910 BIS-(3,5-DIPHENYL-1,2-DITHIOLIUM) TETRACHLOROFERRATE(III) CHLORIDE and six-membered rings, the dimensions of the cation are virtually identical with those found in its [MC14] 2-salts (M = Fe, Hg) (Rusholme, 1970). As with other 1,2-dithiolium cations, bond lengths and bond angles are indicative of substantial cyclic delocalization in the five-membered ring system.We are grateful to the Science Research Council for support of these studies.References BALT, S. (1967) The crystal structures of 2,2'-bipyridine.2IC1 and 2,2'-bipyridine.2IBr have been determined from three-dimensional diffractometer data to give R = 2.9 % and 4.0 % respectively. 2,2'-Bipyridine. 21C1 crysstallizes in P21/n with a= 11"833 (7), b= 12.427 (7), c= 10.163 (5)/~, and fl= 101.76 (3)°; Z=4. 2,2'-Bipyridine.2IBr crystallizes in Pnna, with a= 12"971 (4), b= 11"163 (4), c= 10"387 (4) A; Z=4. In the chlorine compound the dihedral angle between the pyridine rings is 88.6 °, in the bromine compound 52"9 °. A short intramolecular approach of the two iodine atoms in the IBr adduct (4.09 A) is observed.