Stoichiometric sensitivity and structural diversity in click-active copper(i) N,S-heterocyclic carbene complexes

Abstract

A series of novel Cu(I) N,S-heterocyclic carbene (NSHC) complexes [Cu(μ-Br)(NSHC)]₂, [Cu(μ-X)(NSHC)]₄ (X = Br or I), [(NSHC)₂Cu(μ-Br)₂Cu(NSHC)], and [(NSHC)₂CuBr] have been isolated from in situ generated CuO^tBu and N-substituted benzothiazolium halides and characterized by X-ray crystallography. Five structural motifs were observed, viz. M_xL_y where x : y = 2 : 2, 4 : 4, 2 : 3, 1 : 2 and 2 : 4, with Cu⋯Cu separation traversing over a wide range of 2.5626(7) to 3.4725(7) Å distances. A preliminary investigation of the catalytic activity of these compounds indicated that the unusual mononuclear complex 6 [(NSHC)₂CuBr] is an active catalyst for the Huisgen 1,3-dipolar cycloaddition of azide and alkynes while complexes 1–5 and 7 were marginally less active.