New geometrical and linkage isomers of the Ru(II) precursor cis,cis,trans-RuCl2(dmso-S)2(dmso-O)(CO):: a spectroscopic and structural investigation

The monocarbonyl Ru(Il)-dmso precursor cis,cis, trans-RUCl2(dmso-O)(2)(dmso-O)(CO) (1) equilibrates slowly in light protected chloroform solution with two new geometrical isomers of formula cis,cis,cis-RuCl2(dmso-S)(2)(dmso-O)(CO) (2) and cis,mer-RuCl2(dmso-S)(3)(CO) (3). The three isomers have similar stabilities in solution. In 2 and 3 the three sulfoxides are in a meridional geometry, with the CO ligand coordinated trans to one of the cis chlorides. The new complexes 2 and 3 differ only in the coordination mode of one of the two trans sulfoxides: they are both S-bonded in 3, while one is S-bonded and the other O-bonded in 2. Thus 2 and 3 are linkage isomers of each other. The three isomers 1-3 are also obtained as a mixture by treatment of cis-RuCl2(dmso)(4) with CO. The spectroscopic characterization of the new compounds 2 and 3 is reported, together with the X-ray structure of 2. Isomer 2 is the first example of a Ru(II)-CO complex in which coordination through the oxygen atom is found for a dmso that is not trans to CO; isomer 3 is the first example of a Ru(Il)-dmso complex featuring three S-bonded dmso ligands with a meridional geometry. Considerations relating the stability of the three isomers to their geometry and to the binding mode of the dmso ligands are reported. (C) 2002 Elsevier Science B.V. All rights reserved.