High-Pressure Synthesis of a Nitrogen-Rich Inclusion Compound ReN₈ ⋅x  N₂ with Conjugated Polymeric Nitrogen Chains

A nitrogen-rich compound, ReN8 ⋅x N2 , was synthesized by a direct reaction between rhenium and nitrogen at high pressure and high temperature in a laser-heated diamond anvil cell. Single-crystal X-ray diffraction revealed that the crystal structure, which is based on the ReN8 framework, has rectangular-shaped channels that accommodate nitrogen molecules. Thus, despite a very high synthesis pressure, exceeding 100 GPa, ReN8 ⋅x N2 is an inclusion compound. The amount of trapped nitrogen (x) depends on the synthesis conditions. The polydiazenediyl chains [-N=N-]∞ that constitute the framework have not been previously observed in any compound. Ab initio calculations on ReN8 ⋅x N2 provide strong support for the experimental results and conclusions.