Showing papers by "Lester Andrews published in 2014"
TL;DR: These silicon-bearing molecules as the lowest-energy isomer of XSiAnF3 represent the first silicon-actinide systems with unusual "triplet" silylenes and Si-An single bonds with multiradical character.
Abstract: We report a series of Si(μ-X)AnF3 (An = Th, U; X = H, F) complexes with silicon–actinide(IV) single bonds and unexpected multiradical features that form rare triplet silylenes. These bridged molecules have been prepared in microscopic scale through reactions of laser-ablated uranium and thorium atoms with silicon fluorides and identified from infrared spectra in argon and neon matrixes and relativistic quantum chemical calculations. Similar neon matrix experiments for the reactions of uranium with CF4 and CHF3 were carried out for comparison. Our density functional theory calculations show that the Si–U single-bonded species Si(μ-X)UF3 (X = H, F) with U(IV) oxidation state and the quasi-agostic bridge ligand of H or F are most stable among all the isomers, whereas the naively anticipated triple-bonded species XSi≡UF3 with U(VI) oxidation state and the double-bonded species XSi•═•UF3 with U(V) oxidation state lie markedly higher in energy. Similar thorium products from reactions with XSiF3 are also found t...
38 citations
TL;DR: Electronic structure, energy, and frequency calculations provide support for the identification of these complexes and the characterization of the N≡U≡N and U≡ N core molecules as terminal uranium nitrides.
Abstract: Reactions of laser-ablated U atoms with N2 molecules upon codeposition in excess argon or neon at 4 K gave intense NUN and weak UN absorptions. Annealing produced progressions of new absorptions for the UN2(N2)1,2,3,4,5 and UN(N2)1,2,3,4,5,6 complexes. The neon-to-argon matrix shift decreases with increasing NN ligation and therefore the number of noble gas atoms left in the primary coordination sphere around the NUN molecule. Small matrix shifts are observed when the secondary coordination layers around the primary UN2(N2)1,2,3,4,5 and UN(N2)1,2,3,4,5,6 complexes are changed from neon-to-argon to nitrogen. Electronic structure, energy, and frequency calculations provide support for the identification of these complexes and the characterization of the N≡U≡N and U≡N core molecules as terminal uranium nitrides. Codeposition of U with pure nitrogen produced the saturated U(NN)7 complex, which UV irradiation converted to the NUN(NN)5 complex with slightly lower frequencies than found in solid argon.
24 citations
TL;DR: Extensive structure and frequency calculations were also done for thorium oxyfluorides and Th2F4,6,8 dimer species to provide the ionization potentials, electron affinities, fluoride affinITIES, Th-F bond dissociation energies, and the energies to bind F2 and F2(-) to a cluster as well as dimerization energies.
Abstract: Laser-ablated Th atoms react with F2 in condensing noble gases to give ThF4 as the major product. Weaker higher frequency infrared absorptions at 567.2, 564.8 (576.1, 573.8) cm–1, 575.1 (582.7) cm–1 and 531.0, (537.4) cm–1 in solid argon (neon) are assigned to the ThF, ThF2 and ThF3 molecules based on annealing and photolysis behavior and agreement with CCSD(T)/aug-cc-pVTZ vibrational frequency calculations. Bands at 528.4 cm–1 and 460 cm–1 with higher fluorine concentrations are assigned to the penta-coordinated species (ThF3)(F2) and ThF5–. These bands shift to 544.2 and 464 cm–1 in solid neon. The ThF5 molecule has the (ThF3)(F2) Cs structure and is essentially the unique [ThF3+][F2–] ion pair based on charge and spin density calculations. Electron capture by (ThF3)(F2) forms the trigonal bipyramidal ThF5– anion in a highly exothermic process. Extensive structure and frequency calculations were also done for thorium oxyfluorides and Th2F4,6,8 dimer species. The calculations provide the ionization poten...
15 citations
TL;DR: Coinage metal atom (Cu, Ag, Au) reactions with SO2 were investigated by matrix isolation infrared absorption spectroscopy and density functional theory electronic structure calculations and there is no evidence of similar interconvertibility for the Cu(η(2)-O2S) and Au( η(1)-SO2) molecules.
Abstract: Coinage metal atom (Cu, Ag, Au) reactions with SO2 were investigated by matrix isolation infrared absorption spectroscopy and density functional theory electronic structure calculations. Both mononuclear complexes M(η1-SO2) (M = Ag, Au) and M(η2-O2S) (M = Ag, Cu) were observed during condensation in solid argon or neon. Interestingly, the silver containing mononuclear complexes are interconvertible; that is, visible light induces the isomerization of Ag(η1-SO2) to Ag(η2-O2S) and vice versa on annealing. However, there is no evidence of similar interconvertibility for the Cu(η2-O2S) and Au(η1-SO2) molecules. These different behaviors are discussed within the bonding considerations for all of the obtained products.
13 citations
TL;DR: In this paper, the CX3-AuCl insertion by Au readily occurs, consistent with previous Au investigations, and subsequent X migration also follows in case the methylidene is reachable.
8 citations