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Author: Subject: Tungsten Ethoxide
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[*] posted on 12-3-2009 at 01:41
Tungsten Ethoxide

How can I prepare Tungsten Ethoxide starting from Sodium Tungstate?
I need it for my Sol-Gel process..

and what about preparing Vanadium Ethoxide from V2O5?
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[*] posted on 12-3-2009 at 04:30

I would have to guess that you will unlikely be able to prepare these ethoxides from sodium tungstate or V2O5 by any simple mean. You would better start from the corresponding chlorides, but why not checking the literature on how it is done? There was a nice e-book on metal alkoxides shared in the References section some time ago. Possibly the link is still working. Surely in there you will find the references to the required published procedures.
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[*] posted on 12-3-2009 at 05:36

It is not difficult to get vanadium alkoxides VO(OR)3 from V2O5, simply refluxing it with a large excess of the anhydrous alcohol will do the trick. However if you then attempt to isolate the alkoxide by evaporating the dilute solution, the water released in the formation will react with the alkoxide to first form polynuclear oxoalkoxides then regenerate V2O5, turning the pale yellow solution a dichromate orange to red. You need to first remove the water through azeotropic distillation, refluxing in a Soxhlet rig with molecular sieves in the extraction thimble, or other means. The Soxhlet method is convenient because you can load the flask up with the alcohol and V2O5, then reflux to react and dry at the same time.

Tungsten ethoxide -

While MoO3 can be treated similar to V2O5 to get Mo(OR)6, the yields are not always good, and I've never seen mention of WO3 doing the same.

U.S. Pat. No. 3,730,857 and Journal of General Chemistry of the USSR (translation of Zhurnal Obshchei Khimii) 1985, 55, 2130-2131. A tungsten anode is dissolved by anodic oxidation in an alcoholic electrolyte solution:

W + 6ROH => W(OR)6 + 3H2

NR4Cl quaternary ammonium salts, NH4Cl, or LiCl have been used as electrolytes.

Alkoxides tend to be quite sensitive to moisture, you'll need a dry box to work with them.
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[*] posted on 12-3-2009 at 09:13

I remember there is a few pages long chapter on the preparation of alcoholates starting from metal oxides in the e-book I previously mentioned, but if I remember correctly the author concluded that except some rare examples, most transition metal oxides were either useless or gave low yields. There was no mention of using water removal to drive the reaction further, but a literature search gives a few interesting examples. The preparation of VO(OEt)3 from V2O5 is described in two patents where ortoesters are used as dehydrating reagents and a very old paper that goes more into depth:

Patents DE2362704, DE2343056: from V2O5 with EtOH/MeC(OMe)3 (33-57% yields) or EtOH/CH(OEt)3 (38% yield)

Vanadic Acid Esters and some other Organic Vanadium Compounds.
Prandtl, Wilhelm; Hess, Ludwig.
Zeitschrift fuer Anorganische Chemie (1913), 82 103-129.
CA abstract: The term "trivanadates" is proposed for the "metavanadates," which have been shown to have the general formula M3V3O9. The following esters were prepd. by heating the V2O5 with various alcs.; the products were colorless or yellow, and mol. wt. detns. showed the simple formulas. The alc. solns. of all were yellow when cold, or quickly became yellow, but colorless when hot; the color change is explained by the soln. containing both reddish yellow hexavanadic esters and colorless trivanadic esters, the equil. between which was displaced toward the colorless compds. as the temp. was raised; cond. measurements supported this conclusion. Ethyl orthovanadate, Et3VO4, was obtained by boiling V2O5 with abs. EtOH under a reflux condenser for 6-8 hrs., filtering and concg. at reduced pressure; product clear yellow liquid, b26 108, d15 1.167, sol. in EtOH, C6H6 and C7H8, solidifies in liquid air to white cryst. mass, decompd. by heating much above 100; addition of 96% EtOH pptd. Et3V3O9, addition of H2O gave a gel, which formed a deep red colloidal soln. on heating with H2O. When heated to 160-170, Et2O, acetone and some ester volatilized, and a compound, V4C16H40O13, was formed, dark green cryst. powder, stable in air, insol. in H2O, dil. acid and alkali, sol. in most organic solvents, could be recrystd. from Et2O and C6H6, decompd. on heating. Propyl orthovanadate, light yellow liquid, d15 1.088, b24 143, properties similar to above; n-butyl orthovanadate, b22 175, isobutyl orthovanadate, d15 1.033, b16 149; tertiary butyl orthovanadate, colorless crystals, m. 45-7, b15 117, easily sol. in organic solvents; isoamyl orthovanadate, light yellow cryst., difficult to free from C5H11OH, m. 70, b18 185-7; tertiary amyl orthovanadate, colorless liquid, d15 0.993, b19 161, b760 206 (decomp.); were also prepd. An attempt to prepare an ester of pyrovanadic acid from Ag4V2O7 in the above manner gave an ortho compd. Ethyl trivanadate, Et3V3O9, was prepd. by boiling V2O5 with abs.
EtOH for 4-6 hrs., filtering, and evapg. in a vacuum desiccator or by concg. by evapg. the EtOH and cooling on ice; product light yellow powder decomp. on heating, changed to hexavanadate, then to V2O5 by H2O. Propyl trivanadate and isoamyl trivanadate, light yellow powders, were also formed. Diethyl monochloro-orthovanadate, (EtO)2VOCl, dark red liquid, d15 1.336, decompd. by light or heating, was obtained from VOCl3 and NaOEt; ethyl dichloro-orthovanadate, EtOVOCl2, red liquid, b49.5 102, was obtained in a similar manner. MeOH dissolved V2O5 on boiling, but no compd. could be isolated; glycerol and BzOH dissolved V2O5 but were oxidized on heating. Esters of hexavanadic acid could not be prepd.; they are products of the action of H2O on the ortho- and trivanadates, and attempts to prep. them resulted in mixts. of tri- and hexavanadates with colloidal V2O5. Aniline hexavanadate, (C6H5NH3)4V4O172H2O, was prepd. in reddish brown glittering monoclinic prisms (cryst. data given) by mixing a soln. of V2O5 in dil. NaOH soln. and aniline-HCl soln.; product sol. H2O, insol. EtOH, Et2O, C6H6, slightly sol. in phenol. An ether addition product of vanadium oxydichloride, VOCl2.2Et2O.2H2O, was prepd. by the action of Na on a mixt. of VCl4 and PhBr as deep blue deliquescent needles, decompd. on heating.

Some preparations from vanadyl chloride:

Patent US4739086: from VOCl3 and NaOEt/EtOH (94% yield)
Patents US4014911, US4014912: from VOCl3 and EtOH/hexane/NH3

VOCl3 made from V2O5:

Synthesis of trialkyl vanadates and trialkyl antimonites.
Voronkov, M. G.; Skorik, Yu. I.
Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya (1958), 503-504.
CA abstract: Refluxing dry V2O5 with excess SOCl2 gave VOCl3, b758 126. This (86.7 g.) added dropwise to 350 ml. dry EtOH with ice cooling followed by a stream of NH3 gave after filtration and distn. of the filtrate 55% (EtO)3 VO, b5 82.5, b11 91, d20 1.167, n20D 1.5103, which rapidly hydrolyzes in air and decomp. in light or on strong heating. Similarly was prepd. (BuO)3 VO, b1 121, b3.5 131, b7 153, d20 1.031, n20D 1.4898. Similarly, SbCl3 (342.2 g.) and 550 ml. abs. EtOH was treated with dry NH3 with cooling yielding after sepn. of NH4Cl 60% Sb(OEt)3, b10 93, d20 1.526, n20D 1.4983. Similarly was prepd. 80% (BuO)3Sb, b10 144, d20 1.280, n20D 1.4799.

The only preparations of WO(OEt)4 that I could find start either with WCl6 or its oxychloride WOCl4. The only exception is the electrochemical preparation not_important cited above (Zhurnal Obshchei Khimii, 55 (1985) 2396-2367).

[Edited on 12/3/2009 by Nicodem]

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