Single-Molecule Activation and Quantification of Mechanically Triggered Palladium–Carbene Bond Dissociation
Anton Razgoniaev, Logan M. Glasstetter, Tatiana B. Kouznetsova, Kacey C. Hall, Maggie Horst, Stephen L. Craig, Katherine J. Franz
Abstract
Metal-complexed N-heterocyclic carbene (NHC) mechanophores are latent reactants and catalysts for a range of mechanically driven chemical responses, but mechanochemical scission of the metal–NHC bond has not been experimentally characterized. Here we report the single-molecule force spectroscopy of ligand dissociation from a pincer NHC–pyridine–NHC Pd(II) complex. The force-coupled rate constant for ligand dissociation reaches 50 s–1 at forces of approximately 930 pN. Experimental and computational observations support a dissociative, rather than associative, mechanism of ligand displacement, with rate-limiting scission of the Pd–NHC bond followed by rapid dissociation of the pyridine moiety from Pd.