Lanthanide Complexes of Amino−Carbenes: On the Samarium−Carbene Bond from DFT Calculations

Abstract

The coordination of the four model amino−carbene ligands A−D to SmCl3 has been theoretically investigated. Strong coordination energies were predicted for all carbenes (ΔG(25 °C) < −35 kcal mol-1 for the monoadducts). The nature of the Sm−carbene bonds was studied by molecular orbital and natural bond orbital (NBO) analyses. No evidence for significant carbene-to-Sm π-donation or Cl-to-carbene back-donation was observed. The strong Sm−carbene bonds, culminating in the abnormal NHC species D, can thus be essentially attributed to carbene-to-Sm σ-donation.