Water molybdenum complexes

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. 

Olefin-metathesis is a useful tool for the formation of unsaturated C-C bonds in organic synthesis.186 The most widely used catalysts for olefin metathesis include alkoxyl imido molybdenum complex (Schrock catalyst)187 and benzylidene ruthenium complex (Grubbs catalyst).188 The former is air- and moisture-sensitive and has some other drawbacks such as intolerance to many functional groups and impurities the latter has increased tolerance to water and many reactions have been used in aqueous solution without any loss of catalytic efficiency. 

Johnson and Pilson [229] have described a spectrophotometric molybdenum blue method for the determination of phosphate, arsenate, and arsenite in estuary water and sea water. A reducing reagent is used to lower the oxidation state of any arsenic present to +3, which eliminates any absorbance caused by molybdoarsenate, since arsenite will not form the molybdenum complex. This results in an absorbance value for phosphate only. 

Molybdenum and tungsten compounds have long been known to catalyze the transformations of alkenes into epoxides and diols by hydrogen peroxide.171"173 This reaction was found to be suitable for the epoxidation of water-soluble alkenes such as allylic alcohols (equation 30)174,175 or unsaturated carboxylic acids (equation 31).171 Tungsten catalysts were found to be more active and selective in aqueous solution than molybdenum complexes. 

Molybdenum(VI) in sea water is complexed with 4-benzoyl-3-methyl-l-phenyl-5-pyrazolone (BMPP) and extracted into isoamyl alcohol. A complete extraction is accomplished between pH 1.0-3.0 One litre of sea water acidified with 10 ml of cone. HC1, is reduced to 200 ml by evaporation. The solution is adjusted to pH 2.5 and extracted with 10 ml of 0.2wt/v% of BMPP in isoamyl alcohol by shaking for 10 min. 911... 

MoH(ti5-C5H5)(CO)2(PCy3)] was more active (2 tumovers/h). Similar but water soluble tungsten and molybdenum complexes are known [223-226] which would allow the use of water as solvent for such reactions. It is noteworthy, though, that ionic hydrogenation of ketones by dihydrogen complexes has so far been observed only in non-aqueous solutions [223,227] perhaps the coordination of a ketone is disfavoured in water due to competition by H20. 

To a solution of 125 mg of the molybdenum complex (0.20 mmol) in 3.2 mL CH2CI2 was added at room temperature 495 /xL 37% aqueous HCl (6.0 mmol) drop wise over 2 min. The mixture was stirred at room temperature for 20 min and 30 mL EtOAc and 30 mL water were then added. The organic layer was washed with 30 mL saturated aqueous NaHCOs, dried over Na2S04, and evaporated. The residue was purified by flash chromatography (2 1, n-hexanes/CH2Cl2) to afford 41.4 mg (+)-( 5,55,65)-6-ethoxy-7-methylen-2-phenyl-9-oxabicyclo[3.3.1]non-2-ene, with 99.5% e.e. as a white solid, in a yield of 80%. Rf = 0.08 (2 1, n-hexane/CH2Cl2), m.p. 42-43°C. 

Calcium zinc molybdate. See Calcium-zinc-molybdenum complex Calcium-zinc-molybdenum complex Synonyms Calcium zinc molybdate Molybdenum white Formula CaO xZnO yMoOa ZH2O Properties Wh. powd. insol. in water dens. 3.00 kg/l... 

Sublimation of the resulting brown residue at 50-60°, O.OOS torr onto a water-cooled probe for 3 days affords 13.6 g (84% yield) of (>i -CjH5)W(CO)2(NO). The corresponding chromium and molybdenum complexes are obtained similarly in yields of 60 and 93%, respectively. 

On the other hand, the oxidative deamination of amines in the coordination sphere of a molybdenum complex [162,163] requires water. Treatment of the complex, [(7r-C5Hs)2Mo(SMe2)Br] PFs with an excess of an amine, RR CHNH2 having hydrogen on the a-carbon (0-H) in water at 60 °C for several hours results in formation of the complex, [(ff-CsHs)2Mo(NH2CHRR )] PFj and the corresponding ketone or aldehyde RR CO, equation (121). 

CO-RMs 14-18 were prepared hy reaction of a terminal allqrne with a tricarbonyl chloro molybdenum complex (13) in the presence of Cul to activate the allgme, with NHEta as a base. This reaction is veiy versatile and produces a structurally diverse selection of potentially therapeutic CO-RMs. The most promising of these CO-RMs is 16. This CO-RM is water soluble presumably because of the p-D-fructopyranose group. This group significantly increases the polarity and therefore water solubility of the complex. 

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