FULL PAPER DOI: 10.1002/ejic.200600864 Two Novel Reactions of a Ruthenium-Coordinated Phenazine – Oxidative Aromatic Ring Hydroxylation and Dimerization via a New C–N Bond Formation Priyabrata Banerjee, [a] Golam Mostafa, [b] Alfonso Castiñeiras, [c] and Sreebrata Goswami* [a] Keywords: Metal-mediated reaction / Phenazine / Ruthenium / Redox chemistry The reaction of [Ru(CH 3 OH) 2 (N∧N) 2 ] 2+ [N∧N = 2,2'-bipyri- dine (bpy) and 1,10-ortho-phenanthroline(phen)] with the phenazine ligand, [HL 1 = 6-p-anisyl-2-(p-anisylamino)- 3(4H)-p-anisylimine-9-methoxyphenazine] in the presence of a base (NEt 3 ) afforded two mononuclear ruthenium com- plexes, [Ru(L 1 )(N∧N) 2 ]X (2), and [Ru(LO)(N∧N) 2 ]X 2 (3), [LO = 7-methoxy-5-(4-methoxyphenyl)-2,3-bis(4-methoxyphen- ylimino)-3,5-dihydro-2H-phenazin-1-one] together with a di- ruthenium complex [(N∧N) 2 RuL 2 Ru(N∧N) 2 ]X 3 (4), [L 2 = 7,8'- dimethoxy-5,10'-bis(4-methoxyphenyl)-2,3'-bis(4-methoxy- phenylamino)-3,2'-bis(4'-methoxyphenylimino)-3,5,2',10'- tetrahydro-[1,5']biphenazinyl-5'-ylium], (X = ClO 4 – or CF 3 SO 3 – ). The complexes 3 and 4 were also obtained from the pure complex 2 under two different experimental condi- tions. Oxidative aromatic ring hydroxylation of the complex 2 produced 3 while the diruthenium complex, 4, was formed by dimerization of 2 via a new C–N bond formation. The products were thoroughly characterized with the help of 1 H Introduction Transition-metal mediated functionalization of C–H bonds is one of the most vigorously pursued [1–4] areas of current synthetic research. In many instances these reac- tions lead to the synthesis of unusual molecules, which otherwise are difficult or even impossible to synthesize using conventional procedures. In recent years we have been working [5–6] on transition-metal promoted aromatic amine fusion reactions, via C–H functionalization, for the synthe- sis of new organic ligands whose coordination chemistry is rich with novel features. One such example [7] is the ferric [a] Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata 700032, India Fax: +91-33-2473-2805 E-mail: icsg@iacs.res.in [b] Department of Physics, Jadavpur University, Jadavpur, Kolkata 700032, India [c] Departamento de Química Inorgánica, Universidade de Santi- ago de Compostela, Campus, Universitario Sur, 15782 Santiago de Compostela, Spain Supporting information for this article is available on the WWW under http://www.eurjic.org or from the author. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Eur. J. Inorg. Chem. 2007, 412–421 412 NMR and ESI-MS spectral measurements. Final authentica- tion of the two complexes of the transformed phenazine li- gands viz. 3 and 4 were made by single-crystal X-ray struc- ture determination of the two representative complexes. These compounds are intensely colored and show transitions in the visible region, which are ascribed as metal-to-ligand charge transfer (MLCT). Notably, intensities of the two MLCT of the compound 4 are significantly higher than those of 2 and 3. Redox properties of the complexes are reported. Electrochemical oxidation of compound 2, even in the pres- ence of trace moisture, produced compound 3. Cyclic voltam- metry of compound 3 shows a reductive response near –0.35 V. Its one-electron reduced product is blue and shows an intense EPR signal at g = 2.001. The voltammogram of the diruthenium complex 4 consists of two responses near 0.70 and 0.85 V. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) chloride-mediated oxidative polymerization of p-anisidine, which produces N-substituted 2-amino-3-iminophenazines via a multiple C–N bond fusion reaction (Scheme 1). Scheme 1. Our interest [6] in the coordination chemistry of 1,2-di- imine ligands and their redox partners prompted us to ex- plore the ligand chemistry of [HL 1 ]. We have shown [7] that