High‐Pressure Synthesis of a Nitrogen‐Rich Inclusion Compound ReN 8 ⋅ x N 2 with Conjugated Polymeric Nitrogen Chains

A nitrogen‐rich compound, ReN 8 ⋅x N 2 , 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 ReN 8 framework, has rectangular‐shaped channels that accommodate nitrogen molecules. Thus, despite a very high synthesis pressure, exceeding 100 GPa, ReN 8 ⋅x N 2 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 ReN 8 ⋅x N 2 provide strong support for the experimental results and conclusions.