Showing papers by "Lester Andrews published in 2009"
TL;DR: This work has highlighted the importance of knowing the carrier and removal status of materials before they are exposed to each other in the intermediate stages of decomposition.
Abstract: 3.1. Sc Group 6772 3.2. Ti Group 6773 3.3. V Group 6775 3.4. Cr Group 6776 3.5. Mn Group 6777 3.6. Fe Group 6779 3.7. Co Group 6780 3.8. Ni Group 6782 3.9. Cu Group 6782 3.10. Zn Group 6784 3.11. Lanthanide Group 6784 3.12. Actinide Group 6785 3.13. Periodic Trends on Bonding and Reactivity 6785 4. Ionic Mononuclear Transition Metal Oxide Species 6787 4.1. Cations 6788 4.2. Anions 6790 4.2.1. Monoxide Anions 6790 4.2.2. Dioxide Anions 6791 4.2.3. Oxygen-Rich Anions 6792 5. Multinuclear Transition Metal Oxide Clusters 6792 5.1. Sc Group 6793 5.2. Ti Group 6793 5.3. V Group 6793 5.4. Cr Group 6797 5.5. Mn Group 6798 5.6. Fe Group 6798 5.7. Co Group 6798 5.8. Ni Group 6798 5.9. Cu Group 6799 6. Summary 6800 7. Acknowledgments 6800 8. References 6800
330 citations
TL;DR: In this paper, the reaction of laser-ablated Pt atoms with CH4 and C2H6 produces CH3−PtH and CH3CH2−ptH via oxidative C−H insertion.
53 citations
TL;DR: In this paper, the subject molecules were trapped in solid neon and identified by isotopic shifts, comparison with earlier argon and nitrogen matrix results, and DFT frequency calculations, and observed neon-argon matrix shifts follow the molecular polarities.
Abstract: Laser-ablated lithium atoms react with oxygen molecules, as do thermal lithium atoms, to form the LiO2 and LiO2Li ionic molecules. In addition excess energy associated with the laser ablation process fosters the endothermic reaction to give LiO and ultimately Li2O, which form in higher yield from the analogous N2O reactions. The subject molecules were trapped in solid neon and identified by isotopic shifts, comparison with earlier argon and nitrogen matrix results, and DFT frequency calculations. The observed neon–argon matrix shifts follow the molecular polarities. Molecular orbitals from theoretical analysis show the highly ionic nature of the electron distribution in the LiO2 and LiO2Li molecules.
47 citations
TL;DR: This investigation shows that the trihydrides bind dihydrogen more weakly than the diHydrides and that the interaction between the central lanthanide and the H(2) molecules occurs via a 6s electron transfer from the lanthanides to the H2 molecules.
Abstract: The results of a combined spectroscopic and computational study of lanthanide hydrides with the general formula MH(x)(H(2))(y), where M = La, Ce, Pr, Nd, Sm, Eu, and Gd, x = 1-4, and y = 0-6 are reported. To understand the nature of the dihydrogen complexes formed with lanthanide metal hydride molecules, we have first identified the binary MH(x) species formed in the ablation/deposition process and then analyzed the dihydrogen supercomplexes, MH(x)(H(2))(y). Our investigation shows that the trihydrides bind dihydrogen more weakly than the dihydrides and that the interaction between the central lanthanide and the H(2) molecules occurs via a 6s electron transfer from the lanthanide to the H(2) molecules. Evidence is also presented for the SmH and EuH diatomic molecules and the tetrahydride anions in solid hydrogen.
28 citations
TL;DR: The quintet FeH(2) molecule and Fe(2)(H( 2))(3) supercomplex undergo reversible near-ultraviolet photochemical rearrangement in solid neon and hydrogen.
Abstract: Laser-ablated iron, ruthenium, and osmium atoms react with hydrogen in excess argon, neon and pure hydrogen to produce the FeH2 molecule, and the FeH2(H2)3, RuH(H2)4, RuH2(H2)4, and (H2)MH complexes (M = Fe, Ru, Os), as identified through infrared spectra with D2 and HD substitution. DFT frequency calculations support the assignment of absorptions observed experimentally. The FeH2 molecule has a quintet ground state with a quasi-linear structure, and is repulsive to the addition of one more H2 ligand: however, with three more H2 ligands, stable triplet and singlet state FeH2(H2)3 supercomplexes can be formed. The quintet FeH2 molecule and FeH2(H2)3 supercomplex undergo reversible near-ultraviolet photochemical rearrangement in solid neon and hydrogen. The RuH2 molecule has a bent triplet ground state and forms the stable singlet RuH2(H2)4 supercomplex, but only the latter is observed in these experiments. In like fashion RuH has a quartet ground state and the doublet RuH(H2)4 complex is trapped in solid h...
22 citations
TL;DR: The present report supports the general trend that the higher oxidation state complexes become more stable on going down the family group column and compares previous Fe, Ru, and Os results.
Abstract: Reactions of laser-ablated Os atoms with halomethanes have been investigated. Small carbyne complexes are produced in reactions of Os atoms with fluoromethanes and identified through matrix infrared spectra and vibrational frequencies computed by density functional theory. The preference for the carbon-osmium triple bond is traced to the low energy of the Os carbyne products. The C-H and C-X stretching absorptions of the carbyne complexes are observed on the high frequency sides of the corresponding precursor bands, which result from the high s character in the C-H bond and interaction between the C-X and C-Os stretching modes, respectively. The calculated Os complex structures show a large variation with the ligands and electronic states, similar to the analogous Ru complex structures. The present report also compares previous Fe, Ru, and Os results and supports the general trend that the higher oxidation state complexes become more stable on going down the family group column.
21 citations
TL;DR: In this article, the carbon−metal bonds of the CCl2═PdCl2 and CClF═PdrCl2 complexes are calculated using the CASPT2 method.
21 citations
TL;DR: The first actinide triplet state pnictinidene molecules, N÷ThF3, PF3, and AsF3 were identified from infrared spectra and comparison to computed vibrational frequencies as mentioned in this paper.
Abstract: Thorium atoms react with NF3, PF3, and AsF3 to produce the first actinide triplet state pnictinidene molecules, N÷ThF3, P÷ThF3, and As÷ThF3, which are trapped in solid argon and identified from infrared spectra and comparison to computed vibrational frequencies. Density functional theory calculations for these lowest energy triplet state products converge essentially to C3v symmetry structures. Spin density calculations show that the two unpaired electrons are mostly localized in nitrogen 2p, phosphorus 3p, or arsenic 4p orbitals. Although thorium has a small spin density, the weak degenerate πα molecular orbitals are populated entirely from the terminal N, P, or As based on DFT natural bond orbital analysis. This is in contrast with HC÷ThF3, which contains degenerate πα molecular orbitals with 81% C and 19% Th character.
19 citations
TL;DR: This first molecule with a uranium-arsenic bond was identified from matrix infrared spectra through comparison with spectra of the uranium nitride and phosphide species, with spectRA using other metals, and with frequencies computed by density functional and multiconfigurational wave function methods.
Abstract: After reactions of uranium atoms with NF3 and PF3 to form the N UF3 and P UF3 molecules, the analogous reaction with AsF3 produced the novel terminal arsenide As UF3. This first molecule with a uranium-arsenic bond was identified from matrix infrared spectra through comparison with spectra of the uranium nitride and phosphide species, with spectra using other metals, and with frequencies computed by density functional and multiconfigurational wave function methods. The latter calculation describes a weak triple bond to uranium in the As UF3 molecule, which has slightly less bonding and more antibonding character than the weak triple bond in P UF3.
19 citations
TL;DR: Laser-ablated Ni, Pd, and Pt atoms were reacted with sulfur molecules emerging from a microwave discharge in argon during condensation at 7 K to find stable D(2h) structures with B(1u) ground states and intense b( 1u) infrared active modes a few wavenumbers higher than the observed values.
Abstract: Laser-ablated Ni, Pd, and Pt atoms were reacted with sulfur molecules emerging from a microwave discharge in argon during condensation at 7 K Reaction products were identified from matrix infrared spectra, sulfur isotopic shifts, spectra of sulfur isotopic mixtures, and frequencies from density functional calculations The strongest absorptions are observed at 5979, 5961, and 5836 cm−1, respectively, for the group 10 metals These absorptions show large sulfur-34 shifts and 32/34 isotopic frequency ratios (10282, 10285, 10298) that are appropriate for S−S stretching modes Of most importance, mixed 32/34 isotopic 1/4/4/2/4/1 sextets identify this product with two equivalent S2 molecules containing equivalent atomic positions as the bisdisulfur π complexes M(S2)2 Our DFT calculations find stable D2h structures with B1u ground states and intense b1u infrared active modes a few wavenumbers higher than the observed values A minor Ni product at 5058, 5027 cm−1 shows the proper sulfur-34 shift for as
18 citations
01 Jan 2009
TL;DR: In this article, the authors used laser ablation/matrix isolation spectroscopy to compare small high-oxidation-state complexes from group 3-8 transition and actinide metal reactions with halo-H insertion.
Abstract: 20 Numerous high-oxidation-state complexes are an essential 21 part of coordination chemistry, and they help to understand 22 thenatureof carbon-transitionmetal bonding interactions. 23 The chemistry of these complexes includes synthetic processes 24 such as metathesis, catalysis, and C-H insertion. The struc25 tures and photochemical properties of such complexes have 26 been explored by theoretical methods and in particular the 27 oxidative insertion of Pd into the CH3-X bond. 28 Laser ablation/matrix isolation spectroscopy has been used 29 recently toprepare small high-oxidation-state complexes from 30 group 3-8 transition and actinide metal reactions with halo-
TL;DR: Sulfur diatomic molecules were reacted with laser ablated Cu, Ag, and Au atoms in excess argon and condensed at 7 K to identify reaction products for each metal from matrix infrared spectra through sulfur-34 isotopic shifts, spectra of sulfur isotopic mixtures, and frequencies calculated by density functional theory.
Abstract: Sulfur diatomic molecules were reacted with laser ablated Cu, Ag, and Au atoms in excess argon and condensed at 7 K. Several reaction products were identified for each metal from matrix infrared spectra through sulfur-34 isotopic shifts, spectra of sulfur isotopic mixtures, and frequencies calculated by density functional theory. The linear centrosymmetric 63CuS2, 65CuS2, and AuS2 metal disulfide molecules were observed at 508.7, 504.8, and 455.9 cm−1, respectively. The bent CuSS, AgSS, and AuSS isomers were identified from 608.6, 580.7, and 601.1 cm−1 S–S stretching fundamentals, respectively. These group 11 metals also formed cyclic tetrasulfur molecules, MS4, in contrast to group 10 metal atoms, which formed side-bonded disulfur complexes M(S2)2.
TL;DR: Computed pyramidal structures for the SMO2 molecules are very similar to those for the analogous trioxides and this functional group in [MO2S(bdt)]2- complexes and additional weaker absorptions are assigned to the (SO2)(SMO2) adducts, which are stabilized by a four-membered ring.
Abstract: Infrared absorptions of the matrix isolated SMO2 (M = Cr, Mo, W) molecules were observed following laser-ablated metal atom reactions with SO2 during condensation in solid argon and neon. The symme...
TL;DR: The present results indicate that C-H insertion and following H migration from C to M also occur in reaction of the actinides with ethylene, suggesting that the H(2) elimination from the dihydrido cyclic intermediate is relatively slow.
Abstract: Reactions of laser-ablated thorium and uranium atoms with ethylene isotopomers have been carried out and the primary products identified in the matrix IR spectra. The dihydrido cyclic and trihydrido ethynyl products (MH2−C2H2 and MH3CCH) are identified from the matrix spectra of both Th and U, whereas the insertion product absorption is observed only in the U spectra. The present results indicate that C−H insertion and following H migration from C to M also occur in reaction of the actinides with ethylene. Formation of the trihydrido ethynyl products is parallel to the previous results of group 4 metals. Metal hydride (MHx) absorptions are not observed in the infrared spectra, suggesting that the H2 elimination from the dihydrido cyclic intermediate is relatively slow. Density functional theory calculations reproduce the vibrational characteristics of the identified products and the relative stabilities. The cyclic triangular ThH2−C2H2 system with two π electrons is aromatic, which contributes to the uniq...
TL;DR: The two unpaired electrons in nitrogen 2p, phosphorus 3p, or arsenic 4p orbitals are shared in different small amounts with empty metal nd orbitals leading to very weak degenerate pialpha molecular orbitals based on bonding orbital analysis and spin density calculations.
Abstract: Laser-ablated Ti, Zr, and Hf atoms react with NF3, PF3, or AsF3 to produce triplet state terminal pnictinidene N÷MF3, P÷MF3, or As÷MF3 molecules, which are trapped in an argon matrix. Products are identified from infrared spectra and comparison to theoretically predicted vibrations. Density functional theory calculations converge to C3v symmetry structures for these lowest energy products. The two unpaired electrons in nitrogen 2p, phosphorus 3p, or arsenic 4p orbitals are shared in different small amounts with empty metal nd orbitals leading to very weak degenerate πα molecular orbitals based on bonding orbital analysis and spin density calculations. This weak π bonding interaction with early transition metal group 4 nd orbitals is optimum for Zr with phosphorus 3p orbitals.
TL;DR: The CS(3) molecule, which was calculated to have a singlet ground state with C(2v) symmetry, dissociated to form the weakly bound SCS-S complex upon visible light irradiation.
Abstract: Cocondensation of carbon disulfide with high-frequency discharged argon at 4 K produced carbon monosulfide and atomic sulfur, which reacted spontaneously upon annealing to form the carbon trisulfide molecule as identified from the multiplets observed in mixed 12C, 13C and 32S, 34S isotopic spectra. On the basis of isotopic substitution and theoretical frequency calculations, infrared absorptions at 1263.3 and 570.1 cm−1 were assigned to predominantly C═S stretching and bending vibrations of CS3 in solid argon. The CS3 molecule, which was calculated to have a singlet ground state with C2v symmetry, dissociated to form the weakly bound SCS−S complex upon visible light irradiation.
TL;DR: These molecules are identified by comparison of the closely related infrared spectra of the analogous phosphide species and with frequencies calculated by density functional theory and multiconfigurational second order perturbation theory (CASSCF/CASPT2).
Abstract: Laser-ablated group 6 metal atoms react with NF3 and PF3 to form the simple lowest energy N MF3 and P=MX3 products, and this investigation has been extended to AsF3. Mo and W atoms react with AsF3 upon excitation by laser ablation or UV irradiation to form stable trigonal As MF3 terminal arsenides. These molecules are identified by comparison of the closely related infrared spectra of the analogous phosphide species and with frequencies calculated by density functional theory and multiconfigurational second order perturbation theory (CASSCF/CASPT2). Computed CASSCF/CASPT2 triple bond lengths for the As MoF3 and As WF3 molecules are 2.240 angstrom and 2.250 angstrom, respectively. The natural bond orders calculated by CASSCF/CASPT2 decrease from 2.67 to 2.60 for P MoF3 to As MoF3 and from 2.74 to 2.70 for P WF3 to As WF3 as the arsenic valence orbitals are less effective than those of phosphorus in bonding to each metal atom and the larger metal orbital size becomes more compatible with the arsenic valence orbitals. The Cr atom reaction gives the arsinidene AsF=CrF2 product instead of the higher energy As CrF3 molecule as the Cr (VI) state is not supported by the softer pnictides. (Less)
TL;DR: The present results support the conclusion that C-H insertion and following H migration from C to M are in fact general phenomena in reactions of early transition metals (Groups 3-6) and actinides with ethylene.
Abstract: Reactions of laser-ablated Group 3 metal atoms with ethylene isotopomers have been carried out, and the primary products have been identified in the matrix IR spectra. The insertion and dihydrido cyclic products (HM-C(2)H(3) and H(2)M-C(2)H(2)) are identified from the matrix IR spectra of Sc and Y, whereas only the insertion product is observed in the La spectra along with many lanthanium hydride absorptions. The observed metal hydride absorptions suggest that the H(2)-elimination reaction becomes faster upon going down the group column, and the trend is also consistent with the energies of the H(2)-elimination products relative to those of the dihydrido cyclic products. The present results support the conclusion that C-H insertion and following H migration from C to M are in fact general phenomena in reactions of early transition metals (Groups 3-6) and actinides with ethylene. The back-donation of electron-deficient Group 3 metals to the pi-cyclic system of H(2)M-C(2)H(2) is evidently much weaker than that of the previously studied systems.