Polycation-Polyanion Architecture of the Intermetallic Compound Mg3- xGa1+ xIr

Olga Sichevych; Yurii Prots; Walter Schnelle; Frank R Wagner; Yuri Grin

doi:10.3390/molecules27030659

Polycation-Polyanion Architecture of the Intermetallic Compound Mg_{3- x}Ga_{1+ x}Ir

Molecules. 2022 Jan 20;27(3):659. doi: 10.3390/molecules27030659.

Authors

Olga Sichevych¹, Yurii Prots¹, Walter Schnelle¹, Frank R Wagner¹, Yuri Grin¹

Affiliation

¹ Max-Planck-Institut für Chemische Physik Fester Stoffe, Nöthnitzer Str. 40, 01187 Dresden, Germany.

Abstract

Mg_3-xGa_1+xIr (x = 0.05) was synthesized by direct reaction of the elements in welded tantalum containers at 1200 °C and subsequent annealing at 500 °C for 30 days. Its crystal structure represents a new prototype and was determined by single-crystal technique as follows: space group P6₃/mcm, Pearson symbol hP90, Z = 18, a = 14.4970(3) Å, c = 8.8638(3) Å. The composition and atomic arrangement in Mg₃GaIr do not follow the 8-N rule due to the lack of valence electrons. Based on chemical bonding analysis in positional space, it was shown that the title compound has a polycationic-polyanionic organization. In comparison with other known intermetallic substances with this kind of bonding pattern, both the polyanion and the polyanion are remarkably complex. Mg_3-xGa_1+xIr is an example of how the general organization of intermetallic substances (e.g., formation of polyanions and polycations) can be understood by extending the principles of 8-N compounds to electron-deficient materials with multi-atomic bonding.

Keywords: 8–N rule; QTAIM; chemical bonding; electron localizability; intermetallic compound; polyanion; polycation.