Kinetic versus thermodynamic control in the selective functionalization of nickel(II) cyclidene macrocyclic complexes

Alkylation reactions on the periphery of nickel(II) cyclidene macrocyclic complexes were carried out with a high degree of selectivity, to produce a family of 17 new complexes encompassing asymmetric monofunctionalized, symmetric or asymmetric difunctionalized products, and incorporating a range of useful structural features. The origin of the remarkable control of reactivity exhibited by these systems is ascribed, based on NMR studies, to kinetic control of the alkylation reaction, and is associated with the conformations adopted by the pendant groups of the macrocycle in solution and also depends on both the steric bulk and the relative reactivity of the alkylating agent.