1,3-Butadienyl Dianions as Non-Innocent Ligands: Synthesis and Characterization of Aromatic Dilithio Rhodacycles

摘要

Herein we report that 1,4-dilithio-1,3-butadienes, a type of 1,3-butadienyl dianion, can act as non-innocent ligands, taking electrons from low-valent transition metals. Dilithio reagents reacted with [{RhCl(cod)}(2)] to give dilithio rhodacycle 3a. Single-crystal X-ray structural analysis revealed the structure of 3a with averaged bond lengths. XPS data suggested that the oxidation state of Rh in 3a was more likely to be Rh3+. CDA/ECDA confirmed the electron-transfer process. Li-7 NMR spectra of 3a and theoretical calculations revealed a considerable aromatic character. In this process, the dilithio compounds behaved as non-innocent ligands and formal oxidants. These results demonstrated that organolithium compounds with suitable pi-conjugation could be used as electron acceptor.