Synthesis of Cationic N-Heterocyclic Carbene Lanthanide Bromide and the Influence of N-Heterocyclic Carbene and Lanthanide Metals

The lithium salt of the novel amido-phenoxo-functionalized NHC L (L = [3,5-tBu2-2-(O)C6H2CH(nBu)NH(CH2)2(C{N(CH)2NiPr})]), (LiL)2 (1), was synthesized by the direct reaction of the salicylaldimino-functionalized imidazolium salt H2L′Br (L′ = [3,5-tBu2-2-(O)C6H2CHN(CH2)2(C{N(CH)2NiPr})]) with 2 equiv of LinBu and structurally characterized. Treatment of LnCl3 with in situ formed 1 in a molar ratio of 1:1 at room temperature yielded the first cationic complexes [LnL2]+[Br]− (Ln = Y (2), Lu (3), Er (4)) in good yields. Treatment of Li(THF)Ln(NiPr2)4 with 2 equiv of H2L′Br at −78 °C afforded the cationic complexes [L′2Ln(THF)]+[Br]− (Ln = Y (5) and Yb (6)) in desired yields. Each central metal in cations [LnL2]+ for 2−4 is coordinated by two L ligands, while the central metal in [L′2Ln(THF)]+ for 5 and 6 is ligated by two ligands and one THF molecule. The structures of NHC lanthanide bromides have been found to depend on both the size of the metal and the ligand.