Please Mind the Gap: Highly Condensed P-N Networks in LiP4 N7 and Li3-x P6 N11-x (NH)x.

Alkali nitridophosphates AP4 N7 and A3 P6 N11 (A=Na, K, Rb, Cs) have been known for decades. However, their Li homologues have remained elusive. In this work, the highly condensed lithium (imido)nitridophosphates LiP4 N7 and Li3-x P6 N11-x (NH)x (x=1.66(3)) were synthesized from LiPN2 and P3 N5 in the multianvil press at 10 GPa. They constitute the first lithium nitridophosphates with 3D networks exhibiting a degree of condensation larger than 0.5 and high thermal stability. LiP4 N7 crystallizes in the orthorhombic space group P21 21 21 with a=4.5846(6) Å, b=8.0094(11) Å, and c=13.252(2) Š(Z=4). Li3-x P6 N11-x (NH)x crystallizes in the triclinic space group P 1 - ${\mathrel{\mathop{{\rm { 1}}}\limits^{{\rm -}}}}$ with Z=2, a=4.6911(11) Å, b=7.024(2) Å, c=12.736(3) Å, α=87.726(11), ß=80.279(11), and γ=70.551(12)°. Both compounds are stable against hydrolysis in air.