Densityfunct ional theory and CASSCF calculations have been used to optimize the geometries of binuclear gold(i) complexes [H3PAu(C C)nAuPH3] (n=1

Density functional calculations for copper clusters Cun and their monocarbonyls CunCO (n≤13) have been performed using the relativistic ECP plus DZ basis set augmented by an f polarization function for copper atom. Equilibrium geometries, harmonic frequencies, and static mean polarizabilities of Cun and CunCO are determined. The feature of CO adsorption on the copper cluster and the effect of CO adsorption on stability and polarizability of the cluster are investigated. Calculations show that CO adsorption on copper clusters is selective in terminal coordination, and the favored adsorption sites are dominated by the local orientation of relevant frontier orbitals and the distribution of overall electrostatic potential surfaces of copper clusters. The interaction of Cun with CO in the copper cluster carbonyls leads to significant odd-even variations of the static polarizability differences between CunCO and the separated components Cun and CO. Size dependences of cohesive energies, CO binding energies, and static mean polarizabilities have been explored.

Activation of C-C and C-H bonds by the Rh(I) and Ir(I) complexes (PCP) MCl (M) Rh, Ir; PCP=C6H3(CH3)(CH2PH2)2) has been studied by density functional methodology. C-H activation from either of the three-coordinate intermediates 1a and 1b has a high barrier (>25 kcal/mol). Direct C-C activation does not occur from either 1a or 1b because the C-C bond is sterically inaccessible. Plausible C-C and C-H activation mechanisms under mild conditions are related to four-coordinate

Mechanisms of N2 dissociative adsorption on small ruthenium clusters are studied by density functional calculations. The calculations indicate that the step of a ruthenium cluster has high activity for N2 activation, where an ensemble of five Ru atoms on the stepped surface of clusters is responsible for the active site. Such high activity arises from a strong charge-transfer interaction due to local phase adaptation between the p* orbital of N2 and the filled cluster valence orbital over the step region. Results from cluster models with different size show that the activation mechanism and the barrier are sensitive to the structural environment of the step. N2 dissociation over the step of the 11-atom cluster is a two-step process, where the rate-determining step has a barrier of 22 kcal mol21. N2 dissociative adsorption on the stepped surface of 15-atom and 21-atom clusters is a one-step process, and the barrier is～7-10 kcal mol21. Theoretical calculations on the 11-atom Os and Fe cluster models reveal a general activity of the stepped sites for N2 activation.