Turnover immobilised catalysts

A large range of different ionic liquids have been screened in the epoxidation of cyclooctene with dioxomolybdenum(VI) complexes and ferf-butyl hydrogenperoxide as oxidant, as shown in Table 5.2.[32] With the diazabutadiene complex, 48, as catalyst, inferior turnover frequencies were observed relative to the reaction in neat substrate or in dichloromethane and the recycling potential of the catalyst turned out to be only limited. Catalyst immobilisation was better with the cationic tris(methylaminomethyl)ethane complex, 49, however at the expense of selectivity. Of the ionic liquids tested, [C4Ciim][Tf2N] gave the best results for both molybdenum complexes. 

Comparable results were further observed when neutral cyclopentadienyl-molybdenum(II) compounds like MoCpCl(CO)3 were used as catalysts in that immobilisation of the catalyst in an ionic liquid afforded lower turnover frequencies relative to the reaction in neat substrate.[33]... 

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