Copper(I) heteroleptic bis(NHC) and mixed NHC/phosphine complexes: Syntheses and catalytic activities in the one-pot sequential CuAAC reaction of aromatic amines

Abstract

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 Bn 2-imy (Bn2-imy = 1,3-dibenzyl-imidazolin-2-ylidene) coligand, showed the best catalytic performance. © 2013 American Chemical Society.