Intramolecular hydrogen-bonding, cation-pi, and pi-stacking interactions affecting cis/trans isomerization: Hexacarbonyltungsten derivatives of pyridyl-substituted arylphosphane ligands

A series of triphenylphosphane- and diphenyl(2-pyridyl)phosphane-substitute d tetracarbonyltungsten derivatives has been prepared. Attractive intramole cular interactions between the phosphane ligands have been studied in both the neutral and protonated complexes; pi -stacking, hydrogen-bonding, and c ation-pi bonding interactions were identified and were found to have an inf luence on the cis/trans isomer-ism of the complexes. It was found that the cis/trans isomerism could be switched by protonation or deprotonation of th e diphenyl(2-pyridyl)phosphane derivatives. The complexes have been charact erized by P-31-, H-1-, and C-13 NMR spectroscopy, X-ray crystallography, IR spectroscopy, and mass spectrometry.