Sr10[Mo2N6][MoN4]2 and β‐Sr3MoN4

Two new phases in the strontium‐molybdenum‐nitrogen phase diagram have been synthesized. Single crystals of Sr10[Mo2N6][MoN4]2 were grown from a mixed sodium‐gallium melt at 900 °C in a sealed niobium tube. It crystallizes in the triclinic space group P 1 (Z = 1) with a = 6.421(1), b = 9.190(2), c = 9.263(2) Å and α = 64.939(5), β = 82.961(6) and γ = 89.692(6)°. The new, orthorhombic polymorph of Sr3MoN4 was synthesized as a polycrystalline powder from an intimate mixture of Sr2N and molybdenum metal in the presence of N2. Rietveld analysis shows it to crystallize in Pbca (Z = 8) with a = 10.4835(2), b = 9.7374(2) and c = 11.5114(2) Å. Studies suggest that excess nitrogen is essential to the formation of this polymorph. Sr10[Mo2N6][MoN4]2 is the first molybdenum nitride to contain the anionic unit [Mo2N6]8‐, which appears as isolated, edge‐sharing pairs of MoN4 that facilitate MoV‐MoV bonding. This compound also contains isolated [MoN4]6‐ tetrahedra and the presence of these two units results in the first mixed valent molybdenum nitride. Resistivity measurements show it to be insulating.