13C and 207Pb NMR Chemical Shifts of Dirhodio- and Dilithioplumbole Complexes: A Quantum Chemical Assessment

Density functional theory (DFT) and zeroth-order regular approximation DFT calculations were performed to investigate the electronic structures and 13C and 207Pb nuclear magnetic resonance (NMR) chemical shifts of metal-coordinated plumboles, namely, monorhodioplumbole ([Rh–plumbole]−), dirhodioplumbole (Rh2–plumbole), and dilithioplumbole (Li2–plumbole), which have a five-membered ring containing lead. The molecular orbital correlation diagram and extended transition state–natural orbitals for chemical valence analysis of the [Rh–plumbole]− and Rh2–plumbole complexes showed that the plumbole is primarily a π-donor, with π-donation being dominant in the Rh2–plumbole complex. The present calculations show that the Pb–Cα internuclear distances are longer in the Rh2–plumbole complex than in [Rh–plumbole]− because of the combined effect of strong π-donation and weak π-back-donation in the Rh2–plumbole complex. The calculated 207Pb and 13Cα NMR chemical shifts agree with the experimental trends reasonably well...