Molecular orbital calculations nickel

In a series of studies of the spectroscopy and photochemistry of nickel(O) -a-diimine complexes, the structural differences among the complexes NiL2 and Ni(CO)2L (L Q-diimine) have been examined by means of molecular orbital calculations and electronic absorption Raman resonance studies.2471, 472 Summing up earlier work, the noninnocence of a-diimine ligands with a flat — N=C—C=N— skeleton in low-valent Ni chemistry and the course of substitution reactions of Ni° complexes with 1,4-diaza-1,3-dienes or a,a -bipyridine have been reviewed.2473... 

Ultra high vacuum studies of nickel and platinum with simple organic molecules like olefins and arenes are described. These surface chemistry studies were done as a function of surface crystallography and surface composition. The discussion is limited to the chemistry of methyl isocyanide, acetonitrile, benzene and toluene, pyridine, trimethylphosphine, ethylene, acetylene and saturated hydrocarbons. Molecular orbital calculations are presented that support the experimental identification of the importance of C-H-M metal bonding for metal surfaces. 

The 2tt molecular orbitals of gas-phase CO are unoccupied. Molecular-orbital calculations for CO chemisorbed on Ni(lOO) indicate that the 5a orbital electrons of CO interact with the 3d,2 orbital of nickel and that there is back-donation to the... 

NLFe" ions have been isolated in a number of salts, for both nickel(in) and nickel(lV). Selected examples of these salts are shown in Table 118. NiF6 is diamagnetic and the electronic spectra have been successfully interpreted in O symmetry (ground state Several spectroscopic and mametic studies and molecular orbital calculations have been performed on NiFi" The complex is low-spin with as... 

The adsorption of acetylene on different nickel halides has been studied by ab initio molecular orbital calculations (Huang and Yang, 1999). The strengths of adsorption on different nickel halides were calculated by ab initio molecular... 

The variable energy photoelectron spectra of [M(T 3-C3H5)2] (M = Ni, Pd, Pt) have been reported 33 and assigned on the basis of molecular orbital calculations. A molecular mechanics force field study of the (i]3-allyl)nickel intermediates in stereoselective nickel(0)-catalysed [4 + 4] cycloadditicms has been teported 36. 

A quantitative consideration on the origin of the EFG should be based on reliable results from molecular orbital or DPT calculations, as pointed out in detail in Chap. 5. For a qualitative discussion, however, it will suffice to use the easy-to-handle one-electron approximation of the crystal field model. In this framework, it is easy to realize that in nickel(II) complexes of Oh and symmetry and in tetragonally distorted octahedral nickel(II) complexes, no valence electron contribution to the EFG should be expected (cf. Fig. 7.7 and Table 4.2). A temperature-dependent valence electron contribution is to be expected in distorted tetrahedral nickel(n) complexes for tetragonal distortion, e.g., Fzz = (4/7)e(r )3 for com-... 

All quantitative calculations done so far to interpret the energy levels in UPS of CO chemisorbed on nickel are based on molecular orbital theory. These methods have had considerable success in explaining UP-spectra of free molecules. It is however by no means obvious that an equivalent treatment of the chemi-... 

Aniline and the fluoroanilines exhibit, 4N contact shifts in the presence of (pentane-2,4-dionato) nickel(II). By comparing the shifts with spin densities calculated by the INDO molecular orbital procedure a structure is proposed for the complexes formed in solution. (137) Contact shifts have also been reported from the 14N spectra of some cobalt(II) nitrate complexes. (138) In the case of [Co(H20)5N03] the chemical shift of the nitrate ligand is reported to be 2360 100 ppm to high frequency of the free nitrate ion. (222)... 

Desulfurization of polynuclear thiophenes was performed by continuous stirring with a Raney nickel catalyst in ethanol at 0-78.8 °C. The major products were biphenyl in the desulfurization of dibenzothiophene, a-phenylnaphthalene in the desulfurization of benzo[b]naphtho[l,2-d]thiophene, and -phenylnaphthalene in the desulfurization of benzo[b]naphtho[2,3-d]thiophene and benzo[b]naphtho[2,l-d]thiophene. Observation of these products shows that the main reaction pathway is the extrusion of a sulfur atom to give the corresponding hydrocarbon. The tt-electron densities of the sulfur atoms, which were calculated by using simple Huckel molecular orbital theory, are considered to be related to the adsorption of the sulfur compounds to the surface and consequently to the C-S bond-breaking rate. 

Figure 2.9. The qualitative behavior of the ground state energy of titanium oxide and nickel oxide calculated with a VB model that includes some ionic contribution (amount X). A pure valence bond wavefunction has = 0 and a molecular orbital state has A = 1. For titanium oxide the MO model predicts an energy closer to the real value than a VB calculation. For nickel oxide the valence bond model is more realistic.

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