AB-INITIO CALCULATIONS OF DIRHENIUM COMPLEXES USING RELATIVISTIC EFFECTIVE CORE POTENTIALS

The electronic structures of the quadruple-bonded complexes Cl-2(OH)(2)ReReCl2(PH3)2 and Re2Cl8-2 were studied using relativistic effective core potentials. Hartree-Fock and multiconfigurational self-consistent field (MCSCF) calculations for these complexes were performed on the ground state and several excited states. Spin-orbit splittings of these states were found using a double-group spin-orbit configuration interaction (CI) program. The quadruple rhenium-rhenium bond was investigated and, as previously shown, was not found at the Hartree-Fock level but was found at the MCSCF level. The criteria chosen for the description of the bonds were Mulliken population analysis, contour plots, and the molecular orbital and CI coefficients. The lowest excited state-for these complexes was found to be a (3)A(1), delta-delta* State with spin-orbit splittings of the order of 40 cm(-1). Calculations are also reported on two spectroscopically important excited states, the delta-delta* singlet state and a ligand-to-metal charge transfer state.