title: Large, weakly basic bis(carboranyl)phosphines: an experimental and computational study.
abstract: The bis(carboranyl)phosphines [μ-2,2'-PPh-{1-(1'-1',2'-closo-C2B10H10)-1,2-closo-C2B10H10}] (I) and [μ-2,2'-PEt-{1-(1'-1',2'-closo-C2B10H10)-1,2-closo-C2B10H10}] (1) have been prepared and spectroscopically and structurally characterised. Crystallographic and DFT computational studies of 1 suggest that the orientation of the ethyl group, relative to the bis(carborane), is the result of intramolecular dihydrogen bonding. This orientation is such that the magnitudes of the2JPHcoupling constants are approximately equal but of opposite sign, and fast exchange between the methylene protons in solution leads to an observed2JPHclose to zero. The steric properties of I, 1 and their derivatives [μ-2,2'-P(Ph)AuCl-{1-(1'-1',2'-closo-C2B10H10)-1,2-closo-C2B10H10}] (2) and [μ-2,2'-P(Et)AuCl-{1-(1'-1',2'-closo-C2B10H10)-1,2-closo-C2B10H10}] (3) have been assessed by Tolman cone angle and percent buried volume calculations, from which it is concluded that the bis(carboranyl)phosphines I and 1 are comparable to PCy3in their steric demands. The selenides [μ-2,2'-P(Ph)Se-{1-(1'-1',2'-closo-C2B10H10)-1,2-closo-C2B10H10}] (4) and [μ-2,2'-P(Et)Se-{1-(1'-1',2'-closo-C2B10H10)-1,2-closo-C2B10H10}] (5) have also been prepared and characterised. The1JPSecoupling constants for 4 and 5 are the largest reported so far for carboranylphosphine selenides and indicate that I and 1 are very weakly basic.
authors.affiliation: Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, UK EH14 4AS. t.kraemer@hw.ac.uk a.j.welch@hw.ac.uk.
authors.forename: Laura E
authors.initials: LE
authors.lastname: Riley
authors.affiliation: Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, UK EH14 4AS. t.kraemer@hw.ac.uk a.j.welch@hw.ac.uk.
authors.forename: Tobias
authors.identifier: http://orcid.org/0000-0001-5842-9553
authors.initials: T
authors.lastname: Krämer
authors.affiliation: Department of Chemistry, University of Bath, Bath, UK BA2 7AY.
authors.forename: Claire L
authors.initials: CL
authors.lastname: McMullin
authors.affiliation: Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, UK EH14 4AS. t.kraemer@hw.ac.uk a.j.welch@hw.ac.uk.
authors.forename: David
authors.initials: D
authors.lastname: Ellis
authors.affiliation: Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, UK EH14 4AS. t.kraemer@hw.ac.uk a.j.welch@hw.ac.uk.
authors.forename: Georgina M
authors.initials: GM
authors.lastname: Rosair
authors.affiliation: A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Vavilov Str., 119991 Moscow, Russia.
authors.forename: Igor B
authors.initials: IB
authors.lastname: Sivaev
authors.affiliation: Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, UK EH14 4AS. t.kraemer@hw.ac.uk a.j.welch@hw.ac.uk.
authors.forename: Alan J
authors.identifier: http://orcid.org/0000-0003-4236-2475
authors.initials: AJ
authors.lastname: Welch