Molybdenum oxide, reaction with, carbonyl

In the reactions with carbonyl compounds9 and carboxylic acids,21 molybdenum(VI) fluoride is converted into molybdenum(VI) tetrafluoride oxide (MoOF4), and with the thiocarbonyl compounds24 into molybdenum(IV) sulfide, but with acid chlorides, its fate is not known. 

Carbonyl Compounds. Cychc ketals and acetals (dioxolanes) are produced from reaction of propylene oxide with ketones and aldehydes, respectively. Suitable catalysts iaclude stannic chloride, quaternary ammonium salts, glycol sulphites, and molybdenum acetyl acetonate or naphthenate (89—91). Lactones come from Ph4Sbl-cataly2ed reaction with ketenes (92). 

The solvent process involves treating phthalonitrile with any one of a number of copper salts in the presence of a solvent at 120 to 220°C [10]. Copper(I)chloride is most important. The list of suitable solvents is headed by those with a boiling point above 180°C, such as trichlorobenzene, nitrobenzene, naphthalene, and kerosene. A metallic catalyst such as molybdenum oxide or ammonium molybdate may be added to enhance the yield, to shorten the reaction time, and to reduce the necessary temperature. Other suitable catalysts are carbonyl compounds of molybdenum, titanium, or iron. The process may be accelerated by adding ammonia, urea, or tertiary organic bases such as pyridine or quinoline. As a result of improved temperature maintenance and better reaction control, the solvent method affords yields of 95% and more, even on a commercial scale. There is a certain disadvantage to the fact that the solvent reaction requires considerably more time than dry methods. 

Molybdenum carbonyls supported on oxides or zeolites show significant activity in a number of organic reactions [1]. Recent studies have shown a very high activity of the catalysts originating from molybdenum carbonyl and Y zeolite also in the water-gas shift (WGS) reaction with a sulfided feed [2]. 

The a-hydrogens of nitroalkanes are appreciably acidic due to resonance stabilization of the anion [CH3NO2, 10.2 CH3CH2NO2, 8.5]. The anions derived from nitroalkanes give typical nucleophilic addition reactions with aldehydes (the Henry-Nef tandem reaction). Note that the nitro group can be changed directly to a carbonyl group via the Nef reaction (acidic conditions). Under basic conditions, salts of secondary nitro compounds are converted into ketones by the pyridine-HMPA complex of molybdenum (VI) peroxide. Nitronates from primary nitro compounds yield carboxylic acids since the initially formed aldehyde is rapidly oxidized under the reaction conditions. 

The formation of mixed metal Mo-Co oxide HDS catalysts on the MCM support occurs in a sequential reaction by first depositing the molybdenum oxide followed by pyrolysis of GolCOlsNO to disperse the Co over the Mo-covered support.The option of co-sonicating the molybdenum carbonyl and cobalt carbonyl nitrosyl concurrently yields catalysts with poorly reproducible stoichiometries. The resulting catalyst (13 wt.% CoO and 43 wt.% M0O3) was examined as an HDS catalyst for dibenzothiophene, and was found to display 1.7 times greater activity than a commercial Co-Mo-Al catalyst. 

The reactivity of molybdenum carbonyls in reaction with Lewis acids is comparable to the reactivity of tungsten carbonyls. The treatment of a nitrile carbonyl compound with an equimolar amount of tetrachlorotin in dichloromethane gives the oxidative-addition product, a mononuclear seven-coordinate compound [MoCl(SnCl3)(CO)3(NCMe)2], in good yield [36, 40]. The same compound was isolated from the reaction of a binuclear compound and acetonitrile. The crystal structure of the reaction product is similar to that... 

While metallocene-derived complexes 103 deserve interest mainly because of their redox properties and applications resulting therefrom, half-sandwich complexes 104 and 105 show more diverse chemical reactions. Based on their synthesis of the fulvalene dianion 102, Smart et al. [99] prepared some molybdenum complexes such as 108 [62% yield based on Na(DME)Cp] by treatment of 102 with molybdenum hexacarbonyl followed by oxidation with bromine. Vollhardt reported the synthesis of a variety of homo- and heterodinuclear fulvalene complexes such as 109-112 by treatment of dihydrofulvalene and respective metal carbonyls. The dichromium complex 110 has some catalytic activity in the hydrogenation of conjugated dienes [110]. The authors report the reaction with iron carbonyls being unsuccessful, whereas the reaction with dicobaltoctacarbonyl resulted in the formation of fulvalene complex 112 lacking a metal-metal bond in 80% yield (Scheme 10.38) [100, 101]. Later, the diiron complex corresponding to 109 was reported [111]. Hermann et al. and Cuenca etal. prepared zirconium(IV) and zirconium(III) fulvalene complexes [112,113]. 

Direct conversions of sulfones to carbonyl compounds have been realized by oxidative desulfonation of the a-carbanions. Molybdenum peroxide (Mo05-Py-HMPA) [266], or bis(trimethylsilyl)peroxide (Mc3SiOOSiMej, BTSP, Table 3.3) [267] were used as oxidants. Hwu s method with BTSP is attractive and was found useful for the preparation of 180-Iahelled compounds [267] in this one-pot reaction Me3SiO behaves as a leaving group and a back-attacking species. 

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