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Synthesis, PtS-type structure, and anomalous mechanics of the Cd(CN) 2 precursor Cd(NH 3 ) 2 [Cd(CN) 4 ]

DOI: 10.1039/C8DT01128A DOI Help

Authors: Chloe S. Coates (University of Oxford) , Joshua W. Makepeace (University of Oxford) , Andrew G. Seel (University of Oxford) , Mia Baise (University College London (UCL)) , Ben Slater (University College London) , Andrew L. Goodwin (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Dalton Transactions , VOL 47 , PAGES 7263 - 7271

State: Published (Approved)
Published: May 2018
Diamond Proposal Number(s): 17375 , 13284

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.

Subject Areas: Chemistry

Instruments: I11-High Resolution Powder Diffraction