Showing papers by "Thomas F. Koetzle published in 1991"

The role of transition metal atoms as hydrogen bond acceptors: a neutron diffraction study of [NPrn4]2[PtCl4]·cis-[PtCl2(NH2Me)2] at 20 K

Abstract: Single-crystal neutron diffraction has allowed accurate characterisation of N–H ⋯ Pt and N–H ⋯ Cl interactions linking the two square-planar platinum(II) units which comprise the dianion of [NPrn4]2[PtCl4]·cis-[PtCl2(NH2Me)2]1: Pt ⋯ H 2.262(11)A, N–H ⋯ Pt 167.1(9)°; Cl ⋯ H 2.318(12)A, N–H ⋯ Cl 151.0(12)°. An extensive network of C–H ⋯ Cl hydrogen bonding between the cation and anion species is also revealed, and provides valuable information on what is one of the least well characterised types of hydrogen bond. A weak C–H ⋯ Pt interaction between one cation unit and the anion is also observed. In the light of this and particularly the stronger intra-anion N–H ⋯ Pt interaction, a new type of three-centre four-electon hydrogen bridge, involving a transition-metal atom, is proposed. Further supporting evidence is drawn from a re-evaluation of spectroscopic data for similar interactions previously reported. This type of interaction is contrasted with the more well known three-centre two-electron M–H⇀M, C–H⇀M, Si–H⇀M and B–H⇀M interactions and compared with conventional four-electron hydrogen bonds. Compound 1 is triclinic, space group P(no.2), Z= 2, with a= 10.680(4), b= 11.926(2), c= 15.350(15)A, α= 93.88(4), β= 100.57(5) and γ= 96.58(4)° at 20 K. Final R(F2)= 0.124, S= 1.136 for 5244 F2 values (F02 > 0.0).

Low-temperature neutron diffraction study of bis(tri-p-tolylphosphine)heptahydridorhenium(VII), [ReH7{P(C6H4CH3-4)3}2]: a polyhydride complex with a short H ⋯ H contact that models an intermediate stage in the oxidative addition of dihydrogen at transition metal centres

Abstract: Low-temperature neutron diffraction shows that the title compound has an H ⋯ H separation [1.357(7)A] intermediate in length between the accepted ranges for ‘classical’ non-bonded dihydrides and more recently reported dihydrogen ligands, thus providing a model for the intermediate stages of oxidative addition of dihydrogen at transition metal centres.

X-ray diffraction study of pentacarbonyl(mu -hydrido)(nonacarbonyldimanganese)rhenium, hmn2re(co)14

Abstract: The preparation of the polynuclear transition-metal complex HMn{sub 2}Re(CO){sub 14} containing a hydride bridging two different metals was brought about by the reaction of a metal hydride 'donor' with a coordinatively unsaturated 'acceptor' obtained from a metal complex containing a labile ligand. The crystal structure of the L-shaped HMn{sub 2}Re(CO){sub 14} is reported herein. 3 tables, 1 figure, 18 ref.