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Alkaline-earth rhodium hydroxides : synthesis, structures, and thermal decomposition to complex oxides
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Cook, Daniel Sean, Clarkson, Guy J., Dawson, Daniel M., Ashbrook, Sharon E., Fisher, Janet M., Thompsett, David, Pickup, David M., Chadwick, Alan V. and Walton, Richard I. (2018) Alkaline-earth rhodium hydroxides : synthesis, structures, and thermal decomposition to complex oxides. Inorganic Chemistry . doi:10.1021/acs.inorgchem.8b01797 (In Press)
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WRAP-alkaline-earth-rhodium-hydroxides-synthesis-thermal-Walton-2018.pdf - Accepted Version - Requires a PDF viewer. Download (1108Kb) | Preview |
Official URL: http://dx.doi.org/10.1021/acs.inorgchem.8b01797
Abstract
The rhodium(III) hydrogarnets Ca3Rh2(OH)12 and Sr3Rh2(OH)12 crystallize 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 centers 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 behavior 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: | Journal Article | ||||||||
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| Divisions: | Faculty of Science > Chemistry | ||||||||
| Journal or Publication Title: | Inorganic Chemistry | ||||||||
| Publisher: | American Chemical Society | ||||||||
| ISSN: | 0020-1669 | ||||||||
| Official Date: | 2018 | ||||||||
| Dates: |
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| Date of first compliant deposit: | 16 August 2018 | ||||||||
| DOI: | 10.1021/acs.inorgchem.8b01797 | ||||||||
| Status: | Peer Reviewed | ||||||||
| Publication Status: | In Press | ||||||||
| Publisher Statement: | “This document is the Accepted Manuscript version of a Published Work that appeared in final form in Inorganic Chemistry copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://pubs.acs.org/doi/10.1021/acs.inorgchem.8b01797 to Published Work, see http://pubs.acs.org/page/policy/articlesonrequest/index.html].” | ||||||||
| Access rights to Published version: | Restricted or Subscription Access |
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