Complexes of the imine/thioether mixed-donor ligand 8-methylthioquinoline with d6-configurated transition metal centers:: synthesis, structures and comparison with complexes of 1-methyl-2-(methylthiomethyl)-1H-benzimidazole

Coordination compounds of chelating 8-methylthioquinoline (MTQ) with the complex fragments Re-1(CO)(3)CI, [Ru-II(bPY)(2)](2+), [Rh-III(C5Me5)Cl](+), [Ir-III(C5Me5)Cl](+), and (PtMe4)-Me-IV were synthesized and structurally characterized. Whereas the ruthenium(II) complex displays the strongest preference of bonding to N versus S, the compound (MTQ)PtMe4 shows the most balanced metal-donor bonding within the chelate ring due to a relatively short bond to S (2.319Angstrom) versus N (2.150Angstrom). The complex fac(MTQ)Re(CO)(3)Cl exhibits a particularly long metal-sulfur bond at 2.472 Angstrom. Cyclic voltammetry of [(MTQ)Ru(bpY)(2)](PF6)(2) reveals one reversible oxidation to Ru-III and three closely spaced reduction waves for the coordinated ligands. In comparison with the imine/thioether chelate ligand 1-methyl-2-(methylthiomethyl)-1H-benzimidazole (mmb) the MTQ ligand with its more rigid chelate setting N(sp(2))-C(sp(2))-C(sp(2))-S forms generally shorter M-S bonds and displays stronger pi acceptor behaviour. (C) 2004 Elsevier B.V. All rights reserved.