Molybdenum Disubstituted Alkylidene Complexes

Through relatively straightforward techniques that begin with Mo­(NAr)­(CH-t-Bu)­[OCMe­(CF3)2]2 (Ar = 2,6-i-Pr2C6H3), we have prepared Mo­(NAr)­(CMePh)­(OMesityl)2, [Mo­(NAr)­(CMePh)­(OC6F5)2]2, Mo­(NAr)­(CMePh)­(OC6F5)2(MeCN), Mo­(NAr)­(CMePh)­(OC6F5)2(bipyridyl), Mo­(NAr)­(CMePh)­(Cl)2(bipyridyl), Mo­(NAr)­(CMePh)­(Cl)­(OHMT)­(MeCN) (OHMT = O-2,6-(2,4,6-Me3C6H2)2C6H3), and Mo­(NAr)­(CMePh)­(Pyrrolide)­(OHMT). X-ray studies reveal that in five compounds the alkylidene isomer (A) is that in which the phenyl group in the alkylidene points toward the imido nitrogen. In Mo­(NAr)­(CMePh)­(OC6F5)2(MeCN) the isomer in which the methyl group points toward the imido nitrogen (isomer B) has cocrystallized with isomer A (12%). In two 14e compounds that contain isomer A, the Mo═C–C angles differ by 30–36°, consistent with a Mo. . .C–Hβ agostic interaction. Several of the complexes reported here react readily with ethylene, 1-decene, or cyclooctene to give the expected products, thus confirming their viability as initiators or intermediates in metathesis reactions.