Molybdenum complexes 4-tolyl

MAO as activator. Generally, the turnover rates for these systems are only moderate, with that for 33 being on the high side at 470 g(PE)/mmol(Ta)/h/atm. Activities for 34 and the vanadium complex CpV(A -p-tolyl)Cl2 were 0.2 and 8.3 g(PE)/mmol(M)/h/atm, respectively (106). Molybdenum- and tungsten-based systems are similarly mediocre catalysts (106). 

Sketch (a) the transition state for a concerted metal atom-assisted 3,9 hydride shift (b) two PNP ligands (c) the ligand used for selective dimerization of butadiene (d) a general structure for molybdenum- and tungsten-based metathesis precatalyst (e) a six-coordinate rathenium precatalyst for metathesis (f) a solid isolated from the reaction between Pd(OAc)j plus PRj (R = o-tolyl) (g) a T-shaped palladium complex and a two-coordinate palladium complex with a monodentate phosphine (h) an iron complex with a seven-membered metallacycle (i) the transition state for metal-catalyzed cyclopropanation (j) a rhodium and a copper precatalyst used in cyclopropanation reactions. 

Legzdins and coworkers [118] reported an unprecedented transformation of NO bound to molybdenum or tungsten in mononitrosyl-diaryl complexes. A solid purple compound CpW(NO)(o-tolyl)2 when exposed to water vapor at ambient temperature gives CpW(0)(N-o-tolyl)(o-tolyl) with concomitant formation of the di-oxo aryl complex CpW(0)2(o-tolyl). The latter is exclusively formed when the reactant is exposed to anhydrous O2 (Scheme 2.5). The mechanism of this conversion is not clear. However, the characteristic chemistry of CpW(NO)(o-tolyl)2 resembles that estabhshed for other CpM(NO)R2 complexes such as CpW(NO)(CH2SiMe3)2, which indicates that it forms simple 1 1 adducts with both typical Lewis acids and bases. Water as the potential Lewis base is an exception and it is interesting to note that if CpW(NO)(o-tolyl)2 is treated with 0H2, the label is found to be incorporated only into the di-oxo aryl product... 

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