Enclathration of X@La4 Tetrahedra in Channels of Zn–P Frameworks in La3Zn4P6X (X = Cl, Br)

Abstract

Two new quaternary lanthanum zinc phosphide-halides were synthesized via high-temperature solid-state reactions. Their complex crystal structures were determined by a combination of X-ray diffraction and advanced solid-state 31P NMR spectroscopy. La3Zn4P6Cl and La3Zn4P6.6Br0.8 share a common structural feature: a polyanionic Zn–P framework with large channels hosting complex one-dimensional cations. The cations are built from X@La4 tetrahedral chains with X = Cl (La3Zn4P6Cl) or Br0.8P0.2 (La3Zn4P6.6Br0.8). The X@La4 tetrahedra share two vertices forming one-dimensional chains. To accommodate larger bromine-containing cations the Zn–P framework is rearranged by breaking and forming several Zn–P and P–P bonds. This results in the formation of a unique [P3]3– cycle, which is isoelectronic to cyclopropane. Analysis of the electron localization and orbital overlaps confirmed the presence of different chemical bonding in the Zn–P networks in the Cl- and Br-containing compounds. La3Zn4P6Cl was predicted to be a ...