13601-55-3Relevant academic research and scientific papers
Preparation and crystal structures of Ni(NH3)2Cl2 and of two modifications of Ni(NH3)2Br2 and Ni(NH3)2I2
Leineweber,Jacobs
, p. 381 - 387 (2000)
Diammine nickel(II) halides, Ni(NH3)2X2 (X = Cl, Br, I), were prepared by decomposition of the corresponding hexaammines at 120°C in dynamical vacuum. Their crystal structures are of the Cd(NH3)2Cl2 type ('β-type', space group Cmmm, Z = 2): for Ni(NH3)2Cl2, a = 8.019 A, b = 8.013 A, c = 3.661 A; for β-Ni(NH3)2Br2, a = 8.273 A, b = 8.297 A, c = 3.851 A. Both were obtained by Rietveld refinement of diffractometer data with standard deviations A. For β-Ni(NH3)2I2, a = b = 8.753(3) A, c = 4.127(1) A, obtained by Guinier film data. In the case of the bromide and the iodide, annealing at 300°C leads to an irreversible structural rearrangement. A new modification is formed which is of the Mg(NH3)2Br2 type ('α-type', space group Pbam, Z = 2): for α-Ni(NH3)2Br2, a = 5.865 A, b = 11.723 A, c = 3.856 A, obtained by Rietveld refinement of diffractometer data with standard deviations 3)2I2, 2a = b = 12.359(3) A, c = 4.126(1) A, obtained by Guinier film data. Both types of structures contain infinite chains of edge-sharing octahedra (∞)/1[NiX(4/2)(NH3)2]. These run parallel to the c-axes of the unit cells of the corresponding structure types and are arranged in different ways relative to one another. The decomposition of hexaammine nickel(II) halides to the corresponding diammines is analyzed in terms of structural analogies. (C) 2000 Academic Press.
Hydrogen bonding in hexamminemetal(II) bromides Br2 (M2+=Ca2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Cd2+) - synergetic effect of M2+
Essmann, R.
, p. 91 - 94 (1995)
IR spectra of isotypic hexamminemetal(II) bromide salts Br2 (K2PtCl6-type structure for M2+=Ca2+, Mn2+, Fe2+, Co2+, Ni2+, Cd2+; tetragonal structure related to the K2PtCl6-type structure for M2+=Cu2+) and of isotopically dilute samples (5percent deuterated) have been recorded in the range 400-4000 cm-1 with regard to the influence of M2+ on the strength of N-H...X- hydrogen bonds.This so-called synergetic effect does not correlate simply with either the ionic radii or electron configuration of M2+, but must be caused by a superposition of electronic and ionic radii effects.Arranging the metal ions with decreasing strength of their synergetic effect leads to the following series: Cu2+>>Co2+>Mn2+>Fe2+>Ni2+>=Cd2+>Ca2+.
Proton density and orientational potential in nickelhexammine salts: a thermodynamic analysis of rotation-translation coupling
Schiebel,Hoser,Prandl,Heger,Paulus,Schweiss
, p. 10989 - 11005 (1994)
The scattering densities of the orientationally disordered protons and deuterons in Ni(NX3)6Y2 (X = H or D; Y = Br, I, NO3 or PF6) are obtained from neutron single-crystal diffraction data at room temperature. While we observe a nearly circular density distribution for Y = PF6, a nuclear density distribution with four maxima on a square shows up for Y = Br, I and NO3. This is a pronounced deviation from the circular distribution that is expected from uniaxial rotational diffusion or reorientational jump models for the dynamics of the orientational disordered ammonia groups. All observed density distributions are consistently explained as the consequence of rotation-translation coupling in an anharmonic crystal potential. The calculated potential parameters, i.e. anharmonicity and strength of the coupling, depend on the type of anion present in the crystal frame. The weak anisotropy in the Y=NO3 and PF6 compounds is the consequence of a nearly eightfold non-crystallographic symmetry of the atoms establishing the hindrance potential.
