Novel Unsymmetrical Ru(III) and Mixed‐valence Ru(III)/Ru(II)Dinuclear Compounds Related to the Antimetastatic Ru(III) Drug NAMI‐A

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‐RuCl3(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.