STABLE CARBENOIDS .38. EVIDENCE OF SIGMA-ALKENYL-IRON(3) INTERMEDIATES IN OXIDATIVE COUPLING AND ELIMINATION REACTION OF LITHIUM POLYCHLOROPOLYENES WITH IRON(3) CHLORIDE

trans-Dichlorovinyllithium(IIa) and 1,2,3,4-tetrachlorobutadienyllithium(IIb) react with FeCl(in3) in THF at -110° to form σ-organoiron(III) compounds, which can be characterized by protolysis, iodolysis and (partial) carboxylation. Nucleophilic reactions of the lithium organyls (II) are described, which allow to differentiate between C-Li and σ-C-Fe bonds. The iron organyls are stable in THF up to- 80°; at higher temperatures they either undergo an oxidative coupling to give the polychloropolyenes (III), or in the absence of suitable oxidizing agents-yield (polychloroalkenyl)acetylenes by way of an eliminative" coupling. The structure of the σ-iron organyls and the mechanisms of their coupling reactions are discussed. © 1969."