COORDINATION CHEMISTRY OF PHERHALOGENATED CYCLOPENTADIENES AND ALKYNES .18. MECHANISTIC STUDIES ON THE METAL HALOGEN EXCHANGE-REACTION OF RING-HALOGENATED METALLOCENES - THE INFLUENCE OF STOICHIOMETRY, TEMPERATURE, SOLVENT AND REACTION-TIME

When [C5Br5]Mn(CO), (1) is treated with butyllithium and hydrolyzed af ter some time, one can always obtain more than one product, independen t of stoichiometry, solvent, temperature and lithiation time. However, the distribution of products strongly depends on the reaction conditi ons. For example, in THF, with a tenfold excess of butyllithium at - 7 8-degrees-C, a conversion of more than 80% into [C5H5]Mn(CO)3 Can be a chieved. In [C5Cl4Br]Mn(CO)3 (2) only a maximum of two halogens can be substituted by hydrogen. These results can be explained in terms of t he competition between butyl lithium and the lithiated species [C5X4Li ]Mn(CO)3 in the halogen-metal exchange reaction.