REVERSIBLE C-H BOND ACTIVATION IN COORDINATIVELY UNSATURATED MOLYBDENUM ARYLOXY COMPLEXES, MO(PME(3))(4)(OAR)H - COMPARISON WITH THEIR TUNGSTEN ANALOGS

Mo(PMe(3))(6) reacts with ArOH (Ar = C(6)H(2)Me(3), C6H3Pr2i) to give aryloxy-hydride derivatives Mo(PMe(3))(4)-(OAr)H in contrast to the cy clometalated derivatives that are obtained for the corresponding tungs ten system. Deuterium labeling and magnetization transfer studies, how ever, demonstrate that the coordinatively unsaturated molybdenum compl exes Mo(PMe(3))(4)(OAr)H are in fact kinetically capable of intramolec ular oxidative addition of a C-H bond to yield cyclometalated derivati ves but that the products so obtained are thermodynamically unstable w ith respect to the aryloxy-hydride derivatives.