Crystal structures of benzoxazolyl–copper(iii,ii,i) complexes and investigation of Cu(ii)-mediated aryl carbon–hydrogen bromination

Abstract

Copper complexes have been frequently involved in many Cu-mediated carbon–hydrogen halogenation reactions. We fortunately obtained three different valence benzoxazolyl–copper complexes, along with aryl carbon–hydrogen bromination, in the self-assembly reaction of ligands with CuBr₂. The complexes have been successfully characterized by X-ray single crystal diffraction analyses. The results indicate that 1 consists of di-brominated p-benzoxazolylphenylamine (L) and an unusual high valence copper(III) complex with tetrahedral geometry, 2 is the first polymeric catenulate di-brominated benzoxazolyl-copper(I) complex and 3 is the mono-brominated benzoxazolyl–copper(II) complex. We speculate proposed mechanisms for the formation of these complexes and the bromination of aryl carbon–hydrogen based on these crystal structures.