Reaction of the antitumor complex trans-[RuIIICl4(Hind)2]−
(Hind = indazole) with an excess of dimethyl sulfoxide (dmso) in acetone afforded the complex trans,trans,trans-[RuIICl2(dmso)2(Hind)2]
(1). Two other isomeric compounds trans,cis,cis-[RuIICl2(dmso)2(Hind)2]
(2) and cis,cis,cis-[RuIICl2(dmso)2(Hind)2]
(3) have been obtained on refluxing cis-[RuIICl2(dmso)4] with 2 equiv. of indazole in ethanol and methanol, respectively. Isomers 1 and 2 react with acetonitrile yielding the complexes trans-[RuIICl2(dmso)(Hind){HN
C(Me)ind}]·CH3CN (4·CH3CN) and trans,cis-[RuIICl2(dmso)2{HN
C(Me)ind}]·H2O (5·H2O), respectively, containing a cyclic amidine ligand resulting from insertion of the acetonitrile C
N group in the N1–H bond of the N2-coordinated indazole ligand in the nomenclature used for 1H-indazole. These are the first examples of the metal-assisted iminoacylation of indazole. The products isolated have been characterized by elemental analysis, IR spectroscopy, UV-vis spectroscopy, electrospray mass-spectrometry, thermogravimetry, differential scanning calorimetry, 1H NMR spectroscopy, and solid-state 13C CP MAS NMR spectroscopy. The isomeric structures of 1–3 and the presence of a chelating amidine ligand in 4 and 5 have been confirmed by X-ray crystallography. The electrochemical behavior of 1–5 and the formation of 5 have been studied by cyclic voltammetry.