Ziegler systems as hydrogenation catalysts.: Part 1. CoBr2/Li [AlH (O-t-butyl)3]3 system as a catalyst for the hydrogenation of anthracene

Abstract The system Li[AlH ( O - t -butyl) 3 ]/CoBr 2 in THF is a very active catalyst for the hydrogenation of anthracene. The rising activity with increasing concentration of the reducing agent can be described in terms of the formation of a 1 : 1 adduct between the catalyst and the reducing agent. If the catalyst is kept in a hydrogen atmosphere prior to the addition of the substrate, its activity decreases rapidly. During the addition of the components of the catalyst, at most 0.5 mol H 2 /Mol CoBr 2 are generated at once, followed by slow H 2 generation which can be described as two parallel first-order reactions. From the immediate H 2 generation it can be deduced that CoBr 2 is reduced to Co I and that the catalyst contains unchanged reducing agent.