The structures of three racemic double salts of [Co(en)3]Cl3 (en is ethane-1,2-diamine, C2H8N2), namely, bis[tris(ethane-1,2-diamine-κ2N,N')cobalt(III)] hexaaquasodium(I) heptachloride, [Co(en)3]2[Na(H2O)6]Cl7, bis[tris(ethane-1,2-diamine-κ2N,N')cobalt(III)] hexaaquapotassium(I) heptachloride, [Co(en)3]2[K(H2O)6]Cl7, and ammonium bis[tris(ethane-1,2-diamine-κ2N,N')cobalt(III)] heptachloride hexahydrate, (NH4)[Co(en)3]2Cl7·6H2O, have been determined, and the structural similarities with the parent compound, tris(ethane-1,2-diamine-κ2N,N')cobalt(III) trichloride tetrahydrate, [Co(en)3]Cl3·4H2O, are highlighted. All four compounds crystallize in the trigonal space group P-3c1. 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(H2O)6]Cl7 has also been redetermined at cryogenic temperatures (120 K) and the disorder noted in a previous report has been accounted for.
Keywords: ammonium; crystal structure; double salt; ethane-1,2-diamine; potassium; sodium; unit-cell volume.