title: Structural chemistry of arachno-nonaboranes.
abstract: Single-crystal conventional-tube and synchrotron X-ray diffraction studies of the anions in [NMe(4)][arachno-B(9)H(12)-4,8-Br(2)] 1 and K[arachno-B(9)H(14)] 2, and also of the series of adducts [arachno-B(9)H(13)-4-L], where L is P(CCH)(3) (3), NHEt(2) (4), NC(5)H(5) (5), or NH(2)CH(2)Ph (6), are reported. Structural studies of 1-6, determined at low temperatures, located all atoms, including bridging and endo-terminal hydrogen atoms. The basic boron-hydride clusters of these, and of all the other known species with the arachno nine-vertex i-nonanborane geometry reported in the literature, are isostructural and feature three bridging and two endo-terminal hydrogen atoms on the open face. This arrangement is different from that previously reported for Cs[arachno-B(9)H(14)] 7 and for [arachno-B(9)H(13)-4-(NCMe)] 9. However, a new X-ray diffraction data set and refinement experimentally confirm the [3 x mu-H, 2 x endo] arrangement for 9 also. The experimental results for 1-6 support recently reported calculations for [B(9)H(14)](-), which predict both the structures and the (11)B NMR chemical shifts. These conclusions are also supported by calculations for 3, 4, and 9 and also for the [arachno-B(9)H(13)-4-(NCS)](-) anion in [NMe(4)][B(9)H(13)(NCS)] 8.
authors.affiliation: School of Chemistry, University of Leeds, Leeds, UK LS2 9JT.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Bould
authors.forename: Robert
authors.initials: R
authors.lastname: Greatrex
authors.forename: John D
authors.initials: JD
authors.lastname: Kennedy
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Ormsby
authors.forename: Michael G S
authors.initials: MG
authors.lastname: Londesborough
authors.forename: Karen L F
authors.initials: KL
authors.lastname: Callaghan
authors.forename: Mark
authors.initials: M
authors.lastname: Thornton-Pett
authors.forename: Trevor R
authors.initials: TR
authors.lastname: Spalding
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Teat
authors.forename: William
authors.initials: W
authors.lastname: Clegg
authors.forename: Hong
authors.initials: H
authors.lastname: Fang
authors.forename: Nigam P
authors.initials: NP
authors.lastname: Rath
authors.forename: Lawrence
authors.initials: L
authors.lastname: Barton