Building trans-philicity (trans-effect/trans-influence) ladders for octahedral complexes by using an NMR probe

Abstract

NMR trans-philicity (trans-effect/trans-influence) ladders have been built for a broad series of octahedral [Cr(CO)₅L]^−/0/+ complexes (50 ligands used) by using a ¹³C NMR probe and quantified through calculation of the Δσ = σ_Cr(CO)5L − σ_Cr(CO)5 NMR parameter employing DFT computational methods. This quantification notably retrieves the experimental trans-orienting series. The excellent linear correlations between the calculated Δσ NMR parameter and well established ligand electronic parameters, such as the ligand constant P_L and the ligand electrochemical parameter E_L(L), that measure the ligand bonding effects in coordination and organometallic chemistry prompt us to introduce the trans-philicity concept as a unified term to cover both the kinetic trans-effect and its thermodynamic (ground state) trans-influence cousin. The trans-philicity for ligand L is defined as the strength of philicity of the coordination site in trans-position to itself. trans-Effect and trans-influence ladders have also been built for the octahedral [Cr(CO)₅L]^−/0/+ complexes based on the calculated intrinsic bond dissociation energy of the Cr–CO_trans bond, IBDE(Cr–CO_trans) to account for the trans-effect and the ν(CO_trans) and ν(Cr–CO_trans) vibrational frequencies, and R(Cr–CO_trans) bond lengths to develop the trans-influence series and compared with the NMR trans-philicity ladder.