Unprecedented long-range 1,7-bromination in gold complexes of N-(aryl) imino functionalized N-heterocyclic carbenes

Abstract

An unique long-range 1,7-bromination reaction is observed in gold(III) complexes of N-(aryl) imino functionalized N-heterocyclic carbene with the bromination occurring at two different carbon (sp(2) and sp(3)) centers spatially separated by ca. 6.4 angstrom but existing in extended conjugation to each other. In particular, the unusual distant 1,7-brominated gold(III) complexes [1-R-3-{N-(pbromo2,6-di-i-propylphenylimino)-2-phenyl-1-bromoethyl}imidazol-2-ylidene]AuBr(3) [R = Me (1d), i-Pr (2d), t-Bu (3d),-CH(2)Ph (4d)] were synthesized cleanly at room temperature under ambient conditions from the reactions of molecular bromine with the gold(I) complexes [1-R-3{ N-(2,6-di-i-propylphenylimino)-2-phenylethyl} imidazol-2-ylidene]AuCl [R = Me (1c), i-Pr (2c), t-Bu (3c),-CH(2)Ph (4c)]. All of the 1,7-bromination products (1d, 2d, 3d and 4d) have been structurally verified by X-ray diffraction studies.