COORDINATION CHEMISTRY OF CHELATING NITROGEN LIGANDS WITH TUNGSTEN CARBONYL NITRILES

The reactions of a series of Schiff base ligands (1-4) prepared by condensation of pyridine-2-carboxaldehyde and 2-X-anilines (X = F, Cl, Br, OMe) with W(CO)3(RCN)3 results in the formation of deeply coloured complexes W(CO)3(1-4)(NCR) which readily react with carbon monoxide to afford W(CO)4(1-4). The ligand 5, prepared from pyridine-2-carboxaldehyde and N,N-dimethylethylenediamine, coordinates to W(CO)3 through the conjugated pyridine-imine chelate to afford complexes with a pendant dimethylamino group which reacts with electrophiles. Of the ligands studied, only the bis-amine, pyridine ligand 8, coordinates to W(CO)3 in a tridentate manner. These reactions provide insight into the geometric and electronic factors which influence coordination of nitrogen containing ligands at a fac-tricarbonyl metal centre.