Novel unsymmetrical Ru(III) and mixed-valence Ru(III)/Ru(II) dinuclear compounds related to the antimetastatic Ru(III) drug NAMI-A

Abstract

In this paper we report the stepwise preparation and the characterization of new unsymmetrical monoanionic Ru(III) dinuclear compounds. [NH4][{trans-RuCl4(Me2SO-S)}(μ-L) {mer-RuCl3(Me2SO-S)(Me2SO-O)}] (L = pyz (1), pym (2)). By a similar synthetic approach we also prepared new mixed-valence Ru(III)/Ru(II) dinuclear compounds of formula [NH4][{trans-RuCl4(Me2SO-S)}(μ-pyz){cis,cis, cis-RuCl2(Me2SO-S)2(CO)}] (L = pyrazine (pyz, 3), pyrimidine (pym, 4)). Moreover, we describe the chemical behavior of compounds 1-4 in physiological solution, also after complete reduction (with ascorbic acid) to the corresponding Ru(II)/Ru(II) species. Overall, the chemical behavior of 1 and 2 after reduction resembles that of the corresponding dianionic and neutral dinuclear species, [{trans-RuCl4(Me2SO-S)}2(μ-L)]2- and [{mer-RuCl3(Me2SO-S)(Me2SO-O)}2(μ -L)]. On the other hand, the mixed-valence dinuclear compounds 3 and 4, owing to the great inertness of the cis,cis,cis-RuCl2(Me2SO-S)2(CO)(1/2μ-L) fragment, behave substantially like the mononuclear species [trans-RuCl4(Me2SO-S)(L)]- in which the terminally bonded L ligand can be considered as bearing a bulky substituent on the other N atom.