Cobalt-catalyzed C–H cyanations: Insights into the reaction mechanism and the role of London dispersion

Abstract

Carboxylate-assisted cobalt(III)-catalyzed C–H cyanations are highly efficient processes for the synthesis of (hetero)aromatic nitriles. We have now analyzed the cyanation of differently substituted 2-phenylpyridines in detail computationally by density functional theory and also experimentally. Based on our investigations, we propose a plausible reaction mechanism for this transformation that is in line with the experimental observations. Additional calculations, including NCIPLOT, dispersion interaction densities, and local energy decomposition analysis, for the model cyanation of 2-phenylpyridine furthermore highlight that London dispersion is an important factor that enables this challenging C–H transformation. Nonbonding interactions between the Cp* ligand and aromatic and C–H-rich fragments of other ligands at the cobalt center significantly contribute to a stabilization of cobalt intermediates and transition states.

Making Base-Assisted C–H Bond Activation by Cp*Co(III) Effective: A Noncovalent Interaction-Inclusive Theoretical Insight and Experimental Validation

“…[7][8][9][10] In contrast, the catalytic activity of Cp*Co(III) complexes has long been ignored and remained mostly unexplored until recently. The recent upsurge of publications dealing with the use of Cp*Co(III)-catalysts in C-H bond functionalizations [11][12][13][14][15][16] was triggered by the remarkable reports by Kanai and Matsunaga [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] (scheme 1) and by Ackerman et al [34][35][36][37][38][39][40][41][42][43][44][45] and followed by a number of other reports. 46,47 In many reported cases this powerful class of cobalt catalysts 11 presents reactivity profiles that differ from their rhodium and iridium analogues.…”

London dispersion effects in the coordination and activation of alkanes in σ-complexes: a local energy decomposition study

“…10 On the other hand, LD is typically considered weaker than covalent or other non-covalent interactions, especially for small systems. 11 In particular, although recent studies have underlined its importance in organometallic chemistry, 4,10,[12][13][14][15][16][17][18][19][20][21][22] its contribution to coordinate covalent bonds is still often ignored or assumed to be negligible. In fact, the interaction between a transition metal (TM) and a ligand (L) is still often described as a simple donor-acceptor interaction and the structure, the catalytic behaviour and the spectroscopic properties of TM complexes are in most cases discussed using orbital models such as the popular Dewar-Chatt-Duncanson (DCD) bonding model.…”

Computational Chemistry as a Conceptual Game Changer: Understanding the Role of London Dispersion in Hexaphenylethane Derivatives (Gomberg Systems)

“…Among others, these interactions explain the hexaarylethane riddle and [the] very short H•••H contacts in tris(3,5-di-tert-butylphenyl)methane." [117] Ultimately, Boeré et al…”