Three pnictides with Sm₆Rh₃₀Si₁₉-type structure: Sm₆Rh₃₀P₁₉, Lu₆Rh₃₀P₁₉ and Eu₆Rh₃₀Sb₁₉

Abstract Single crystals of the phosphides Sm 6 Rh 30 P 19 and Lu 6 Rh 30 P 19 were synthesized from the elements with the bismuth flux technique. Polycrystalline Eu 6 Rh 30 Sb 19 was obtained from the elements by arc-melting and subsequent annealing. The structures of the phosphides were refined from single-crystal X-ray diffractometer data: P 6 3 / m , a = 1,555.07(9), c = 383.38(2) pm, wR 2 = 0.0500, 1044 F 2 values, 58 variables for Sm 6 Rh 30 P 19 and a = 1,551.99(15), c = 376.32(3) pm, wR 2 = 0.0725, 1022 F 2 values, 58 variables for Lu 6 Rh 30 P 19 . Sm 6 Rh 30 P 19 and Lu 6 Rh 30 P 19 crystallize with the Sm 6 Rh 30 Si 19 -type structure, which is closely related to the Yb 6 Co 30 P 19 type. The rhodium and phosphorus atoms build up three-dimensional [Rh 30 P 19 ] networks (225–255 pm Rh–P and 276–288 pm Rh–Rh in Sm 6 Rh 30 P 19 ) which leave hexagonal prismatic cavities for the rare earth atoms. The phosporus atoms on the c axis have distorted octahedral rhodium coordination and show disorder on the c axis (refinement with a split position). Temperature dependent magnetic susceptibility data of Eu 6 Rh 30 Sb 19 show Curie-Weiss behavior with an experimental magnetic moment of 7.78(1) µ B Eu atom −1 and θ P = −9.6(1) K, compatible with divalent europium. The europium atoms in Eu 6 Rh 30 Sb 19 are ordered antiferromagnetically at T N = 3.9(4) K which is corroborated by specific heat data. The divalent ground state of europium is manifested in the 151 Eu Mössbauer spectrum with an isomer shift value of −10.44(1) mm s −1 at 78 K. The 121 Sb Mössbauer spectrum with an isomer shift of −7.12(2) mm s −1 (envelope signal of the four crystallographically independent antimony sites) underpins the antimonide character.