Approaches Towards the Syntheses of New Molybdenum Complexes as Models for the Active Site in Nitrogenase Enzymes

The present study aims to mimic the catalytic properties of the Mo center in the active site of the nitrogenase enzyme. The phosphorous-sulfur ligands PS3, PS3’ and PS3* were used to synthesize Mo-thiolate complexes of the formula [Mo(PS3)L2] where L is NO, N2 or a related molecule. The starting material [Mo(NO)2Cl2] allows for the study of structure and reactivity at the Mo center via IR spectroscopy of the NO region. Reactions of the starting material in various solvent systems to form complexes of the formulation [Mo(NO)2Cl2L2] confirmed the stationary nature of the cis NO ligands. Reactions with PS3 and PS3’ worked best in methanol, giving clean spectra with two NO peaks, as expected for a cw conformation; the reaction with PS3* worked best in THF. A crystal structure of air-stable [Mo(NO)2Cl2(C2H5CN)2] was successfully obtained and analyzed using X-ray crystallography. The bond angles in the structure compare favorably to accepted octahedral complexes