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of SummaryTwo stable monopicolinate complexes of ruthenium(II), [Ru(bipy)2(pic)]C10 4 and [Ru(pap)2(pic)]C104 [bipy = 2,2'-bipyridine, pic = picolinate anion, pap = 2-(phenylazo)-pyridine], were prepared and characterized. The complexes are diamagnetic and behave as 1 : 1 electrolytes in MeCN solution. In the i.r. spectra, they show characteristic vibrations of bipy or pap, pic and C10 Z. In MeCN solution, both complexes display three intense absorption bands in the visible region, which have been assigned to metal-to-ligand charge-transfer transitions. Each complex shows a reversible ruthenium(II)-ruthenium(III) oxidation in MeCN, the formal potential (E~ being 0.75 V versus a saturated calomel reference electrode (SCE) for [Ru-(bipy)z(pic)] + and 1.44 V versus SCE for [Ru(pap)z(pic)] +. Multiple reductions of the coordinated bipy and pap ligands have also been observed.

of Summary Using 1,2-naphthoquinone-1-oxime (HL) as the principal ligand, four mixed-ligand ruthenium oximate complexes -namely [Ru(bipy)2(L)]C104, [Ru(pap)a(L)]-C10 4, [Ru(bipy)(L)2 ] and [Ru(PPh3)2(L)2 ], where bipy = 2,2'-bipyridine and pap = 2-(phenylazo)pyridinehave been synthesized and characterized. In all these complexes, Ru exists in the + 2 state. They are diamagnetic and, in solution, show several intense metal-toligand charge transfer (MLCT) transitions in the vis. region. In MeCN solution, all four complexes show a reversible Run-Ru m oxidation on the positive side of a standard calomel electrode (s.c.e.), the potential of which varies with the compositions of the complexes. Reductions of the coordinated co-ligands (bipy or pap) are also observed.

fl-Ketooxime [RC(O)C(NOH)R] (R = Me or Ph) ligands (HL) react with [Ru(PPh3)3C12] in refluxing EtOH to yield [Ru(PPh3)2(L)2'] complexes. For R=Me, one isomer was obtained, while two isomers were isolated when R = Ph, due to a bulk effect. The complexes are diamagnetic and absorb intensely in the vis. region due to MLCT transitions. In MeCN and CH2C12 solution, Ru n_ Ru m oxidation occurs in the 0.69-0.92V versus s.c.e.range. The oxidation potential depends on both the electronic nature of R and the stereochemistry of the complexes.