Molybdenum complexes oxidative addition

The addition of an oxygen atom to an olefin to generate an epoxide is often catalyzed by soluble molybdenum complexes. The use of alkyl hydroperoxides such as tert-huty hydroperoxide leads to the efficient production of propylene oxide (qv) from propylene in the so-called Oxirane (Halcon or ARCO) process (79). 

Preparative Methods to 5mL aqueous hydrogen peroxide solution (30%) is added, in portions, 1 g molybdenum(VI) oxide at 20 °C. The mixture is stirred at 20 °C for 20 min and at 40 °C for 4 h. After most of the molybdenum oxide has dissolved the mixture is filtered. The yellow solution is treated at 10 °C with 1 equiv of ligand dissolved in approx. 4 mL methanol. The mixture is stirred for 30 min at 20 °C, concentrated and kept 12 h at 0 °C. When the complex does not crystallize after addition of dichloromethane or benzene, the mixture is diluted with ethanol and carefully (shield protection) concentrated on a rotary evaporator. The procedure is repeated five times. The mixture is then further concentrated. The complex is usually obtained as a yellow microcrystalline powder, but if it is obtained as an oil the addition of diethyl ether with stirring at 5 °C yields a yellow powder. 

A Bm-containing molybdenum stannyl complex has been synthesized by oxidative addition of [Me2Sn(Bm)]Cl to Mo(0) precursors (Fig. 5.14) or through reactions of halostannanes with Na[Mo-(CO)3(Bm)]. The crystal structure of [Mo(CO)3(SnMe2Cl)(Bm)] in which Bm bridges both molybdenum and tin centers is also reported.26... 

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