Hexakis dimethylamido ditungsten and Tungsten IV Chloride

Submitted by MALCOLM H. CHISHOLM and JAMES D. MAR TIN Checked by JOHN E. HILLf and IAN P. ROTHWELLf 

Tungsten(VI) chloride (50.0 g, 0.126 mol) and two-thirds of an equivalent of red phosphorous (2.60 g, 0.084 mol) are placed into chamber C of the reaction vessel shown in Fig. 1. The reaction vessel is then evacuated ( 10 torr) 

W2(NMe2)e, (W=W), is an air- and moisture-sensitive yeUow crystaUine solid that may be stored for long periods under an inert atmosphere. It is appreciably soluble in hydrocarbon solvents. The HNMR spectrum shows one broad resonance at 3.4 ppm (CgDg, 25°C). Other physical and chemical properties are described in the literature.  

Reviewers have commented that the dark brown color resulting from some minor impurity may be removed by adding activated charcoal to a toluene solution of crude WjfNMejls. which is then filtered, yielding a clear yellow solution. After removal of solvent, the product was obtained in a 38% yield. 

Yields of this reaction may vary between 40 and 80% depending on reaction conditions. We find the yields to be strongly dependent on the quality of the WCI4. We also have found that best yields are obtained when (1) the THF slurry of LiNMe is added slowly, 45 min to 1 h, and (2) the reactions are performed under conditions no more concentrated than those described here. 

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