Pentacarbonyl methoxymethylcarbene tungsten

Pentacarbonyl(methoxymethylcarbene)tungsten(0) is a dull-yellow, crystalline solid mp 52°. It is appreciably more stable thermally and oxidatively than its chromium analog in the solid state at room temperature and may be stored at 5° for a period of 1 or 2 weeks without significant decomposition. It is soluble in aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and other common laboratory solvents such as benzene, 1,4-dioxane, tetrahydrofuran, chloroform, dichloromethane, and methanol it is slightly soluble in ethanol. The infrared spectrum (cyclohexane solution) has v(CO) bands at 2075, 1980, 1960, and 1947 cm 1. The nmr spectrum in chloroform-d has the methoxy proton resonance at t6.17 and the methyl proton resonance at t7.69. Other physical properties are reported in the literature.6,7 

The nitrogen flow is stopped and the inlet and outlet of the flask are stoppered. The benzene solution is then stirred for 5 min by means of a magnetic stirring bar. The methanolic hydrochloric acid solution is then added dropwise to the stirred benzene solution over a period of 15-20 min during this time the solution becomes deep-red in color and sodium chloride precipitates. Stirring is continued for 2 hr. The following operations are performed in the open air. The volume of the reaction mixture is reduced to a minimum with the aid of a Roto-evaporator, and 80 mL of water and 100 mL of n-hexane are added successively to the residue. The aqueous layer is quickly discarded and the organic layer dried over 5 g of anhydrous sodium sulfate for a few minutes. The sodium sulfate is removed by filtration, and the volume of the filtrate is reduced with the aid of a roto-evaporator to leave a dark-red, oily residue. 

A Fluorosil (100-200 mesh) column (25 cm x 3 cm) is charged with the oily residue, and elution is initiated with n-hexane saturated with nitrogen. The dark-red band which moves down the column is collected, and the volume of the dark-red effluent is reduced to about 5 mL with the aid of a Roto-evaporator. 

The solution is then transferred to a 25-mL beaker. This solution is next concentrated in a stream of nitrogen, immersed in a Dry Ice-acetone slush (—78°). Crude [Cr(CO)5 (C(CH3)(SC6H6) ] precipitates from the solution and is collected by filtration and air-dried. Yield is 1.3 g (50%). The crude [Cr(CO)5 (C(CH3)(SC6H5) ] may be recrystallized from the minimum amount of n-hexane-diethyl ether (1 1) solution. Anal. Calcd. for C13H805SCr C, 47.55 H, 2.44. Found C, 47.56 H, 2.65. 

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