Tim M. Greene

Photo-reversible isomerisation of trans- to cis-[W(CO)4(η2-alkene)2] complexes in low-temperature matrices

Abstract Reversible isomerisation of trans- to cis-[W(CO)4(η2-alkene)2] complexes has been induced in argon matrices at low temperatures under the action of selective irradiation. UV photolysis (λ ≈ 313 nm) of trans-[W(CO)4(η2-alkene)2] (alkene = cyclopentene or 1-pentene) in an argon matrix at 16 K results in formation of the cis isomer as the primary photoprocess. The isomerisation is reversed under the action of visible light (λ ≈ 445 nm). Species such as [W(CO)4(alkene)(Ar)] are also formed in small concentrations. Experiments involving annealing, selective photolysis and the use of CO- or alkene-doped matrices have been performed to investigate the mechanism of the photo-isomerisation process. These studies suggest a dissociative mechanism via expulsion of the alkene ligand.

The molecular structure of chloromethylphosphine, CClH2PH2, as determined by gas-phase electron diffraction and ab initio computations

Abstract The gas-phase structure of chloromethylphosphine, CClH 2 PH 2 , has been determined by electron diffraction employing constraints derived from ab initio computations at the CISD(fc) 6−31+ G ∗∗ level. At 293K, the compound exists in two conformations, anti and gauche (phosphorus lone pair relative to the CCl bond); the mole fraction of the gauche conformer is 0.22(5). Important experimental structural parameters ( r g /pm, ∠ α /deg) for the anti and gauche conformers, respectively, are (values without e.s.d.s indicate that the difference between the parameters for the two conformers was fixed at the theoretical value): r (CP) = 186.3(3), 187.4; r (CCl) = 179.1(5), 179.0; r (PH) = 141.5(4), 142.9; PCCl = 115.7(1), 107.8(5) [ CISD(fc) 6−31+ G ∗∗ 116.5, 110.6 ]. The large difference between the PCCl angles in the conformers can be rationalised on the basis of overlaps between non-bonding and antibonding molecular orbitals.

Amidoalane, amidogallane and amidoindane, H2MNH2 (M = Al, Ga or In): a matrix study of three prototypal molecules with the potential for M–N multiple bonding

Photolysis of Al, Ga or In atoms (M) isolated in NH3-doped Ar matrices gives first the divalent amido derivative HMNH2 (λ = 436 nm) and then the univalent and trivalent amido derivatives MNH2 and H2MNH2 (λ = 200–800 nm); the measured and calculated properties of H2MNH2 are outlined.

Photo-induced tautomerisation ofmethyltrioxorhenium(VII): the intermediate in olefinmetathesis?

Matrix-isolated [CH3ReO3] tautomerises to [H2CRe(O)2OH] under the influence of UV light; the carbene has been characterised in its normal and 2H- and 13C-enriched isotopic forms by its IR spectrum with results well replicated by quantum chemical calculations.