Alain Serafini

Une extension de la méthode CNDO/2 á l'étude des complexes d'éléments de transition

An extension of the CNDO/2 formalism, similar to the method of Clack, Hush and Yandle but with a different parametrisation, is proposed for investigating the electronic structure of transition metal complexes. The results for Ni(CO)4 and Ni(PF3)4 agree well with those ofab initio calculations and with some experimental data. Such a semi-empirical approach may be performed, usingab initio results as reference data, in order to interpret the physical and chemical behaviour of largeseries of complexes in their ground state.

Une extension de la méthode CNDO/2 à l'étude des complexes d'éléments de transition@@@An extension of the CNDO/2formalism for the study of transition metal complexes: II. Cr(CO)6 et Fe(CO)5@@@II. Cr(CO)6 and Fe(CO)5

The previously proposed extension of the CNDO/2 formalism is used for investigating the electronic structure of Cr(CO)6 and Fe(CO)5. Thus, the ordering and the eigen values of molecular energy levels agree well with results provided byab initio calculations and photoelectron spectroscopy. The formal charge on metal is found to be in any case positive, as in Ni(CO)4 and Ni(PF3)4. Moreover, the validity of our parametrization is supported by the pretty agreement which exists between energy levels distribution and electronic structure provided by our technique and Veillardsab initio results for Ni(CN)42−. The parameters for the (Cr, Fe, Ni) set are now available and will allow to study large series of complexes in order to interpret their physical and chemical behaviour.

Non-empirical pseudopotentials (PSIBMOL algorithm) for molecular calculations: The Rh2Cl2(CO)4 complex

The electronic structure of Rh2Cl2(CO)4 in the ground state is computed using the recently proposed PSIBMOL (Pseudo-potentials + IBMOL/H) formalism. The drawing of the total and differential isoelectronic contour maps supports the idea that there does not exist any rhodium-rhodium bond in such a binuclear complex, the origins of the preferred bent conformation having to be found elsewhere.

Molecular orbital study of the bridge bonding in an electron deficient molecule [(CH3)2ALH]2

The electronic distribution in the AlH2Al bridge of the dimethyl aluminium hybride dimer was computed through ab initio SCF calculation. Comparison with diborane shows an increased role of the ionic Al+H22−Al+ structures with respect to the usual covalent three-center bonds.