Pyridine-2-carboxaldehyde as ligand:: Synthesis and derivatization of carbonyl complexes

Thermally induced carbonyl substitutions on [M(CO)(5)X] (M = Mn, X = Cl, Br; M = Re, X = Br) or room temperature displacement of acetonitrile from [Mo(eta(3)-methallyl) Cl(CO)(2)(NCMe)(2)] produce stable crystalline complexes containing pyridine-2-carboxaldehyde (pyca) as chelate kappa(2)(N,O) ligands (1a-d). These react with ethylglycine to afford iminopyridine complexes 2a-d containing an amino ester pendant arm in high-yield. Treatment with silver salts produce halide abstraction affording neutral complexes 3a-d containing coordinated perchlorate or triflate which can be replaced by triphenyl phosphine to give cationic complexes 4a-d. As con. rmed by spectroscopy and X-ray crystallography the pyca ligand remains bonded as chelate kappa(2)(N,O) throughout these processes.