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

Abstract

The lithium salt of the novel amido-phenoxo-functionalized NHC L (L = [3,5-t 1), was synthesized by the direct reaction of the salicylaldimino-functionalized imidazolium salt H 2 L 0 Br (L) with 2 equiv of Li n Bu and structurally characterized. Treatment of LnCl 3 with in situ formed 1 in a molar ratio of 1:1 at room temperature yielded the first cationic complexes(2), Lu (3), Er (4)) in good yields. Treatment of Li(THF)Ln(N i Pr 2 ) 4 with 2 equiv of H 2 L 0 Br at -78 5) and Yb ( 6)) in desired yields. Each central metal in cations [LnL 2 ] þ for 2-4 is coordinated by two L ligands, while the central metal in [L 0 2 Ln(THF)] þ 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.

Enol-functionalized N-heterocyclic carbene lanthanide amide complexes: Synthesis, molecular structures and catalytic activity for addition of amines to carbodiimides

“…The coordination geometry around each 5-coordinated metal can be best described as a distorted trigonal bipyramid with the two carbene carbon atoms (C(3) and C (18) (5) for 1, 2.621(4) for 2, 2.581(5) for 3, 2.463(4) for 4) in 1e4 are compared to each other when the differences in ion radius among these metals were considered. The values can also be comparable with those found in the related lanthanide NHC complexes [7,12,13].…”

“…All reactions went smoothly to give the corresponding complexes L 2 LnN(TMS) 2 (Ln ¼ Nd (2), Sm (3), Yb (4)) as blue crystals for 2, light yellow and yellow crystals for 3 and 4 in the yields similar to that for complex 1 (Scheme 1). The C carbene resonate in 13 C NMR spectroscopy of complexes 2e4 could not be detected as the cases for the NHC complexes of the corresponding lanthanide metals reported previously [7,9,10,12]. The confirmation of complexes 2e4 were unequivocally established by X-ray crystal structure analyses.…”

Selective and catalytic carbon dioxide and heteroallene activation mediated by cerium N-heterocyclic carbene complexes

“…The 1 H NMR spectra of all four lanthanide complexes bearing alkyl R groups ( i Pr or t Bu) contain a complex set of paramagnetic resonances indicating C 1 symmetry and a unique environment for each ligand. In agreement with the 1 H spectrum of 1Ce iPr the 13 C{ 1 H} NMR spectrum is also complicated, containing three carbene chemical shifts ( δ = 174.8 ppm, 187.8 ppm, 192.3 ppm), slightly broadened compared to the rest of the spectrum (average fwhm 12 Hz), and shifted compared to similar diamagnetic lanthanide NHC complexes (normal region ≈ 200–238 ppm for Y III and Ce IV ) 14,17,19,29,30. However in contrast, spectra of 1Ce Mes contain a single set of paramagnetically shifted resonances indicating C 3 symmetry in solution on the 1 H NMR spectroscopic timescale and 13 C NMR spectroscopy of 1Ce Mes displays a single carbene resonance at 184.2 ppm.…”

Recent Advances in Rare Earth Complexes Containing N-Heterocyclic Carbenes: Synthesis, Reactivity, and Applications in Polymerization

“…When the reaction of Li[Y(N i Pr2)]4 with an aryloxo-tethered NHC precursor and n BuLi was carried out at room temperature, the Y complex 39 supported by a bridging bisphenoxo group was obtained, presumably derived from the cleavage of the NHC ligand ( Figure 11) [63]. Cationic amido-phenoxo-functionalized NHC-ligated Ln bromides (Ln = Y (40), Lu (41), Er (42)) were obtained from the transmetalation reaction of LnCl3 with NHC-ligated Li in a molar ratio of 1:1 at room temperature, which could also be in situ formed by the salicylaldimino-functionalized imidazolium bromide with n BuLi (Figure 11) [64]. On the other hand, half-sandwich Sc complexes bearing a CGC-type NHC (43, 49, and 53) exhibited medium to high catalytic activity in the polymerization of ethylene, while the Y and Lu analogues were inactive.…”

“…A series of CCC-pincer 2,6-xylenyl bis(carbene)-ligated Ln dibromides (60)(61)(62)(63)(64)(65)(66)(67)(68)(69) were synthesized via the treatment of imidazolium dibromide proligands and LnCl 3 with dropwise addition of n BuLi (Figure 15) [79,80]. The Y, Nd, Gd, Dy, and Ho complexes exhibited high activity and cis-1,4 selectivity (99.6%, 25 • C) in the polymerization of isoprene under activation with AlR 3 (R = Me, Et, i Bu) and [Ph 3 C][B(C 6 F 5 ) 4 ], while the others were inactive.…”