CRYSTAL-STRUCTURES AND PROPERTIES OF NEW TERNARY IRIDIUM PHOSPHIDES

Four new ternary iridium phosphides were prepared by reaction of the e lements at 900-1100-degrees-C. Their structures were determined by mea ns of single-crystal X-ray methods. EuIrP (a = 6.272(1) angstrom) and BaIrP (a = 6.531(1) angstrom) crystallize in a SrSi2-type derivative s tructure (LaIrSi-type structure; P2(1)3; Z = 4). Eulr2P2 (a = 6.671(1) , c = 7.055(1) angstrom) and SrIr2P2 (a = 6.693(1), c = 7.061(1) angst rom) form a new structure (P3(2)21; Z = 3). All the P atoms and half o f the Ir atoms build up a three-dimensional framework with the Eu(Sr) atoms and the remaining Ir atoms in the cavities. The latter atoms for m threefold screws along [001] with short Ir-Ir distances. Magnetic me asurements of EuIrP and EuIr2P2 show that europium is divalent in both compounds.