Alkoxides tungsten

Tungsten, tris(2,3-dimercapto-2-butenedinitrile)-structure, 1,63 Tungsten alkoxides physical properties, 2,346 synthesis, 2,339... 

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. 

To prevent the latter mentioned subsequent reactions, the bulky phos-phaalkyne Ph C P as well as tungsten alkoxides of reduced size as, e.g., [W2(ONp)6] were employed in these three-component reactions with no significant success [15]. The crucial steps for the side-product free synthesis of the phosphido complexes 18 are the introduction of a phosphaalkyne possessing a moderate steric bulkiness, which lies between those of f-BuC=P and Ph C P, and resulting from the P-NMR studies (cf. Eq. 5), a reaction temperature mode allowing the complete metathesis reaction to take place at very low temperatures over a long period of time until all the phosphaalkyne has been converted into the metathesis products (about 12 h) only then is the reaction mixture allowed to reach room temperature. We found that MesC=P meets these steric requirements, and the three-component-reaction between MesC=P, [W2(Of-Bu)6] and [M(CO)5(thf)] (M = Cr, W), carried out at -78 °C and warmed up to ambient temperature within 15 h, succeeded in the synthesis and isolation of the phosphido complex 18a,b (Scheme 2) [15]. Furthermore, if t-BuC=P is incorporated into these reactions, the steric requirements of the alkoxide dimer has to be slightly increased. Thus, f-BuC=P reacts with [W2(OPh )6] and [M(CO)5(thf)] (M=Cr, W) under the... 

Tungsten, hexahydridotris(diisopropyiphenylphosphine)-structure, 700 Tungsten alkoxides physical properties, 346 synthesis, 339 Tungsten complexes alkoxy carbonyl reactions, 355 alkyl alkoxy reactions, 358 amides... 

The ether elimination is also observed as the first step in thermal decomposition of these alkoxides. The same reaction appears also to be responsible for the observed difference in the hydrolytic behavior of molybdenum and tungsten alkoxides the hydrolysis of the W alkoxides leads as for the majority of other metal alkoxides to the formation of hydroxospecies, forming sols and gels on polycondensation, while in the case of Mo alkoxides the added water, being a stronger acid than alcohols, acts as a catalyst for the ether elimination reaction and causes the formation of individual isopolyanions (independently of the nature of the alkyl radical or quantity of water added) [1774] ... 

Complex formation of molybdenum and tungsten alkoxides with the alkoxides of other metals formation of bimetallic alkoxides... 

The complex formation of tungsten alkoxides with the alkoxides of other metals than the alkali, bismuth, and rhenium (see Section 12.21) has not been investigated in detail, and therefore the major attention below will be paid to the description of the bimetallic alkoxides of molybdenum. 

The reactions and nature of multiple bonds between two metal atoms form a lively area of research and debate (1,2). Many examples of triple bonds between metals are known, including the extensively studied molybdenum or tungsten alkoxide, M2(OR)6, and amido, M2(NR2)6, complexes (3). Classic examples of quadruple bonds are epitomized by [Re2Cl8]2 (4) and molybdenum acetate, Mo2(OCOMe)4 (5). 

Metal-metal bonds and metal-carbon bonds in the chemistry of molybdenum and tungsten alkoxides. ... 

Tungsten alkoxide, W lOEtls, is commercially available and is soluble in alcoholic solution. Tungsten alkoxide solution infiltrates the voids and is solidified in the voids by a sol-gel method as described by Holland Ethanol solution of WClg can infiltrate the voids of... 

The tungsten alkylidyne complex W(=CBu )(OBu )3, which, if monomeric, is only 12-electron, catalyses the metathesis of 3-heptyne at a spectacular rate. Note that the presence of strongly Ti-donating alkoxy groups destabilizes some of the metal d-orbitals (p. 1 51) so that the 18-electron rule is no longer expected to hold. In this case the reactions are too fast to obtain evidence for tungstenacy-clobutadiene intermediates. Another route to the catalysts, however, is provided by the remarkable reaction between the triply bonded tungsten alkoxides W IOR) and alkynes. 

Engweiler, J., J. Harf, and A. Baiker, WO /TiOj catalysts prepared by grafting of tungsten alkoxides Morphological properties and catalytic behavior in the selective reduction of NO by NH3.Catal. 159 (1996) 259-269. 

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