Molybdenum Oxo−Imido Aryloxide Complexes: Oxo Analogues of Olefin Metathesis Catalysts

The novel 16-electron molybdenum oxo−imido bis(aryloxide) complexes [Mo(NtBu)(O)(2,6-Me2C6H3O)2(py)] (1) and
[Mo(NtBu)(O)(2,6-iPr2C6H3O)2(py)] (2) have been prepared by the salt elimination reactions of [Mo(NtBu)(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 π donor in the complexes, resulting in an Mo−O bond order of less
than 2.5. Reaction of [Mo(NtBu)(O)Cl2(DME)] with Li(OCH2tBu) instead gave the novel complex [Mo(NtBu)(OCH2tBu)3Cl(py)] (3).