Novel polypyridyl ruthenium(II) complexes containing oxalamidines as ligands

The complexes [Ru(bpy)(2)(H(2)TPOA)](PF6)(2). 4H(2)O (1); [Ru(Me-bpy)(2)(H( 2)TPOA)](PF6)(2). 2H(2)O (2); [Ru(bpy)(2)(H(2)TTOA)](PF6)(2). 2H(2)O (3); [ Ru(Me-bpy)(2)(H(2)TTOA)](PF6)(2). 2H(2)O (4) and {[Ru(bpy)(2)](2)(TPOA)}(PF 6)(2). 2H(2)O (5) (where bpy is 2,2'-bipyridine; Me-bpy is 4,4'-dimethyl-2, 2'-bipyridine; H(2)TPOA is N,N',N",N"'-tetraphenyloxalamidine; H(2)TTOA is N,N',N",N'"-tetratolyloxalamidine) have been synthesised and characterised by H-1 NMR, FAB MS, infrared spectroscopy and elemental analysis. The X-ray investigation shows the coordination of the still protonated oxalamidine m oiety via the 1,2-diimine unit. The dimeric compound (5) could be separated in its diastereoisomers (5') and (5") by repeated recrystallisation. The d iastereomeric forms exhibit different H-1 NMR spectra and slightly shifted electronic spectra. Compared with the model compound [Ru(bpy)(3)](2+), the absorption maxima of (1)-(5) are shifted to lower energies. The mononuclear complexes show Ru(III/II)-couples at about 0.9 V versus SCE, while for the dinuclear complex two well defined metal based redox couples are observed at 0.45 and 0.65 V, indicating substantial interaction between the two meta l centres. (C) 2000 Elsevier Science S.A. All rights reserved.