Equilibria in complexes of N-heterocyclic molecules. Part 19. Reactions of tris(2,2′-bipyridyl)-, tris(1,10-phenanthroline)-, and bis(2,2′-bipyridyl)dicyano-ruthenium(III) in aqueous solution
Abstract
The reactions of [Ru(bipy)3]3+, [Ru(phen)3]3+, and [Ru(bipy)2(CN)2]+ in aqueous solution have been followed (bipy = 2,2′-bipyridyl, phen = 1,10-phenanthroline). Neither [Ru(bipy)3]3+ nor [Ru(phen)3]3+ racemizes or dissociates in aqueous solution, contrary to earlier reports. Both react to form new species which appear to be covalently hydrated. Further reaction takes place at the ligand with [Ru(phen)3]3+, but the formation of the new species is at least initially reversible. The reaction to form new purple compounds, one of which can be isolated, is completely reversible in the case of [Ru(bipy)3]3+, and with retention of optical configuration. The series of reactions described fits the known reactions involving the tervalent complexes when they are reduced and a mechanism for the known formation of H2O2 is provided. The CN groups in [Ru(bipy)2(CN)2]+ react in aqueous solution to yield [Ru(bipy)2(OH2)2]3+ by a series of complex steps. Solid Ru(bipy)2(SCN)2·4H2O can be isolated from such reaction mixtures following reduction and addition of [SCN]– ion.
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