Coordination chemistry of perhalogenated cyclopentadienes and alkynes: XVIII. Mechanistic studies on the metal-halogen exchange reaction of ring-halogenated metallocenes: The influence of stoichiometry, temperature, solvent and reaction time

Abstract

When [C 5Br 5]Mn(CO) 3 ( 1) is treated with butyllithium and hydrolysed after some time, one can always obtain more than one product, independent of stoichiometry, solvent, temperature and lithiation time. However, the distribution of products strongly depends on the reaction conditions. For example, in THF, with a tenfold excess of butyllithium at −78°C, a conversion of more than 80% into [C 5H 5]Mn(CO) 3 can be achieved. In IC 5 Cl 4Br]Mn(CO) 3 ( 2) only a maximum of two halogens can be substituted by hydrogen. These results can be explained in terms of the competition between butyl lithium and the lithiated species [C 5X 4Li]Mn(CO) 3 in the halogen-metal exchange reaction.