The synthesis and structural analysis of cis-β-{(1,6-di(2′- pyridyl)(2,5-dibenzyl-2,5-diazahexane O(1,2-diazahexane))(1,2-benzoquinone diimine))ruthenium(II)} and related complexes

Several isomers are possible when N4-tetradentate ligands coordinate to form metal complexes. Here we report the synthesis and structural analysis of cis-β-{[1,6-di(2′-pyridyl)(2,5-dibenzyl-2,5-diazahexane)(1, 2-benzoquinone diimine)]ruthenium(II)} formed exclusively from the β-precusor, β-{[1,6-di(2′-pyridyl)(2,5-dibenzyl-2,5-diazahexane) (dimethylsulfoxide)chloride] ruthenium(II)} hexaflourophosphate. Ruthenium(II) complexes synthesised from 1,6-di(2′-pyridyl)-2,5-dibenzyl-2,5- diazahexane, produce only two isomers which can be separated by recrystallisation into α- and β-[Ru(picenbz2)(dmso)Cl]PF6 (where picenbz2 is 1,6-di(2′-pyridyl)-2,5-dibenzyl-2,5-diazahexane). The distinctively different proton NMR spectra of the isomers are an especially convenient feature with which to assess separation. Isomeric structure of the precursor, α or β, is conserved upon coordination of a bidentate ligand, such as benzene-1,2-diamine, 4,5-dimethyl-benzene-1,2-diamine, naphthalene-2,3-diamine, 2,2′-bipyridine, 1,10-phenanthroline or dipyrido[3,2-d:2′3′-f] quinoxaline, to produce complexes of the type α- or β-[Ru(picenbz2)(bidentate)](PF6)2. The synthesis, separation and characterisation of the α- and β-precursors and the α- and β-[Ru(picenbz2)(bidentate)](PF6)2 complexes are reported. Moreover, the crystal structures have been determined for β-[Ru(picenbz2)(dmso)Cl]PF6.0. 5H2O (C30H37N4O1.5F6PSClRu); it is triclinic, space group P1, a = 9.987, b = 12.883, c = 14.287 Å, α = 72.11, β = 78.65, γ = 88.39° and Z = 2 and β-[Ru(picenbz2)(bqdi)](PF6)2, (C34H38N6F12P2Ru) which is triclinic, space group P1, with a = 10.129, b = 10.338, c = 19.587 Å, α = 104.42, β = 93.36, γ = 92.00°and Z = 2. The structures were determined at room temperature and refined by least-squares methods to R = 0.044 for 5109 and R = 0.075 for 3057 non-zero diffractometer data, respectively, for the dmso and bqdi species above.