The crystal structures and doublet emission properties of hexaam(m)ine Cr(III) complexes

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(NH3)(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(NH3)(Me(2)tn)(2,3-tri)]HgCl5.1.5H(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(NH3)(pn)(3,3-tri)]HgCl5 . 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(NH3)(chxn)(3,3-tri)HgCl5 (3) (monoclinic, P2(1)/n) and mer-[Cr(NH,)(chxn)(2,3-tri)]HgCl5 . 2H(2)O (6) (monoclinic, P2(1)c). In 2, 3, 5 and 6 above, the chloromercury(II) formula unit is a distorted tetrahedral HgCl42- plus an isolated Cl- ion. The Hg2C73- formula unit in mer-[Cr(NH3)(tn)(2,3-tri)]Hg2Cl7.H2O (4) (triclinic, P (1) over bar) adopts an Hg2C73- plus HgCl42- arrangement. A novel [Hg4Cl17](9-) stoichiometry is found in mer-[Cr(NH3)(en)(3,3-tri)](3)[HgCl4](4) . Cl . 3H(2)O (1) (triclinic, P1). The E-2(g)-(4)A(2g) (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. (C) 2001 Elsevier Science B.V. All rights reserved.