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

A series
of 2-coordinate heteroleptic Cu­(I) complexes of the general
formula [Cu­(IPr)­(L)]­PF6 (2–5, 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 1–7 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 2–4 proved
to be generally superior compared to their mixed NHC/phosphine counterparts 5–7. 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.

一系列通式为[Cu(IPr)(L)]PF₆（2~5，L为N-杂环卡宾(NHC)或膦配体）的二配位异配型铜(I)配合物，可通过两种合成路径制备：(i) 以膦配体或原位生成的游离N-杂环卡宾对前驱体[CuCl(IPr)](1)进行氯取代反应；或(ii) 以[CuCl(IPr)](1)为前驱体，采用银-NHC转移法合成（其中IPr = 1,3-双(2,6-二异丙基苯基)咪唑啉-2-卡宾）。前驱体1与双膦配体反应，可得到通式为[Cu(IPr)(L₂)]PF₆（6和7，L₂为双膦配体）的三配位异配型铜(I)配合物。对配合物1~7开展了催化一锅法串联铜催化叠氮-炔环加成（CuAAC）研究，该反应以芳香胺作为芳基叠氮的前驱体。研究结果显示，杂双(N-杂环卡宾)配合物2~4的催化性能整体优于其混合NHC/膦配体对应配合物5~7。其中，带有共配体Bn₂-imy（Bn₂-imy = 1,3-二苄基咪唑啉-2-卡宾）的配合物[Cu(Bn₂-imy)(IPr)]PF₆(2)展现出最优的催化性能。