Hexaam(m)ine Cr(III) complexes are reviewed on which X-ray data were published or of which the phosphorescence was measured in the crystalline state. In addition complexes of the type mer-[Cr(NH 3 )(diamine)(triamine)] 3 + have been prepared. In all cases, the complex cations were crystallised as chloromercury(II) salts and single-crystal X-ray structures have been determined for six systems. Apart from mer-[Cr(NH 3 )(Me 2 tn)(2,3-tri)]HgCl 5 .1.5H 2 O (5) (monoclinic, C2/c) which has both endo and exo forms in the lattice, the other six complexes adopt the exo-mer-triamine configuration. The 1,2-diaminopropane (pn) ligand in mer-[Cr(NH 3 )(pn)(3,3-tri)]HgCl 5 .2H 2 O (2) (monoclinic, P2 1 /c) is end-for-end disordered and the 1,2-cyclohexane diamine ligand (chxn) is the trans-(RR,SS)-isomer in both mer-[Cr(NH 3 )(chxn)(3,3-tri)]HgCl 5 (3) (monoclinic, P2 1 /n) and mer-[Cr(NH 3 )(chxn)(2,3-tri)]HgCl 5 .2H 2 O (6) (monoclinic, P2 1 c). In 2, 3, 5 and 6 above, the chloromercury(II) formula unit is a distorted tetrahedral HgCl 4 2 - plus an isolated Cl - ion. The Hg 2 Cl 7 3 - formula unit in mer-[Cr(NH 3 )(tn)(2,3-tri)]Hg 2 Cl 7 .H 2 O (4) (triclinic, P1) adopts an HgCl 3 - plus HgCl 4 2 - arrangement. A novel [Hg 4 Cl 1 7 ] 9 - stoichiometry is found in mer-[Cr(NH 3 )(en)(3,3-tri)] 3 [HgCl 4 ] 4 .Cl.3H 2 O (1) (triclinic, P1). The 2 E g - 4 A 2 g (O h ) intercombination bands were measured at 20 K both in absorption and emission. The phosphorescence decay curves of selected single emission lines were determined at temperatures 18<T<200 K. Quantitative correlation were found between the intensity of the vibronic sidebands and the deviation from octahedral symmetry and between the phosphorescence decay times and the mean N' Cr N H torsion angle.