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 N-4-tetradentate ligands coordinate to form metal complexes. Here we report the synthesis and structural analysis of cis-beta-{[1,6- di(2'-pyridyl)( 2,5- dibenzyl-2,5- diazahexane)(1,2-benzoquinone diimine)] ruthenium(II)} formed exclusively from the beta-precusor, beta-{[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 alpha- and beta-[Ru(picenbz(2))(dmso)Cl]PF6 (where picenbz(2) 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, alpha or beta, 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 alpha- or beta-[Ru( picenbz(2))( bidentate)](PF6)(2). The synthesis, separation and characterisation of the alpha- and beta- precursors and the alpha- and beta-[ Ru( picenbz2)( bidentate)]( PF6) 2 complexes are reported. Moreover, the crystal structures have been determined for beta[ Ru( picenbz2)( dmso) Cl] PF(6.)0.5H(2)O (C(30)H(37)N(4)O(1.5)F(6)PSC1Ru); it is triclinic, space group P-1, a = 9.987, b = 12.883, c = 14.287 angstrom, alpha = 72.11, beta=78.65, gamma=88.39 degrees and Z=2 and beta- Ru( picenbz2)(bqdi)](PF6)(2), ( C34H38N6F12P2Ru) which is triclinic, space group P-1, with a = 10.129, b = 10.338, c = 19.587 angstrom, alpha = 104.42, beta=93.36, gamma=92.00 degrees 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.