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Copper(I) Heteroleptic Bis(NHC) and Mixed NHC/Phosphine Complexes: Syntheses and Catalytic Activities in the One-Pot Sequential CuAAC Reaction of Aromatic Amines

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posted on 09.12.2013, 00:00 by Shuai Guo, Miao Hui Lim, Han Vinh Huynh
A series of 2-coordinate heteroleptic Cu­(I) complexes of the general formula [Cu­(IPr)­(L)]­PF6 (25, L = NHC or phosphine) have been synthesized via either (i) chlorido substitution by phosphine or in situ generated free NHC or (ii) the Ag–NHC transfer protocol using [CuCl­(IPr)] (1) as a precursor (IPr = 1,3-bis­(2,6-diiso­propyl­phenyl)­imidazolin-2-ylidene). The reactions of precursor 1 with diphosphine ligands afforded 3-coordinate heteroleptic Cu­(I) complexes of the type [Cu­(IPr)­(L2)]­PF6 (6 and 7, L2 = diphosphine). Complexes 17 have been subjected to a catalytic one-pot sequential CuAAC study, in which aromatic amines serve as the precursors to aryl azides. Hetero-bis­(NHC) complexes 24 proved to be generally superior compared to their mixed NHC/phosphine counterparts 57. Overall, complex [Cu­(Bn2-imy)­(IPr)]­PF6 (2), bearing the Bn2-imy (Bn2-imy = 1,3-dibenzyl-imidazolin-2-ylidene) coligand, showed the best catalytic performance.

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