Coordination chemistry of arylphosphanes:binding and interligand interactions in chromium, molybdenum and tungsten carbonyl complexes

Abstract The first part of this work consisted of a study of the coordination chemistry of aromatic (P,S) and (P,O) heterodonor phosphanes with Cr(CO) 6 , Mo(CO) 6 and W(CO) 6 . The (P,S) donor ligands having one or two o -thiomethoxyphenyl groups, preferred bidentate coordination mode, while the (P,O) donor ligands, having one, two or three o -methoxyphenyls, formed monodentate phosphorus bound complexes. Steric and electronic parameters affecting the coordination chemistry of the phosphanes are discussed for the monodentate complexes. In the second part, triphenylphosphane and 2- and 4-pyridyldiphenylphosphane substituted tungsten tetracarbonyl derivatives was prepared, and attractive intramolecular interactions between the phosphane ligands were studied for both the neutral and the protonated complexes. Hydrogen bonding, π -stacking and cation-π bonding interactions were established, and observed to influence the cis/trans isomerism of the complexes. Cis/trans isomerism could be tuned by protonation, and deprotonation of the pyridyldiphenylphosphane derivatives. All the complexes were characterised by 1 H, 13 C-{ 1 H} and 31 P-{ 1 H} NMR spectroscopy, X-ray crystallography, IR spectroscopy, and either elemental analysis or mass spectroscopy