Condensation reaction vs. ligand exchange with first-row transition metal cations: a theoretical study of Cu~+ heteroleptic model complexes

摘要

Analysis of the evolution of the binding energy to a late first-row transition metal cation M~+ shows that the third ligand is significantly less strongly bound than the two first. The present study suggests that a new type of cluster-assisted reactions could be induced by the metal center when it is tri-coordinated. Cu~+ complexes have been chosen as models for the quantum chemical calculations (density functional and post-Hartree-Fock ab initio). First, an emphasis is made on the analysis of the evolution of the binding energy as the coordination number n varies from 1 to 4 in Cu~+ (H_2O)_n and Cu~+(CO)_n. The evolution of the electronic repulsion between the σ donating orbitals of the ligands and the 3d orbitals is discussed in details. Second, we consider the successive substitution reactions of CO by H_2O ligand from Cu~+(CO)_n (n = 1-4). Our calculations suggest that rather than the simple substitution reaction of CO by ROR' (R,R' = H, alkyl), formation of an acid or ester could occur in the coordination sphere of the metal. Whereas kinetics is likely to be unfavorable in the case of Cu~+, such condensation reaction of ROR' and CO could be observed with late first-row transition metal cations such as Fe~+.