AN AIR-STABLE CARBENE AND MIXED CARBENE DIMERS

The air-stable crystalline carbene 1,3-dimesityl-4,5-dichloroimidazol- 2-ylidene (2) is produced from the chlorination of 1,3-dimesityimidazo l-2-ylidene (1) by 2 equiv of carbon tetrachloride. The physical and s pectroscopic properties of the carbene are reported. The features whic h contribute to the exceptional stability of the carbene are discussed . Further reaction of 2 with carbon tetrachloride leads to reduction o f CCl4 to dichlorocarbene. The formation of the mixed carbene ''dimers '' (olefins) from in situ generated dichlorocarbene and various imidaz ol(in)-2-ylidenes is also reported. The tellurones derived from 1 and 2 are synthesized and compared.