Stereochemistry of Ruthenium Bis-chelate Disulfoxide Complexes. A Molecular Mechanics Investigation

A topological analysis of bis-chelate disulfoxide metal complexes is presented together with the results of molecular mechanics calculations on dichloro-1,2-bis(methylsulfinyl)ethane Ru(II) complexes. The goal of the work is to study the influence of the nonbonded atom interactions arising from linkage and cis-trans isomerism, combined with different arrangements of the sulfur chiral centers, on the strain energy of the compounds. The calculated strain energies show that the van der Waals and electrostatic interactions largely favor the S-bonding with respect to a mixed S,O-bonding and the cis isomers with respect to the trans isomers. Different arrangements of the chiral sulfur centers yield markedly different molecular energies; in general, meso ligands produce strain energies lower than racemic ligands. A "conformation discriminator" DeltaC has been introduced for the description of the ring conformations in the case of cycles characterized by marked inequalities of bond lengths and angles.