Multianvil Synthesis, X‐Ray Powder Diffraction Analysis, ³¹P‐MAS‐NMR, and FTIR Spectroscopy as well as Material Properties of γ‐P₃N₅, a High‐Pressure Polymorph of Binary Phosphorus(V) Nitride, Built‐Up from Distorted PN₅ Square Pyramids and PN₄ Tetrahedra.

Abstract

For Abstract see ChemInform Abstract in Full Text.

High-Pressure Synthesis of Melilite-type Rare-Earth Nitridophosphates RE2P3N7 and a Ba2Cu[Si2O7]-type Polymorph

“…However, the point symbol of the phyllo-net is established in the structural chemistry of metal−organic frameworks (MOFs) under topological type 3,4L13, which is not unexpected, since MOFs usually constitute of atavistic nets. 60,61 The bond geometry is similar to the mcm-case (Figure 5), with little skewed N−P−N bond angles in the P1 Q 4 -tetrahedra (between 106.0 and 114.7°) and distorted P2 Q 3 -tetrahedra with angles ranging from 101.1 to 117.8°. The P2−N4 [1] bond length (1.57 Å) is shorter than the P2−N [2] distances (1.64− 1.68 Å) causing this distortion yielding a bond angle variance 59 of 60.1°2.…”

“…Hence the two-periodic layer can be described by the vertex symbol (5 3 ) 2 (5 4 ) or point symbol {5 3 } 2 {5 4 .8 2 }, the latter being determined by TOPOS. 56 The coexistence of Q 3 -and Q 4 -type bridging tetrahedra within a plane layer results in the degree of condensation κ = P/N = 3:7. An unbranched fundamental dreier chain running along [100] subsumes the single-layer tetrahedra network as {uB, 1 2 ∞} }[P 3 N 7 ] according to Liebau.…”

“…The Liebau nomenclature for this two-dimensional net is {uB, 1 ∞ 2 }[P 3 N 7 ] due to a repetition unit consisting of an unbranched dreier-chain running along [100]. 55 The Pr 2 P 3 N 7 structure comprises two different P-sites that are part of Q 3and Q 4 -bridging tetrahedra in the ratio 2:1. Reminiscent of the melilite structure type, this causes a degree of condensation of P/N = 3:7, which is rather unusual; in silicates, monolayered nets usually exhibit a molar ratio 2:5.…”

“…The incorporation of all-side vertex-sharing Q 4 -tetrahedra in a two-periodic net has interesting structural implications revealed by tiling theory. The method for enumerating the tile-k-transitive tiling patterns of the Euclidian plane has been published by Huson, 66 and the solutions for up to three symmetry-inequivalent tiles are contained in the program 2Dtiler.…”

“…67,72 The inclusion of four-coordinated vertices, as found in both of the here discussed RE 2 P 3 N 7 polymorphs, in this enumeration multiplies the theoretical number of tiling patterns to a total of seven uninodal, 129 binodal, and 1585 trinodal nets. 66,72 Thus, a successful incorporation of Q 4 -tetrahedra in a two-periodic structure theoretically proliferates the structural possibilities, of course bearing in mind that not all tiling patterns are realizable due to the limitations of bond lengths and angles. 73 Structural Evolution of mcm-and bex-RE 2 P 3 N 7 Phases.…”