Activation Barriers for Cobalt(IV)-Centered Reductive Elimination Correlate with Quantified Interatomic Noncovalent Interactions

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, kappa(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.

Automated summary

In this study, a combination of theoretical and experimental approaches was used to analyze weak interligand noncovalent interactions in Co(IV) [Cp*Co(phpy)X](+) cobaltacycles. The independent gradient model/intrinsic bond strength index (IGM/IBSI) method was employed to evaluate the dependence of the catalytically desired reductive elimination pathway (RE) on the nature of the X ligand. The results showed that the barrier for activation of the RE pathway is directly correlated with the IBSI of the X-to-carbanionic chelate's carbon, indicating the possibility of in silico prediction of efficient Cp*Co-catalyzed directed X-functionalization of an aromatic C-H bond based on X ligand properties. Experimental evidence supported the theoretical conclusions.