Layered Compounds BaM2Ge4Ch6 (M = Rh, Ir and Ch = S, Se) with Pyrite-Type Building Blocks and Ge-Ch Heteromolecule-Like Anions

TL;DR

This study reports the synthesis, structure, and bonding features of layered BaM2Ge4Ch6 compounds with pyrite-type units, revealing rare heteromolecule-like anions and unusual Ge valence states through experimental and theoretical analysis.

Contribution

It introduces a new class of layered compounds with pyrite-type building blocks and heteromolecule-like anions, expanding understanding of their structural and electronic properties.

Findings

Pyrite-type units are used as building blocks in layered compounds.

Strongly polarized covalent Ge-Ch bonds form heteromolecule-like anions.

Ge exhibits an unusual valence state (~+1) in the structure.

Abstract

Structure and chemical features of layered compounds BaM2Ge4Ch6 (M = Rh, Ir; Ch = S, Se) synthesized under high-pressure and high-temperature method are systematically studied. These compounds crystallize in an orthorhombic phase with space group Pbca (No. 61). The remarkable structural feature is to have the M-Ge-Ch pyrite-type building units, stacking with Ba-Ch layers alternatively along c axis. It is very rare and novel that pyrite-type subunits as the building blocks in the layered compounds. Theoretical calculations and experimental results indicate that there are strongly polarized covalent bonds between Ge and Ch atoms, forming heteromolecule-like anions in these compounds. Moreover, Ge atoms in this structure exhibit unusual valence state (~ +1) due to the tetrahedral coordination environment of Ge atoms along with M and Ch atoms simultaneously.