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Synthesis, PtS-type structure, and anomalous mechanics of the Cd(CN)2 precursor Cd(NH3)2[Cd(CN)4]

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Abstract

We report the nonaqueous synthesis of Cd(CN)2 by oxidation of cadmium metal with Hg(CN)2 in liquid ammonia. The reaction proceeds via an intermediate of composition Cd(NH3)2[Cd(CN)4], which converts to Cd(CN)2 on prolonged heating. Powder X-ray diffraction measurements allow us to determine the crystal structure of the previously-unreported Cd(NH3)2[Cd(CN)4], which we find to adopt a twofold interpenetrating PtS topology. We discuss the effect of partial oxidation on the Cd/Hg composition of this intermediate, as well as its implications for the reconstructive nature of the deammination process. Variable-temperature X-ray diffraction measurements allow us to characterise the anisotropic negative thermal expansion (NTE) behaviour of Cd(NH3)2[Cd(CN)4] together with the effect of Cd/Hg substitution; ab initio density functional theory (DFT) calculations reveal a similarly anomalous mechanical response in the form of both negative linear compressibility (NLC) and negative Poisson's ratios.

Graphical abstract: Synthesis, PtS-type structure, and anomalous mechanics of the Cd(CN)2 precursor Cd(NH3)2[Cd(CN)4]

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Publication details

The article was received on 23 Mar 2018, accepted on 06 May 2018 and first published on 07 May 2018


Article type: Paper
DOI: 10.1039/C8DT01128A
Citation: Dalton Trans., 2018, Advance Article
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    Synthesis, PtS-type structure, and anomalous mechanics of the Cd(CN)2 precursor Cd(NH3)2[Cd(CN)4]

    C. S. Coates, J. W. Makepeace, A. G. Seel, M. Baise, B. Slater and A. L. Goodwin, Dalton Trans., 2018, Advance Article , DOI: 10.1039/C8DT01128A

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