Disproportionation of dihalogenocyclopentadienylcobalt complexes to cobaltocenium salts

Abstract

Di-iodocyclopentadienylcobalt has been prepared; it is quite insoluble in non-co-ordinating solvents and decomposes in co-ordinating solvents to give the cobaltocenium ion and cobalt(II). Dibromocyclopentadienylcobalt decomposes more quickly, even in light petroleum, again to cobaltocenium; the order of stability to disproportionation is Co(C₅H₅)l₂ > Co(C₅H₅)Br₂ > Co(C₅H₅)Cl₂. Neither dihalogenocyclopentadienylrhodium complexes nor dihalogenopentamethylcyclopentadienyl-cobalt, -rhodium, or -iridium complexes show this behaviour.