Formation of paramagnetic intermediates under the conditions of Brookhart-type catalyst activation and operation

The formation of two types of paramagnetic species in the catalytic system NiBr2(DAB)/ MAO under real catalytic conditions was found. These are NiII are NiI complexes with the diimine ligand and complexes with the radical anion ligand in the coordination sphere. Under catalysis conditions, these forms are in equilibrium with each other, the equilibrium being shifted towards the radical anion form upon substrate addition.