Double-salt formation in crystal structures containing [Co(en) 3 ]Cl 3 .

The structures of three racemic double salts of [Co(en) 3 ]Cl 3 (en is ethane-1,2-diamine, C 2 H 8 N 2 ), namely, bis[tris(ethane-1,2-diamine-κ 2 N,N')cobalt(III)] hexaaquasodium(I) heptachloride, [Co(en) 3 ] 2 [Na(H 2 O) 6 ]Cl 7 , bis[tris(ethane-1,2-diamine-κ 2 N,N')cobalt(III)] hexaaquapotassium(I) heptachloride, [Co(en) 3 ] 2 [K(H 2 O) 6 ]Cl 7 , and ammonium bis[tris(ethane-1,2-diamine-κ 2 N,N')cobalt(III)] heptachloride hexahydrate, (NH 4 )[Co(en) 3 ] 2 Cl 7 ·6H 2 O, have been determined, and the structural similarities with the parent compound, tris(ethane-1,2-diamine-κ 2 N,N')cobalt(III) trichloride tetrahydrate, [Co(en) 3 ]Cl 3 ·4H 2 O, are highlighted. All four compounds crystallize in the trigonal space group P\overline{3}c1. When compared with the parent compound, the double salts show a modest increase in the unit-cell volume. The structure of the chiral derivative [Λ-Co(en) 3 ] 2 [Na(H 2 O) 6 ]Cl 7 has also been redetermined at cryogenic temperatures (120 K) and the disorder noted in a previous report has been accounted for.