The Preparation, Characterization, and Pressure-Influenced Dihydrogen Interactions of Tetramethylphosphonium Borohydride

Tetramethylphosphonium borohydride was synthesized via an ion metathesis reaction in a weakly-coordinating aprotic environment. [(CH ) P]BH , in contrast to related [(CH ) N] compounds which tend to crystallize in a tetragonal system, adopts the distorted wurtzite structure ( 6 mc), resembling some...

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Bibliographic Details
Published in:Materials 2023-07, Vol.16 (15), p.5334
Main Author: Jaroń, Tomasz
Format: Article
Language:English
Subjects:
Borohydrides
Chemical synthesis
Crystals
Decomposition
Exothermic reactions
High pressure
Hydrogen
Metathesis
Phase transitions
Radiation
Raman spectra
Reagents
Software
Solvents
Spectrum analysis
Stainless steel
Temperature
Wurtzite
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Summary:Tetramethylphosphonium borohydride was synthesized via an ion metathesis reaction in a weakly-coordinating aprotic environment. [(CH ) P]BH , in contrast to related [(CH ) N] compounds which tend to crystallize in a tetragonal system, adopts the distorted wurtzite structure ( 6 mc), resembling some salts containing analogous ions of As and Sb. [(CH ) P]BH decomposes thermally in several endo- and exothermic steps above ca. 240 °C. This renders it more stable than [(CH ) N]BH , with a lowered temperature of decomposition onset by ca. 20 °C and solely exothermic processes observed. Raman spectra measured at the 0-10 GPa range indicate that a polymorphic transition occurs within 0.53-1.86 GPa, which is further confirmed by the periodic DFT calculations. The latter suggests a phase transition around 0.8 GPa to a high-pressure phase of [(CH ) N]BH . The 6 mc phase seems to be destabilized under high pressure by relatively closer dihydrogen interactions, including the C-H…H-C contacts.
ISSN:1996-1944
1996-1944
DOI:10.3390/ma16155334