The ternary platinides CaGa5Pt3 and EuGa5Pt3

The ternary platinides CaGa5Pt3 (a = 2082.5(4), b = 406.05(8), c = 739.2(1) pm) and EuGa5Pt3 (a = 2085.5(5), b = 412.75(9), c = 738.7(1) pm) were synthesized from the elements in sealed high-melting metal tubes in an induction furnace. CaGa5Pt3 and EuGa5Pt3 are isotypic with CeAl5Pt3 and isopointal with the YNi5Si3 type intermetallic phases (space group Pnma, oP36 and Wyckoff sequence c 9). The structure of EuGa5Pt3 was refined from single crystal X-ray diffractometer data: wR2 = 0.0443, 1063 F 2 values and 56 variables. The gallium and platinum atoms build up a three-dimensional [Ga5Pt3]2− polyanionic network in which the europium atoms fill slightly distorted hexagonal prismatic voids. The Ga–Pt distances within the network range from 249 to 271 pm, emphasizing the covalent bonding character. Temperature dependent magnetic susceptibility measurements indicate diamagnetism for CaGa5Pt3 and isotypic BaGa5Pt3. EuGa5Pt3 behaves like a Curie–Weiss paramagnet above 50 K with an experimental magnetic moment of 8.17(1) µB/Eu atom, indicating divalent europium. Antiferromagnetic ordering sets in at T N = 8.5(1) K. The divalent ground state of europium is confirmed by 151Eu Mössbauer spectroscopy. EuGa5Pt3 shows a single signal at 78 K with an isomer shift of −9.89(4) mm s−1. Full magnetic hyperfine splitting with a hyperfine field of 25.0(2) T is observed at 6 K in the magnetically ordered regime.

EuTMg2 (T = Pd, Ag, Ir, Pt, Au), EuTCd2 (T = Pd, Pt, Au) and CaRhMg2 – intermetallic compounds with orthorhombically distorted tetrahedral magnesium (cadmium) substructures

The magnesium- and cadmium-rich intermetallic phases EuTMg2 (T = Rh, Pd, Ag, Ir, Pt, Au), EuTCd2 (T = Pd, Pt, Au) and CaRhMg2 were synthesized from the elements in sealed niobium or tantalum ampoules and with heat treatments in muffle or induction furnaces. The samples were characterized by powder X-ray diffraction and the structures were refined from single crystal X-ray diffractometer data. EuTMg2 (T = Pd, Ag, Pt, Au) and EuTCd2 (T = Pd, Pt, Au) crystallize with the MgCuAl2 type, space group Cmcm, while EuRhMg2, EuIrMg2 and CaRhMg2 adopt the YSiPd2 type, space group Pnma. The striking crystal chemical motif of both series of compounds are networks of puckered Mg(Cd) hexagons in ABAB stacking sequence that derive from the aristotype AlB2; however, with different tiling. Temperature dependent magnetic susceptibility and 151Eu Mössbauer spectroscopic measurements indicate stable divalent europium. Antiferromagnetic ordering sets in at 20.2 (EuIrMg2), 22.3 (EuPdMg2), 21.3 (EuAgMg2), 10.9 (EuPdCd2) and 15.5 K (EuPtCd2), respectively. The stable antiferromagnetic ground states are substantiated by metamagnetic transitions. The 151Eu isomer shifts show a linear correlation with the valence electron count for the whole series of EuTMg2, EuTCd2, EuTIn2 and EuTSn2 phases.

A europium kagome lattice in the solid solution Eu3−х Sr х Pt4Zn12 – first zinc representatives of the Gd3Ru4Al12 type

Eu3Pt4Zn12 and Sr3Pt4Zn12 form a complete solid solution Eu3−x Sr x Pt4Zn12. Samples with x = 0, 0.5, 1, 1.5, 2, 2.5 and 3 were synthesized from the elements in sealed tantalum ampoules in an induction furnace. All samples were characterized by powder X-ray diffraction and the structures of Sr3Pt3.93Zn12.07, Eu1.80Sr1.20Pt4Zn12 and Eu3Pt3.68Zn12.32 were refined from single crystal X-ray diffractometer data. The new compounds are isotypic with Gd3Ru4Al12, space group P63/mmc. The striking building units in these phases are the kagome networks occupied by the europium and strontium atoms and Pt1@Zn8 and Pt2@Zn8 distorted cubes. Besides the Eu/Sr mixing within the solid solution, the structure refinements indicated small homogeneity ranges induced by Pt/Zn mixing. The europium containing samples of the solid solution Eu3−x Sr x Pt4Zn12 are Curie–Weiss paramagnets and the experimental magnetic moments manifest stable divalent europium. The samples with x = 0, 0.5 and 2 order magnetically: T N = 15.4(1) K for x = 0, T C = 12.4(1) K for x = 0.5 and T N = 4.0(1) K for x = 2. The 3 K magnetization isotherms tend toward Brillouin type behavior with increasing europium dilution. The divalent ground state of Eu3Pt4Zn12 is further confirmed by 151Eu Mössbauer spectroscopy with an isomer shift of −9.66(2) mm s−1 at 78 K. In the magnetically ordered state Eu3Pt4Zn12 shows full magnetic hyperfine field splitting (23.0(1) T).

Complexes of divalent europium with dotp and dotpph

Two complexes of divalent europium, with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis(methylene phosphonate) (dotp) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis(methylene P-phenylphosphinate) (dotpph), were obtained by electrochemical synthesis. In both compounds the Eu2+ cation is 8-coordinate, surrounded by 4 oxygen...

Ternary plumbides ATPb2 (A = Ca, Sr, Ba, Eu; T = Rh, Pd, Pt) with distorted, lonsdaleite-related substructures of tetrahedrally connected lead atoms

The plumbides CaTPb2 (T = Rh, Pd), EuTPb2 (T = Rh, Pd, Pt), SrTPb2 (T = Rh, Pd, Pt) and BaTPb2 (T = Pd, Pt) were obtained by direct reactions of the elements in sealed tantalum tubes in an induction furnace. The moisture sensitive polycrystalline samples were characterized by X-ray powder diffraction. They crystallize with the orthorhombic MgCuAl2-type structure, space group Cmcm. The structures of CaRhPb2 (a = 433.78(3), b = 1102.06(8), c = 798.43(6) pm, wR = 0.0285, 432 F2 values and 16 variables) and EuPdPb2 (a = 457.24(5), b = 1158.27(13), c = 775.73(8), wR = 0.0464, 464 F2 values and 16 variables) were refined from single crystal X-ray diffractometer data. The characteristic structural motif is the distorted tetrahedral substructure built up by the lead atoms with Pb–Pb distances of 326–327 pm in CaRhPb2 and of 315–345 pm in EuPdPb2. With increasing size of the alkaline earth (Eu) cation, the lead substructure becomes more anisotropic with a shift of the [TPb2] polyanions from three- to two-dimensional, leading to significantly increased moisture sensitivity. Temperature dependent magnetic susceptibility studies reveal Pauli paramagnetism for SrRhPb2, SrPtPb2, BaPdPb2 and BaPtPb2. EuRhPb2 and EuPdPb2 are Curie–Weiss paramagnets with stable divalent europium as is also evident from 151Eu Mössbauer spectra. EuRhPb2 is a ferromagnet with TC = 17.7(2) K, while EuPdPb2 orders antiferromagnetically at TN = 15.9 K. This is in agreement with the full magnetic hyperfine field splitting of the 151Eu Mössbauer spectra at T = 6 K.