LiMoN₂: The First Metallic Layered Nitride

We report the first example of a layered ternary lithium nitride in which the lithium can be deintercalated and reintercalated. The synthesis of LiMoN₂ is also the first example of a ternary nitride formed from either the ammonolysis of a molecular organometallic molecule, Li₂Mo(N^tBu)₄ or the ammonolysis of a ternary oxide, Li₂MoO₄. Elucidation of the unique structure, in a classic illustration, required both synchrotron X-ray and neutron diffraction data. The space group is JR3 with lattice parameters (Å; from the neutron data) of a = 2.8674 (2) and c = 15.801 (2). The ideal structure consists of MoN₂ layers with Mo in trigonal prismatic holes and Li in octahedral holes between the MoN₂ layers. The presence of cation anti-site defects was clearly indicated by the joint X-ray/neutron data refinement; the structure is best described as (Li_0.85Mo_0.15)_oct(Mo_0.85Li_0.15)_tpN₂. LiMoN₂ is Pauli paramagnetic with χ₀ = 0.59 X 10^-6 emu g^-1. We have employed a variety of different oxidizing agents for the deintercalation of the lithium from LiMoN₂ and have been able to deintercalate up to 64% of the lithium. This deintercalated species can be reintercalated with n-butyllithium at room temperature. In contrast, electrochemical studies show a large hysteresis in the charge/discharge cycles with no reversibility.