Phase Transitions in Tetramethylammonium Hexachlorometalate Compounds (TMA)2MCl6 (M = U, Np, Pt, Sn, Hf, Zr)

A study of the phase transitions occurring in tetramethylammonium hexachlorometalate compounds with M = UIV, NpIV, ZrIV, SnIV, HfIV, and PtIV were performed using single‐crystal X‐ray diffraction across the temperature range 120–400 K. When the crystals are cooled, movement of the octahedral [MCl6]2...

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Bibliographic Details
Published in:European journal of inorganic chemistry 2017-11, Vol.2017 (41), p.4834-4839
Main Authors: Autillo, Matthieu, Wilson, Richard E.
Format: Article
Language:English
Subjects:
Actinides
Anions
Bonding strength
Cations
Chemical bonds
Crystals
Deuteration
Hydrogen bonding
Inorganic chemistry
INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Isotope effect
Phase transitions
Raman spectra
Raman spectroscopy
Single crystals
Structure elucidation
Transition temperature
Zirconium
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Summary:A study of the phase transitions occurring in tetramethylammonium hexachlorometalate compounds with M = UIV, NpIV, ZrIV, SnIV, HfIV, and PtIV were performed using single‐crystal X‐ray diffraction across the temperature range 120–400 K. When the crystals are cooled, movement of the octahedral [MCl6]2– anions induces a phase transition from Fm3m to Fd3c with a doubling of the unit cell. For the actinide compounds, no correlation between the f‐electron configuration and the transition temperature was observed; instead, a correlation between the transition temperatures and both the [MCl6]2– anion and the TMA cation size is highlighted. Two phase transitions were observed and characterized. The first phase transition occurs with the ordering of the TMA cation and the second from a rotation of the [MCl6]2– octahedra. A third phase transition was observed at lower temperatures and was ascribed to a tetragonal distortion of the [MCl6]2– anions. Synthesis and study of the deuterated compounds did not show a significant isotope effect. Raman spectra of the protonated and deuterated compounds indicate only weak hydrogen bonding interactions between the TMA cations and the [MCl6]2– octahedra. Phase transitions in tetramethylammonium hexachlorometalate compounds were studied by single‐crystal X‐ray diffraction. Several phase transitions were observed and characterized over the investigated temperature range, revealing correlations with the size of the metalate anion.
ISSN:1434-1948
1099-0682
DOI:10.1002/ejic.201700764