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

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 (sp² and sp ³) centers spatially separated by ca. 6.4 Å but existing in extended conjugation to each other. In particular, the unusual distant 1,7-brominated gold(iii) complexes [1-R-3-{N-(p-bromo-2,6-di-i- propylphenylimino)-2-phenyl-1-bromoethyl}imidazol-2-ylidene]AuBr₃ [R = Me (1d), i-Pr (2d), t-Bu (3d), -CH₂Ph (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), -CH₂Ph (4c)]. All of the 1,7-bromination products (1d, 2d, 3d and 4d) have been structurally verified by X-ray diffraction studies.