Modifications to the primary and secondary coordination sphere of CoII complexes direct reactivity with O2.

A series of 15 CoX2 (X = Cl, Br, I) pyridine pyrazole complexes were synthesized featuring systematic variations of both the primary and secondary coordination spheres. These studies identified the distinct roles served by each modifification on the redox properties as well as reactivity with O2. In addition to thermally reversible O2 reactivity, we found that complexes with a CoI2 core were catalysts for hydrogen atom transfer reactions and complexes with BBN-substituted ligands with a CoCl2 or CoBr2 could catalyze oxygen atom transfer reactions.