New dioxomolybdenum(VI) catalysts for the selective oxidation of terminal n-alkenes with molecular oxygen

New dioxomolybdenum(VI) complexes of the type MoO₂L₂ [L = (2'-pyridyl)alcoholate] are able to change considerably the product distribution of the metal catalyzed autoxidation process. With the catalyst bis[N,O-{(2'-pyridyl)pentan-3-olato}]dioxomolybdenum(VI) (2) the epoxide is formed as the main product in the autoxidation process of 1-octene. The product selectivity is increased from 24% (epoxide, autoxidation) to 58% upon treatment of 1-octene with molecular oxygen (1 bar and 100°C) in the presence of 2. An additional advantage is that the catalyst can be recovered. The synthesis and the characterization of the new dioxomolybdenum(VI) complexes and the ligands is described in addition to their catalytic properties. The structure of the new complex bis[N,O-{(2'-pyridyl)pentan-3-olato}]dioxomolybdenum(VI) (2) was determined by X-ray diffraction: monoclinic space group P 2₁/c, a = 1444.5(2) pm. b = 1052.4(1) pm, c = 1511.5(2) pm, β = 115.86(1)°, V = 2068(1)* 10⁶ pm³. The epoxidation data indicate an important influence of the ligand sphere of the catalyst on the product distribution. We have now the possibility of fine tuning the complexes in the metal catalyzed autoxidation reaction.