Bis-aryloxo-functionalized NHC complexes of ytterbium(III): Syntheses and structures of Yb[O-4,6-tBu2-C6H2-2-CH2{C(RNCHCHN)}]2N(iPr)2 (R = iPr, Me)

The transamination of anionic homoleptic amido ytterbium complex, LiYb[N(i-Pr)2]4 with aryloxo-functionalized N-heterocyclic carbene (NHC) precursor, HO-4,6-di-tBu-C6H2-2-CH2{CH[i-Pr-NCHCHN]}Cl (H2LCl) 1 and HO-4,6-di-tBu-C6H2-2-CH2{CH[Me-NCHCHN]}Cl (H2L′Cl) 2, and BuLi in 1:2:1 molar ratio in THF at 0 °C afforded the first bisaryloxo- NHC monoamido ytterbium complexes, L2Yb [N(i-Pr)2] 3 and L2′Yb[N(i-Pr)2]4, respectively. The same reactions in the molar ratio of 1:1 without BuLi yields also the complex 3 and 4, not the bis-amido mono aryloxo-NHC complex {LYb[N(i-Pr)2]2} and {L′Yb[N(i-Pr)2]2}. The in situ low-temperature reaction of 2 with two equivalents of BuLi, followed by addition of one equivalent of YbCl3 in THF does not afford the expected LYbCl2, instead, [Li(DME)3][YbCl4(DME)] 5 and a dimeric imidazole-aryloxo lithium {[O-4,6-di-tBu-C6H2-2-CH2{CH(MeNCHCHNH)}]Li(THF)}26 which results from the 1,2-benzyl migration in N-heterocyclic carbene, are obtained. Complexes 3, 4, 5 and 6 have been characterized by elemental analysis and X-ray crystallography, and by NMR spectroscopy for 6.

Graphical abstractThe first bis-aryloxo-functionalized NHC ytterbium complexes monoamido were conveniently prepared in high yield by the transamination of LiYb[N(i-Pr)2]4 with the corresponding aryloxo-functionalized imidazoliums and BuLi.Figure optionsDownload full-size imageDownload as PowerPoint slide