Nonempirical parameters of the nonlocal core pseudopotential for the second and third row elements

For the core pseudopotential (CP) model constructed in terms of Bonifacic-Huzinaga nonlocal CP theory, parameters of the local component of CP are calculated for the second-and third-row elements. The resulting CP are associated with the Coulomb, exchange, and correlation potentials created by the nuclear charge and electron density of the core electrons. The electronic structure and potential energy surface are calculated for the hydrides of the second-row elements (LiH, CH₄, NH₃, H₂O, HF); the calculations are performed by the nonempirical nonlocal CP method. The results of these calculations agree well with those of SCF MO LCAO ab initio calculations and with experimental data.     

Dipole moment derivatives from MINDO/3 semi-empirical MO calculations

Dipole moment derivatives for CO, NO, CO₂, H₂O, HCN, BF₃, CH₄, C₂H₄, C₂H₆, CH₃F, F₂CO and H₂CO molecules have been evaluated using MINDO/3 MO calculations. The values are compared with those obtained by other semi-empirical MO methods.     

Theoretical investigation on hydroformylation reactions : I. Structures and reactivities of cobalt carbonyls and hydrocarbonyls

Extended Hückel Theory calculations have been carried out in a study of the most important cobalt carbonyls and hydrocarbonyls involved in the hydroformylation reaction. The geometries of the stable isomers of Co₂(CO)₈, Co₂(CO)₇, Co(CO)₄, Co(CO)₃ have been calculated and used to interpret the changes in the IR spectrum of Co₂(CO)₈ observed on varying the temperature. The reaction paths for the interconversions of the stable isomers have also been investigated. The optimized geometry of HCo(CO)₄ agrees well with the experimental structure. The C_s symmetry found for the most stable isomer of HCo(CO)₃ is of much interest, serves to explain the formation of the complex with olefins.     

Evolution of Graphene Supported RuN (N=1–4) Clusters in CO Atmosphere: A First-Principles Investigation

We investigated the evolution of Ru clusters containing 1–4 atoms supported on graphene in CO atmosphere with extensive first principle-based calculations. Exothermic CO adsorption induces gradual structure reorganization and change of the Ru−Ru, Ru-graphene, and Ru-CO interactions within these Ru carbonyls. The upper limits of CO on a surface of Ru cluster are 3, 6, 10 and 12 for Ru₁, Ru₂, Ru₃ and Ru₄, respectively. The further CO adsorption enhances steric hindrance at the Ru-graphene interface that finally leads to release of undercoordinated Ru carbonyls into gas phase. Competing with the CO adsorption and sintering of Ru species for better thermostability, disintegration of multinuclear surface Ru carbonyls to atomically dispersed Ru species on graphene is still feasible. The current findings bring more insights into the evolution and interconversion of Ru carbonyls in a CO atmosphere and may help to understand the superior performance of heterogeneous transition metal catalysts in operation conditions.     

Core-valence correlation effects for molecules containing first-row atoms. Accurate results using effective core polarization potentials

The accuracy of employing effective core polarization potentials (CPPs) to account for the effects of core-valence correlation on the spectroscopic constants and dissociation energies of the molecules B₂, C₂, N₂, O₂, F₂, CO, CN, CH, HF, and C₂H₂ has been investigated by comparison to accurate all-electron benchmark calculations. The results obtained from the calculations employing CPPs were surprisingly accurate in every case studied, reducing the errors in the calculated valence D _e values from a maximum of nearly 2.5 kcal/mol to just 0.3 kcal/mol. The effects of enlarging the basis set and using higher-order valence electron correlation treatments were found to have only a small influence on the core-valence correlation effect predicted by the CPPs. Thus, to accurately recover the effects of intershell correlation, effective core polarization potentials such as the ones used in the present work provide an attractive alternative to carrying out computationally demanding calculations where the core electrons are explicitly included in the correlation treatment. Received: 11 May 1998 / Accepted: 27 July 1998 / Published online: 28 October 1998     

Mixed-metal cluster chemistry. 26 . Proclivity for “all-terminal” or “plane-of-bridging-carbonyls” ligand disposition in tungsten-triiridium clusters

Reaction of WH(CO)₃(η-C₅Me₅) with IrCl(CO)₂(4-H₂NC₆H₄Me) affords WIr₃(μ-CO)₃(CO)₈(η-C₅Me₅) in low yield. A structural study reveals a WIr₂-centred plane of bridging carbonyls, in contrast to the crystal structure of WIr₃(CO)₁₁(η-C₅H₅) (all-terminal carbonyl distribution). DFT calculations reveal an increasing proclivity to adopt an all-terminal CO disposition for clusters MIr₃(CO)₁₁(η-C₅H₅) in the gas phase on proceeding from M=Cr to Mo and then W, consistent with structural studies in the solid state for which the tungsten-containing cluster is the only all-terminal example. Increasing electron donation from the ligands in the tungsten system (either from phosphine substitution or cyclopentadienyl permethylation) suffices to impose a plane of bridging carbonyls in the ground state structure. ¹³C NMR fluxionality studies reveal that CO exchange mechanism(s) for WIr₃(CO)₁₁(η-C₅H₅) and the related tetrahedral cluster W₂Ir₂(CO)₁₀(η-C₅H₅)₂ are very fast and involve all carbonyls on the clusters. DFT calculations on MIr₃(CO)₁₁(η-C₅H₅) (M=Cr, Mo) substantiate a ‘merry-go-round’ mechanism for carbonyl scrambling in these systems, a result which is consistent with the scrambling behaviour seen in the NMR fluxionality studies on the W-containing congener.     

Molecular calculations with the MODPOT,VRDDO, and MODPOT/VRDDO procedures. IV. Boron hydrides and carboranes

Reference completely ab initio 6–3G and nonempirical 3G/MODPOT (ab initio effective core model potential) LCAO -MO -SCF calculations (using the same valence atomic orbital basis) were performed for a series of boron hydrides (B₄H₁₀, B₅H₉, B₅H₁₁, and B₆H₁₀) and a test 3G/MODPOT + VRDDO (variable retention of diatomic differential overlap for charge conserving integral prescreening) calculation were also performed for B₅H₉, B₆H₁₀, and B₁₀H₁₄. The agreement between the ab initio 6–3G and the corresponding 3G/MODPOT calculations was excellent for valence orbital energies, gross atomic populations, and dipole moments. The results also compared favorably to previous ab initio minimum STO basis results of Lipscomb and coworkers. The 3G/MODPOT + VRDDO calculations verified that for such spatially compact molecules (such as boron hydrides, which are fragments of polyhedra), the VRDDO procedure does not result in a noticeable savings in computer time for molecules of the size and shape of B₅H₉ and B₆H₁₀, in contrast to the savings previously realized for organic molecules of comparable atomic size. However, the agreement in calculational results between the 3G/MODPOT and the 3G/MODPOT +VRDDO results was still as extremely close as it had been for the organic molecules. 3G/MODPOT calculations were also carried out for B₈H₁₂, B₉H₁₅, B₁₀H₁₄, B₁₀H₁₄^?2, 1,2-C₂B₄H₆, and 1,6-C₂B₄H₆ and the results compared to the previous minimum STO basis results. For B₁₀H₁₄, the 3G/MODPOT +VRDDO method led to savings in computer time of 28% over the 3G/MODPOT method itself. The agreement of the 3G/MODPOT results with available experimental photoelectron spectral data for B₅H₉ and 1,6-C₂B₄H₆ was as good as that of the previous ab initio minimum STO basis calculations.     

Photochemical reactions of metal carbonyls [M(CO)6 (M = Cr,Mo and W), Re(CO)5Br,Mn(CO)3Cp] with 2-hydroxyacetophenone methanesulfonylhydrazone (apmsh)

Five new complexes, [M(CO)₅(apmsh)] [M = Cr; (1), Mo; (2), W; (3)], [Re(CO)₄Br(apmsh)] (4) and [Mn(CO)₃(apmsh)] (5) have been synthesized by the photochemical reaction of metal carbonyls [M(CO)₆] (M = Cr, Mo and W), [Re(CO)₅Br], and [Mn(CO)₃Cp] with 2-hydroxyacetophenone methanesulfonylhydrazone (apmsh). The complexes have been characterized by elemental analysis, mass spectrometry, f.t.-i.r. and ¹H spectroscopy. Spectroscopic studies show that apmsh behaves as a monodentate ligand coordinating via the imine N donor atom in [M(CO)₅(apmsh)] (1–4) and as a tridentate ligand in (5).     

The reactions of Cr(CO)6, Fe(CO)5, and Ni(CO)4 with O2 yield viable oxo‐metal carbonyls

Transition metal complexes with terminal oxo and dioxygen ligands exist in metal oxidation reactions, and many are key intermediates in various catalytic and biological processes. The prototypical oxo‐metal [(OC)₅Cr? O, (OC)₄Fe? O, and (OC)₃Ni? O] and dioxygen‐metal carbonyls [(OC)₅Cr? OO, (OC)₄Fe? OO, and (OC)₃Ni? OO] are studied theoretically. All three oxo‐metal carbonyls were found to have triplet ground states, with metal‐oxo bond dissociation energies of 77 (Cr? O), 74 (Fe? O), and 51 (Ni? O) kcal/mol. Natural bond orbital and quantum theory of atoms in molecules analyses predict metal‐oxo bond orders around 1.3. Their featured ν(MO, M = metal) vibrational frequencies all reflect very low IR intensities, suggesting Raman spectroscopy for experimental identification. The metal interactions with O₂ are much weaker [dissociation energies 13 (Cr? OO), 21 (Fe? OO), and 4 (Ni? OO) kcal/mol] for the dioxygen‐metal carbonyls. The classic parent compounds Cr(CO)₆, Fe(CO)₅, and Ni(CO)₄ all exhibit thermodynamic instability in the presence of O₂, driven to displacement of CO to form CO₂. The latter reactions are exothermic by 47 [Cr(CO)₆], 46 [Fe(CO)₅], and 35 [Ni(CO)₄] kcal/mol. However, the barrier heights for the three reactions are very large, 51 (Cr), 39 (Fe), and 40 (Ni) kcal/mol. Thus, the parent metal carbonyls should be kinetically stable in the presence of oxygen. © 2014 Wiley Periodicals, Inc.     

The electrochemical behavior of metal carbonyls in a mixture of a room temperature molten salt and benzene

The electrochemical oxidation of six metal carbonyls was studied in a mixture of the high Lewis acid, room temperature molten salt, composed of aluminum chloride and ethylpyridinium bromide (2:1 molar ratio) and benzene (50% v/v). Chromiuim hexacarbonyl was found to be reversibly oxidized to the seventeen electron cationo Cr(CO)⁺₆, isoelectronic with vanadium hexacarbonyl. Some stability was also found for the corresponding 17 electron cation of iron pentacarbonyl. The other carbonyl compounds studied Mo(CO)₆, W(CO)₆, Re₂(CO)₁₀, and Mn₂(CO)₁₀ exhibit electrochemical behavior characteristic of chemical and electrochemical reactions following the electron transfer reaction. Based on the large dependence of the oxidation potentials on the nature of the central metal atom in this solvent, it is proposed that the metal carbonyls interact with electron deficient species in the melt, decreasing the σ donor ability of the ligand, but increasing its π acceptor capabilities.     

Structure and infrared spectroscopy of group 6 transition-metal carbonyls in the gas phase: DFT studies on M(CO)n (M = Cr, Mo, and W; n = 6, 5, 4, and 3)

B3LYP-based density functional theory (DFT) calculations with effective core potentials (ECPs) (LANL2DZ) on M and 6-311+G(2d) all-electron basis function sets on C and O are used to interpret the symmetry characteristic vibrational absorption patterns of CO ligands in the "naked" coordinatively unsaturated transition-metal carbonyls M(CO)n-1 (M = Cr, Mo, and W; n = 4-6) observed by a time-resolved infrared absorption spectroscopy after the UV pulse laser photolysis of M(CO)6 in the gas phase. The UV photolysis results can be reasonably explained by the trends in the calculated bond dissociation enthalpies of M(CO)n-1-CO for group 6 metal carbonyls. M(CO)n-1 produced through one CO elimination from M(CO)n is found out to keep its parent skeleton, resulting in the structure with symmetry of C4v for M(CO)5, C2v for M(CO)4, and C3v for M(CO)3.     

Effective-core-potential calculations of sulphur,selenium and tellurium dioxides and dihydrides

The ground-state electronic structures of SO₂, SeO₂, TeO₂, SH₂, SeH₂ and TeH₂ have been calculated with effective core potentials. Satisfactory agreement with experimental molecular geometries was achieved in the dioxides only after d-functions were included in the basis sets for S, Se and Te; however, these d-functions were not essential for the dihydrides. The importance of electron correlation to the determination of dissociation energy is also evident from these calculations.     

Reaction of methyl trichloroacetate with vinyltrimethylsilane in the presence of metal carbonyls

Reaction of methyl trichloroacetate with vinyltrimethylsilane initiated by metal carbonyls yields, depending on the crbonyl, methyl-2,2,4-trichloro-4trimethyl-silyl butyrate [with Mn₂(CO)₁₀ or Re₂(CO)₁₀], 2,2-dichloro-4-trimethylsilyl--butyrolactone [with Fe(CO)₅ or Mo(CO)₆], or a mixture of adduct and lactone [with Cr(CO)₆ or W(CO)₆]. Prior nucleophilic addition of potassium acetate to metal carbonyls of Fe, Mo, Cr, and W suppresses lactonization and an adduct is formed. In the case of Fe(CO)₅, HMPA, DMF, and PPh₃ react analogously.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2615–2618, November, 1989.     

The application of the simplified form of the quasiequilibrium theory to the mass spectra of some mononuclear metal carbonyls

The concept of molecular ions and metal-containing fragment ions formed in the mass spectra of the mononuclear metal carbonyls, M(CO)₆ (M = Cr, Mo,W), Fe(CO)₅, Ni(CO)₄, containing the metal in an excited state appears to violate the quasi-equilibrium theory. Calculations, using the simplified form of the theory, show that the high values obtained for the heats of formation of the metal ions determined by mass spectrometry axe consistent with the “excess energies” representing kinetic shifts.     

Synthesis and Characterization of the products from reaction of Metal Carbonyls [M(CO)6 (M Cr,Mo, W), Re(CO)5Br,Mn(CO)3Cp] with Salicylaldehyde Methanesulfonylhydrazone

Five new complexes, [M(CO)₅(salmsh)] (M?=?Cr;?1,?Mo;?2,?W;?3), [Re(CO)₄Br(salmsh)], 4, and [Mn(CO)₃ (salmsh)], 5, have been synthesized by the photochemical reaction of metal carbonyls with salicylaldehyde methanesulfonylhydrazone (salmsh). The complexes have been characterized by elemental analyses, EI mass spectrometry, FT-IR and ¹H NMR spectroscopy. The spectroscopic studies show that salmsh behaves as a monodentate ligand coordinating via the imine N donor atom in 1–4 and as a tridentate ligand in 5.     

Theoretical studies of organometallic compounds. I. All electron and pseudopotential calculations of Ti(CH3)nCl4 − n (n = 0–4)

The performance of effective core potentials (ECP) and model potentials (MP) has been studied by calculating the geometries and reaction energies of isodesmic reactions for the molecules Ti(CH₃)_nCl_{4 ? n} (n = 0–4) at the Hartree–Fock level of theory. The results are compared with data from all electron calculations and experimental results as far as available. The all electron calculations were performed with a 3-21G basis set from Hehre and a (53321/521/41) basis set from Huzinaga. For the ECP calculations the potentials developed by Hay and Wadt, and for the MP calculations, the model potentials developed by Sakai and Huzinaga, are employed. © 1992 by John Wiley & Sons, Inc.     

Structure and properties of transition-metal compounds. A systematic study of basis set effects in ab initioSCF calculations

The recently developed Gaussian basis functions [2] were used in calculations on the ground electronic states of molecules containing transition-metal atoms: ScF₃, TiCl₄, ZrCl₄, Cr(CO)₆, Ni(CO)₄, CuF, CuCl, Zn(CH₃)₂, and Cd(CH₃)₂. The usefulness of minimal basis sets, the importance of splitting of the valence part of the minimal basis sets, the role of the triple splitting of the d-block functions, and the need for p-, d-, and f-type polarization functions were discussed in the context of the geometrical structure and the firstorder electronic properties of the transition-metal atom compounds.     

Kinetische untersuchungen über reaktionen von metall-komplexen : XVI. Substitutionsreaktionen von metallcarbonylkomplexen des chroms,molybdäns und wolframs; einige neue kinetische und mechanistische aspekte

Metal carbonyls today are classical representatives of coordination compounds, thanks primarily to the pioneering work of Walter Hieber and his school. One of their most characteristic properties is that they undergo substitution reactions with a great number of Lewis bases L. In these reactions, either one or several CO ligands (in very rare cases all CO ligands) are replaced.Substitution reactions of the type:

are known for practically all metal carbonyls. Detailed studies have been made particularly on the reactions of chromium, molybdenum and tungsten carbonyl compounds, including kinetic and mechanistic investigations. The present review is concerned with recent results in this area with special emphasis on carbene carbonyl complexes. The point is made that the reaction possibilities shown by the compounds of general composition M(CO)₆, M(CO)₅L, M(CO)₄LL′, M(CO)₄(LL) and M(CO)₃(LLL) (M = Cr, Mo, W; L (or L′) = unidentate, LL = bidentate, LLL = tridentate ligand) are important not only for synthetic purposes, but also exhibit interesting mechanistic characteristics.