Structure of a Gold(Ⅲ) Hydroxide and Determination of Its Solubility

Translated title of the contribution: Structure of a Gold(III) Hydroxide and Determination of Its Solubility

Daisuke Kawamoto, Hiroaki Ando, Hironori Ohashi, Yasuhiro Kobayashi, Tetsuo Honma, Tamao Ishida, Makoto Tokunaga, Yoshihiro Okaue, Satoshi Utsunomiya, Takushi Yokoyama

Research output: Contribution to journalArticle

Abstract

<p>A representative gold(III) complex ion ([AuCl<sub>4</sub>]<sup>−</sup>), successively hydrolyzes to form [AuCl<sub>4−</sub><i><sub>n</sub></i>(OH)<i><sub>n</sub></i>]<sup>−</sup> (<i>n</i> = 0–4) in aqueous solution as the pH increases and, finally, precipitates. It has been referred to as "gold(III) hydroxide" for the past fifty years. However, whether the precipitate is gold(III) hydroxide (Au(OH)<sub>3</sub>) or hydrous gold(III) oxide (Au<sub>2</sub>O<sub>3</sub>·<i>n</i>H<sub>2</sub>O) has remained uncertain. Few studies have been conducted to determine its chemical and physical properties. The aim of this investigation is to identify the precipitate and to determine its solubility. The precipitate was X-ray amorphous. Based on the transmission electron microscopy (TEM) observation, the shape was spherical and the particle diameter was approximately 9 nm. From the results of <sup>197</sup>Au Mössbauer spectroscopy, Au L<sub>3</sub>-edge X-ray absorption (XA) spectroscopy and thermogravimetry/differential thermal analysis (TG/DTA) measurements, the precipitate composition was estimated to be Au(OH)<sub>3</sub>. Based on the composition, its structure was proposed to be a linear polymer. Moreover, its solubility at 298 K was determined to be 0.00120 g/100 g of H<sub>2</sub>O. This chemical and physical properties information of Au(OH)<sub>3</sub> is essential for gold chemistry, for example, for preparing supported gold catalyst.</p>
Translated title of the contributionStructure of a Gold(III) Hydroxide and Determination of Its Solubility
Original languageJapanese
Pages (from-to)1385-1390
Number of pages6
JournalBulletin of the Chemical Society of Japan
Volume89
Issue number11
DOIs
Publication statusPublished - 2016

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