Multi‐Center vs. Two‐Center Bonding within the Hetero‐Polyanion in Eu2GaPt2 and its Prototype Ca2SiIr2

Abstract

The compound Eu2GaPt2 was synthesized from the elements in a sealed tantalum tube. Its Ca2SiIr2‐type crystal structure was refined from single‐crystal X‐ray diffraction data: space group C2/c, a = 9.8775(6), b = 5.8621(6), c = 7.9677(5) Å, β = 102.257(4)°, RF = 0.039, 1344 observed reflections, and 25 variable parameters. The platinum (iridium) atoms in Eu2GaPt2 and Ca2SiIr2 form linear chains of dumbbells [2c(Pt–Pt) or 2c(Ir–Ir) bonds, respectively]. These chains are interconnected to 2D polyanions in Eu2GaPt2 by the gallium atoms forming 4c(Ga–Pt–Ga–Pt) or by silicon atoms forming 2c(Si–Ir) bonds in Ca2SiIr2. The polyanion bonds to the europium (calcium) matrix via the pseudo lone‐pairs at the gallium (silicon) atoms.