Quantum chemical investigations of intramolecular isomerization in RuH2(CO)2(PMe3)2

The coordination of CO to the ruthenium complex RuH2(PCy3)2 has been investigated by means of the DFT/B3LYP method. The modeling of PCy3 by PMe3 fits better with the experimental results than phosphine PH3. Several isomers have been calculated on the potential energy surface and the three lowest isomers were found to have very similar energies in perfect agreement with experimental results. The most stable isomer presents the phosphines in trans position while the two carbonyl ligands are in cis position. The isomerization process between the two most stable isomers has been studied. The value of the isomerization barrier is 113.5 kJ mol−1. The thermodynamic analysis of CO and H2 bonding indicates a strong interaction between the carbonyl ligand and the metallic center. The good catalytic activity of this compound may be interpreted in terms of the great facility of dihydrogen molecules to be replaced by carbonyls.