Preparation and Crystal Structures of Ni(NH3)2Cl2 and of Two Modifications of Ni(NH3)2Br2 and Ni(NH3)2I2

✍ Scribed by A. Leineweber; H. Jacobs

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 243 KB
• Volume: 152
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2000.8666

✦ Synopsis

Diammine nickel(II) halides, Ni(NH 3 ) 2 X 2 (X ‫؍‬ Cl, Br, I), were prepared by decomposition of the corresponding hexaammines at 1203C in dynamical vacuum. Their crystal structures are of the Cd(NH 3 ) 2 Cl 2 type (99 -type::, space group Cmmm, Z ‫؍‬ 2): for Ni(NH 3 ) 2 Cl 2 , a ‫؍‬ 8.019 A s , b ‫؍‬ 8.013 A > , c ‫؍‬ 3.661 A > ; for -Ni(NH 3 ) 2 Br 2 , a ‫؍‬ 8.273 A > , b ‫؍‬ 8.297 A > , c ‫؍‬ 3.851 A > . Both were obtained by Rietveld re5nement of di4ractometer data with standard deviations < 0.001 A > . For -Ni(NH 3 ) 2 I 2 , a ‫؍‬ b ‫؍‬ 8.753(3) A > , c ‫؍‬ 4.127(1) A > , obtained by Guinier 5lm data. In the case of the bromide and the iodide, annealing at 3003C leads to an irreversible structural rearrangement. A new modi5cation is formed which is of the Mg(NH 3 ) 2 Br 2 type (99 -type::, space group Pbam, Z ‫؍‬ 2): for -Ni(NH 3 ) 2 Br 2 , a ‫؍‬ 5.865 A > , b ‫؍‬ 11.723 A > , c ‫؍‬ 3.856 A > , obtained by Rietveld re5nement of diffractometer data with standard deviations < 0.001; for -Ni(NH 3 ) 2 I 2 , 2a ‫؍‬ b ‫؍‬ 12.359(3) A > , c ‫؍‬ 4.126(1) A s , obtained by Guinier 5lm data. Both types of structures contain in5nite chains of edge-sharing octahedra 1

[NiX 4/2 (NH 3 ) 2 ]. These run parallel to the c-axes of the unit cells of the corresponding structure types and are arranged in di4erent ways relative to one another. The decomposition of hexaammine nickel(II) halides to the corresponding diammines is analyzed in terms of structural analogies.