I'm hoping someone can help me tighten up my understanding of the origins of the differences between Ni and Pd catalysis.
I understand that Ni has higher charge density and this is the reason for it's larger capacity for oxidative addition for say an aryl halide. It also has access to the oxidtaion states (0), (I), (II), (III) and sometimes (IV). Palladium conversely only shuttles between (0) and (II) in a standard cross-coupling reaction. I believe the lower first ionisation energy can account for the increased tendency of Ni to do SET but I don't know how best to explain why all the additional oxidation states are available to Ni and not for Pd.
thanks in advance, Cat