Lucky Number 13: A 13-Layer Polytype of the Alkyne Hydrogenation Catalyst CaGaGe

Kelsey L Hodge; Matthew B Gray; Wolfgang Windl; Joshua E Goldberger

doi:10.1021/acs.inorgchem.1c02051

Lucky Number 13: A 13-Layer Polytype of the Alkyne Hydrogenation Catalyst CaGaGe

Inorg Chem. 2021 Oct 4;60(19):14530-14534. doi: 10.1021/acs.inorgchem.1c02051. Epub 2021 Sep 17.

Authors

Kelsey L Hodge¹, Matthew B Gray¹, Wolfgang Windl², Joshua E Goldberger¹

Affiliations

¹ Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States.
² Department of Materials Science and Engineering, The Ohio State University, 140 West 19th Avenue, Columbus, Ohio 43210, United States.

PMID: 34533935
DOI: 10.1021/acs.inorgchem.1c02051

Abstract

Polytypism, the ability of materials to form crystal structures with different stacking sequences, occasionally causes materials with the same stoichiometry and similar local structures to have profoundly different properties. Herein, we discover a metastable 13-layer trigonal (13T) polytype of CaGaGe, a layered intermetallic phase comprised of [GaGe]^2- honeycombs separated by Ca²⁺. 13T-CaGaGe is synthesized from arc-melting the elements, and its structure is elucidated via neutron powder diffraction. Air-stable 13T-CaGaGe has one misaligned [GaGe]^2- layer for every 13 and transforms into the more stable 4-layer hexagonal (4H) CaGaGe polytype after annealing at 500 °C. Transition-metal-free 13T-CaGaGe shows remarkable activity in the catalytic hydrogenation of phenylacetylene to styrene and ethylbenzene, much higher than the 4H polytype. This work identifies the first 13-layer polytype for any crystal structure and further establishes the influence of polytypism on catalysis.