Tungsten alkoxides synthesis

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

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... 

Johansson A., Roman M., Seisenbaeva GA., Kloo L., Szabo Z., Kessler V.G. The solution thermolysis approach to molybdenum(V) alkoxides synthesis, soUd state and solution structures of the bimetallic alkoxides of molybdenum(V) and niobium(V), tantalum(V) and tungsten(VI). J. Chem. Soc., Dalton Trans. 2000 387... 

The compounds of these two elements belong apparently to the most studied and most fully characterized alkoxoderivatives of metals. The particular features of their synthesis and physicochemical properties are discussed in detail in a large number of review publications authored by Chisholm [370] who made tremendous contributions to the development of the chemistry of these substances. The synthetic routes to the bimetallic alkoxide derivatives of molybdenum and tungsten (VI) along with the discussion of their physicochemical properties and application prospects are also reviewed in [1638, 908],... 

Heterometal alkoxide precursors, for ceramics, 12, 60-61 Heterometal chalcogenides, synthesis, 12, 62 Heterometal cubanes, as metal-organic precursor, 12, 39 Heterometallic alkenes, with platinum, 8, 639 Heterometallic alkynes, with platinum, models, 8, 650 Heterometallic clusters as heterogeneous catalyst precursors, 12, 767 in homogeneous catalysis, 12, 761 with Ni—M and Ni-C cr-bonded complexes, 8, 115 Heterometallic complexes with arene chromium carbonyls, 5, 259 bridged chromium isonitriles, 5, 274 with cyclopentadienyl hydride niobium moieties, 5, 72 with ruthenium—osmium, overview, 6, 1045—1116 with tungsten carbonyls, 5, 702 Heterometallic dimers, palladium complexes, 8, 210 Heterometallic iron-containing compounds cluster compounds, 6, 331 dinuclear compounds, 6, 319 overview, 6, 319-352... 

In spite of the difficulties involved (98) in the synthesis of the dialkylamide and bis(trimethylsilyl) amide reagents, the procedure was increasingly employed for the synthesis of metal alkoxides, particularly in their lower oxidation states [e.g., Cr" and Mn11 (99)]. This method proved to be specially useful for the preparation of alkoxides of molybdenum and tungsten in their 3- and 4-oxidation states (7) and more recently of U2(0-f-Bu)8-(r-Bu0H) (100) ... 

The remarkable utility of the amide route has been established by the synthesis of alkoxides of molybdenum and tungsten (M) in their lower oxidation states (+3 or +4), e.g. [M(0R)3] and [M(OR)4] . Derivatives of the empirical formula M(OR)3 are of special interest as, in these, association occurs primarily through the formation of metal-metal triple (M=M) bonds rather than through the normal alkoxo bridges (Eq. 2.113)... 

Kim J. Y., Sriram M. A., McMichael P. H., Kumata P. N., Phillips B. L., Risbud S. H. New molecular precursors from the reaction of hydrazine and aluminum alkoxide for the synthesis of powders in the Al-O-N system. J. Phys. Chem. B 1997 101 4691-4696 Kim J.H., Kim K.L. A study ofpreparation of tungsten nitride catalysts with high surface area. Appl. Catalyst A General 1999 181 103-111... 

In the preparative section 3.2 devoted to metal-carbene complexes, it is shown how the a-elimination reaction from high oxidation state early-transition-metal-alkyl complexes is one of the general methods of synthesis of Schrock s Ta and Nb alkylidene complexes. The other direction, formation of an alkylidene from an alkylidyne complex, can also be a valuable route to metal alkylidenes. For instance, Schrock s arylamino-tungsten-carbynes can be isomerized to imido-tungsten-carbene by using a catalytic amount of NEts as a base. These compounds are precursors of olefin metathesis catalysts by substitution of the two Cl ligands by bulky alkoxides (dimethoxyethane then decoordinates for steric reasons), and this route was extended to Mo complexes ... 

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