Reversible Polymerization of Adamantane‐type [P4N10]10− Anions to Honeycomb‐type [P2N5]5− Layers under High‐Pressure

• Published in: Chemistry : a European journal 2018-01, Vol.24 (3), p.736-742
• Main Authors: Bertschler, Eva‐Maria, Niklaus, Robin, Schnick, Wolfgang
• Format: Article
• Language: English
• Subjects: Anions; Atomic properties; Atomic structure; Beta rays; Chemical synthesis; Chemistry; Conformation; Crystal structure; density functional calculations; Diffraction; high-pressure chemistry; Honeycomb construction; layered compounds; Lithium; Lithium isotopes; Magnetic resonance spectroscopy; Mathematical analysis; nitrides; NMR spectroscopy; Phosphorus; Polymerization; Pressure; Single crystals; solid-state structures; Temperature dependence; Temperature effects; Transition pressure; X ray powder diffraction
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201704975

The high‐pressure polymorph Li5P2N5 of Li10P4N10 (=“2 Li5P2N5”) was synthesized by high‐pressure/high‐temperature reaction of LiPN2 and Li7PN4 or β‐Li10P4N10 at 9 GPa, using the Li3N self‐flux method in a Walker‐type multianvil assembly. Li5P2N5 is the first lithium nitridophosphate with a layered structure and is made up of corner sharing PN4 tetrahedra forming a corrugated honeycomb‐type layer of linked sechser‐rings in chair conformation. The arrangement of the P atoms is analogous to that of black phosphorus. The structure was elucidated from single‐crystal X‐ray data. To confirm the structure Rietveld refinement, 6Li, 7Li and 31P solid‐state NMR spectroscopy were conducted. To corroborate Li5P2N5 as the corresponding high‐pressure polymorph of β‐Li10P4N10 DFT calculations and temperature dependent X‐ray powder diffraction were carried out. DFT calculations estimated the transition pressure to 6.5 GPa (without accounting for temperature), which is in line with the synthesis pressure. Polymerization: Adamantane‐type [P4N10]10− anions of β‐Li10P4N10 polymerize to [P2N5]5− layers at 9 GPa. The high‐pressure polymorph Li5P2N5 is the first lithium nitridophosphate with a layered structure and is made up of honeycomb‐type layers of linked sechser‐rings of PN4 tetrahedra in chair conformation. To corroborate Li5P2N5 as the corresponding high‐pressure polymorph of β‐Li10P4N10, DFT calculations and temperature dependent X‐ray powder diffraction were carried out.