Transition metal complexes of the novel hexadentate ligand 1,4-bis(di(N-methylimidazol-2-yl)methyl)phthalazine

By Roggan, Stefan; Limberg, Christian; Knispel, Christina & Tilley, T. Don
Published in Dalton Trans. The Royal Society of Chemistry 2011

Abstract

The novel polydentate ligand 1, 4-bis(di(N-methylimidazol-2-yl)methyl)phthalazine, bimptz, has been synthesized and its coordination chemistry was investigated. Bimptz is neutral and contains a central phthalazine unit, to which two di-(N-methylimidazol-2-yl)methyl groups are attached in the 1, 4-positions. This ligand therefore provides up to 6 donor sites for coordination to metal ions. A series of metal complexes of bimptz was prepared and their molecular structures were determined by X-ray diffraction. Upon reaction of bimptz with two equivalents of MnCl2[middle dot]4H2O, CoCl2[middle dot]6H2O and [Ru(dmso)4Cl2], the dinuclear complexes [Mn2(bimptz)([small micro]-Cl)2Cl2] (1), [Co2(bimptz)(CH3OH)2([small micro]-Cl)2](PF6)2 (3) and [Ru2(bimptz)(dmso)2([small micro]-Cl)2](PF6)2 (4), respectively, were isolated. The latter were found to have similar solid state structures with octahedrally coordinated metal centers bridged by the phthalazine unit and two chloro ligands. The cobalt and ruthenium complexes 3 and 4 were isolated as PF6- salts and contain neutral methanol and dmso ligands, respectively, at the terminal coordination sites of the metal centres. The mononuclear ruthenium complex [Ru(Hbimptz)2](PF6)4 (6) was obtained from the reaction of two equivalents bimptz with [Ru(dmso)4Cl2]. In complex 6, three donor sites per ligand molecule are used for coordination of the Ru(ii) center. In each bimptz ligand, one of the remaining, dangling N-methylimidazole rings is protonated and forms a hydrogen bond with the unprotonated N-methylimidazole ring of the other bimptz ligand.

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