Molybdenum alkoxides

Molybdenum, tris(phenylenedithio)-structure, 1,63 Molybdenum alkoxides physical properties, 2,346 synthesis, 2,339 Molybdenum blue liquid-liquid extraction, 1,548 Molybdenum cofactor, 6,657 Molybdenum complexes acrylonitrile, 2,263 alkoxides, 3,1307 alkoxy carbonyl reactions, 2,355 alkyl, 3,1307 alkyl alkoxy reactions, 2,358 alkyl peroxides oxidation catalyses, 6,342 allyl, 3,1306... 

C). The exact role of the base is not clear, but it may accelerate the formation of the molybdenum alkoxide complex from a bound alcohol ligand. 

The reason for the difference in structure from the Mo materials to the Nb materials can be rationalized on the basis of comparative rates of nuclealion and growth.1161 Mo (V) is less Lewis acidic than Nb (V) and hence the rate of hy drolysis for molybdenum alkoxides at a... 

Costa et al. have prepared a chiral molybdenum alkoxide complex, 67, and used it for the sulfoxidation (reaction 7.8) of sulfide, 68, at low temperature with t-butylhydroperoxide (TBHP) in CHCl [55]. They successfully controlled the production of sulfones, 69, or sulfoxides, 70, by the variation of oxidant mol% and reaction temperature in reaction of methyl phenyl sulfide, 71, but enantioselectivity did not gain by their catalytic system. 

Molybdenum alkoxides, Mo2(OR)e, react in hydrocarbon solvents reversibly with two moles of CO2 to yield the corresponding bis (alkyl carbonates) (Eq. 2.285). ... 

Although the tungsten initiators allow a variety of functionalized monomers to be studied, the analogous molybdenum complexes show an even greater tolerance of functional groups.525,526 The synthetic route developed for Mo(NAr)(CHR)(OR )2 allows for a wide variety of imido, alkoxide and alkylidene substituents to be prepared, and several (e.g., (210) and (211)) are commercially available527"530... 

Reactions of Metal-Metal Bonded Alkoxides of Molybdenum and Tungsten... 

Having established structural and electronic analogies between metal oxides and alkoxides of molybdenum and tungsten, the key remaining feature to be examined is the reactivity patterns of the metal-alkoxides. Metal-metal bonds provide both a source and a returning place for electrons in oxidative-addition and reductive elimination reactions. Stepwise transformations of M-M bond order, from 3 to 4 (37,38), 3 to 2 and 1 (39) have now been documented. The alkoxides M2(0R)6 (MiM) are coordinatively unsaturated, as is evident from their facile reversible reactions with donor ligands, eq. 1, and are readily oxidized in addition reactions of the type shown in equations 2 (39) and 3 (39). 

Metal-metal bonds in molybdenum and tungsten alkoxides provide a ready source of electrons for oxidative-addition reactions and addition reactions involving ir-acidic ligands. 

In the preceding paper, Malcolm Chisholm (1) has presented a cogent case for the modeling by metal alkoxides of certain aspects of the structural chemistry and reactivities of metal oxides. The focus of this work has been the dinuclear and polynuclear alkoxides of molybdenum and tungsten, an area of research which has also attracted our interest 02-4) and upon which I would now like to take this opportunity to comment. 

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

Also non-heteroatom-substituted tungsten [440,443,444,451,452,461], molybdenum [437], and chromium carbene complexes [440] have been prepared by a-abstraction of alkoxide. 

Molecular recognition, calmodulin, 46 447 Mollusks, arsenic in, 44 150, 167, 168, 170 Molten salts electrolysis, 31 11 oxygen activation, 44 328-329 Molybdate ions, tetrahedral, 39 194-195 Molybdenite, 17 108 Molybdenum, 45 1 acetylene complexes of, 4 104 alkoxides... 

Molybdenum-based systems of general formifla Mo(N-ArO(CHCMe2R) (ORO2 (Ar = 2,6-Me2-C6H3, 2,6-zPr2 - CeHs R = Me, Ph R = CMes, CMe(CF3)2), usually referred to as Schrock initiators, represent highly active initiators, particiflarly when used in combination with electronegatively substituted alkoxides (Fig. 1). 

Again several alkyls add—molybdenum, chromium, iron, cobalt, nickel, the alkali metal alkyls and aluminum alkyls react. A tin alkoxide has recently been studied by Russian workers and found to add to acetylenes. Mercury chloride, of course, adds and two cobalt—cobalt bonded compounds add to acetylene. The second is questionable because it dissociates in solution and the reaction may be a radical reaction, one cobalt adding to each end of the triple bond. 

The dihalides react with alcohols leading to the formation of an enormous range of alkoxides and even aryloxides [Mo(NO)(Me2pzb)X(OR)] as detailed in Table 7, The crystal structure of [Mo(NO)(Me2pzb)a(OPr1)] has been determined,125 and the molybdenum shows normal octahedral six-coordination, albeit with a very short Mo-O bond. 

Reaction of [Mo(NO)(Me2pzb)I(OR)] with silver acetate in the presence of the alcohol ROH leads to the bis(alkoxides) [Mo(NO)(Me2pzb)(OR)2]. The mixed alkoxides were similarly prepared.126 The structures of several dialkoxides (Et, Pr Pr , Pr Et, Et) have been investigated in detail in view of the rather bulky character of the ligands at molybdenum. 

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