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Issue 16, 2011
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Thermally triggered reductive elimination of bromine from Au(III) as a path to Au(I)-based coordination polymers

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Abstract

Four new [AuBr2(CN)2]-based coordination polymers, Zn(pyz)(NCMe)2[AuBr2(CN)2]2 (1; pyz = pyrazine), Co(pyz)[AuBr2(CN)2]2·H2O (2) and [M(bipy)2(AuBr2(CN)2)][nBu4N][AuBr2(CN)2]2 (bipy = 4,4′-bipyridine), where M = Co (5) and Zn (6), were synthesized and three of them structurally characterized. 1 forms 1-D chains connected by pyz ligands while isostructural 5 and 6 form 3-D frameworks via [AuBr2(CN)2] and bipy linkers. Aqueous suspensions of 2, 5 and 6 or their precursors in situ (preferred) were heated hydrothermally to 125 °C, triggering the reductive elimination of bromine from the Au(III) centres, which yielded the [Au(CN)2]-based coordination polymers M(pyz)[Au(CN)2]2, where M = Zn (3) or Co (4) and Zn(bipy)[Au(CN)2][Au{Br0.68(CN)0.32}CN] (7), or a mixture of cyanoaurate(I)-containing products in the case of 5 and 6. The structural characterization of 3 revealed a [Au(CN)2]/pyz-based framework similar to previously reported Cu(pyz)[Au(CN)2]2, whereas 7 formed an intricate network consisting of individual 2-D networks held together by Au⋯Au interactions and featuring the rare [AuBrCN] unit. The kinetics of the thermally-induced reductive elimination of Br2 from K[AuBr2(CN)2] in 1-BuOH yielded a t½ of approx. 10 min to 4 h from 98 to 68 °C, and activation parameters of ΔH = 131(15) kJ mol−1 and ΔS = 14.97(4) kJ K−1mol−1, indicating that the elimination of the halogen provides the highest barrier to activation.

Graphical abstract: Thermally triggered reductive elimination of bromine from Au(iii) as a path to Au(i)-based coordination polymers

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Publication details

The article was received on 15 Dec 2010, accepted on 03 Feb 2011 and first published on 11 Mar 2011


Article type: Paper
DOI: 10.1039/C0DT01772H
Citation: Dalton Trans., 2011,40, 4140-4146
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    Thermally triggered reductive elimination of bromine from Au(III) as a path to Au(I)-based coordination polymers

    J. S. Ovens and D. B. Leznoff, Dalton Trans., 2011, 40, 4140
    DOI: 10.1039/C0DT01772H

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