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 thes e states were found using a double-group spin-orbit configuration inte raction (CI) program. The quadruple rhenium-rhenium bond was investiga ted and, as previously shown, was not found at the Hartree-Fock level but was found at the MCSCF level. The criteria chosen for the descript ion of the bonds were Mulliken population analysis, contour plots, and the molecular orbital and CI coefficients. The lowest excited state-f or 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.