Structure and bonding in metal sulfoxide complexes: an update

Average S-O bond distances were calculated, from accurate X-ray data, for free and coordinated sulfoxides, showing a decrease from free sulfoxides (avearge 1.492(1) Angstrom) to S-bonded metal complexes (average 1.4738(7) Angstrom). On the contrary, the S-O bond distance increases in H-bonded uncoordinated sulfoxides (S-(OH)-H-..., average 1.513(2) Angstrom), and more markedly in O-bonded metal complexes (average 1.528(1) Angstrom). Longer S-O bond lengths are found in the [(sulfoxide-O)(2)H](+) (average 1.541(3) Angstrom) and [(sulfoxide-O)H](+) cations (average 1.587(2) Angstrom). This trend is consistent with that of the SO stretching frequencies, and is definitely supported by quantum chemical calculations for dmso, [(dmso)H](+), and platinum and ruthenium dmso complexes. DFT quantum chemical investigations about linkage isomerism and isomer equilibration are also reported and discussed with reference to the experimental evidence. Finally, the stereochemistry of ruthenium sulfoxide complexes is discussed on the basis of molecular mechanics calculations, showing the role of intramolecular steric interactions. (C) 2003 Elsevier B.V. All rights reserved.