title: Quantum-Chemical Investigations of Stabilizing Interactions in μ-Diborylcarbene Dicobalt Complexes with a Planar Tetracoordinate Carbon Atom.
abstract: Quantum-chemical methods have been employed to study the nature of stabilization in dinuclear cobalt complexes of the general formula [{(C5 H5 )Co}2 (μ-CR(1) 2 BCBR(2) R(3) )] (6) as well as the "antivan't Hoff-Le Bel" configuration of the planar tetracoordinate carbon (ptC) atom of the bridging diborylcarbene ligand 9. Extended Hückel and ab initio Hartree-Fock calculations have been carried out for the model compounds 6b (R(1) = R(2) = R(3) = H) and 6c (R(1) = R(2) = H; R(3) = C6 H5 ). Ab initio electron deformation density maps and natural population analysis calculations show that complexes 6 are stabilized through push-pull effects by which the ptC experiences π electron density delocalization and σ electron density accumulation. The calculated electronic configuration of the ptC in the free ligand 9b is σ(2.978) π(1.501) , and in 6b σ(3.944) π(1.356) . Electron density donation from one cobalt atom to an aryl group on the bridging ligand further contributes to the stabilization of the complexes 6.
authors.affiliation: Chemische Institute der Universität, Im Neuenheimer Feld 270 D-69120 Heidelberg (Germany), Fax: Int. code +(6221)545-609.
authors.forename: I
authors.initials: I
authors.lastname: Hyla-Kryspin
authors.forename: R
authors.initials: R
authors.lastname: Gleiter
authors.forename: M M
authors.initials: MM
authors.lastname: Rohmer
authors.forename: J
authors.initials: J
authors.lastname: Devemy
authors.forename: A
authors.initials: A
authors.lastname: Gunale
authors.forename: H
authors.initials: H
authors.lastname: Pritzkow
authors.forename: W
authors.initials: W
authors.lastname: Siebert
keywords: ab initio calculations; cobalt; planar carbon