“Catch and release” of the CpN3 ligand using cobalt: dissociation, protonation, and C–H bond thermochemistry

Abstract

The coordination chemistry of an amine-rich CpN3 ligand has been explored with cobalt. We demonstrate that in the presence of NaCo(CO)4, the cationic precursor [CpN3]+ yields the complex CpN3CoI(CO)2. While 2e oxidation generates new CoIII complexes such as [CpN3Co(NCMe)3]2+ and CpN3CoI2(CO), subsequent ligand loss is facile, generating free [CpN3]+ or the protonated dication [CpN3H]2+. We have structurally characterized both these ligand release products via single crystal X-ray diffraction and obtained thermochemical C–H bond strengths via experiment and density functional theory (DFT). Upon reversible 1e reduction, the radical cation [CpN3H]˙+ has a weak C–H BDFE of 52 kcal mol−1 in acetonitrile. Mechanistic analysis shows that [CpN3H]˙+ undergoes radical–radical disproportionation in the absence of exogenous H-atom acceptors, which is supported by deuterium isotope labelling experiments. Structural comparison of these organic molecules shows a high degree of iminium-like electron delocalization over the C–N bonds connected to the central five-membered ring.

Graphical abstract: “Catch and release” of the CpN3 ligand using cobalt: dissociation, protonation, and C–H bond thermochemistry

Supplementary files

Article information

Article type
Paper
Submitted
28 mai 2024
Accepted
17 juin 2024
First published
18 juin 2024

Dalton Trans., 2024, Advance Article

“Catch and release” of the CpN3 ligand using cobalt: dissociation, protonation, and C–H bond thermochemistry

S. Luhach, R. A. Lalancette and D. E. Prokopchuk, Dalton Trans., 2024, Advance Article , DOI: 10.1039/D4DT01560F

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