Zintl phase variations through cation selection. Synthesis and structure of A21Cd4Pn18 (A = Eu, Sr, Ba; Pn = Sb, Bi).

Four new Zintl compounds, Ba21Cd4Sb18, Ba21Cd4Bi18, Sr21Cd4Bi18, and Eu21Cd4Bi18, have been synthesized and structurally characterized. Despite the similarity in their chemical formulas and regardless of their identical electronic requirements, the structures of the Ba compounds and the Sr and Eu compounds are subtly different. Due to the cations, a cleavage of a selected pnicogen-cadmium bond occurs and the structures adapt to a novel packing of the resultant heteronuclear anions.