Idiosyncratic Ag7Pt2O7: An Electron Imprecise yet Diamagnetic Small Band Gap Oxide

• Published in: Angewandte Chemie International Edition 2020-11, Vol.59 (45), p.19910-19913
• Main Authors: Thakur, Gohil S., Dinnebier, Robert, Hansen, Thomas C., Assenmacher, Wilfried, Felser, Claudia, Jansen, Martin
• Format: Article
• Language: English
• Subjects: Chemical bonds; Chemical compounds; Communication; Communications; Composition; Crystal structure; Diamagnetism; electron diffraction; Electrons; Platinum; Silver; silver clusters; silver oxoplatinate; Substructures; subvalent silver
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202008874

The seminal qualitative concepts of chemical bonding, as presented by Walter Kossel and Gilbert Newton Lewis back in 1916, have lasting general validity. These basic rules of chemical valence still serve as a touchstone for validating the plausibility of composition and constitution of a given chemical compound. We report on Ag7Pt2O7, with a composition that violates the basic rules of chemical valence and an exotic crystal structure. The first coordination sphere of platinum is characteristic of tetravalent platinum. Thus, the electron count corresponds to Ag7Pt2O7*e−, where excess electrons are associated with the silver substructure. Such conditions given, it is commonly assumed that the excess electrons are either itinerant or localized in Ag−Ag bonds. However, the material does not show metallic conductivity, nor does the structure feature Ag‐Ag pairs. Instead, the excess electrons organize themselves in 2e−4c bonds within the silver substructure. This subvalent silver oxide reveals a new general facet pertinent to silver chemistry. An electron imprecise silver oxoplatinate displaying a unique structure is reported. Silver atoms are condensed as interconnected cuboctahedra in a honeycomb network, hosting excess electrons localized pairwise within contracted Ag4 tetrahedra (red and blue lines).