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Three new iridium aluminum intermetallics CaAl4Ir2, SrAl4Ir2, and EuAl4Ir2 were synthesized from the elements using silica or tantalum ampoules. They crystallize in the tetragonal crystal system with space group P4/ncc and lattice parameters of a = 782.20(1) and c = 779.14(2) pm for CaAl4Ir2, a = 797.62(1) and c = 772.75(2) pm for SrAl4Ir2, and finally a = 791.78(5) and c = 773.31(5) pm for EuAl4Ir2. All compounds crystallize isostructurally and adopt a new structure type that can be derived from the KAu4In2 type structure. To compare the structures from a crystallographic point of view, a group–subgroup relation between KAu4In2 and EuAl4Ir2 as well as KAu4In2 and KAu4Sn2 have been established using the Bärnighausen formalism. Finally, quantum-chemical calculations have been conducted, showing that in all three title compounds, a polyanionic [Al4Ir2]δ– network exists with significant (polar) bonding interactions, while the respective Caδ+, Srδ+, and Euδ+ cations are located in octagonal channels. Graphical abstract

YNiIn and YCuIn form complete solid solutions YNiIn1−x Al x and YCuIn1−x Al x , which were characterized on the basis of X-ray powder diffraction. The ZrNiAl type crystal structures (space groups P 6 ‾ 2 m $P\overline{6}2m$ ) of YNiAl (a = 0.70386(9), c = 0.38327(4) nm, wR 2 = 0.0424), YNiIn0.77Al0.23 (a = 0.73895(9), c = 0.37707(4) nm, wR 2 = 0.0498) and YCuIn0.63Al0.37 (a = 0.73404(7), c = 0.39045(4) nm, wR 2 = 0.0314) were refined from the single crystal X-ray diffraction data. Exemplarily the electronic structure of YNiAl was studied, manifesting substantial Ni–Al bonding within the three-dimensional [NiAl] substructure. Comparison of YNiAl with isotypic YNiIn shows stronger Ni–Al bonding as compared to Ni–In. Magnetic susceptibility measurements of YNiIn1−x Al x (x = 0.1, 0.2, 0.7 and 0.9), YNiIn and YNiAl in the temperature range 3–300 K indicated Pauli paramagnetic behaviour with molar magnetic susceptibility of about 0.15–0.22 × 10−3 emu/mol.

During attempts to synthesize new platinides in the ternary system Sr–Al–Pt, single crystals of SrAl5Pt3 and Sr2Al16Pt9 were obtained from a reaction of the elements with the nominal composition Sr4Al13Pt9. Both orthorhombic structures were refined based on single crystal x-ray diffraction data (SrAl5Pt3: Pnma, Wyckoff sequence c 9, a = 2065.04(7), b = 413.74(1), c = 738.98(3) pm, wR2 = 0.0310, 867 F 2 values, 56 variables; Sr2Al16Pt9: Immm, Wyckoff sequence l 4 j 2 ihga, a = 416.69(2), b = 1193.53(6), c = 1832.38(9) pm, wR2 = 0.0517, 671 F 2 values, 49 variables); full atomic ordering was observed in both cases. In order to analyze the bonding situation of these new platinides, quantum-chemical calculations were conducted. According to density functional theory both compounds are polar intermetallics with high negative charges on the Pt atoms and covalently bonded [Al5Pt3]/[Al16Pt9] networks showing strong Pt–Al alongside of weak Al–Al and Pt–Pt bonding.

The quaternary rare-earth-metal hafnium copper arsenides REHfCu2+δAs3 (where RE = La-Nd; δ ≈ 0.17) were obtained by direct reactions of the elements at 1073 K. They adopt a noncentrosymmetric orthorhombic crystal structure (space group Pmn21; a = 397.73(3)-392.37(2) pm, b = 1062.68(8)-1055.23(6) pm, c = 1307.25(9)-1291.40(7) pm for RE = La-Nd), which can be considered to be a Cu-deficient superstructure of the ternary Zr2Ni3P3-type structure found among metal-rich pnictides with a metal-to-nonmetal ratio close or equal to 2:1. The RE atoms occupy trigonal prismatic (CN6) and monocapped trigonal prismatic (CN7) sites, the latter resulting from the occurrence of Cu vacancies, the Hf atoms occupy octahedral sites (CN6), and the Cu atoms occupy tetrahedral sites (CN4). Band structure calculations on idealized models LaHfCu2As3 and LaHfCu2.5As3 suggest that the bonding situation improves by fractional occupation of the Cu3 site via depopulation of antibonding Cu-As states.

TbPdAl2 and the solid solution Tb1–xLuxPdAl2 (x = 0.1–1) have been synthesized via arc-melting techniques using the elements as starting materials and crystallize in the orthorhombic MgCuAl2-type s...

Five Zintl phases in the ternary system Eu–M–Pn (M = Al, In; Pn = As, Sb, Bi) were prepared from the elements in tantalum containers. Eu5In2As6 and Eu5In2Sb6 crystallize in the orthorhombic Ca5Ga2As6 type structure (Pbam, oP26), while Eu5In2Bi6 is isostructural to orthorhombic Ca5Al2Bi6 (Pbam, oP26). Eu3AlAs3 adopts a monoclinic structure type (P21/c, mP28), which is isopointal to Rb3TlO3, and Eu3GaAs3 (Cmce, oS56), finally, crystallizes in the orthorhombic Ba3AlSb3 type structure. All structures have been refined from single crystal X-ray diffraction experiments and can be considered to be Zintl phases with a valence precise sum formula according to (Eu2+)5(In3+)2(Pn3−)4(Pn2−)2 and (Eu2+)3(M3+)(As3−)3. They all feature [MPn4] tetrahedra, which are connected in different ways. While in the Ca5Ga2As6 and Ca5Al2Bi6 type representatives double strands via Pn–Pn bonds are formed, in Eu3AlAs3 and Eu3GaAs3, [M2As6]6− tetrahedral dimers exist. The divalent europium atoms are located in between the chains, providing electroneutrality. The magnetic properties of four compounds have been investigated and complex (antiferro)magnetic ordering has been observed at TN = 16.1(1) (Eu5In2As6), 17.8(1) K (Eu5In2Sb6), 10.0(1) K (Eu3AlAs3) and 10.7(1) K (Eu3GaAs3). The effective magnetic moment and 151Eu Mossbauer spectroscopic investigations unambiguously proved the divalent character of the Eu atoms. The spectra recorded below the magnetic ordering showed a (full) hyperfine field splitting. Additionally, 121Sb Mossbauer spectroscopic studies have been conducted on the antimonide Eu5In2Sb6. Finally, computational studies of Eu3AlAs3 and Eu5In2Sb6 indicate semiconducting behavior for the arsenide with a bandgap of ca. 1 eV, while an increased metallicity, manifested in a pseudo gap for the antimonide, is visible at the Fermi level.

The new Y2Co3Ga9 and Gd3Ru4Al12 type representatives M2T3Al9 (M = Ca, Sr, Eu; T = Ir, Pt) and M3Rh4Al12 (M = Ca, Eu) have been synthesized from the elements by heating the respective elemental compositions in sealed tantalum tubes. The samples were analysed by powder X-ray diffraction to check their purity. By applying different temperature treatments, their phase purity and crystallinity were enhanced. The crystal structures of Ca3Rh4Al12 and Eu3Rh4Al12 (hexagonal Gd3Ru4Al12 type, P63/mmc) as well as Ca2Ir3Al9 and Ca2Pt3Al9 (orthorhombic Y2Co3Ga3 type, Cmcm) were refined from single-crystal X-ray diffraction data. All structures can be described based on distorted cube-like T@Al8 units that are connected to form strands. Additionally, an Al11 supertetrahedral building block can be identified within the structures. While the trigonal bipyramidal core of the cluster contains substantial bonding interactions in the case of the M3Rh4Al12 members, the connection via common edges in the case of the M2Ir3Al9 compounds seems to weaken these interactions. The differences in the bonding situation and the question why these different structure types are formed for the different transition metals has been targeted by quantum-chemical calculations. The calculated formation energy using three different reaction paths suggests that the stability of these phases is highly dependent on the side phases involved, even though Ca3T4Al12 phases are in general thermodynamically more favourable. According to the Bader analysis of the two polyanions, an improved covalent bonding can be observed in the [T4Al12]δ- over the [T3Al9]δ- framework.

Systematically twinned olivenite (Cu2(AsO4)OH) single crystals from Cap Garonne, Mine du Pradet, France, were studied by X-ray diffraction: P 21/n, a = 822.69(6) pm, b = 861.88(9) pm, c = 594.06(9) pm, β = 90.000(6)°, wR = 0.0224, 1621 F 2 values, 79 variables and a domain ratio of 0.501(1)/0.499(1). The temperature dependence of the magnetic susceptibility was well reproduced with a square-spin cluster model and an antiferromagnetic spin-exchange parameter of J/k B = 157(3) K.

Over 20 new compounds of the RE6T5Al7 series (RE = Sc, Y, Ce–Nd, Sm, Gd–Lu; T = Ru, Ir; Yb6Ir5Ga7 type structure; superstructure of MgZn2; fully ordered Nb6.4Ir4Al7.6 type) have been synthesized. They crystallize in the hexagonal crystal system with space group P63/mcm. Their lattice parameters are in the ranges of a = 935–963 and c = 851–874 pm for the RE6Ru5Al7 and a = 913–966 and c = 825–865 pm for the RE6Ir5Al7 series. Four structures (Ho6Ru5Al7, Yb6Ru4.68(1)Al7.32(1), Sc6Ir5Al7, and Ho6Ir4.53(1)Al7.47(1)) have been refined from single-crystal data, indicating fully ordered structures for Ho6Ru5Al7 and Sc6Ir5Al7; however, T/Al mixing was observed on one crystallographic site for Ho6Ir4.53(1)Al7.47(1) and on two sites for Yb6Ru4.68(1)Al7.32(1). The Sc-, Y-, and Lu-containing compounds exhibit Pauli paramagnetism in line with a filled d band for Ru and Ir. Ce6Ru5Al7 exhibits mixed-valent behavior, while Yb6Ru5Al7 is solely trivalent. The other compounds exhibit paramagnetism and ferromagnetic phase tran...

The gallium-rich quaternary intermetallic compounds REPt2Ga3In (RE = Y, Gd–Yb) were synthesized by arc melting of the elements. Small single crystals were grown by induction heating the arc-melted buttons in sealed tantalum ampoules. The REPt2Ga3In phases were characterized through X-ray powder patterns. The structures of GdPt2Ga2.95In1.05 [a = 1760.28(4) pm, b = 429.09(5) pm, c = 675.37(14) pm, wR2 = 0.0618, 1104 F2 values, and 45 parameters] and TbPt2Ga3.14In0.86 [a = 1746.56(3) pm, b = 427.05(5) pm, c = 672.69(13) pm, wR2 = 0.0554, 1086 F2 values, and 45 parameters] were refined from X-ray single-crystal diffractometer data. These gallide indides are the first ternary ordered representatives of the orthorhombic NdRh2Sn4-type structure, space group Pnma. The striking basic building units are platinum-centered trigonal prisms Pt1@Gd2Ga4 and Pt2@Gd2Ga2In2 with larger edge lengths for the indium-substituted prism. Refinements of the occupancy parameters indicate the formation of small homogeneity ranges. The indium atoms are positioned at the edges of adjacent prisms and form zig-zag chains (330 pm In–In) extending along the y-axis. Temperature-dependent magnetic susceptibility data of GdPt2Ga3In show Curie–Weiss paramagnetism with an anomaly observed at T = 12.7(1) K, proven as intrinsic by zero-field heat capacity measurements, pointing towards a stable canted antiferromagnetic ground state.

Four new MPtAl2 (M=Ca, Sr, Ba, Eu) compounds, adopting the orthorhombic MgCuAl2 -type structure, have been synthesized from the elements using tantalum ampoules. All compounds are obtained as platelet-shaped crystallites and exhibit an increasing moisture sensitivity with increasing size of the formal M cation. Structural investigations indicate a pronounced elongation of the crystallographic b-axis, which results in a significant distortion of the [PtAl2 ]δ- polyanion. Within the polyanion, layer-like arrangements can be found with bonding Pt-Al interactions within the slab; the increase of the b-axis can be attributed to increasing Al-Al distances and therefore decreasing interactions between the slabs, caused by the differently-sized formal M cations. While the alkaline earth (M=Ca, Sr) representatives exhibit Pauli paramagnetism, BaPtAl2 shows diamagnetic behavior, finally EuPtAl2 is ferromagnetic with TC =54.0(5) K. The effective magnetic moment indicates that the Eu atoms are in a divalent oxidation state, which is confirmed by 151 Eu Mossbauer spectroscopic investigations. Measurements below the Curie-temperature show a full magnetic hyperfine field splitting with Bhf =21.7(1) T. 27 Al and 195 Pt magic-angle spinning NMR spectroscopy corroborates the presence of single crystallographic sites for the Pt and Al atoms. The large 27 Al nuclear electric quadrupolar coupling constants confirm unusually strong electric field gradients, in agreement with the structural distortions and the respective theoretical calculations. X-ray photoelectron spectroscopy has been utilized to investigate the charge transfer within the polyanion. The Pt 4f binding energy decreases with decreasing electronegativity / ionization energy of the alkaline earth elements, suggesting an increasing electron density at the Pt atoms. Theoretical investigations underline the platinide character of the investigated compounds by Bader charge calculations. The analysis of the integrated crystal orbital Hamilton population (ICOHP) values, electron localization function (ELF) and isosurface analyses lead to a consistent structural picture, indicating stable layer-like arrangements of the [PtAl2 ]δ- polyanion.

The rare-earth metal-rich RE14T3Al3 series (RE = Y, Gd–Tm, Lu) was extended to the transition metals T = Cu, Rh, and Pd. All compounds have been prepared by arc-melting the rare-earth elements with appropriate amounts of TAl precursors. The compounds crystallize in the tetragonal Gd14Co3In2.7-type structure with space group P42/nmc. Two structures (Y14Rh2.97(1)Al3.03(1): a = 952.99(4) pm, c = 2292.98(10) pm, wR2 = 0.0423, 2225 F2 values, 63 variables; Y14Pd3.16(1)Al2.84(1): a = 955.06(5) pm, c = 2298.77(10) pm, wR2 = 0.0416, 2225 F2 values, 63 variables) have been refined from single-crystal data, indicating T/Al mixing on two crystallographic sites. The lattice parameters of all synthesized representatives have been refined from Guinier powder X-ray diffraction data. The Y and Lu containing compounds show Pauli paramagnetic behavior, indicating that the transition metal atoms have filled d bands and exhibit no localized magnetic moment. From the other compounds only Er14Pd3Al3 was obtained as an X-ray pure sample. It shows paramagnetism, in line with the rare-earth atoms in the trivalent oxidation state and antiferromagnetic ordering below TN = 8.0(1) K. Detailed magnetic investigations on the other members were impossible due to the presence of, e.g., RE3T trace impurities.

Eu2 Ir3 Al9 , synthesized from the elements in tantalum tubes, is one of the rare examples for trivalent europium in the field of intermetallic compounds. The compound crystallizes in the Y2 Co3 Ga9 -type structure (space group Cmcm), with lattice parameters fitting in between the isostructural samarium and gadolinium compounds. In the crystal structure, the Eu atoms form Al3 -triangle-centered honeycomb layers and exhibit a coordination number of 17 in the shape of a fivefold-capped hexagonal prism (Eu@Ir6 Al6 +Al5 ). Magnetic measurements indicate an overall low susceptibility, in line with van Vleck paramagnetism caused by the Eu3+ cations. Fits of the susceptibility yield a coupling constant of λ=290(10) K and an effective magnetic moment of μeff =4.56(1) μB , in line with a slight hybridization of the 7 F0 and 7 F1 state. 151 Eu Mossbauer spectroscopic investigations unambiguously prove the presence of solely Eu3+ in the bulk material.

The new intermetallic compound Ba6Pt22Al53 was obtained from reaction of the elements. The title compound crystallizes in the hexagonal crystal system with lattice parameters of a = 1427.5(3) and c = 1614.3(4) pm and space group P63/mcm (Z = 2) and adopts a new structure type (Pearson code hP162, Wyckoff sequence l2k3j2i2hg2ecb). In the structure, the Pt and Al atoms form a complex polyanionic [Pt22Al53]δ- network, while the Ba cations reside in cavities. The structure can be described as a packing of layers, formed by the Pt@Aln polyhedra parallel to (001). The layers are stacked in an ABCB fashion. Within the [Pt22Al53] framework, one of the shortest Pt-Al distances (239 pm) reported is found, suggesting extremely strong covalent bonding interactions. Due to slightly enhanced displacement parameters of the Al9 site, temperature dependent single-crystal X-ray diffraction (285 and 90 K) and low-temperature heat capacity experiments were conducted. However, no structural phase transition was observed down to 2 K. With the help of DFT calculations, the bonding situation was elucidated in detail, verifying the strong heteroatomic bonding and the destabilization of the structure upon in silico distortions. Mulliken charge calculations confirm the picture of the polyanionic framework and cationic Ba atoms within the cavities.

A temperature induced valence phase transition from Yb3+ at higher temperatures to Yb2+ at lower temperatures was observed at T = 110(1) K for intermetallic YbPd2Al3. The title compound has been prepared from the elements in sealed tantalum ampoules. The structure was refined from single-crystal data and the title compound was found to crystallize in the hexagonal YNi2Al3 type structure with space group P6/mmm and lattice parameters of a = 929.56(7) and c = 420.16(3) pm (300 K data). Full ordering of the Pd and Al atoms within the [Pd2Al3] δ- polyanion was observed. Magnetic measurements revealed an anomaly in the dc susceptibility data and intermediate valent Yb at higher temperature, as observed from the effective magnetic moment. The proposed valence phase transition was also observed as a λ-type anomaly in heat capacity measurements (T = 108.4(1) K), however, no systematic shift of the λ-peak was observed in field dependent heat capacity measurements. An antiferromagnetic ordering at this temperature, however, could be excluded, based on field-dependent susceptibility measurements and magnetization isotherms. No dynamic phenomenon was observed in ac susceptibility measurements, excluding e.g. spin-glass behavior. Subsequent temperature dependent single-crystal and powder X-ray diffraction experiments indicated a steep increase in the length of the c axis around T = 110 K upon cooling. However, no structural phase transition was found via single-crystal diffraction experiments conducted at 90 K. The anomaly was also observed in other physical measurements of e.g. the electrical resistivity, indicating a clear change in the electronic structure of the material. X-ray photoelectron spectroscopy conducted at room temperature shows the presence of both, Yb2+ and Yb3+, underlining the mixed-valent state. Members of the solid solution Yb1-x Ca x Pd2Al3 (x = 0.33, 0.67, 1) were finally used to further study the charge ordering and the present temperature induced valence phase transition.

The rare earth metal-rich RE 14 T 3Al3 series (RE=Y, Gd–Tm, Lu; T=Co, Ni) have been prepared by arc-melting the rare earth metals with appropriate amounts of TAl precursors. All compounds crystallize in the tetragonal crystal system with space group P42/nmc in the Gd14Co3In2.7-type structure. Two structures (Y14Co2.78(1)Al3.22(1): a=952.99(4), c=2292.98(10) pm, wR2=0.0423, 2225 F 2 values, 63 variables; Y14Ni3.07(2)Al2.93(2): a=955.06(5), c=2298.77(10) pm, wR2=0.0416, 2225 F 2 values, 63 variables) have been refined from single-crystal data, indicating T/Al mixing on one crystallographic site. The lattice parameters of all members have been refined from powder X-ray diffraction experiments. The Y and Lu containing compounds for T=Co and Ni exhibit Pauli paramagnetic behavior, indicating that the Co and Ni atoms exhibit no localized magnetic moment in line with a filled 3d band. The other compounds show paramagnetism, in line with the rare earth atoms in the trivalent oxidation state. Detailed magnetic investigations, however, were impossible due to the presence of e.g. RE 3 T trace impurities.

The quaternary rare-earth-metal hafnium copper arsenides REHfCu

The new Y2Co3Ga9 and Gd3Ru4Al12 type representatives M2T3Al9 (M = Ca, Sr, Eu; T = Ir, Pt) and M3Rh4Al12 (M = Ca, Eu) have been synthesized from the elements by heating the respective elemental compositions in sealed tantalum tubes. The samples were analysed by powder X-ray diffraction to check their purity. By applying different temperature treatments, their phase purity and crystallinity were enhanced. The crystal structures of Ca3Rh4Al12 and Eu3Rh4Al12 (hexagonal Gd3Ru4Al12 type, P63/mmc) as well as Ca2Ir3Al9 and Ca2Pt3Al9 (orthorhombic Y2Co3Ga3 type, Cmcm) were refined from single-crystal X-ray diffraction data. All structures can be described based on distorted cube-like T@Al8 units that are connected to form strands. Additionally, an Al11 supertetrahedral building block can be identified within the structures. While the trigonal bipyramidal core of the cluster contains substantial bonding interactions in the case of the M3Rh4Al12 members, the connection via common edges in the case of the M2Ir3Al9 compounds seems to weaken these interactions. The differences in the bonding situation and the question why these different structure types are formed for the different transition metals has been targeted by quantum-chemical calculations. The calculated formation energy using three different reaction paths suggests that the stability of these phases is highly dependent on the side phases involved, even though Ca3T4Al12 phases are in general thermodynamically more favourable. According to the Bader analysis of the two polyanions, an improved covalent bonding can be observed in the [T4Al12]δ- over the [T3Al9]δ- framework.

The rare earth metal-rich cobalt and nickel aluminium compounds with the general compositions RE 6Co2Al (RE=Sc, Y, Nd, Sm, Gd–Tm, Lu) and RE 6Ni2.25Al0.75 (RE=Y, Gd–Tm, Lu) have been synthesised from the elements by arc-melting, followed by annealing. Single-crystal X-ray diffraction experiments on Y6Co2.02(1)Al0.98(1) (Ho6Co2Ga type; Immm; a=944.1(2), b=952.4(2), c=999.0(2) pm; wR2=0.0452, 1123 F 2 values, 35 variables) and Y6Ni2.26(1)Al0.74(1) (Ho6Co2Ga type; Immm; a=938.30(5), b=959.45(5), c=996.05(6) pm; wR2=0.0499, 1131 F 2 values, 35 variables) revealed that the compounds form solid solutions according to the general formula RE 6(Co/Ni)2+ x Al1−x with different homogeneity ranges. The compounds of the Ni series can be obtained in X-ray pure form only with the nominal composition RE 6Ni2.25Al0.75. A significant increase of the U 22 component of the anisotropic displacement parameters of the Co/Ni2 atoms (4g site) was observed that requires a description of the structure with a split-position model at RT. Further investigations by low temperature (90 K) single-crystal X-ray diffraction experiments of Y6Co2.02(1)Al0.98(1) showed a significant decrease of U 22. Magnetic measurements were conducted on the X-ray pure members of the RE 6Co2Al (RE=Y, Dy–Tm, Lu) series. Antiferromagnetic ordering was observed for the members with unpaired f electrons with Néel temperatures up to T N=48.0(1) K and two spin reorientations for Dy6Co2Al.

Several rare earth metal containing pseudo-ternary compounds in the RE 2 TAl3 series (RE=Sc, Y, La–Nd, Sm, Gd–Lu; T=Ru, Rh, Ir) have been synthesized from the elements by arc-melting or in tantalum capsules. Within the Rh series, the compounds with RE=La–Nd crystallize in the cubic MgCu2-type (Fd3̅m) structure. For Sm besides the cubic Laves phase also the hexagonal Laves phase (MgZn2 type, P63/mmc) is found. For the remaining compounds of both series, also the hexagonal MgZn2-type structure is observed. The structures of Ho2Ru0.96(1)Al3.04(1) (a=547.4(1), c=875.7(1) pm, wR=0.0397, 201 F 2 values, 13 variables), Sc2Rh1.01(1)Al2.99(1) (a=528.0(1), c=852.8(1) pm, wR=0.0228, 184 F 2 values, 13 variables), Ho2Rh1.00(1)Al3.00(1) (a=546.5(1), c=873.8(1) pm, wR=0.0590, 222 F 2 values, 13 variables) and Tb2Ir1.06(1)Al2.94(1) (a=550.8(1), c=870.0(1) pm, wR=0.0743, 221 F 2 values, 13 variables) have been refined from single-crystal data, indicating T/Al mixing on both crystallographic Zn sites of the aristotype. The Sc, Y, La and Lu containing compounds exhibit Pauli-paramagnetic behavior, while the other compounds show paramagnetism, in line with the rare earth atoms in the trivalent oxidation state. Ferro- and antiferromagnetic ordering up to T C=50.2(1) K for Gd2RhAl3 is observed, while Sm2RuAl3 shows van Vleck paramagnetism and Yb2RuAl3, finally, exhibits only partially trivalent Yb atoms, evident from a reduced magnetic moment and increased lattice parameters.

Over 20 new compounds of the RE

Eu2Pt6Al15 has been prepared from the elements via arc-melting and subsequent temperature treatment; the structure was refined from single crystal X-ray diffraction data. The compound crystallizes in an orthorhombic (3 + 1)D commensurately modulated structure (Sc2Pt6Al15 type) with space group Cmcm(α,0,0)0s0 (α = 2/3). Full ordering of the Pt and Al atoms within the [Pt6Al15]δ− polyanion was observed. Magnetic measurements revealed an anomaly in the susceptibility data at T = 41.6(1) K, which was also observed as λ-type anomaly in heat capacity measurements (T = 40.7(1) K). Temperature dependent powder X-ray diffraction experiments indicated a drastic shortening of the c axis (−18 pm, −1.1%) around 45 K, while the a axis nearly remains the same (−1 pm, −0.2%). Measurements of the electrical resistivity verified the anomaly, indicating a clear change in the electronic structure of the material. The observed anomalies in the physical measurements can be explained by a temperature driven first order valence ...

The quaternary arsenide LaHf2Ni5−xAs4 was prepared by reaction of the elements in a tube furnace, followed by heating in an induction furnace. LaHf2Ni5−xAs4 (x ​= ​0.25(1)) crystallizes in a new monoclinic structure in space group P21/m (with cell parameters of a ​= ​9.6766(16) A, b ​= ​3.9280(7) A, c ​= ​9.8605(17) A, β ​= ​93.339°) and can be regarded as a filled variant of the monoclinic LaZr2Ni4−xAs4-type structure. The structure of LaHf2Ni5−xAs4 contains As-centred trigonal prisms arranged in propeller-shaped units, which are linked together by single trigonal prisms. The Hf atoms occupy square pyramidal sites (CN5), while the Ni atoms occupy tetrahedral sites (CN4). Band structure calculations and bonding analysis suggest that this compound is a metallic conductor, the origin of the conductivity being largely attributed to Hf–Hf and Hf–Ni interactions.

The P-H functionalized Al/P-based frustrated Lewis pair (FLP) Mes(H)P-C[Al{CH(SiMe3)2}2]=C(H)-tBu (3) has the typical functionality of FLPs with Lewis acidic and basic centers in a single molecule and is able to transfer the P bound H atom to activated substrates. Nevertheless, 3 reacted with NH3 only by adduct formation with the N atom coordinated to Al (5). The relatively low basicity of the P atom prevented the for-mation of a hydrogen bridge between P and Al. Similarly, benzil and 3 afforded a simple adduct (6) with only one C=O group bonded to P and Al. The second C=O group and the P-H moiety were unaffected. 6 has two stereogenic centers, and the resulting diastereomers were identified by crystal structure determinations. Migration of the P bound H atom was only observed for substrates containing basic N atoms. Nitriles gave heterocyclic iminophosphine adducts (7) in which the N-H groups were coordinated to the Al at-oms. An isocyanate and two isothiocyanates afforded adducts via Al-X and P-C bond formation (X = O, S), and phosphaurea derivatives (8a to 8c) resulted from H shift to the exocyclic N atoms. A carbodiimide reacted with 3 by the formation of a phosphaguanidine (8d) with the imine N atom coordinated to Al. The latter reactions proceed under mild conditions and represent formally the hydrophosphination of unsaturated substrates.

The compounds of the REPt6Al3 series (RE = Ce–Nd, Sm, Gd, Tb) were obtained by reaction of the elements via arc-melting. They were characterized by powder and single-crystal X-ray diffraction (NdPt6Al3: wR = 0.0432, 759 F2 values, 33 variables) as well as by magnetic susceptibility measurements. The isostructural compounds crystallize with a new structure type in the trigonal crystal system with space group R3c, twelve formula units in the unit cell, and lattice parameters of a = 752–755 and c = 3882–3945 pm. The crystal structure can be described by different slabs stacked along [001]. One layer features Pt3 triangles, centering the cavities of a flat honeycomb RE layer that are arranged in a ···ABCA′B′C′··· sequence. The other layer consists of condensed hexagonal [Pt6Al6] prisms, centered by Pt atoms, separating the before mentioned slabs. Magnetic measurements revealed that all rare-earth atoms are in the trivalent oxidation state, however, due to the low lanthanoide content magnetic ordering phenomena were observed only at low temperatures [SmPt6Al3: TC = 5.0(1) K; GdPt6Al3: TC = 7.3(1) K; TbPt6Al3: TN = 3.6(1) K].

The intermetallic compound CaAu2Al2, and the members of the solid solutions SrAu2–xAl2+x (0 ≤ x ≤ 0.33) and Ba3Au5+xAl6–x (x = 0, 0.14, 0.49) were synthesized from the elements in sealed tantalum ampoules. The Ca compound crystallizes with the orthorhombic ThRu2P2 type structure, whereas the targeted SrAu2Al2 was found to form a solid solution according to SrAu2–xAl2+x. For the Ba system no “BaAu2Al2” was found, however, Ba3Au5+xAl6–x was discovered to crystallize in the monoclinic space group C2/c with its own structure type. The samples were investigated by powder X-ray diffraction and their crystal structures were refined on the basis of single-crystal X-ray diffraction data. All compounds were characterized furthermore by susceptibility measurements. The crystallographic aluminum sites of CaAu2Al2 and Ba3Au5Al6 can be differentiated by 27Al solid state NMR spectra on the basis of their different electric field gradients, in agreement with theoretical calculations. The electron transfer from the alkaline earth metals and the aluminum atoms onto the gold atoms was investigated by X-ray photoelectron spectroscopy (XPS) classifying these intermetallics as aurides, in full agreement with the calculated Bader charges.

The five ternary intermetallic compounds M 2Pt6Al15 (M=Ca, Sc, Y, La, Lu) were prepared from the elements by arc-melting. The crystal structure was determined via single crystal X-ray diffraction. The title compounds crystallize in a superstructure of the RE 0.67Pt2Al5 type structure (P63/mmc) in the monoclinic crystal system with space group P121/m1 (Sc2Pt6Al15: a=734.19(2), b=1628.96(10), c=734.19(2) pm, β=119.999(3)°; wR=0.0356, 3034 F 2 values, 68 variables). The superstructure can be derived by the superspace formalism using (3+2)D or (3+1)D interpretations of the diffraction data. The structural relation to the subcell structure is discussed on the basis of a group-subgroup scheme. In the crystal structure strongly bonded [Pt2Al4] δ− slabs are alternatingly stacked with ordered layers containing M atoms and Al3 triangles.

A total of 35 intermetallic aluminum compounds have been synthesized from the elements via arc melting and characterized by powder X-ray diffraction. A total of 15 of them have been previously reported; however, detailed property investigations were missing. Compounds of the RETMAl

Four new MPtAl

The feasibility of high-resolution

The feasibility of high-resolution 175Lu solid-state NMR spectroscopy in intermetallic compounds crystallizing with cubic crystal structures is explored by magic-angle spinning NMR at different magnetic flux densities. The large quadrupole moment of this isotope (3.49 × 10−28 m2) restricts observation of the NMR signal to nearly perfectly ordered crystalline samples. Signals are successfully detected and analyzed in the binary pnictides LuPn (NaCl-type structure; Pn = P, As, Sb) and the intermetallic compounds LuPtSb and LuAuSn, both crystallizing with the MgAgAs-type structure. Sources of line broadening are discussed based on field-dependent static and MAS-NMR spectra, providing guidance with respect to measurement conditions resulting in reliable results. The results highlight the importance of ionic/covalent bonding effects for the detectability of the signal, which reduce the probability of real structure effects commonly observed in intermetallic compounds. No 175Lu NMR signals can be observed in various cubic Heusler compounds. This is attributed to mixed site occupancies and other structural defects producing electric field gradients whose interaction with the 175Lu quadrupole moments broadens the signal beyond detection.

A total of 35 intermetallic aluminum compounds have been synthesized from the elements via arc melting and characterized by powder X-ray diffraction. A total of 15 of them have been previously repo...

Eu

SrPt3Al2, a CaCu5 relative (P6/mmm; a = 566.29(3), c = 389.39(3) pm; wR2 = 0.0202, 121 F2 values, 9 parameters), and Sr2Pd2Al, isostructural to Ca2Pt2Ge (Fdd2; a = 1041.45(5), b = 1558.24(7), c = 604.37(3) pm; wR2 = 0.0291, 844 F2 values, 25 parameters) have been prepared from the elements. The crystal structures have been investigated by single crystal X-ray diffraction. Structural relaxation confirmed the electronic stability of SrPt3Al2, while orthorhombic Sr2Pd2Al might be a metastable polymorph as it is energetically competitive to its monoclinic variant. Both compounds are predicted to be metallic conductors as their density-of-states (DOS) are non-zero at the Fermi level. COHP bonding analysis coupled with Bader effective charge analysis suggest that the title compounds are polar intermetallic phases in which strong Pt–Al and Pd–Al covalent bonds are present, while a significant electron transfer from Sr atoms to the [Pt3Al2]δ– or [Pd2Al]δ– network is found.

The new intermetallic compound Sr2Pd4Al5 was prepared from the elements by reaction in niobium ampoules. The structure was refined from single-crystal data, which indicate the formation of a new structure type in the orthorhombic crystal system [a = 1814.49(10), b = 431.64(4), c = 1102.47(4) pm] with space group Pnma (wR2 = 0.0251, 1666 F2 values, 68 parameters). Full ordering of the transition-metal and aluminum sites was observed. The compound can be described as a polar intermetallic phase with a polyanionic [Pd4Al5]δ– network; however, a quite unique bonding situation was found within this framework. In addition to the usual Pd–Al bonding, significant contributions to the stability of the framework caused by homoatomic Pd–Pd and Al–Al interactions can also be found. Structural relaxation confirmed the electronic stability and predicted the compound to be a metallic conductor.

This work describes the growth of crack-free single crystals of KEu(WO4)2 and their characterization with respect to spectroscopic properties. The crystal structure of KEu(WO4)2 was refined from single crystal X-ray diffractometer data at 293 (KY(WO4)2 type, C2/c, a = 1069.88(7), b = 1046.87(5), c = 760.47(5) pm, β = 130.774(4)°, wR2 = 0.0513, 1247 F2 values and 57 variables) and 90 K (a = 1067.69(4), b = 1048.45(4), c = 757.87(3) pm, β = 130.784(2)°, wR2 = 0.1078, 1237 F2 values and 57 variables). It turns out that KEu(WO4)2 is a promising material for some demanding application areas due to its excellent thermal stability. Temperature dependent spectroscopy revealed that the thermal quenching temperature T1/2 of the crystalline material is 699 K (426 °C). From time dependent emission spectra the fluorescence lifetime τr was determined to be 498 ± 2 μs at 3 K. The decay time moderately declines down to 480 μs at room temperature pointing to the presence of very little thermal quenching at ambient conditions. A strong decline of the emission integral and decay time is not observed before reaching almost 600 K. Finally, the quantum efficiency was determined to be about 64% at room temperature and the asymmetry ratio for the 5D0 -7F2 to 5D0 -7F1 emission multiplets is about 10.8, which means that the Eu3+ spectrum is dominated by the 5D0 – 7F2 transition. 151Eu Mossbauer spectroscopic and temperature dependent magnetic susceptibility data confirm stable trivalent europium.

REPd5Al2 compounds with RE = Ce–Gd as well as Y and Lu have been previously synthesized. Although some compounds with the small lanthanides also exist, the compounds with intermediate-sized rare-earth elements (RE = Tb–Yb) had not been prepared. We report on the missing members of the REPd5Al2 (RE = Tb–Yb) series as well as on the new REPt5Al2 (RE = Y, Gd–Tm, Lu) series, which we have synthesized and structurally as well as magnetically characterized. All members crystallize isostructurally in the ZrNi2Al5 type with an anti-arrangement of the T = Pd/Pt and Al atoms. YPd5Al2 and LuPd5Al2, as well as the respective platinum homologs, YPt5Al2 and LuPt5Al2, have been characterized also by 27Al magic-angle spinning nuclear magnetic resonance spectroscopy. Consistent with the XRD analysis, the spectra indicate the existence of only one distinct Al site in the structure.

Na

Na2Au3Al, the first experimentally prepared compound in the ternary Na–Au–Al system, crystallizes in the cubic crystal system with space group P4132 (a = 771.42(2) pm). It can be described as a P-centered ternary ordered variant of the F-centered Laves phase MgCu2 and is isostructural to Mo3Al2C. A phase width was found for the series Na2Au4–xAlx allowing a successive substitution of Au by Al. The primitive structure forms for x ≥ 0.5. Na2Au3Al is diamagnetic at room temperature but metallic in nature, as seen from susceptibility and electrical resistivity measurements. Band structure calculations and X-ray photoelectron spectroscopy confirm the metallic nature of the title compound as states are found at the Fermi level of the DOS, along with its “auride” character. 23Na and 27Al solid-state-NMR investigations show the existence of both a disordered (x = 0.5 and 0.75) and a fully ordered (x = 1.0) representative within this series. Both COHP and Bader charge analyses suggest the presence of strong Au–Al ...

The three intermetallic compounds SrAuGa, BaAuAl and BaAuGa were synthesised from the elements in niobium ampoules. The Sr compound crystallises in the orthorhombic KHg2 -type structure (Imma, a=465.6(1), b=771.8(2), c=792.6(2) pm, wR2 =0.0740, 324 F2 values, 13 variables), whereas the Ba compounds were both found to crystallise in the cubic non-centrosymmetric LaIrSi-type structure (P21 3, BaAuAl: a=696.5(1) pm; wR2 =0.0427, 446 F2 values, 12 variables; BaAuGa: a=693.49(4) pm, wR2 =0.0717, 447 F2 values, 12 variables). The samples were investigated by powder X-ray diffraction and their structures refined on the basis of single-crystal X-ray diffraction data. The title compounds, along with references from the literature (CaAuAl, CaAuGa, CaAuIn, and SrAuIn), were characterised further by susceptibility measurements and 27 Al and 71 Ga solid-state NMR spectroscopy. Theoretical calculations of the density of states (DOS) and the NMR parameters were used for the interpretation of the spectroscopic data. The electron transfer from the alkaline-earth metals and the group 13 elements onto the gold atoms was investigated through X-ray photoelectron spectroscopy (XPS), classifying these intermetallics as aurides.

During phase analytical investigations in the rare-earth element rich side of the ternary system cerium-gold-aluminum, the new ternary rare-earth (RE) gold aluminides with a composition of RE16AuxAl13-x (RE = La-Nd, Sm, x≤ 3.37) have been synthesized first by reactive eutectics of RE/Au with Al. Single crystals of high quality can be obtained by this method. The title compounds can be selectively prepared by annealing arc-melted beads of appropriate composition below the peritectic point of the respective system. Like prototypic La16Al13, the representatives of the solid solution RE16AuxAl13-x (RE = La-Nd, Sm; x≤ 3.37) crystallize in the hexagonal crystal system (space group P6[combining macron]2m, a = 916.6-890.4 pm, c = 1122.4-1090.1 pm) with one formula unit per unit cell. Single crystal investigations revealed Au/Al mixing on three of the four crystallographic aluminum sites. These sites form an empty (Au/Al)11 barrelane analogous unit, coordinated solely by the respective rare-earth atoms. In addition one independent Al site with a fivefold capped trigonal prismatic arrangement, a so called Edshammar polyhedron, exists. Magnetic measurements of Ce16Au3Al10 revealed two antiferromagnetic transitions with Neél-temperatures of 7.7(1) and 2.7(1) K and a magnetic moment of μeff = 2.48(1) μB, Pr16Au3Al10 shows ferromagentic ordering with a Curie-temperature of 19.8(1) K and a magnetic moment of μeff = 3.58(1) μB.

The new intermetallic compound Sr2Pd4Al5 was prepared from the elements by reaction in niobium ampoules. The structure was refined from single-crystal data, which indicate the formation of a new structure type in the orthorhombic crystal system [a = 1814.49(10), b = 431.64(4), c = 1102.47(4) pm] with space group Pnma (wR2 = 0.0251, 1666 F2 values, 68 parameters). Full ordering of the transition-metal and aluminum sites was observed. The compound can be described as a polar intermetallic phase with a polyanionic [Pd4Al5]δ– network; however, a quite unique bonding situation was found within this framework. In addition to the usual Pd–Al bonding, significant contributions to the stability of the framework caused by homoatomic Pd–Pd and Al–Al interactions can also be found. Structural relaxation confirmed the electronic stability and predicted the compound to be a metallic conductor.

The title compound is prepared from the elements (Nb tube, 1073 K, 7 d) and characterized by powder XRD, XPS, 27Al MAS NMR spectroscopy, magnetic measurements, and DFT band structure calculations.