Synthesis and Coordination of the New Chiral Tridentate O,N,O Ligand 2,6-Bis[(1S,2S,5R)-(−)-menthyl]pyridine to Molybdenum(VI) and Vanadium(V) Oxo Complexes: Crystal Structures of [(2,6-Bis{(−)-menthyl}pyridine)MoO2] and [(2,6-Bis{(−)-menthyl}pyridine)VO]2(μ-O)

Abstract

The novel tridentate chiral ligand 2,6-bis{(−)-menthyl}pyridine (1), was readily prepared from the reaction of 2,6-dilithiopyridine with (−)-menthone. Reaction of 1 with VO(OiPr)3 and [MoO2(acac)2] resulted in the formation of the new metal-oxo complexes [VO(ONO)]2(μ-O) (2) and [MoO2(ONO)] (3) [ONO = (1− 2 H)]. Both metal-oxo compounds 2 and 3 have demonstrated the ability to catalyze the asymmetric oxidation of prochiral olefins with tBuOOH as the oxidant. The compounds 1−3 have been fully characterized by 1H, 13C and 51V (where appropriate) NMR spectroscopy, mass spectrometry, microanalysis and IR spectroscopy. Furthermore, the molecular structures of 2 and 3 have been determined by single-crystal X-ray diffraction.