Variable binding modes of pyridine in molybdenum complexes supported by novel P-pyridine-P ligands

Low oxidn. state molybdenum complexes bind N_2 and in some cases reduce it to NH_3. We have previously demonstrated that molybdenum complexes supported by terphenyl diphosphine ligand platforms bind and activate small mols. We report herein the synthesis and characterization of mononuclear Mo complexes supported by two isomers of a novel ligand framework: 3,5-bis(2-(diisopropylphosphino)phenyl)pyridine (PNP^(3,5)) and 2, 6-bis(2-(diisopropylphosphino) phenyl) pyridine (PNP^(2,6)). Metalation of the phosphines with Mo(CO)_3 (MeCN)_3 results in the formation of MoPNP(CO)_3 complexes. The PNP^(3,5) isomer shows binding via the pyridine π system, while the PNP^(2,6) via the nitrogen lone pair. Oxidn. results in Mo species. Upon photolysis, CO ligand substitution occurs to give Mo- acetonitrile complexes. All reported compds. have been structurally characterized. Their electronic structures and reactivity will be discussed