174646-09-4Relevant academic research and scientific papers
Synthesis and structures of the μ-vinylidene binuclear nickel complexes [Ni2(μ-CCH2)(dmpm)2Cl2] and [Ni2(μ-CCH2)(dppm)2Br2]: Comparison of the electronic structures of nickel A-frames
Heise, Jerald D.,Nash, John J.,Fanwick, Phillip E.,Kubiak, Clifford P.
, p. 1690 - 1696 (1996)
The reaction of bis(cyclooctadiene)nickel(0) with bis(dimethylphosphino)methane (dmpm) and 1,1-dichlorovinylidene in THF yields the vinylidene-bridged binuclear nickel A-frame complex [Ni2(μ-C=CH2)(dmpm)2Cl2] (1a). The structure of 1a was determined by X-ray crystallography. The Ni-Ni separation is 2.898(2) A?, and the vinylidene carbon-carbon bond distance is 1.35(2) A?. The structure of the bis(diphenylphosphino)methane (dppm) bridged μ-vinylidene complex [Ni2(μ-C=CH2)(dppm)2Br2] (2b) was also determined by X-ray crystallography. The Ni-Ni separation of 2.874(2) A? for 2b is comparable to that of 1a. The series of μ-vinylidene nickel A-frames with substituted terminal ligands [Ni2(μ-C=CH2)PR2CH2PR 2)2X2] (X = Cl, Br, I, R = Me; X = Cl, Br, I, NCS, OCN; R = Ph) were prepared and characterized. The nickel A-frames with different bridging ligands [Ni2(μ-C=E)(dppm)2Cl2] (E = O, NPh) were also examined. Extended Hu?ckel molecular orbital (EHMO) calculations indicate that the HOMO in these nickel A-frame complexes is primarily metal based and that the LUMO is derived primarily from the π* system of the μ-C=CH2 ligand. The σ-donating ability of the diphosphine ligands affects the electronic structure of these complexes primarily by stabilizing interactions between the filled d-orbital manifold and the b2 orbital of the vinylidene fragment.
