Exploring Polymorphism in Metal Carbodiimides from Graph Theory

Inorganic Chemistry, vol. 64, pp. 22201–22209

Abstract

Preparing new solid-state materials incorporating the molecular anion NCN 2– presents a considerable synthetic challenge given the metastable nature of many of these compounds. Hence, it is rather uncommon to observe polymorphism which restricts the possibilities of structural and functional exploration of NCN-based materials. Here we propose the concept of topological complexity from graph theory as a tool for exploring metal-carbodiimide polymorphism. Thus, we report the synthesis of a new modification of Y 2 (NCN) 3 adopting a trigonal structure with R 3̅ c symmetry, distinct from the previously reported monoclinic structure. Likewise, a new metastable Li 2 Sn(NCN) 3 modification with hexagonal P 6 3 / mmc symmetry has been found, the first example of polymorphism in a ternary carbodiimide. This new phase adopts a layered structure similar to FeNCN, with triangular networks of Li + and Sn 4+ cations in a fully disordered structure. In addition, a hexagonal to orthorhombic phase transition of Li 2 Sn(NCN) 3 can be thermally induced. The structures of the new polymorphs are topologically simpler and favored by relatively low reaction temperatures (≈350 °C). These findings demonstrate the potential of topological complexity as a new alternative for the design of synthetic conditions and for the rational prediction of such NCN-based or similar materials.

Authors 5

1. Juan Medina‐Jurado Aachen Chair of Solid-State and Quantum Chemistry Institute of Inorganic Chemistry

   Institute of Inorganic Chemistry of the Slovak Academy of Sciences · RWTH Aachen University

   Affiliation as printed

   Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry

   RWTH Aachen University

   Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry, RWTH Aachen University, 52056 Aachen, Germany

2. Hicham Bourakhouadar Aachen Chair of Solid-State and Quantum Chemistry Institute of Inorganic Chemistry

   Institute of Inorganic Chemistry of the Slovak Academy of Sciences · RWTH Aachen University

   Affiliation as printed

   Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry

   RWTH Aachen University

   Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry, RWTH Aachen University, 52056 Aachen, Germany

3. Lothar Schrey Aachen Chair of Solid-State and Quantum Chemistry Institute of Inorganic Chemistry

   Institute of Inorganic Chemistry of the Slovak Academy of Sciences · RWTH Aachen University

   Affiliation as printed

   Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry

   RWTH Aachen University

   Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry, RWTH Aachen University, 52056 Aachen, Germany

4. Alex J. Corkett

   Forschungszentrum Jülich

   Affiliation as printed

   Forschungzentrum Jülich GmbH

   Jülich Center for Neutron Science-2 (JCNS)

   Jülich Center for Neutron Science-2 (JCNS), Forschungzentrum Jülich GmbH, 52425 Jülich, Germany

5. Richard Dronskowski corresponding Aachen Chair of Solid-State and Quantum Chemistry Institute of Inorganic Chemistry

   Institute of Inorganic Chemistry of the Slovak Academy of Sciences · RWTH Aachen University

   Affiliation as printed

   Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry

   RWTH Aachen University

   Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry, RWTH Aachen University, 52056 Aachen, Germany