High-Pressure Synthesis of Metal-Inorganic Frameworks Hf(4) N(20) ⋅N(2) , WN(8) ⋅N(2) , and Os(5) N(28) ⋅3 N(2) with Polymeric Nitrogen Linkers

Polynitrides are intrinsically thermodynamically unstable at ambient conditions and require peculiar synthetic approaches. Now, a one-step synthesis of metal-inorganic frameworks Hf(4) N(20) ⋅N(2) , WN(8) ⋅N(2) , and Os(5) N(28) ⋅3 N(2) via direct reactions between elements in a diamond anvil cell at pressures exceeding 100 GPa is reported. The porous frameworks (Hf(4) N(20) , WN(8) , and Os(5) N(28) ) are built from transition-metal atoms linked either by polymeric polydiazenediyl (polyacetylene-like) nitrogen chains or through dinitrogen units. Triply bound dinitrogen molecules occupy channels of these frameworks. Owing to conjugated polydiazenediyl chains, these compounds exhibit metallic properties. The high-pressure reaction between Hf and N(2) also leads to a non-centrosymmetric polynitride Hf(2) N(11) that features double-helix catena-poly[tetraz-1-ene-1,4-diyl] nitrogen chains [-N-N-N=N-](∞) .