The copper(I) catalyzed halogen exchange reactions of 3-bromo-2-iodonitrobenzene with tetrabutylammonium dibromo- and dichlorocuprates(I) have previously been studied kinetically in chlorobenzene.1 The reaction of the halogeno-arene with the dibromocuprate anion was a reversible second-order reaction, first-order in both arene and anion, whereas no appreciable reversibility was noticed in the exchange with the dichlorocuprate anion, also of second order. The exchange reactions of 2,3-dibromonitrobenzene with tetrabutylammonium dichloro- and bromo- chlorocuprates(I) have also been investigated'(see Table 1).
The crystal structures of the tetrabutylammonium salts have been determined from single-crystal X-ray diffraction data. The dibromo- as well as the dichlorocuprates(I) are linear monomers.2 The most plausible description of the
structure of bromochlorocuprate(I) entails one dichlorocuprate(I) ion, one dibromocuprate(I) ion and two bromochlorocuprate(I) ions per unit ce11. This was confirmed by an infrared spec-trum.