Treatment of ReX(CO)3(dppm) [X = Cl or Br; dppm = bis(diphenylphosphino)methane] with halogens gives the seven-coordinate ReX3(CO)2(dppm) complexes as well as ReBr4(dppm). The ReCl3(CO)(bipy), ReBr4(bipy) and ReBr3Cl(bipy) complexes and the previously characterised ReX3(CO)2(bipy) have all been isolated from the ReX(CO)3(bipy) — X2 systems, (bipy = 2,2′-bipyridyl).