Molybdenum compounds sulfoxides

L = dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), and triphenylphos-phine oxide (OPPh3). The former illustrates how simple polyethers may stabilize the hydrated dioxomolybdenum(VI) bromide core. The others are representative examples of addition compounds with ligands that are able to displace water from the coordination sphere of molybdenum but at the same time are not sufficiently basic toward the proton to cause formation of hydrobromides and molybdates. 

All plants depend on nitrate reductase to accomplish the seemingly trivial reaction of nitrate reduction to nitrite, often the first step of nitrogen assimilation into compounds required for growth (5, 22). Many bacteria use molybdenum or tungsten enzymes in anaerobic respiration where the terminal electron acceptor is a reducible molecule other than oxygen, such as nitrate (2, 50), polysulfide (51), trimethylamine oxide (33, 52) or dimethyl sulfoxide (DMSO) (2, 29, 30). 

Organic hydroperoxides are generally used for the preparation of sulfoxides from sulfides, - while sulfones can be obtained in neutral organic solvents in the presence of metal catalysts such as V, Mo and Ti oxides at 50-70 C. Two polymer-supported reagents which involve peroxy acid groups and bound hypervalent vanadium(V) and molybdenum(VI) compounds have been developed for facile oxidation of sulfoxides to sulfones. 

Peroxide complexes of molybdenum(VI) are intermediates in industrially important epoxidation reactions. The so-called Mimoun-type complexes [Mo 0(02)2LaxLeq]° " (12) generally exhibit pentagonal-bipyramidal structures, with an axial 0x0 group trans to Lax and Leq, and two peroxo groups in the equatorial plane. These complexes are effective reagents for the selective oxidation of alcohols to aldehydes, amines to nitroso compounds, sulfldes to sulfoxides and then to sulfones, phenols to o-quinones, and in the sulfoxidation of thianthrene-5-oxide. 

Hydroperoxides in the presence of vanadium molybdenum, or titanium compounds give high yields of aliphatic tert. amine oxides from the corresponding amines and sulfones from thio-ethers or sulfoxides. 

Oxidation of Alcohols. Diphenyl sulfoxide has been employed as an oxidant in conjunction with molybdenum (VI) and osmium (VIII) catalysts for the conversion of alcohols to carbonyl compounds. Diphenyl sulfoxide in combination with catalytic quantities of Mo02(acac)2 oxidizes alcohols to ketones or aldehydes. Higher yields are obtained with allylic or benzylic alcohols. Catal)dic OSO4 in association with Ph2SO can oxidize primary and secondary alcohols to aldehydes and ketones in the... 

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