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71.
Perturbative solution of the RPA equation. An application to the calculation of rotational strengths
The RPA equation is solved by perturbation in Møller-Plesset (MP) and Epstein-Nesbet (EN) partitions, which are first compared on a specific example. To still accelerate the faster one (EN), a third scheme is proposed, which involves preliminary diagonalization within a limited subset
, followed by usual EN perturbation between
and the rest of the whole configuration space. Criteria for the choice of
are given. 相似文献
72.
Roland Wilberger Holger Piotrowski Marcus Warchhold Ingo‐Peter Lorenz 《无机化学与普通化学杂志》2003,629(14):2485-2492
Novel Neutral and Cationic Mono‐Aziridine Complexes of the Type [CpMn(CO)2Az], [CpCr(NO)2Az]+, and [(Ph3P)(CO)4ReAz]+ via CO‐, Hydride‐, and Chloride‐Elimination Reactions The monoaziridine complexes 1 — 5 are obtained by three differently induced substitution reactions. The photolytically induced CO substitution reaction of [CpMn(CO)3] with 2, 2‐dimethylaziridine leads to the neutral N‐coordinate aziridine complex [Cp(CO)2Mn{$\overline{N(H)CMe2C}$ H2}] ( 1 ). The protonation of [(Ph3P)(CO)4ReH] with CF3SO3H and consecutive treatment with 2, 2‐dimethylaziridine or 2‐ethylaziridine gives the salt‐like aziridine complexes [(Ph3P)(CO)4Re{$\overline{N(H)CMe2C}$ H2}](CF3SO3) ( 2 ) or [(Ph3P)(CO)4Re{ H2}](CF3SO3) ( 3 ) by hydride elimination reactions. The like‐wise salt‐like complexes [Cp(NO)2Cr{$\overline{N(H)CMe2C}$ H2}](BF4) ( 4 ) and [Cp(NO)2Cr{ H2}](CF3SO3) ( 5 ) are synthesized from [CpCr(NO)2Cl] by chloride elimination with AgX (X = BF4, CF3SO3) in the presence of 2, 2‐dimethylaziridine or 2‐ethylaziridine, respectively. As a result of X‐ray structure analyses, the metal atoms are trigonal pyramidally ( 1, 4, 5 ) or octahedrally ( 2, 3 , cis‐position) configurated; the intact three‐membered rings coordinate through the distorted tetrahedrally configurated N atoms. All compounds 1‐5 are stable with respect to the directed thermal alkene elimination to give the corresponding nitrene complexes; the IR, 1H‐ and 13C{1H}‐NMR, and MS spectra are reported and discussed. 相似文献
73.
P. Cabral do Couto R. C. Guedes B. J. Costa Cabral J. A. Martinho Simes 《International journal of quantum chemistry》2002,86(3):297-304
We are reporting ab initio and density functional theory (DFT) calculations for the phenol O–H bond dissociation energy in the gas phase and in phenol–water clusters. We have tested a series of recently proposed functionals and verified that DFT systematically underestimates the O–H bond dissociation energy of phenol. However, O–H bond dissociation energies in water clusters are in reasonable agreement with experimental data for phenol in solution. We have evaluated electronic difference densities in phenol–water, phenoxy–water, and water, and we are suggesting that the representation of this quantity gives an interesting picture of the electronic density rearrangement induced by hydrogen bond interactions in phenol–water clusters. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001 相似文献
74.
Hydrotris(3, 5‐dimethylpyrazol‐1‐yl)borate and hydrotris(3‐phenylpyrazol‐1‐yl)borate decompose during reactions with [ReOCl3(PPh3)2] and [NEt4]2[Re(CO)3Br3], respectively. The generated pyrazole ligands form complexes with the rhenium(V) oxo and the rhenium(I ) tricarbonyl cores. X‐ray crystal structures of the oxo‐bridged dimer [Cl(PPh3)(O)Re(μ‐O)(μ‐Me2pz)2Re(O)(HMe2pz)Cl] ( 1 ) and [Re(CO)3(HPhpz)2(Phpz)] ( 2 ) (HMe2pz = 3, 5‐dimethylpyrazole, HPhpz = 3‐phenylpyrazole) show that the substituted pyrazoles can readily deprotonate and act as monodentate or bridging anionic ligands. Re‐N bond lengths between 2.09 and 2.14Å have been observed for the bridging and between 2.12 and 2.23Å for the terminal pyrazole ligands. 相似文献
75.
Alistair J Usher Nigel T Lucas Simon Petrie Mark G Humphrey Anthony C Willis 《Journal of organometallic chemistry》2004,689(1):50-57
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. 相似文献
76.
F. Sanem Koçak 《Journal of organometallic chemistry》2006,691(23):5030-5037
Thermal substitution reaction of Cr(CO)4(η2:2-1,5-cyclooctadiene), Mo(CO)4(η2:2-norbornadiene), and W(CO)5(η2-bis(trimethylsilyl)ethyne) with N,N′-bis(ferrocenylmethylene)ethylenediamine (bfeda) yields M(CO)4(bfeda) complexes which could be isolated from the reaction solution and characterized by elemental analysis, MS, IR, and NMR spectroscopy. In the case of tungsten, W(CO)5(bfeda) is formed as intermediate and then undergoes the ring closure reaction yielding the ultimate product W(CO)4(bfeda). The electrochemical behavior of the M(CO)4(bfeda) complexes was studied by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in dichloromethane with tetrabutylammonium tetrafluoroborate as electrolyte. Constant potential electrolysis of the complexes was performed successively at their peak potentials at 0 °C in their CH2Cl2 solution and the electrolysis was followed by in situ recording the electronic absorption spectra in every 5 mC. In the electrolysis of Cr(CO)4(bfeda), the central Cr(0) is oxidized first and electrolysis continues with oxidations of two ferrocenyl groups until the end of totally three moles of electron passage per mole of complex. In the electrolysis of Mo(CO)4(bfeda) and W(CO)4(bfeda) the first oxidation occurs on the central atom forming a short-lived species which undergoes an intramolecular one-electron transfer and is reduced back to M(0) while one of the ferrocene units is oxidized to the ferrocenium cation at the same time. This indicates that the electron is transferred from iron to the central metal atom. 相似文献
77.
Ansgar Schäfer Christian Huber Jürgen Gauss Reinhart Ahlrichs 《Theoretical chemistry accounts》1993,87(1-2):29-40
Summary Experimentally known copper selenium clusters show extraordinary geometrical features, especially short Cu-Cu distances. We report the first theoretical investigation of Cu2Se and Cu4Se2. Various quantum chemical methods (SCF, MP2, CPF, CCSD, CCSD(T), LDF) are applied to determine the importance of dynamic electron correlation. We find that inclusion of correlation does not essentially change the electronic structure of the clusters but has a strong influence on geometries. To reduce the computational effort we apply effective core potentials (ECPs) in combination with small, but carefully optimized basis sets. The applicability of simple modellings of correlation energies for approximate inclusion of correlation effects in SCF geometry optimizations is tested. 相似文献
78.
The importance of palladium complexes in catalytic processes is well-demonstrated by its applications in hydrogenation processes in industry. Mixed metal clusters of palladium are of interest as the palladium ion can attain either a 16- or 18-electron configuration which is an important feature for catalytic processes. Recent developments in the preparation, characterization, chemical and physical properties of these clusters are discussed in this review. 相似文献
79.
Feng Wang Nick Andriopoulos Neil Wright Ellak I. von Nagy-Felsobuki 《Journal of Cluster Science》1991,2(3):203-217
Ab initio molecular orbital calculations using the STO-6G and STO6-21G basis sets have been performed for the cluster series Li
n
+
, Li
n
, and Li
n
–
(wheren=2–7). Thirty-two optimized structures are discussed and reported, many of which (especially for the anionic structures) have not yet been considered. The calculations suggest that for all three species the optimum geometries are planar. Of the two levels of theories that were investigated, STO-6G//STO-6G and STO6-21G//STO-6G, the latter hybrid theory was found to be less reliable. In particular, for the anionic structures these calculations should provide a platform from which more sophisticated, i.e., configuration interaction, geometry optimization can be performed. 相似文献
80.
Olivia Vidoni Stefan Neumeier Nathalie Bardou Jean-Luc Pelouard Günter Schmid 《Journal of Cluster Science》2003,14(3):325-336
The elaboration of closed-packed monolayers of Au55(PPh3)12Cl6 clusters on oxidized and non-oxidized GaAs surfaces is reported. The first part of this work describes the use of silanethiol modified GaAs oxide surfaces to trap 18 nm gold colloids and Au55(PPh3)12Cl6 clusters. The surfaces characterized by AFM measurements present high-quality coverage on a quite long range for both metallic species. The second part is devoted to the elaboration of Au55(PPh3)12Cl6 cluster monolayers on non-oxidized p-type GaAs substrates, functionalized with dithiol molecules. AFM measurements demonstrate the presence of closed-packed two-dimensional arrangements of Au55 clusters. 相似文献