Skip to main content

Alkaline-Earth Rhodium Hydroxides: Synthesis, Structures, and Thermal Decomposition to Complex Oxides

Cook, Daniel S., Clarkson, Guy J., Dawson, Daniel M., Ashbrook, Sharon E., Fisher, Janet M., Thompsett, David, Pickup, David M., Chadwick, Alan V., Walton, Richard I. (2018) Alkaline-Earth Rhodium Hydroxides: Synthesis, Structures, and Thermal Decomposition to Complex Oxides. Inorganic Chemistry, 57 (17). pp. 11217-11224. ISSN 0020-1669. (doi:10.1021/acs.inorgchem.8b01797?) (KAR id:69342)

PDF Author's Accepted Manuscript
Language: English
Download (641kB) Preview
[thumbnail of Rhodium Hydroxides Paper Revised - unmarked.pdf]
This file may not be suitable for users of assistive technology.
Request an accessible format
Official URL


The rhodium (III) hydrogarnets Ca3Rh2(OH)12 and Sr3Rh2(OH)12 crystallise as polycrystalline powders under hydrothermal conditions at 200°C from RhCl3·3H2O and either Ca(OH)2 or Sr(OH)2 in either 12 M NaOH or KOH. Rietveld refinements against synchrotron powder X-ray diffraction (XRD) data allow the first crystal structures of the two materials to be determined. If BaO2 is used as a reagent and the concentration of hydroxide increased to hydroflux conditions (excess NaOH) then single crystals of a new complex rhodium hydroxide, BaNaRh(OH)6, are formed in a phase-pure sample, with sodium included from the flux. Structure solution from single-crystal XRD data reveals isolated octahedral Rh centres that share hydroxides with 10-coordinate Ba and two independent 8-coordinate Na sites. 23Na magic-angle spinning NMR confirms the presence of the two crystallographically distinct Na sites and also verifies the diamagnetic nature of the sample, expected for Rh(III). The thermal behaviour of the hydroxides on heating in air was investigated using X-ray thermodiffractometry, showing different decomposition pathways for each material. Ca3Rh2(OH)12 yields CaRh2O4 and CaO above 650°C, from which phase-pure CaRh2O4 is isolated by washing with dilute nitric acid, a material previously only reported by high-pressure or high-temperature synthesis. Sr3Rh2(OH)12 decomposes to give a less crystalline material with a powder XRD pattern that is matched to the 2H-layered hexagonal perovskite Sr6Rh5O15, which contains mixed-valent Rh3+/4+, confirmed by Rh K-edge XANES spectroscopy. On heating BaNaRh(OH)6 a complex set of decomposition events takes place via transient phases.

Item Type: Article
DOI/Identification number: 10.1021/acs.inorgchem.8b01797?
Subjects: Q Science > QD Chemistry
Divisions: Divisions > Division of Natural Sciences > School of Physical Sciences
Depositing User: Alan Chadwick
Date Deposited: 02 Oct 2018 14:55 UTC
Last Modified: 16 Feb 2021 13:58 UTC
Resource URI: (The current URI for this page, for reference purposes)
  • Depositors only (login required):


Downloads per month over past year