In this joint theoretical and experimental study, an analysis of weak interligand
noncovalent interactions within Co(IV) [Cp*Co(phpy)X]+ cobaltacycles (phpy = 2-phenylenepyridine, κ
C,N
) was carried out by using the independent gradient model/intrinsic bond strength
index (IGM/IBSI) method to evaluate the dependency of the catalytically desired reductive
elimination pathway (RE) on the nature of the X ligand. It is shown that the barrier
for activation of the RE pathway correlates directly with the IBSI of the X-to-carbanionic
chelate’s carbon. This correlation suggests that in silico prediction of which X ligand is more prone to operate an efficient Cp*Co-catalyzed
directed X-functionalization of an aromatic C–H bond is attainable. A set of experiments
involving various sources of X ligands supported the theoretical conclusions.
Key words
metallacycles - cobalt catalysis - density functional theory - noncovalent interactions
- reductive elimination - C–H bond activation
