Theoretical studies nickel 5-ligands

Burello, E., Marion, P., Galland, J.-C., Chamard, A. and Rothenberg, G. (2005) Ligand descriptor analysis in nickel-catalysed hydrocyanation a combined experimental and theoretical study. Adv. Synth. Catal., 347, 803. 

Transition Metal Compounds. - Macchi et al. performed the first experimental electron density study of a 7t-ligand -coordinated to a metal atom.156 They considered this work as an experimental test of the Dewar-Chatt-Duncanson (DCD) bonding formalism and expected that their work would provide information concerning the 7r-complex versus the metallacycle dichotomy. The authors claim that the successful application of AIM to the experimentally determined p has been the most important step in the coupling of X-ray studies and theoretical chemistry. Their paper reports on the determination of an accurate electron density of crystalline bis(l,5-cyclooctadiene)-nickel, Ni(COD)2 (Figure 11) by X-ray diffraction at 125 K. 

Palladium is the metal involved in most reductive elimination reactions, although they can also occur with nickel, platinum and others. New H-H, C-H, and C-C bonds may be formed, the last being specially significant for synthetic purposes [2]. Many studies, both experimental [3] and theoretical [4] have been made in order to understand the mechanism of reductive elimination reactions and to account for the effect of different factors, such as the specific metal involved, type of fragments to be eliminated, role of other ligands. 

There is now a growing literature of nickel organometallic complexes that contain carbon dioxide or related cumulene ligands that result from reactions with carbon monoxide. The first structurally characterized complex of carbon dioxide was the nickel complex Ni(G02)(PCy3)2 reported in 1975. A more recent study of this complex provides the complete assignments of the vibrational spectra and theoretical calculations of different isomers in support of a mechanism for CO2 fluxionality that involves end-on coordination. The tridentate pincer ligand 2,6-bis((diiso-propylphosphino)methyl)phenyl (PGP) has been used to form the square-planar Ni(ii) hydroxide complex Ni(OH)(PGP). The complex Ni(OH)(PCP) reacts with CO to give a binuclear /X-GO2 complex (Equation (2)). 

At the time of this writing, no studies specifically addressing theoretical or physical studies of nickel complexes with carbene ligands were reported. 

Iron and nickel have also been used to catalyze the intramolecular [5+2] cycloadditions. Louie s group reported a nickel-promoted intramolecular [5+2] cycloaddition when studying the nickel-catalyzed rearrangement of cyclopropylen-ynes (see (25)) [57]. The reaction course strongly depended on the substituents of the substrates and the ligands used, and has also recently been studied theoretically by Houk and co-workers [58]. 

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