Preparation and crystal structure of the Copper Silicon Polyphosphide Cu 4 SiP 8

The new compound Cu 4 SiP 8 was prepared by solid state reaction of the elemental components. It crystallizes with a new structure type, which was determined from single‐crystal X‐ray diffractometer data: I4 1 /a, a = 1 218.6(2) pm, c = 573.2(2) pm, Z = 8, R = 0.023 for 970 structure factors and 31 variable parameters. Tetrahedral SiP 4 groups are linked via additional phosphorus atoms to a three‐dimensionally infinite silicon phosphorus network, accommodating Cu 2 pairs with octahedral phosphorus coordination as is known for the closely related structure of CuP 2 . Using oxidation numbers the compound may be rationalized by the formula (Cu +1 ) 4 Si +4 (P 0 ) 4 (P −2 ) 4 in agreement with the Zintl‐Klemm concept.