A novel cis-push-pull effect in cycloruthenated azobenzene thiocarbonyl-containing complexes: Crystal and molecular structures of [RuX(CS)(η2-C,N-C6H4N=NPh)(PPh 3)2](X = Cl, I)

Treatment of [RuHCl(CS)(PPh3)3] with Hg(o-C6H4N=NC6H5)2 affords [RuCl(CS)(η2C,N-o-C6H4N=NC 6H5)(PPh3)2] (1) in good yield, where the cyclometallated azobenzene ligand coordinates through an ortho-C and one azo-N to give a five-membered chelate ring. Reaction of 1 with AgNO3 followed by NaBr or NaI affords the chloride-exchanged products [RuX(CO)(η2C,N-o-C6H4N=NC6H 5)(PPh3)2] (2, 3), whereas reaction of 1 with AgOC(O)Me or NaS2CNEt2·2H2O gives the halide mono-phosphine-substituted complexes [Ru(CS)(LL)(η2C,N-o-C6H4NNC 6H5)(PPh3)] (4, 5). In the solid-state structures of 1 and 3 there are significant changes in the bond lengths for the cyclometallated azobenzene ligand are observed relative to free azobenzene. These are discussed, with the aid of spectroscopic and crystallographic data, in terms of a cis-push-pull effect. © 2001 Elsevier Science B.V. All rights reserved.