Extended Anionic Network in Mixed‐Valent Nitridocobaltates(I/II) Ln Co ₂ N ₂ ( Ln = La, Pr, Nd)

Nitridometallates with extended anionic frameworks exhibit a variety of intriguing electronic properties, including band magnetism, metal‐metal bonding, and superconductivity. Such extended framework materials are scarce with late transition metals due to the requirement of high metal oxidation states and nitrogen content. This study presents a family of nitridocobaltates Ln Co 2 N 2 ( Ln = La, Pr, Nd) with an extended layered cobalt‐nitrogen network related to the Kagome lattice that was synthesized at 8 GPa in a large volume press. The compounds crystallize in the trigonal space group R with alternating layers of unusual trigonal planar CoN 3 and octahedral Ln N 6 polyhedra. Magnetization and powder neutron diffraction studies indicate a metallic ground state and the suppression of magnetic ordering of the rare earth moments due to their arrangement on a trigonal lattice. The compounds have a surprising mixed‐valent Co +I/+II state, which is high for nitridocobaltates. This study demonstrates the structural diversity available in late nitridometallates via high‐pressure synthesis, which can now be explored systematically.