[6795-81-9] · C2Cl6Hg · Bis(trichloromethyl)mercury · (MW 437.33)
Physical Data: mp 141 °C.
Solubility: sol ether, THF, CHCl3; insol cold H2O, petroleum ether.
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.
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
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
José Barluenga, Miguel Tomás & José M. González
Universidad de Oviedo, Spain