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

Journal article

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.

Authors: Coates, C; Makepeace, J; Seel, A; Baise, M; Slater, B

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Royal Society of Chemistry
• Journal: Dalton Transactions
• Volume: 47
• Issue: 21
• Pages: 7263-7271
• Publication date: 2018-05-07
• Acceptance date: 2018-05-06
• DOI: 10.1039/c8dt01128a
• EISSN: 1477-9234
• ISSN: 1477-9226
• Pmid: 29762616
• Language: English