High-Pressure Synthesis of a Pentazolate Salt

TL;DR

This paper reports the first successful high-pressure synthesis of a solid cesium pentazolate salt containing isolated N5- anions, achieved through laser heating in a diamond anvil cell, guided by theoretical predictions.

Contribution

It demonstrates the synthesis of a novel pentazolate salt under high pressure, revealing new bonding mechanisms and the role of extreme conditions in creating high nitrogen content compounds.

Findings

Successful synthesis of cesium pentazolate salt (CsN5)

Identification of aromatic N5- anions in the crystal structure

Insight into high-pressure formation of nitrogen-rich compounds

Abstract

The pentazolates, the last all-nitrogen members of the azole series, have been notoriously elusive for the last hundred years despite enormous efforts to make these compounds in either gas or condensed phases. Here we report a successful synthesis of a solid state compound consisting of isolated pentazolate anions N5-, which is achieved by compressing and laser heating cesium azide (CsN3) mixed with N2 cryogenic liquid in a diamond anvil cell. The experiment was guided by theory, which predicted the transformation of the mixture at high pressures to a new compound, cesium pentazolate salt (CsN5). Electron transfer from Cs atoms to N5 rings enables both aromaticity in the pentazolates as well as ionic bonding in the CsN5 crystal. This work provides a critical insight into the role of extreme conditions in exploring unusual bonding routes that ultimately lead to the formation of novel high nitrogen content species.