Europium(II) Heptaphosphide EuP7 [1] Europium(II)heptaphosphid EuP7 [1]

Abstract

The novel polyphosphide EuP7 was prepared under controlled conditions by the reaction of the elements in salt melts at 750-800 K. EuP7 forms black prismatic crystals not attacked by diluted mineral acids and bases. The thermal decomposition yields EuP3 at 700 K and in further steps EuP2, Eu3P4 and EuP, respectively. According to the crystal structure as well as the electrical, optical and magnetic properties EuP7 is a semiconductor (EG = 0.9 eV; EG (vert) = 1.1 eV) with divalent europium (μ = 7.55 B.M.). The compound crystallizes in the monoclinic space group P21/n with a = 1148.8(7) pm, b = 570.0(3) pm, c = 1061.0(6) pm, and β= 106.08°(5); (X-ray diffraction data; 1479 hkl, R = 0.031). The P-atoms are connected (P-P) = 218.0-223.5 pm) to a 2-dimensional infinite polyanionic structure with homonuclear 3-bonded and 2-bonded P-atoms in the ratio 5:2. The polyanionic network contains P6-rings (chair conformation) as well as P8-rings and P10-rings. The Eu-atoms are bonded to 9 P-atoms (1,4,4-polyhedra) with bond distances ranging from 306.6 to 326.6 pm. The Eu-atoms complete the tetrahedral environment of the P-atoms