Bis(trichloromethyl)mercury1

Hg(CCl3)2

[6795-81-9]  · C2Cl6Hg  · Bis(trichloromethyl)mercury  · (MW 437.33)

(source of :CCl2 by thermal treatment;2,3 furnishes cyclopropanes by reaction with alkenes4)

Physical Data: mp 141 °C.

Solubility: sol ether, THF, CHCl3; insol cold H2O, petroleum ether.

Analysis of Reagent Purity: IR,5 Raman,5 NMR (13C and 119Hg),6 and NQR (35Cl).7

Preparative Method: reaction of Mercury(II) Chloride (HgBr2 has proven to be unreactive) with Sodium Trichloroacetate (1:2 molar ratio) in dry monoglyme at reflux for 1 h affords Hg(CCl3)2 as a crystalline solid after purification.

Purification: recrystallization from CHCl3.

Handling, Storage, and Precautions: flame-dried glassware and an atmosphere of dry nitrogen are used for the reactions. Organomercury(II) compounds should be carefully handled and skin contact and inhalation should be particularly avoided. All reactions must be conducted in a well-ventilated hood.

Pyrolysis.

Gas phase pyrolysis of Hg(CCl3)2 at 350 °C gave mainly C2Cl4 and minor amounts of C2Cl6.2,3 Similar pyrolysis in the presence of excess cyclopentadiene yields chlorobenzene, originated from addition of :CCl2 to the C=C bond of the diene. Further and compelling evidence for carbene generation under pyrolytic conditions arises from investigations by matrix isolation techniques after the gas phase pyrolysis, allowing characterization of the intermediate species.2,3

Cyclopropanation of Alkenes.

A major reaction of some a-haloorganomercurials is their ability to cyclopropanate alkenes.1 When dealing with Hg(CCl3)2, the reaction takes place at elevated temperatures and gives only modest yields (eq 1).4 Yields can be slightly improved by raising the temperature. Thus, for example, running the reaction in an autoclave for 15 min, cyclohexene yields 25% of cyclopropanation at 200 °C, but 36% at 250 °C.4


1. (a) Seyferth, D. PAC 1970, 23, 391. (b) Seyferth, D. ACR 1972, 5, 65. (c) Zeller, K.-P.; Straub, H. MOC 1974, 13/2b, 351. (d) Larock, R. C. Organomercury Compounds in Organic Synthesis; Springer: Berlin, 1985; Chapter X, pp 327-413.
2. Mal'tsev, A. K.; Mikaélyan, R. G.; Nefedov, O. M. IZV 1971, 199 (CA 1971, 75, 19 592q); BAU 1971, 188.
3. Mal'tsev, A. K.; Mikaélyan, R. G.; Nefedov, O. M.; Hauge, R. H.; Margrave, J. L. PNA 1971, 68, 3238.
4. Logan, T. J. JOC 1963, 28, 1129.
5. Goggin, P. L.; Goodfellow, R. J.; Kessler, K.; Prescott, A. M. JCS(D) 1978, 328.
6. Goggin, P. L.; Goodfellow, R. J.; McEwan, D. M.; Griffiths, A. J.; Kessler, K. JCR(S) 1979, 194.
7. Wulfsberg, G.; West, R.; Rao, V. N. M. JOM 1975, 86, 303.

José Barluenga, Miguel Tomás & José M. González

Universidad de Oviedo, Spain



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