Tungsten hexacarbonyl

The color and solubilities of these chromium(III) ammines are very similar to those of the corresponding cobalt(III) complexes.5 The chlorides, bromides, nitrates, and perchlorates in the acidopentamminechromium(III) series are not very soluble in water, whereas the analogous aquopentamminechromium(III) salts are soluble. In aqueous solutions, these chromium(III) ammines are much more readily decomposed than the corresponding cobalt(III) ammines. Decomposition may be perceptible within a few minutes. The absorption spectra of aqueous solutions of some acidopentamminechromium(III) salts have been studied.6,7 

Mori J. Chem. Soc. Japan, Pure Chem. Sect., 74, 253 (1953). 

Submitted by Dallas T. Hurd Checked by Eugene O. BrimmI 

For many years, the only available procedure for preparing the hexacarbonyls of chromium, molybdenum, and 

Carbon monoxide is admitted slowly and the pressure boosted to ca. 1600 p.s.i. The vessel is allowed to stand connected to the gas line for 10 minutes, and the valve is then closed. The shaking mechanism is adjusted for widest possible oscillation to allow the steel ball to roll back and forth to shatter the ampoule and mix the reactants. The vessel is heated to 100° and maintained at this temperature for 4 to 6 hours, f The vessel is allowed to cool, and then with the valve at the top the contained gas is bled off through the vent line. The pressure vessel is opened in a hood, and its contents are transferred into a 1-1. distilling flask containing ca. 500 ml. of water. The ether is distilled off at low temperature. When the ether has been removed, the receiver is changed and the water in the flask boiled. The tungsten hexacarbonyl is carried over into the receiver with the steam, j Water is removed on a Buchner funnel, and the product is purified by redistillation from 3 to 5% sodium hydroxide solution, by vacuum sublimation at 60 to 70°, or by crystallization from ethyl ether. The yield varies from 6 to 8 g. (68 to 90%), depending upon conditions.  

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Various appHcations such as lubricant additives, dyes, pigments, and catalysts are under investigation. Tungsten can be deposited from tungsten hexacarbonyl, but carbide formation and gas-phase nucleation present serious problems (1,2). As a result, tungsten halides are the preferred starting material. 

Tungsten triiodide [15513-69-6] prepared by the action of iodine on tungsten hexacarbonyl in a sealed tube at 120°C (18). 

Another class of complexes involves rj (N)-coordinated species of the Nl-unsubstituted pyrazoles. Chromium hexacarbcMiyl and pyrazole or 3,5-dimethyl-pyrazole form [(Hpz)Cr(CO)5] ot [(Hpz )Cr(CO)5] irrespective of the ratio of reactants. In similar circumstances, tungsten hexacarbonyl yields both [(Hpz)W(CO)5]... 

Molybdenum and tungsten hexacarbonyls are able to form anionic complexes (AsPli4)2[(OC)4M( -pz)2M(CO)4] upon reaction with sodium pyrazolate and PluAsCl (72CB3203). The cationic complexes [(rj -Cp)2Mo(/Lt-pz)2Mo(rj -Cp)2] " (n = 2, 3) are known as well (74HCA1988). The other representatives of the complexes containing an exobidentate ligand (26) are derived from 4//-pyrazoles [70ZAAC(379)169]. 

Tungsten hexabromide, 25 379 Tungsten hexacarbonyl, 25 377 Tungsten hexachloride, 25 378 uses for, 25 387... 

Nucleophilic acyl complexes can be 0-alkylated with hard electrophiles to yield the corresponding alkoxy- or (acyloxy)carbene complexes. The first carbene complex ever isolated [61] was prepared by this route the intermediate, anionic acyl complex was generated by addition of phenyllithium to tungsten hexacarbonyl (Figure 2.3). 

Tungsten hexacarbonyl is used to produce tungsten coatings on base metals. This is done by deposition of the carbonyl on the metal surface, which decomposes to leave a tungsten coating. 

Tungsten hexacarbonyl is produced by heating tungsten metal with carbon monoxide at high pressure. Also, carbonyl can be prepared by reducing the tungsten hexachloride by heating with iron powder under carbon monoxide pressure. 

Diene complexes of the type [W(CO)4(diene)l (VI M = W) are formed by cyclo-octa-1,5-diene (79, 151), hexa-1,5-diene (151), and dimethyldi-vinylsilane (158) on heating with tungsten hexacarbonyl. Cycloheptatriene (158) displaces cyclo-octa-1,5-diene and 1 mol. of carbon monoxide from its tungsten complex ... 

Treatment of tungsten hexacarbonyl with a mixture of cyclo-octa-1,3,5-and -1,3,6-triene gives the complex [W(OO iCslIiohJ (85). The hydrocarbon is believed to be the 1,3,6-triene, acting as a diene, but for the reasons mentioned (see Section III,H) it is possible that the ligand is bicyclo[4,2,0]-octa-2,4-diene (XV). 

Tungsten hexacarbonyl on treatment with bicyclo-[4,3,0Jnona-2,4,8-triene(C9Hio) gives a brick red complex [W(CO)3(C9Hi0)J which appears to be completely analogous to the molybdenum complex [Mo(CO).i(CaH,t))] of structure (VIII) (142). 

Tungsten hexacarbonyl is reported to form a number of stable complexes with acetylenes (116, 118), but no details have been published. 

Although commercially available (Aldrich), polymeric tungsten tetrachloride is routinely prepared by McCarley s method,7,15 which is given below. Tungsten hexachloride and tungsten hexacarbonyl (Strem) are used without further purification. Sodium-mercury amalgam (0.5 wt%) is prepared in a 500-mL two-necked round-bottomed flask equipped with a N2 gas inlet and a stopper, by adding 6.83 g (297 mmol) of sodium metal in small pieces ( 0.1-0.2 cm3) to 100 mL of mercury. 

An unanticipated catalytic reaction of olefinic hydrocarbons was described in 1964 by Banks and Bailey.1 2 They discovered that C3-C8 alkenes disproportionate to homologs of higher and lower molecular weight in the presence of alumina-supported molybdenum oxide [Eq. (12.1)], cobalt oxide-molybdenum oxide, molybdenum hexacarbonyl, or tungsten hexacarbonyl at 100-200°C, under about 30 atm pressure ... 

In contrast, tungsten hexacarbonyl (Fig. 3.7c) has a four-fold axis. In feet, it has three C4 axes (1) one running from top to bottom, (2) one running from left to right, (3) one running Grom front to back. (In addition, it has other rotation axes. Can you find them )... 

Metal Hexacarbonyls. Strohmeier and Gerlach (68) noted that the ultraviolet irradiation of chromium, molybdenum, or tungsten hexacarbonyls caused photodissociation into M(CO)B and CO. In donor solvents, the M(CO)6 was stabilized forming a yellow product whereas in cyclohexane the colorless M(CO)a was reformed (69). 

It is worthwhile to note that in the reaction of the group 6B metal hexacarbonyls with the azide anion to provide isocyanatometallates, a concerted mechanism is proposed based on kinetic parameters which involves a three-centered transition state (7), and that the activation enthalpy is some 22.6 kJ lower for tungsten than for chromium (52). This reactivity sequence correlates with an increase in M-CO bond distances going from chromium to tungsten hexacarbonyl (53-55). 

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