Ligand-Dependent Multi-State Reactivity in Cobalt(III)-Catalyzed C–H Activations

Cobalt­(III)-promoted
C–H activation reactions have witnessed explosive progress
in recent few years. However, the roles played by the various spin
states of Co­(III) center in C–H activation reactivity remain
elusive. To resolve this conundrum, herein we go beyond the commonly
used DFT methods to explore three typical Co­(III)-promoted C–H
activation systems. Our high-level coupled cluster modelings demonstrate
that multistate reactivity (MSR) involving three spin states operates
for C­(sp2)–H and C­(sp3)–H activations
with non-Cp-Co­(III) type catalyst, while single-state reactivity (SSR)
involving only one singlet spin state operates for C­(sp2)–H activation with Cp-Co­(III) type catalyst. This ligand-dependent
reaction scenario of MSR/SSR reveals the high complexity in mechanisms
of Co­(III)-promoted C–H activations.