Binuclear organometallic compounds containing planar tetra co-ordinated carbon atoms: theoretical study on geometrical and bonding patterns

Abstract

Structure and bonding in the binuclear complex 1, the metallacyclocumulene, 2 and the metal-acetylene complex, 3, are studied using Density Functional Theory. The C-C bond lengths in metal-acetylene complex mainly depend on the diffuseness of the orbitals of the metal atom. Since the C1-C2-C3 angle in 2 changes to give effective overlap as the size of the metal is changed, the central C-C bond length of the cumulene remains nearly constant. In many ways the ML₂ fragments determine that the bond angles C1-C2-C3 and C4-C3-C2 and the distance C2-C3 to have effective overlap with the C₄H₂ frame. Four in-plane delocalized molecular orbitals and two p molecular orbitals perpendicular to the MC₄M' plane contribute to the stability of the planar tetra coordination around the two central carbon atoms. At the B3LYP/LANL2DZ levels, the stability of the complex, 1, increases with decrease in the size of the M'.