A comparison of donor–acceptor interactions of N-heterocyclic carbenes and sulfonium ylides in coordination with coinage metal ions

Abstract

This study seeks to characterize the structure and nature of metal–ligand bonds in sulfonium ylide complexes [{S(R)2CHCOC10H7}2 → M]+ and N-heterocyclic carbene complexes [{NHC(R)2}2 → M]+ {M = Cu(I), Ag (I), Au(I) and R = F, Cl, Br, H, Me, Si(CH3)3} at PBE/def2-SVP level of theory which is nominated among eight scrutinized DFT methods. Compared to sulfonium ylides, NHC(R)’s form stronger bonds with coinage metal ions not only in the presence of electron-donating substituents (R = H, Me, Si(CH3)3) but also in the presence of electron-withdrawing substituents (R = F, Cl, Br). Besides, the nature of C → M bonds in the complexes is analyzed through the charge and energy decomposition analysis EDA-NOCV. In both studied complexes, the electrostatic nature of C → M bond is a dominant term in the interaction energy. The comparison of EDA-NOCV results for C → M bonds in both [{S(R)2CHCOC10H7}2 → M]+ and [{NHC(R)2}2 → M]+ complexes indicates that sulfonium ylide ligands S(R)2CHCOC10H7 are slightly better σ-donors and weaker π-acceptors than their corresponding NHC(R) ligands.