Isomerism in the cis-dichloro-tris(dimethyl sulfoxide)(carbonyl)ruthenium(II) complex:: a density functional theory investigation

The structures of six isomers (1-6) of the cis-RuCl(2)dimethyl sulfoxide)(3)(CO) complex were optimized using the B3LYP density functional method. The calculated bond lengths well reproduce the trend of the experimental values, available for two isomers (1, 2), although a general overestimate is found. The molecular energies were calculated both in gas phase and in chloroform and methanol solutions, showing that the cis,cis,cis-RuCl2(dmso-S)(2)(dmso-O)(CO) complex (2) exhibits the lowest energy. The gas phase results are in fairly good agreement with the isomer population of the three experimentally observed isomers (1-3), and exclude the presence of complexes with one S-bonded dmso ligand trans to CO (5, 6), because of their much higher energies. The fact that the calculated low energy isomer, cis,trans,cis-RuCl2(dmso-S)(2)(dmso-O)(CO) (4), was not detected in solution might be attributed to kinetic factors. (C) 2002 Elsevier Science B.V. All rights reserved.