Molybdenum dioxomolybdenum complex

TBHP and the molybdenum catalysts are soluble in imidazohiun-based RTlLs. The system becomes biphasic when the olefinic substrate is added. In all cases, the TOFs of the catalytic reactions are considerably lower with the ionic solvent than when performed without the ionic solvent (data reported in Table 9). This slower catalytic reaction may be due to dilution effects and phase transfer problems, especially with the olefin, which is quite insoluble in the RTIL. The conversion appears to be strongly temperature-dependent, as decreasing the temperature from 55 °C to 35 °C reduces the conversion by ca. 50% (entries 7 and 8, Table 9). With the dioxomolybdenum complexes 1 and 2, the epoxidation reaction proceeds with 100% selectivity (Table 9), whereas some diol is formed with the catalyst 3. 

Ferreira, P, Gon9alves, 1., Kiihn, F., et al. (2000). Mesoporous Silicas Modified with Dioxo-molybdenum(VI) Complexes synthesis and Catalysis., Eur. J. Inorg. Chem., 10, pp. 2263-2270 Nunes, C., Valente, A., PiUinger, M., et al. (2003). Molecular Structure-Activity Relationships for the Oxidation of Organic Compounds Using Mesoporous Silica Catalysts Derivatised with Bis(halogeno)dioxomolybdenum(VI) Complexes, Chem. Eur. J., 9, pp. 4380 390 Monteiro,... 

Oxo complexes dominate the chemistry of molybdenum in its higher oxidation states,5 80,92 93 and play a major role in the catalytic activity of molybdenum in biological systems (see Section 36.6.7). MoIV complexes have been characterized containing the monooxo (MoO 2+ and the trans-dioxomolybdenum(IV) Mo02 cores, but no compound has been isolated analogous to the ds-dioxomolybdenum(VI) species described in Section 36.5. Crystal structure determinations have been accomplished for a number of MoIV complexes, and some typical examples are listed in Table 3.80... 

While some molybdenum complexes such as Mo03(dien) were found to be inactive,236 the rates of molybdenum-catalyzed epoxidation of alkenes were found to be independent of the structure of the complex used, after an induction period representing the time for exchange of anionic ligands by the alkyl hydroperoxide. cis-Dioxomolybdenum(VI) diolates such as (78) were isolated... 

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. 

B., Balula, S., Gago, S., et al. (2009). Comparison of Liquid-Phase Olefin Epoxidation Catalysed by Dichlorobis-(Dimethylformamide) Dioxomolybdenum(Vl) in Homogeneous Phase and Grafted onto MCM-41,7. Mo/. Catal.A Chem.,291,pp. 110-117 Yang, Q., Coperet, C., Li, C., et al. (2003). Molybdenum Containing Surface Complex for Olefin Epoxidation, New J. Chem., 27, pp. 319-323. 

Cis-molybdenum(VI) dioxide forms biscatecholate coordination compounds. The third position is already blocked by the two cis-oriented oxo ligands. The reaction of bis(acetylacetonate) cis-dioxomolybdenum with carbonyl-substituted catecholates in the presence of lithium carbonate results in the formation of bis catecholate cis-dioxomolybdenum(VI) complexes that are in equilibrium with their dimers. 

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