@article {2392, title = {Theoretical study of the electronic spectra of s-triazine vapour}, journal = {Canadian Journal of Chemistry-Revue Canadienne De Chimie}, volume = {87}, number = {8}, year = {2009}, note = {ISI Document Delivery No.: 493VQTimes Cited: 3Cited Reference Count: 37Chong, Delano P.}, month = {Aug}, pages = {1148-1153}, type = {Article}, abstract = {The ionization and excitation spectra of valence and core electrons of s-triazine in the gas phase are studied with ab initio, density functional, and semi-empirical methods. The results are compared with available experimental data and previous calculations. New estimates are proposed for the ionization energies of both valence and core electrons. The calculated excitation energies are consistent with experiment.}, keywords = {AB-INITIO, AZINES, core-electron binding energies, DENSITY-FUNCTIONAL THEORY, DFT, electron spectra, ESCA, EXCHANGE-CORRELATION POTENTIALS, EXCITATION-ENERGIES, excitations, HYDROGEN, IONIZATION-POTENTIALS, ionizations, MOLECULAR CALCULATIONS, N-2, photoelectron spectra, s-triazine, SPECTROSCOPY, UV absorption}, isbn = {0008-4042}, url = {://000269766800008}, author = {Chong, D. P.} } @article {1579, title = {N-N splitting of a functionalized mu-eta(1):eta(2) coordinated N-2 ligand leading to a mu-nitrido mu-imido core: mechanistic insight from DFT}, journal = {Dalton Transactions}, number = {9}, year = {2006}, note = {ISI Document Delivery No.: 021NKTimes Cited: 5Cited Reference Count: 35}, pages = {1137-1140}, type = {Article}, abstract = {Silylation of a dinuclear tantalum complex containing a side- on end-on coordinated dinitrogen ligand initiates a sequence of reactions ultimately leading to a bis(mu-imido) structure. DFT is employed to determine the energetics of the entire reaction cascade. Particular emphasis is put on the unprecedented N-N cleavage reaction of the functionalized, mu-eta(1):eta(2) coordinated dinitrogen ligand. A mechanism for this reaction is derived theoretically and the corresponding transition state is determined.}, keywords = {ammonia, ATOMS, BOND-CLEAVAGE, END-ON, MOLECULAR CALCULATIONS, POTENTIALS, REACTIVITY, SIDE-ON, SPECTROSCOPIC PROPERTIES, TANTALUM DINITROGEN COMPLEX}, isbn = {1477-9226}, url = {://000235989700003}, author = {Studt, F. and MacKay, B. A. and Fryzuk,Michael D. and Tuczek, F.} } @article {1492, title = {XeCu covalent bonding in XeCuF and XeCuCl, characterized by Fourier transform microwave spectroscopy supported by quantum chemical calculations}, journal = {Journal of the American Chemical Society}, volume = {128}, number = {23}, year = {2006}, note = {ISI Document Delivery No.: 050PDTimes Cited: 28Cited Reference Count: 64}, month = {Jun}, pages = {7613-7621}, type = {Article}, abstract = {XeCu covalent bonding has been found in the complexes XeCuF and XeCuCl. The molecules were characterized by Fourier transform microwave spectroscopy, supported by MP2 ab initio calculations. The complexes were prepared by laser ablation of Cu in the presence of Xe and SF6 or Cl-2 and stabilized in supersonic jets of Ar. The rotational constants and centrifugal distortion constants show the XeCu bonds to be short and rigid. The Xe-131, Cu, and Cl nuclear quadrupole coupling constants indicate major redistributions of the electron densities of Xe and CuF or CuCl on complex formation which cannot be accounted for by simple electrostatic effects. The MP2 calculations corroborate the XeCu bond lengths and predict XeCu dissociation energies similar to 50- 60 kJ mol(-1). The latter cannot be accounted for in terms of induction energies. The MP2 calculations also predict valence molecular orbitals with significant shared electron density between Xe and Cu and negative local energy densities at the XeCu bond critical points. All evidence is consistent with XeCu covalent bonding.}, keywords = {AB-INITIO, DIPOLE MOMENTS, ELECTRIC-RESONANCE METHOD, GAUSSIAN-BASIS SETS, HYPERFINE CONSTANTS, KR, LASER-ABLATION, MOLECULAR CALCULATIONS, ROTATIONAL SPECTRA, VANDERWAALS COMPLEX}, isbn = {0002-7863}, url = {://000238099500051}, author = {Michaud, J. M. and Gerry, M. C. L.} } @article {1270, title = {Lewis adducts of the side-on end-on dinitrogen-bridged complex [{(NPN)Ta}(2)(mu-H)(2)(mu-eta(1):eta(2)-N-2)] with AlMe3, GaMe3, and B(C6F5)(3): Synthesis, structure, and spectroscopic properties}, journal = {Chemistry-a European Journal}, volume = {11}, number = {2}, year = {2005}, note = {ISI Document Delivery No.: 887VLTimes Cited: 12Cited Reference Count: 49}, month = {Jan}, pages = {604-618}, type = {Article}, abstract = {{Reaction of the side-on end-on dinitrogen complex [{(NPN)Ta}(2)(mu- H)(2)(mu-eta(1):eta(2)-N-2)] (1; in which NPN= (PhNSiMe2CH2)(2)PPh), with the Lewis acids XR3 results in the adducts [{(NPN)Ta}(2)(mu-H)(2)(mu-eta(1):eta(2)-NNXR3)]}, keywords = {CHEMISTRY, CLEAVAGE, COORDINATED, density functional calculations, DINITROGEN, DINITROGEN COMPLEXES, DINUCLEAR TANTALUM COMPLEX, EFFECTIVE CORE POTENTIALS, FIXATION, MOLECULAR CALCULATIONS, MOLYBDENUM CENTER, N-2 LIGAND, NITROGEN, Raman spectroscopy, REACTIVITY, tantalum, TRIS(PENTAFLUOROPHENYL)BORANE}, isbn = {0947-6539}, url = {://000226333500014}, author = {Studt, F. and MacKay, B. A. and Johnson, S. A. and Patrick, B. O. and Fryzuk,Michael D. and Tuczek, F.} } @article {817, title = {Even-tempered slater-type orbitals revisited: From hydrogen to krypton}, journal = {Journal of Computational Chemistry}, volume = {25}, number = {8}, year = {2004}, note = {ISI Document Delivery No.: 814YZTimes Cited: 42Cited Reference Count: 11}, month = {Jun}, pages = {1030-1036}, type = {Article}, abstract = {Even-tempered Slater-type orbital basis sets were developed in 1973, based on total atomic energy optimization. Here, we revisit ET STOs and propose new sets based on past experience and recent computational studies. From preliminary atomic and molecular tests, these sets are shown to be very well balanced and to perform, at lower cost, almost as well as a very large (close to complete) basis set. (C) 2004 Wiley Periodicals, Inc.}, keywords = {basis sets, BASIS-SETS, even-tempered, MOLECULAR CALCULATIONS, Slater-type orbitals, STO}, isbn = {0192-8651}, url = {://000221011300003}, author = {Chong, D. P. and Van Lenthe, E. and Van Gisbergen, S. and Baerends, E. J.} } @article {943, title = {Rotational spectra, structures, hyperfine constants, and the nature of the bonding of KrCuF and KrCuCl}, journal = {Inorganic Chemistry}, volume = {43}, number = {13}, year = {2004}, note = {ISI Document Delivery No.: 831AQTimes Cited: 32Cited Reference Count: 76}, month = {Jun}, pages = {3871-3881}, type = {Article}, abstract = {Rotational spectra of KrCuF and KrCuCl have been measured in the frequency range 8-18 GHz, using a pulsed jet cavity Fourier transform microwave spectrometer. The molecules were prepared by ablating Cu metal with a pulsed Nd:YAG laser (1064 nm) and allowing the plasma to react with appropriate precursors (Kr plus SF6 or Cl-2) contained in the backing gas of the jet (Ar or Kr). Rotational constants, internuclear distances, vibration frequencies, and 83 Kr, Cu, and Cl nuclear quadrupole coupling constants have all been evaluated, The Kr-Cu bonds are short and the complexes are rigid. The Kr-83 coupling constant of KrCuF is large (128.8 MHz). The Cu nuclear quadrupole coupling constants differ radically from those of uncomplexed CuF and CuCl molecules. The results are supported by those of ab initio calculations, which have also yielded Mulliken populations, MOLDEN plots of valence molecular orbitals and Laplace concentrations, and electron localization functions. The results are consistent with those reported earlier for other noble gas-noble metal halide complexes. The results have been used to assess the nature of the bonding in the complexes and have produced good evidence for weak noble gas-noble metal chemical bonding.}, keywords = {CHEMICAL-BONDS, DIPOLE MOMENTS, ELECTRIC-RESONANCE METHOD, FOURIER-TRANSFORM SPECTROSCOPY, GAUSSIAN-BASIS, MICROWAVE-SPECTRA, MOLECULAR CALCULATIONS, NUCLEAR-QUADRUPOLE MOMENTS, SETS, SUBMILLIMETER-WAVE SPECTRA, VANDERWAALS COMPLEX}, isbn = {0020-1669}, url = {://000222165700023}, author = {Michaud, J. M. and Cooke, S. A. and Gerry, M. C. L.} } @article {994, title = {Spectroscopic properties and quantum chemistry-based normal coordinate analysis (QCB-NCA) of a dinuclear tantalum complex exhibiting the novel side-on end-on bridging geometry of N-2: Correlations to electronic structure and reactivity}, journal = {Journal of the American Chemical Society}, volume = {126}, number = {1}, year = {2004}, note = {ISI Document Delivery No.: 761ZMTimes Cited: 16Cited Reference Count: 40}, month = {Jan}, pages = {280-290}, type = {Article}, abstract = {The vibrational properties and the electronic structure of the side-on end-on N-2-bridged Ta complex ([NPN]Ta(mu-H))(2)(mu-eta(1):eta(2)-N-2) (1) (where [NPN] = (PhNSiMe2CH2)(2)PPh) are analyzed. Vibrational characterization of the Ta-2(mu-N-2)(mu-H)(2) core is based on resonance Raman and infrared spectroscopies evaluated with a novel quantum chemistry-based normal coordinate analysis (QCB-NCA). The N-N stretching frequency is found at 1165 cm(-1) exhibiting a N-15(2) isotope shift of -37 cm(-1). Four other modes of the Ta2N2H2 core are observed between 430 and 660 cm(-1). Two vibrations of the bridging hydrido ligands are also identified in the spectra. On the basis of experimental frequencies and the QCB-NCA procedure, the N-N force constant is determined to be 2.430 mdyn -Angstrom(-1). The Ta-N force constants are calculated to be 2.517 mdyn Angstrom(-1) for the Ta-eta(1)-N-2 bond and 1.291 and 0.917 mdyn Angstrom(-1) for the Ta-eta(2)-N-2 bonds, respectively. DFT calculations on 1 suggest that the bridging dinitrogen ligand carries a charge of -1.1, which is equally distributed over the two nitrogen atoms. However, orbital analysis reveals that the terminal nitrogen makes lower contributions to the pi orbitals and much higher contributions to the pi* orbitals of the N-2 ligand than the bridging nitrogen. This suggests that reactions of the dinitrogen ligand with electrophiles should preferentially occur at the terminal N atom, in agreement with experimental results.}, keywords = {ACTIVATION, CLEAVAGE, DINITROGEN FIXATION, EFFECTIVE CORE POTENTIALS, FUNCTIONALIZATION, LIGAND, MOLECULAR CALCULATIONS, MOLYBDENUM, NITROGEN-FIXATION, REDUCTION PATHWAY}, isbn = {0002-7863}, url = {://000187945400064}, author = {Studt, F. and MacKay, B. A. and Fryzuk,Michael D. and Tuczek, F.} } @article {750, title = {DFT calculation of core-electron binding energies}, journal = {Journal of Electron Spectroscopy and Related Phenomena}, volume = {133}, number = {1-3}, year = {2003}, note = {ISI Document Delivery No.: 754ZWTimes Cited: 40Cited Reference Count: 70}, month = {Nov}, pages = {69-76}, type = {Article}, abstract = {A total of 59 core-electron binding energies (CEBEs) were studied with the Amsterdam Density Functional Program (ADF) program and compared with the observed values. The results indicate that a polarized triple-zeta basis set of Slater-type orbitals is adequate for routine assessment of the performance of each method of computation. With such a basis set, seven density functionals were tested. In addition, the performance of 21 energy density functionals were computed from the density calculated with the statistical average of orbital potentials (SAOP). Among all the choices tested, the best density functional for core-electron binding energies of C to F turns out to be the combination of Perdew-Wang (1986) functional for exchange and the Perdew-Wang (1991) functional for correlation, confirming earlier studies based on contracted Gaussian-type orbitals. For this best functional, five Slater-type orbital basis sets were examined, ranging from polarized double-zeta quality to the largest set available in the ADF package. For the best functional with the best basis set, the average absolute deviation (AAD) of the calculated value from experiment is only 0.16 eV (C) 2003 Elsevier B.V. All rights reserved.}, keywords = {ADF, BASIS-SETS, CEBE, CHEMICAL-SHIFTS, CONJUGATED, core-electron binding energy, CORRECT ASYMPTOTIC-BEHAVIOR, DENSITY-FUNCTIONAL CALCULATION, DFF, ESCA, EXCHANGE-ENERGY, GENERALIZED GRADIENT APPROXIMATION, MOLECULAR CALCULATIONS, MOLECULES, PHOTOELECTRON-SPECTROSCOPY, X-RAY-EMISSION, XPS}, isbn = {0368-2048}, url = {://000187364200010}, author = {Takahata, Y. and Chong, D. P.} } @article {745, title = {Side-on bridging coordination of N-2: Spectroscopic characterization of the planar Zr2N2 core and theoretical investigation of its butterfly distortion}, journal = {Chemistry-a European Journal}, volume = {9}, number = {2}, year = {2003}, note = {ISI Document Delivery No.: 638VDTimes Cited: 14Cited Reference Count: 37}, month = {Jan}, pages = {520-530}, type = {Article}, abstract = {The vibrational and electronic structure of the side-on N-2-bridged Zr complex [{(P2N2)Zr}(2)(u-n(2):n(2)-N-2)] (P2N2=PhP(CH2SiMe2NSiMe2CH2)(2)PPh) were analyzed. The vibrational characterization of the planar Zr2N2 core was based on resonance Raman and infrared spectroscopy. In the Raman spectrum, the N-N stretching band is found at 775 cm(-1) with an isotope shift of 22 cm(-1). Due to its appearance in many overtones and combination modes, the metal-metal stretch is assigned to the peak at 295 cm(-1). The two ungerade modes of the Zr2N2 core were identified in the infrared spectrum. Based on these four vibrations of the Zr2N2 unit, a quantum chemical assisted normal coordinate analysis (OCA-NCA) was performed. The force constants for the N-N and Zr-N bonds were calculated to be 1.53 and 2.58 mdyn Angstrom(-1), respectively. The butterfly distortion of the Zr2N2 unit obtained in DFT geometry optimizations of planar side-on N-2-bridged Zr complexes was analyzed in more detail. It was found that on bending of the Zr2N2 core, the lone pairs of the axial amide ligands are rotated by 90degrees. The bent Zr2N2 unit is 11 kcal mol(-1) lower in energy than the planar core due to a more uniform distribution of electron density between the metal atoms and NZ and delocalization of electron density from the amide ligands to the Zr2N2 unit. The spectroscopic implications of this distortion are analyzed.}, keywords = {ZR(MU-ETA(2)-N-2)ZR, coordination modes, CRYSTAL-STRUCTURE, DIHYDROGEN, DINITROGEN COMPLEX, DINITROGEN COMPLEXES, END-ON, EXCHANGE, METAL, MOLECULAR CALCULATIONS, NITROGEN, POTENTIALS, REDUCTION, SPECTROSCOPY, vibrational, ZIRCONIUM}, isbn = {0947-6539}, url = {://000180592000018}, author = {Studt, F. and Morello, L. and Lehnert, N. and Fryzuk,Michael D. and Tuczek, F.} } @article {5196, title = {The elusive 16-electron Cp*M(NO)Me-2 (M = Mo, W) complexes and their spontaneous conversions to Cp*M(NMe)(O)Me isomers}, journal = {Journal of the American Chemical Society}, volume = {123}, number = {26}, year = {2001}, note = {ISI Document Delivery No.: 447QPTimes Cited: 17Cited Reference Count: 115}, month = {Jul}, pages = {6272-6282}, type = {Review}, abstract = {Treatment of [Cp*Mo(NO)Cl mu(-Cl)](2) with magnesium (Me2Mg.dioxane, MeMgCl) or aluminum (Me3Al) methylating reagents affords the known compound [Cp*Mo(NO)Me(mu 0Cl)](2) (1). Similar treatment of the dicbloro precursor with MeLi in ethereal solvents generates an equimolar mixture of 1 and the trimethyl "ate" complex, Cp*MoMe3(NO-Li(OEt2)(n)). (2-Et2O). Reaction of 2-Et2O with a source of [Me](+) forms Cp*MoMe3(dropN-OMe) (3), a rare terminal alkoxylimido complex. Metathesis of the chloro ligands of [Cp*Mo-(NO)Cl(mu -Cl)](2) by MeLi in toluene at low temperatures produces the target dimethyl complex. Cp*Mo(NO)-Me-2 (4). in 75\% isolated yield. In solution, 4 is predominantly a monomeric species, whereas in the solid state it adopts a dimeric or oligomeric structure containing isonitrosyl bridges as indicated by IR and N-15/C-13 NMR spectroscopies. Hydrolysis of 4 affords meso- and rac-[Cp*Mo(NO)Me](2)(mu -O)(5), and the reactions of 4 with a range of Lewis bases. L, to form the 18e adducts Cp*Mo(NO)(L)Me-2 (e.g., Cp*Mo(NO)(PMe3)Me-2 (7)), have established it to be the most electrophilic complex of its family. Acidolysis of the methyl groups of 4 is also facile. Most notably, 4 is thermally unstable in solution and undergoes isomerization via nitrosyl N-O bond cleavage to its oxo(imido) form, Cp*Mo(NMe)(O)Me (11), which is isolable from the final reaction mixture as the mu -oxo-bridged adduct formed by 4 and 11, i.e., Cp*Mo(NO)Me2(mu -O)Cp*Mo(NMe)Me (4 <{\textendash} 11). The rate of this isomerization is significantly faster for the tungsten dimethyl complex; hence, Cp*W(NO)- (NO)Me-2 (12) is not isolable free of a supporting donor interaction and can only be isolated as Cp*W(NO)-Me-2(mu -O)Cp*W(NMe)Me (12 <{\textendash} 13) or Cp*W(NO)Me-2(PMe3) (14) adducts.}, keywords = {ALPHA-OLEFINS, COORDINATED NITRIC-OXIDE, CRYSTAL-STRUCTURE, EFFECTIVE CORE POTENTIALS, INSERTION, LIGAND REDISTRIBUTION REACTIONS, MIGRATORY, MOLECULAR CALCULATIONS, OLEFIN POLYMERIZATION, ORGANOMETALLIC NITROSYL CHEMISTRY, POLYMERIZATION CATALYSTS}, isbn = {0002-7863}, url = {://000169584200009}, author = {Sharp, W. B. and Daff, P. J. and McNeil, W. S. and Legzdins,Peter} } @article {4995, title = {Intermolecular C-H activation of hydrocarbons by tungsten alkylidene complexes: An experimental and computational mechanistic study}, journal = {Organometallics}, volume = {20}, number = {23}, year = {2001}, note = {ISI Document Delivery No.: 493VBTimes Cited: 17Cited Reference Count: 65}, month = {Nov}, pages = {4939-4955}, type = {Article}, abstract = {Cp*W(NO)(CH2CMe3)(2) (1) and Cp*W(NO)(CH2CMe3)(CH2C6H5) (2) under moderate conditions (70 degreesC, 40 h) generate the reactive complexes Cp*W(NO)(=CHCMe3) (A) and Cp*W(NO)(=CHC6H5) (B), respectively, which activate hydrocarbon solvents via the addition of C-H across the M=C bond. The alpha -deuterated derivative Cp*W(NO)(CD2CMe3)(2) (1-d(4)) undergoes intramolecular H/D exchange within the neopentyl ligands, consistent with the formation of a-neopentane complexes prior to neopentane elimination. The thermolysis of 1 in a 1:1 molar mixture of tetramethylsilane-h(12) and tetramethylsilane-d(12) (70 degreesC, 40 h) yields an intermolecular KIE of 1.07(4):1. Thermolysis of I and 2 in 1:1 benzene/benzene-d(6) yields intermolecular KIEs of 1.03(5):1 and 1.17(19):1, respectively. The KIE values are inconsistent with rate-determining C-H bond addition to the M=C linkage and indicate that coordination of the substrate to the metal center is the discriminating factor in alkane and arene intermolecular competitions. The complexes Cp*W(NO)(CH2CMe3)(C6D5) (5-d(5)) and CP*W(NO)(CH2C6H5)(C6D5) (6-d(5)) convert to the respective H/D scrambled products Cp*W(NO)(CHDsynCMe3)(C6D4H1) (5{\textquoteright}-d(5)) and Cp*W(NO)(CHDsynC6H5)(C6D4H1) (6{\textquoteright}-d(5)) under thermolytic conditions, consistent with the occurrence of reversible aromatic sp(2) C-H bond cleavage. The results suggest that the previously reported discrimination between the aryl and benzyl products of toluene activation by A and B originates from coordination of toluene to the metal center in two distinct modes. Supporting DFT calculations on the activation of toluene by CpW(NO)(=CH2) (C) indicate that aromatic sp(2) C-H bond activation proceeds through a pi -arene complex, while benzylic sp(3) C-H bond activation proceeds through a eta (2)(C,H),sigma -phenylmethane complex. The principal factor behind the preferential formation of the aryl products appears to be the relative energies of formation of these intermediates.}, keywords = {BOND ACTIVATION, EFFECTIVE CORE POTENTIALS, EXCHANGE, METAL-ALKANE COMPLEXES, METHANE, METHYL-HYDRIDE, MOLECULAR CALCULATIONS, MOLYBDENUM, ORGANOMETALLIC NITROSYL CHEMISTRY, REDUCTIVE ELIMINATION}, isbn = {0276-7333}, url = {://000172243200026}, author = {Adams, C. S. and Legzdins,Peter and McNeil, W. S.} } @article {5063, title = {Pure rotational spectra, structures, and hyperfine constants of OC-AuX (X = F, Cl, Br)}, journal = {Inorganic Chemistry}, volume = {40}, number = {24}, year = {2001}, note = {ISI Document Delivery No.: 492RMTimes Cited: 20Cited Reference Count: 54}, month = {Nov}, pages = {6123-6131}, type = {Article}, abstract = {Rotational spectra of OC-AuX (X = F, Cl, Br) have been measured in the frequency range 5-21 GHz, using a pulsed jet cavity Fourier transform microwave spectrometer. The molecules were prepared by ablating. Au metal with a Nd:YAG laser and allowing the vapor to react with CO plus a halide precursor contained in the Ar backing gas of the jets. For OC-AuCl and OC-AuBr these are I the first high-resolution spectroscopic measurements; for OC-AuF these are the first observations of any kind. Ail three molecules are linear. Rotational constants, centrifugal distortion constants, and nuclear quadrupole coupling constants have been precisely evaluated. The geometries determined for all three molecules show CO bond lengths close to that of free CO, plus relatively long Au-C bonds. These results are corroborated by ab initio calculations, which have also produced Mulliken populations showing significant sigma -donation from CO to Au, plus some pi -back-donation from An to CO. There are major changes in the Au, Cl, and Br nuclear quadrupole coupling constants when CO bonds to AuX, consistent with the formation of strong Au-C bonds. The structural properties of OC-AuF are somewhat different from those of OC-AuCl and OC-AuBr.}, keywords = {AUCL, CARBONYL, COMPLEXES, CU(CO)CL, FIELD, GAUSSIAN-BASIS SETS, GOLD, MICROWAVE-SPECTRA, MOLECULAR CALCULATIONS, SPECTROSCOPY}, isbn = {0020-1669}, url = {://000172181400007}, author = {Evans, C. J. and Reynard, L. M. and Gerry, M. C. L.} } @article {4866, title = {The hyperfine structures of ScCl and ScF}, journal = {Journal of Molecular Spectroscopy}, volume = {199}, number = {2}, year = {2000}, note = {ISI Document Delivery No.: 278NYTimes Cited: 20Cited Reference Count: 48}, month = {Feb}, pages = {275-283}, type = {Article}, abstract = {The Fourier transform microwave spectra of gaseous ScF and ScCl have been measured in their (1)Sigma(+) ground electronic states. Transitions have been observed for ScF (J = 1-0) and for both (SCCl)-Cl-35 and (SCCl)-Cl-37 (J = 1-0 and J = 2-1) in the ground vibrational state, and for (SCCl)-Cl-35 (J = 1-0 and J = 2-1) in the first excited vibrational state. The nuclear quadrupole coupling constants of Sc and of both isotopes of Cl, the spin-rotation constants for all the nuclei and the nuclear spin-nuclear spin constants for both molecules, have been determined. From these hyperfine constants, the electronic structures of ScF and ScCl have been investigated and comparisons have been made to similar molecules. ScCl has been found to be highly ionic. For (ScCl)-Cl-35, the equilibrium bond length has been reevaluated and the vibration frequency and dissociation energy have been estimated. A simple approach to account for the Sc quadrupole coupling constants has been shown to be flawed. (C) 2000 Academic Press.}, keywords = {DIPOLE-MOMENTS, ELECTRONIC-STRUCTURE, GAUSSIAN-BASIS SETS, LASER-ABLATION, MOLECULAR CALCULATIONS, ROW ATOMS, SCANDIUM MONOCHLORIDE, SINGLET-STATES, SPECTROSCOPY, SPIN INTERACTIONS}, isbn = {0022-2852}, url = {://000084996900015}, author = {Lin, W. and Beaton, S. A. and Evans, C. J. and Gerry, M. C. L.} } @article {4669, title = {A computational study of two-state conformational changes in 16-electron [CpW(NO)(L)] complexes (L = PH3, CO, CH2, HCCH, H2CCH2)}, journal = {Chemistry-a European Journal}, volume = {5}, number = {5}, year = {1999}, note = {ISI Document Delivery No.: 194UQTimes Cited: 20Cited Reference Count: 52}, month = {May}, pages = {1598-1608}, type = {Article}, abstract = {Electronically and coordinatively unsaturated [Cp*W(NO)(L)] complexes have been postulated as intermediates in several related systems. Model [CpW(NO)(L)] compounds (L= PH3, CO, CH2, H2CCH2, HCCH) have been investigated theoretically by means of density functional theory computational techniques. The structural parameters calculated for saturated [CpW(NO)(PH,)(L)] complexes are in good agreement with the solid-state molecular structures determined crystallographically for the corresponding [Cp*W(NO)(PMe3)(L)] compounds. The 16-electron, singlet [CpW(NO)(L)] species have geometries comparable to those of the same fragment in the phosphine adducts and include a highly pyramidal conformation at W. The energy of the triplet spin state is calculated to be close to or even lower than that of the singlet state for these unsaturated compounds, and depends largely on the pi-bonding capabilities of L (Delta Es-t=Delta E-t-Delta E-s = - 3.3 kcalmol(-1) (PH3), + 2.8 (CO), + 2.4 (CH2), +6.3 (H2CCH2), -2.3 (HCCH)). The optimization of partially constrained structures in both spin states allows for a conformational analysis of the [CpW(NO)(L)] species. The inversion of the conformation of the pyramidal singlet [CpW(NO)(L)] complexes via the planar-at-W triplet species (two-state pathway) is calculated to be competitive with the equivalent process solely along the singlet spin hypersurface. Rotation of the W-CH, bond in the singlet carbene species is also found to proceed more readily via a two-state pathway. The preferred alkyne conformation, the unusually stable triplet states, and the strong W-to-L sc-donation observed in these systems may all be rationalized by the relatively high energies of the occupied orbitals of the formally WO compounds.}, keywords = {ACTIVATION, CROSSOVER, density functional calculations, H BOND, LIGAND, ligand effects, MOLECULAR CALCULATIONS, ORGANOMETALLIC NITROSYL CHEMISTRY, OXIDATIVE ADDITION, pi interactions, PIANO-STOOL COMPLEXES, REACTIVITY, REDUCTIVE ELIMINATION, SPIN, SPIN-STATE, TUNGSTEN}, isbn = {0947-6539}, url = {://000080212600026}, author = {Smith, K. M. and Poli, R. and Legzdins,Peter} } @article {4326, title = {Density functional study of spin state in CpM(NO)X-2 (M=Mo, Cr; X=Cl, NH2, CH3): Spectrochemical and nephelauxetic effects in organometallic compounds}, journal = {Organometallics}, volume = {17}, number = {4}, year = {1998}, note = {ISI Document Delivery No.: YY508Times Cited: 19Cited Reference Count: 83}, month = {Feb}, pages = {615-622}, type = {Article}, abstract = {The relationship between spin state and metal-ligand bonding interactions in CpM(NO)Xa species was investigated using density functional computational techniques. The geometries of CpM(NO)Cl-2 (M = Cr, Mo), CpCr(NO)(NH2)X, and CpCr(NO)(CH3)X (X = Cl, CH3) were optimized at the DFT-B3LYP level for both the diamagnetic (S = 0) and paramagnetic (S = 1) electronic configurations. While the geometric parameters of the singlet compounds matched well with structures determined experimentally, the Cr-NO bond lengths in the triplet Species exceeded the experimentally observed range by a significant margin, thereby indicating a propensity for nitrosyl-ligand dissociation from the high-spin complexes. The order of relative singlet vs triplet spin-state stability (expressed as Delta Es-t (kcal/mol)) was determined to be CpCr(NO)Cl-2 (8.20) > CpCr(NO)(CH3)Cl (1.52) approximate to CpCr(NO)(NH2)Cl (0.95), > CpCr(NO)(CH3)(2) (-2.37) > CpCr(NO)(NH2)CH3 (-9.55) > CpMQ(NO)Cl-2 (-17.62). The amide pi-donation increases the HOMO-LUMO energy splitting, thus favoring the diamagnetic configuration. The alkyl ligand reduces the electron-electron repulsion through orbital expansion, thereby lowering the relative energy of the singlet state. Extended Huckel molecular-orbital calculations were performed on the DFT-optimized structures to help rationalize the metal-ligand bonding interactions, and interelectron repulsions were quantified by evaluation of the Coulomb (S) and exchange (K) integrals based on the B3LYP-optimized triplet spin-state geometries.}, keywords = {DINITROGEN CLEAVAGE, EFFECTIVE CORE POTENTIALS, GROUP-6 COMPLEXES, LIGANDS, MOLECULAR CALCULATIONS, NITROSYL CHEMISTRY, OLEFIN POLYMERIZATION, PI-ACCEPTOR, POLYMERIZATION CATALYSTS, TRANSITION-METAL COMPLEXES, X-RAY}, isbn = {0276-7333}, url = {://000072154500023}, author = {Legzdins,Peter and McNeil, W. S. and Smith, K. M. and Poli, R.} } @article {4407, title = {Metal-based chirality and spin state change in 16-electron CpML2 systems: a computational study of CpW(NO)(PH3)}, journal = {Chemical Communications}, number = {17}, year = {1998}, note = {ISI Document Delivery No.: 116QXTimes Cited: 11Cited Reference Count: 35}, month = {Sep}, pages = {1903-1904}, type = {Article}, abstract = {Density functional theory calculations indicate that CpW(NO)(PH3) possesses a planar triplet ground state, a result with significant implications for the inversion of configuration of 16e, d(6) CpML2 species.}, keywords = {alkane, ALKYL, BOND ACTIVATION, C-H ACTIVATION, EFFECTIVE CORE POTENTIALS, INTERMEDIATE, IRIDIUM(III) COMPLEXES, METHANE, MOLECULAR CALCULATIONS, REACTIVITY}, isbn = {1359-7345}, url = {://000075737000060}, author = {Smith, K. M. and Poli, R. and Legzdins,Peter} }