H-1-NMR STUDY OF THE SOLVOLYSIS OF THE PARAMAGNETIC TETRACHLORO-BIS(IMIDAZOLE)RUTHENIUM(III) ANION IN WATER, METHANOL, AND DIMETHYL-SULFOXIDE

The H-1 NMR signals of the Ru(III) species present in solution are considerably broadened and shifted by paramagnetism, but they can be used to follow chloride displacement in the trans-[RuCl(4)Im(2)](-) ion. This anion remains predominant for several hours at room temperature in D2O, but its signals are progressively replaced by those of a monoaqua [RuCl3(D2O)Im(2)] complex. Over a period of days, two new sets of peaks appear, corresponding to two isomers of [RuCl2(D2O)(2)Im(2)](+). The same behaviour is observed for the 1-methyl- and 4-methylimidazole analogues. These reactions can be driven backwards by addition of KCl, but [RuCl(4)Im(2)](-) is not quantitatively regenerated in solution even for 6 M NaCl. Within several months, the [RuCl2(D2O)(2)Im(2)](+) isomers further aquate to a single species [RuCl(D2O)(3)Im(2)](2)+. In CD3OD, displacement of the first chloride of [RuCl(4)Im(2)](-) takes place faster, over several hours, but substitution stops at the [RuCl3(CD3OD)Im(2)] stage. In DMSO, substitution occurs very slowly. The [RuCl3(DMSO)Im(2)]:[RuCl(4)Im(2)](-) mixture (1:2) obtained after 12 days starts to show very slow reduction to two Ru(II) species, one of which precipitates as yellow crystals. From X-ray diffraction work (monoclinic, P2(1)/n, a = 9.951, b = 8.564, c = 10.527 Angstrom, beta = 92.95 degrees, R = 0.033), the compound was identified as [RuCl2(DMSO-d(6))(2)Im(2)], where the metal has a trans-trans-trans coordination and the DMSO ligands are S-bonded.