Tungsten(VI) Chloride-Tetramethylstannane


[13283-01-7]  · Cl6W  · Tungsten(VI) Chloride-Tetramethylstannane  · (MW 396.61) (SnMe4)

[594-27-4]  · C4H12Sn  · Tungsten(VI) Chloride-Tetramethylstannane  · (MW 178.87)

(alkene metathesis catalyst1)

Physical Data: WCl6: dark blue crystals; mp 275 °C; bp 347 °C. SnMe4: bp 74-75 °C.

Solubility: WCl6: sol ethanol, ether, benzene, carbon tetrachloride. SnMe4: sol all organic solvents.

Form Supplied in: reaction of Tungsten(VI) Chloride and Tetramethylstannane produces a poorly characterized species, which is thought to be a metal-carbene complex.2 The compound obtained by mixing these two reagents is typically used without additional purification. Tungsten(VI) chloride is sold as a solid of high purity, often packaged in ampules. Tetramethylstannane is sold as a neat liquid.

Purification: tetramethylstannane is purified by distillation under nitrogen at atmospheric pressure.

Handling, Storage, and Precautions: WCl6: corrosive and moisture sensitive; stored in ampules. SnMe4: highly toxic; can be stored for long periods in a refrigerator. The reagent prepared by combination of tungsten(VI) chloride and tetramethylstannane is typically used immediately after mixing the two reagents.

Alkene Metathesis.

The compound generated from tungsten(VI) chloride and tetramethylstannane is a catalyst for the alkene metathesis reaction.3 Unlike many alkene metathesis catalysts, tungsten(VI) chloride-tetramethylstannane is compatible with ester functionality.4-7 The most important use of tungsten(VI) chloride-tetramethylstannane is in the ring opening metathesis polymerization (ROMP) of cycloalkenes;1 however, a few examples have been presented using this reagent for organic synthesis. Self-metathesis of methyl 9-octadecenoate (cis or trans) with tungsten(VI) chloride-tetramethylstannane leads to a 2:1:1 ratio of methyl 9-octadecenoate (starting material), 9-octadecene, and dimethyl 9-octadecenedioate, respectively (eq 1).4 This system is presumably at equilibrium. Cometathesis of cyclooctene and alkenic esters by tungsten(VI) chloride-tetramethylstannane leads to dienoic esters (eq 2).6 Similarly, the chain length of the unsaturated fatty acid ester methyl oleate can be shortened by cometathesis with hexane (eq 3).7 In general, the cometathesis reactions do not proceed efficiently since all possible metathesis products are produced to some extent.

1. Ivin, K. Olefin Metathesis; Academic: London, 1983.
2. For a recent attempt to identify this compound, see: Thorn-Csanyi, E.; Kessler, M. J. Mol. Catal. 1991, 65, 253.
3. For a review of alkene metathesis reaction in organic synthesis, see: Grubbs, R. H.; Pine, S. H. COS 1991, 5, 1115.
4. van Dam, P. B.; Mittelmeijer, M. C.; Boelhouewer, C. CC 1972, 1221.
5. Wilson, S. R.; Schalk, D. E. JOC 1976, 41, 3928.
6. Otton, J.; Colleuille, Y.; Varagnat, J. J. Mol. Catal. 1980, 8, 313.
7. Matyska, B.; Dosedlova, A.; Petrusova, L.; Balcar, H. CCC 1989, 54, 455.

James W. Herndon

University of Maryland, College Park, MD, USA

Copyright 1995-2000 by John Wiley & Sons, Ltd. All rights reserved.