Molybdenum complexes, with

The tert-huty hydroperoxide is then mixed with a catalyst solution to react with propylene. Some TBHP decomposes to TBA during this process step. The catalyst is typically an organometaHic that is soluble in the reaction mixture. The metal can be tungsten, vanadium, or molybdenum. Molybdenum complexes with naphthenates or carboxylates provide the best combination of selectivity and reactivity. Catalyst concentrations of 200—500 ppm in a solution of 55% TBHP and 45% TBA are typically used when water content is less than 0.5 wt %. The homogeneous metal catalyst must be removed from solution for disposal or recycle (137,157). Although heterogeneous catalysts can be employed, elution of some of the metal, particularly molybdenum, from the support surface occurs (158). References 159 and 160 discuss possible mechanisms for the catalytic epoxidation of olefins by hydroperoxides. 

Add to the sample solution (containing 1 -25 g of Mo) 4 mL of 1 3 sulphuric acid, 3 drops of 85 per cent phosphoric(V) acid, and 0.5 g of citric acid. Dilute with water to 20 mL and add 2 mL of dithiol solution. Allow to stand at room temperature for 2 hours. Extract the molybdenum complex with 13 mL and 10 mL portions respectively of re-distilled butyl acetate, and make up to 25.0 mL with this solvent in a graduated flask filter through glass wool if not entirely clear. Determine the absorbance of the solution at 670 nm. Prepare a calibration curve as detailed in Section 6.14. 

For a chiral molybdenum-based catalyst available in situ from commercial components, see (a) Aeilts SL, Cefalo DR, Bonitatebus PJ, Houser JH, Hoveyda AH, Schrock RR (2001) Angew Chem Int Ed 40 1452 (b) For the first enantiomerically pure solid-sup-ported Mo catalyst, see Hultzsch KC, Jernelius JA, Hoveyda AH, Schrock RR (2002) Angew Chem Int Ed 41 589 (c) For a chiral Mo catalyst, allowing RCM to small- and medium-ring cyclic amines, see Dolman SJ, Sattely ES, Hoveyda AH, Schrock RR (2002) J Am Chem Soc 124 6991 (d) For a novel adamantyl imido-molybdenum complex with advanced selectivity profiles, see Tsang WCP, Jernelius JA, Cortez GA, Weatherhead GS, Schrock RR, Hoveyda AH (2003) J Am Chem Soc 125 2591... 

The formation of molybdenum complexes with diols (formed by olefin oxidation) was proved for the use of the molybdenum catalysts. Therefore, the participation of these complexes in the developed epoxidation reaction was assumed [242]. 

The key step involves C-H bond activation, and produces a molybdenum complex with hydride and ketone ligands from the alkoxide ligand. Subsequent... 

Sakthivel, A., Zhao, J., Hanzlik, M., Chiang, A. S. T., Herrmann, W. A. and Kuhn, F. E. Heterogenization of organometallic molybdenum complexes with siloxane functional groups and their catalytic application, Adv. Synth. Catal., 2005, 347, 473 483. 

PhS, p-tolS) initially yields the bis(nitrile) complexes [MI2(CO) (NCMe)2(i72-RC2R )]. which dimerize to yield the iodo-bridged complexes [ M(/t-I)I(CO)(NCMe)(T)2-RC2R ) 2].245 The reactions of the diphenylacet-ylene molybdenum complex with donor ligands and alkynes are shown in Scheme 6. 

Epoxidation of olefins (2, 287). The procedure for epoxidation of olefins with t-butyl hydroperoxide catalyzed by molybdenum hexacarbonyl has been published. Kinetic data have been obtained from the reaction. The mechanism is believed to involve I) reversible complex formation between the catalyst and the hydroperoxide, 2) reversible inhibition by the coproduct alcohol, and 3) reaction of the hydroperoxide-molybdenum complex with the olefin to form the epoxide and by-product alcohol. 

The conversion of ketones into a-hydroxy ketones can be achieved by the oxidation of enolates or enol ethers. A special reagent for enolates is the oxodiperoxy molybdenum complex with pyridine and hexamethylphos-phoramide. The reaction is applied to aromatic aliphatic ketones and cyclic ketones and furnishes 34-81% yields of a-hydroxy ketones with up to 26% of a-diketones (equation 401) [531]. 

Figure 2.8.8 Molecular structures of the molybdenum complexes with the N-alkyl-substituted bis-stannylene 20 (right) and the N-donor-substituted bis-stannylene 22 (right)...

Ccrvilla, A., Domenech, A., Llopis, E., Vicente, E, and Tamarit, R. 1994b. Molybdenum complexes with slcrically-hindcrcd thio-carboxylate ligands. Electrochemical properties of the anionic complex bis(2,2-diphenyl-2-mercaptoethanoate) dioxomolybdatefVI) in protic solvents. Inorganica ChimicaActa 221, 117-124. 

Extraction of the molybdenum complex with a-benzoinoxime (formula 31.1) into CHCI3, from 0.01-2 M HCl is a selective method for separating molybdenum [1 ]. Under the conditions employed in the extraction of the molybdenum a-benzoinoxime complex Mo, Mo02(C 4H 202N)2, only W, V, Cr, and Pd are also extracted. Tungsten and vanadium are not extracted in the presence of phosphoric acid and Fe(II). 

---