bromo-, and iodo-carbene complexes of manganese and rhenium were obtained on nucleophilic addition of X− (X = F, Cl, Br, I) to various cationicdicarbonyl(cyclopentadienyl)arylcarbyne complexes [C5H5(CO)2MCR]+ Y− (M = Mn, Re). This reaction is influenced by the kind of anion Y− as well as solvent effects and depends on the ability of the substituent R to withdraw electron density from the carbyne carbon