Metal-ligand cooperative activation of HX (X=H, Br, OR) bond on Mn based pincer complexes

Abstract

Reversible dissociation of H−X bond (M−L+H−X→M(X)-L(H); (Formula presented.)) is an important step during pre-activation, catalysis and possible deactivation of acid-base cooperative pincer based transition metal catalysts (M−L). Herein we carried out a high-throughput computational investigation of the thermodynamic stability of different adducts in various functionalized Mn(I) based pincer complexes. We used a combination of density functional theory (DFT) and density functional tight binding (DFTB) calculations to analyze (Formula presented.) of >700 (M(X)-L(H)) intermediates based on functionalized variants of four pincer type ligand scaffolds derived from PCP, CNC, PNP and SNS ligands. We discovered linear scaling relations between (Formula presented.) of various species. Strongest correlations were found between species of similar size and chemical nature e. g. (Formula presented.) correlated best with (Formula presented.) and worst with (Formula presented.). Such scaling relations can be useful for property based screening of catalysts and selection of (co)solvent/substrate/base for optimized reaction conditions. We also investigated the influence of the ligand backbone and the functionalization of donor and backbone sites in the ligand. Our analysis reveals the crucial role of the second coordination sphere functionalization for the reactivity of the complexes with impact in some cases exceeding that of the variation of the functional groups directly attached to the donor atoms.