Molybdenum oxo-imido aryloxide complexes: Oxo analogues of olefin metathesis catalysts

The novel 16-electron molybdenum oxo-imido bis(aryloxide) complexes [Mo((NBu)-Bu-t)(O)(2,6-Me2C6H3O)2(py)] (1) and[Mo((NBu)-Bu-t)(O)(2,6-(Pr2C6H3O)-Pr-i)(2)(py)] (2) have been prepared by the salt elimination reactions of[Mo((NBu)-Bu-t)(O)Cl2-(DME)] with the appropriate lithium aryloxide and from the cycloaddition reactions of tert-butyl isocyanate with the appropriate molybdenum dioxo bis(aryloxide) complex [Mo(O)(2)(OAr)(2)(py)(n)]. Complexes 1 and 2 are the first isolable and crystallographically characterized molybdenum oxo-imido aryloxide complexes. The geometry around the metal in complexes 1 and 2 is best described as a distorted trigonal bipyramid, with the imido and pyridine ligands occupying the axial positions and the oxo and aryloxide ligands in the equatorial plane. X-ray and IR data have confirmed that the imido ligand is the dominant pi donor in the complexes, resulting in an Mo-O bond order of less than 2.5. Reaction of[Mo((NBu)-Bu-t)(O)Cl-2(DME)] with Li(OCH2(t)Bu) instead gave the novel complex [Mo((NBu)-Bu-t)(OCH2t-Bu) Cl-3(py)] (3).