Carbene mechanism diselenides

Trifluoromethyl thiirane is formed by the action of tris(diethylamino)-phosphineon l-chloromethyl-2,2,2-trifluoroethyldisulfide [S2] (equation 73) Difluoromethyl phenyl selenide is prepared by treatment of lithium phenyl-selemde with chlorodifluoroniethane via a carbene mechanism [Si] (equation 44) Bis(2,2,2-trifluoroethyl)diselenide is formed in the reaction of 2,2,2-trifluoroethyl mesylate with lithium diselenide [84] (equation 74). 

A theoretical study of the mechanism of ruthenium-catalyzed formation of pyran-2-one and the corresponding sulfur and selenium analogues 8 from acetylene and CX2 (X = O, S, Se) has been reported (Equation 3) <2004NJC153>. This cyclotrimerization reaction has been experimentally carried out using carbon disulfide as a substrate <2002JA28>. The proposed mechanism involves formation of a bicyclic metal carbene intermediate. Formation of this intermediate seems to be particularly unfavorable energetically in the case of carbon diselenide. 

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