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

Coordination chemistry of cyclic (alkyl)(amino)carbene (CAAC) ligands has blossomed in recent years, exemplified by their strong sigma-donating and pi-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, ((R)CAAC)M(CH2SiMe3)(3)(R = Me and Et, M = Sc, Y and Lu). In addition, when Ml(3)(Et2O)(n) (M = Y and Yb) were employed as metal precursors, bis(CAAC)-stabilized rare-earth metal triiodide complexes ((Me)CAAC)(2)Ml(3) (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 sigma donors to trivalent rare-earth metal ions and may be involved in pi-bonding upon reduction.