Polar Intermetallics Pr Co Ge and Pr Co Ge with Planar Hydrocarbon-Like Metal Clusters.

Planar hydrocarbon-like metal clusters may foster new insights linking organic molecules with conjugated π-π bonding interactions and inorganic structures in terms of their bonding characteristics. However, such clusters are uncommon in polar intermetallics. Herein, we report two polar intermetallic phases, Pr Co Ge and Pr Co Ge , both of which feature such planar metal clusters, namely, ethylene-like [Co Ge ] clusters plus the concatenated forms and polyacene-like [Co Ge ] ribbons in Pr Co Ge , and 1,2,4,5-tetramethylbenzene-like [Co Ge ] cluster in Pr Co Ge . Just as in the related planar organic structures, these metal-metalloid species are dominated by covalent bonding interactions. Both compounds magnetically order at low temperature with net ferromagnetic components: Pr Co Ge through a series of transitions below 150 K and Pr Co Ge through a single ferromagnetic transition at 19 K. Spin-polarized electronic structure calculations for Pr Co Ge reveal strong spin-orbit coupling within Pr and considerable magnetic contributions from Co atoms. This work suggests that similar structural chemistry can emerge for other rare-earth/late-transition-metal/main-group systems.