Trivalent rare-earth metal cyclic (alkyl)(amino)carbene complexes

Abstract

Coordination chemistry of cyclic (alkyl)(amino)carbene (CAAC) ligands has blossomed in recent years, exemplified by their strong σ-donating and π-accepting ability. However, trivalent rare-earth metal CAAC complexes remain elusive. By using M(CH₂SiMe₃)₃(THF)₂ (M = Sc, Y and Lu) as precursors, we synthesized mono CAAC coordinated rare-earth metal trisalkyl complexes, (^RCAAC)M(CH₂SiMe₃)₃ (R = Me and Et, M = Sc, Y and Lu). In addition, when MI₃(Et₂O)_n (M = Y and Yb) were employed as metal precursors, bis(CAAC)-stabilized rare-earth metal triiodide complexes (^MeCAAC)₂MI₃ (M = Y and Yb) could be obtained. All new compounds were characterized by X-ray crystallography, elemental analysis and NMR spectroscopy. Density functional theory calculations were conducted for these rare-earth metal CAAC complexes to gain insight into their electronic structures and bonding interactions. The bonding analysis unveils that the CAAC ligands act as σ donors to trivalent rare-earth metal ions and may be involved in π-bonding upon reduction.