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

Abstract

Thermally induced carbonyl substitutions on [M(CO)₅X] (M = Mn, X = Cl, Br; M = Re, X = Br) or room temperature displacement of acetonitrile from [Mo(η³-methallyl)Cl(CO)₂(NCMe)₂] produce stable crystalline complexes containing pyridine-2-carboxaldehyde (pyca) as chelate κ²(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 confirmed by spectroscopy and X-ray crystallography the pyca ligand remains bonded as chelate κ²(N,O) throughout these processes.