Synthesis, characterization and theoretical investigations of molybdenum carbonyl complexes with phosphorus/nitrogen/phosphorus ligand as bidentate and tridentate modes

Abstract

Carbonyl complexes of molybdenum with the phosphorus/nitrogen/phosphorus ligand, PNP-Mo(CO)n, where n = 3, 4 and PNP is N,N-bis[2-(diphenylphosphino)ethyl]phenylamine have been synthesized and characterized by 1H, 31P{1H} NMR, IR (ATR and solution state), Raman, X-ray diffraction, MS and elemental analysis. DFT calculations of the complexes were also performed. The PNP-Mo(CO)4 complex in which the binding mode is bidentate cis-phosphine and, facial and meridional isomers of PNP-Mo(CO)3 in which the binding mode is tridentate were obtained. The facial isomer and the tetracarbonyl complexes were successfully synthesized and purified; however, it was not possible to isolate the meridional isomer. Only a few crystals of the meridional isomer were detected and used for X-ray analysis. When the facial isomer was dissolved in CH2Cl2 or in THF, it was found to undergo decomposition thereby generating the tetracarbonyl complex, meridional isomer, Mo(0) as a dark precipitate along with some facial isomer that was left intact in solution. The reason that the facial isomer was the preferred structure with respect to the meridional isomer was also investigated.