CHROMIUM(II) COMPLEXES OF ORTHO-PHENYLENEDIAMINE - THE CRYSTAL AND MOLECULAR-STRUCTURES OF BIS(ORTHO-PHENYLENEDIAMINE-KAPPA-N)-BIS(THIOCYANATO-KAPPA-N)CHROMIUM(II) AND BIS(ORTHO-PHENYLENEDIAMINE-KAPPA-2N,N') BIS(ORTHO-PHENYLENEDIAMINE-KAPPA-N)CHROMIUM(II) TRIFLUORO-METHANESULFONATE

The following chromium(II) complexes of o-phenylenediamine (opd) have been isolated: [Cr(opd)2-(NCS)2], [Cr(opd)4]Br2, [Cr(opd)2\2].1.5EtOH, [Cr(opd)Cl2], [Cr(opd)6]Cl2 and [Cr(opd)4] [CF3SO3]2. From the patterns of bands assigned to NH2 and CN stretching vibrations in the infrared spectra the first two complexes contain monodentate diamine, the next two bidentate diamine and the last two both mono- and bi-dentate diamine; thus [Cr(opd)6]Cl2 is more correctly formulated as [Cr(opd)4]Cl2.2opd. Crystal-structure determinations confirm the assignments for [Cr(opd)2(NCS)2] and [Cr(opd)4][CF3SO3]2. The thiocyanato complex crystallises in the monoclinic space group P2(1)/c with a = 11.027(3), b = 5.828(2), c = 13.431 (2) angstrom, beta = 103.93(2)-degrees and Z = 2. The structure was refined to R = 0.040 for 1551 observed reflections. There are trans-planar units in which the bond distances are Cr-NH2 (monodentate diamine) 2.160(2) and Cr-NCS 2.036(2) angstrom, with S atoms of isothiocyanato groups of adjacent units in the axial positions, Cr-S 2.972(2) angstrom forming a thiocyanatobridged structure. The triflate crystallises in the orthorhombic space group Pbca, with a = 8.978(8), b = 22.455(7), c = 16.842(2) angstrom and Z = 4. The structure was refined to R = 0.061 for 1863 observed reflections. The co-ordination sphere consists of two bidentate diamine molecules, mean Cr-N 2.119 angstrom, with two more distant, axially positioned, monodentate molecules at 2.669(5) angstrom. In accordance with its structure [Cr(opd)2(NCS)2] exhibits antiferromagnetic behaviour as does [Cr(opd)Cl2] which is a chloride-bridged polymer. The triflate and the remaining complexes show simple paramagnetic behaviour (90-300 K). Attempts to prepare a chromium(II) complex of a tetraazamacrocyclic ligand by reaction of the o-phenylenediamine complexes with acetylacetone were unsuccessful; either no reaction took place or the benzodiazepinium chloride was isolated.