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

Abstract

The monocarbonyl Ru(II)–dmso precursor cis, cis, trans-RuCl 2(dmso-S) 2(dmso-O)(CO) ( 1) equilibrates slowly in light protected chloroform solution with two new geometrical isomers of formula cis, cis, cis-RuCl 2(dmso-S) 2(dmso-O)(CO) ( 2) and cis, mer-RuCl 2(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-RuCl 2(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(II)–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.