) pm, Hf...B-Hb 69.4(3), Hb-B-Hb 108.4(4), Hb-B-Ht 110.6(3), B...Hf...B-Hb 166(1) degrees. A notable feature is the large magnitude of the Hf...B and Hf-Hb anharmonicity parameters, attributed to the fluxional hydrogen atom exchange process. The properties are compared with those of related tetrahydroborates..
authors.affiliation: School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh, UKEH9 3JJ.
authors.forename: Konstantin B
authors.initials: KB
authors.lastname: Borisenko
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Downs
authors.forename: Heather E
authors.initials: HE
authors.lastname: Robertson
authors.forename: David W H
authors.initials: DW
authors.lastname: Rankin
authors.forename: Christina Y
authors.initials: CY
authors.lastname: Tang