Ternary rare-earth arsenides REZn3As3 (RE = La-Nd, Sm) and RECd3As3 (RE = La-Pr)

Ternary rare-earth zinc arsenides REZn(3)As(3) (RE = La-Nd, Sm) with polymorphic modifications different from the previously known defect CaAl(2)Si(2)-type forms, and the corresponding rare-earth cadmium arsenides RECd(3)As(3) (RE = La-Pr), have been prepared by reaction of the elements at 800 °C. LaZn(3)As(3) adopts a new orthorhombic structure type (Pearson symbol oP28, space group Pnma, Z = 4, a = 12.5935(8) ?, b = 4.1054(3) ?, c = 11.5968(7) ?) in which ZnAs(4) tetrahedra share edges to form ribbons that are fragments of other layered arsenide structures; these ribbons are then interconnected in a three-dimensional framework with large channels aligned parallel to the b direction that are occupied by La(3+) cations. All remaining compounds adopt the hexagonal ScAl(3)C(3)-type structure (Pearson symbol hP14, space group P6(3)/mmc, Z = 2; a = 4.1772(7)-4.1501(2) ?, c = 20.477(3)-20.357(1) ? for REZn(3)As(3) (RE = Ce, Pr, Nd, Sm); a = 4.4190(3)-4.3923(2) ?, c = 21.4407(13)-21.3004(8) ? for RECd(3)As(3) (RE = La-Pr)) in which [M(3)As(3)](3-) layers (M = Zn, Cd), formed by a triple stacking of nets of close-packed As atoms with M atoms occupying tetrahedral and trigonal planar sites, are separated by La(3+) cations. Electrical resistivity measurements and band structure calculations revealed that orthorhombic LaZn(3)As(3) is a narrow band gap semiconductor.     

Ternary rare-earth titanium antimonides RE2Ti(11-x)Sb(14+x) (RE = Sm, Gd, Tb, Yb)

The isostructural rare-earth titanium antimonides RE 2Ti 11 - x Sb 14 + x ( RE = Sm, Gd, Tb, Yb) have been synthesized by arc-melting reactions of the elements. Single-crystal X-ray diffraction revealed that they adopt a new structure type (Pearson symbol oP54, space group Pnma, Z = 2; a = 15.8865(6)-15.9529(9) A, b = 5.7164(2)-5.7135(3) A, c = 12.9244(5)-12.9442(7) A for RE = Sm-Yb). The structure consists of titanium-centered octahedra (CN6) and pentagonal bipyramids (CN7) connected to form a 3D framework whose cavities are filled with RE atoms. 1D linear skewers of titanium atoms, within face-sharing octahedral chains, and similar skewers of antimony atoms, associated with the titanium-centered pentagonal bipyramids, extend along the b direction. On proceeding from Sm 2Ti 11Sb 14 to Tb 2Ti 10.41(1)Sb 14.59(1) and Yb 2Ti 10.58(1)Sb 14.42(1), antimony atoms are disordered within some of the titanium sites. Resistivity measurements on the samarium and ytterbium members indicated metallic behavior.     

Synthesis, structure, chemical bonding, and magnetism of the series RELiGe2 (RE = La-Nd, Sm, Eu)

This article focuses on the synthesis and the crystal chemistry of six members of a series of rare-earth metal based germanides with general formula RELiGe(2) (RE = La-Nd, Sm, and Eu). The structures of these compounds have been established by single-crystal X-ray diffraction (CaLiSi(2) structure type, space group Pnma, Z = 4, Pearson symbol oP16). The chemical bonding within this atomic arrangement can be rationalized in terms of anionic germanium zigzag chains, conjoined via chains of edge-shared LiGe(4) tetrahedra and separated by rare-earth metal cations. The structure can also be viewed as an intergrowth of AlB(2)-like and TiNiSi-like fragments, or as the result of the replacement of 50% of the rare-earth metal atoms by lithium in the parent structure of the REGe monogermanides. Except for LaLiGe(2) and SmLiGe(2), the remaining four RELiGe(2) phases exhibit Curie-Weiss paramagnetism above about 50 K. In the low temperature regime, the localized 4f electrons in CeLiGe(2), PrLiGe(2), and SmLiGe(2) order ferromagnetically, while antiferromagnetic ordering is observed for NdLiGe(2) and EuLiGe(2). The calculated effective magnetic moments confirm RE(3+) ground states in all cases excluding EuLiGe(2), in which the magnetic response is consistent with Eu(2+) configuration (J = S = 7/2). The experimental results have been complemented by tight-binding linear muffin-tin orbital (TB-LMTO) band structure calculations.     

Structure and physical properties of ternary rare-earth cobalt bismuth intermetallics (RE)12Co5Bi (RE = Y, Gd, Tb, Dy, Ho, Er, Tm)

The rare-earth intermetallic compounds (RE)12Co5Bi (RE = Y, Gd, Tb, Dy, Ho, Er, Tm) were prepared by arc-melting and annealing at 600 degrees C. These compounds extend the previously known (RE)6M2+xX1-x (M = Co, Ni; X = Ga, In, Sn, Pb) series with the Ho6Co2Ga-type structure to X = Bi. The crystal structure of Ho12Co5Bi was refined by the Rietveld method from powder X-ray diffraction data obtained using synchrotron radiation (Pearson symbol oI36, orthorhombic, space group Immm, Z = 2, a = 9.37598(14) A, b = 9.37871(14) A, c = 9.85465(13) A). Unlike other Ho6Co2Ga-type compounds, the 2a site in Ho12Co5Bi is exclusively occupied by Co atoms. Four-probe electrical resistivity measurements on sintered polycrystalline samples of (RE)12Co5Bi indicated metallic behavior. Magnetic measurements revealed behavior ranging from frequency-dependent maxima in the ac susceptibility for Y12Co5Bi to possible ferrimagnetic ordering for Gd12Co5Bi to antiferromagnetic ordering with metamagnetic transitions for the remaining compounds. As confirmed by band structure calculations using Y12Co5Bi as a model compound, Y-Y and Y-Co interactions are the most important bonding components, but matrix effects are likely responsible for anomalously short Co-Co contacts in the structure.     

Layered rare-earth gallium antimonides REGaSb(2) (RE = La--Nd, Sm).

The ternary rare-earth gallium antimonides, REGaSb(2) (RE = La--Nd, Sm), have been synthesized through reaction of the elements. The structures of SmGaSb(2) (orthorhombic, space group D(5)(2)-C222(1), Z = 4, a = 4.3087(5) A, b = 22.093(4) A, c = 4.3319(4) A) and NdGaSb(2) (tetragonal, space group D(19)(4h)-I4(1)/amd, Z = 8, a = 4.3486(3) A, c = 44.579(8) A) have been determined by single-crystal X-ray diffraction. The SmGaSb(2)-type structure is adopted for RE = La and Sm, whereas the NdGaSb(2)-type structure is adopted for RE = Ce--Nd. The layered SmGaSb(2) and NdGaSb(2) structures are stacking variants of each other. In both structures, two-dimensional layers of composition (2)(infinity)[GaSb] are separated from square nets of Sb atoms [Sb] by RE atoms. Alternatively, the structures may be considered as resulting from the insertion of zigzag Ga chains between (2)(infinity)[RE Sb(2)] slabs. In SmGaSb(2), all of the Ga chains are parallel and the (2)(infinity)[SmSb(2)] layers are stacked in a ZrSi(2)-type arrangement. In NdGaSb(2), the Ga chains alternate in direction, resulting in a doubling of the long axis relative to SmGaSb(2), and the (2)(infinity)[NdSb(2)] layers are stacked in a Zr(3)Al(4)Si(5)-type arrangement. Extended Hückel band structure calculations are used to explain the bonding in the [GaSb(2)](3-) substructure.     

Closely related rare-earth metal germanides RE2Li2Ge3 and RE3Li4Ge4 (RE = La-Nd, Sm): synthesis, crystal chemistry, and magnetic properties

Reported are the syntheses, crystal structures, and magnetic susceptibilities of two series of closely related rare-earth metal-lithium germanides RE(2)Li(2)Ge(3) and RE(3)Li(4)Ge(4) (RE = La-Nd, Sm). All title compounds have been synthesized by reactions of the corresponding elements at high temperatures, and their structures have been established by single-crystal X-ray diffraction. RE(2)Li(2)Ge(3) phases crystallize in the orthorhombic space group Cmcm (No. 63) with the Ce(2)Li(2)Ge(3) structure type, while the RE(3)Li(4)Ge(4) phases crystallize in the orthorhombic space group Immm (No. 71) with the Zr(3)Cu(4)Si(4) structure type, respectively. Both of their structures can be recognized as the intergrowths of MgAl(2)Cu- and AlB(2)-like slabs, and these traits of the crystal chemistry are discussed. Temperature-dependent direct-current magnetization measurements indicate Curie-Weiss paramagnetism in the high-temperature regime for RE(2)Li(2)Ge(3) and RE(3)Li(4)Ge(4) (RE = Ce, Pr, Nd), while Sm(2)Li(2)Ge(3) and Sm(3)Li(4)Ge(4) exhibit Van Vleck-type paramagnetism. The data are consistent with the local-moment magnetism expected for RE(3+) ground states. At temperatures below ca. 20 K, magnetic ordering transitions have been observed. The experimental results have been complemented by tight-binding linear muffin-tin orbital electronic-band-structure calculations.     

Hydrothermal preparation,structures, and NLO properties of the rare earth molybdenyl iodates,RE(MoO2)(IO3)4(OH) [RE = Nd,Sm, Eu

The reactions of RE(IO3)3 [RE = Nd, Sm, Eu] with I2O5 and MoO3 in a 1:2:2 molar ratio at 200 degrees C in aqueous media provide access to RE(MoO2)(IO3)4(OH) [RE = Nd (1), Sm (2), Eu (3)] as pure phases as determined from powder X-ray diffraction data. Single crystal X-ray diffraction experiments demonstrate that these compounds are isostructural and crystallize in the chiral and polar space group P2(1). The structures are composed of three-dimensional networks formed from eight-coordinate, square antiprismatic RE3+ cations and MoO2(OH)+ moieties that are bound by bridging iodate anions. The Mo(VI) centers are present in distorted octahedral environments composed of two cis-oxo atoms, a hydroxo group, and three bridging iodate anions arranged in a fac geometry. There are four crystallographically unique iodate anions in the structures of 1-3, one of these is actually present in the form of a IO3+1 polyhedron where a short interaction of 2.285(4) A is formed between the iodate anion and the hydroxo group bound to the Mo(VI) center. This interaction results in significant distortions of the iodate anion similar to those found in tellurites with TeO3+1 units. Two of the four iodate anions are aligned along the polar b-axis, imparting the required polarity to these compounds. Second-harmonic generation (SHG) measurements on sieved powders of 1 show a response of 350 x alpha-quartz. Crystallographic data: 1, monoclinic, space group P2(1), a = 6.9383(5) A, b = 14.0279(9) A, c = 7.0397(5) A, beta = 114.890(1) degrees, Z = 2; 2, monoclinic, space group P2(1), a = 6.9243(6) A, b = 13.963(1) A, c = 7.0229(6) A, beta = 114.681(1) degrees, Z = 2; 3, monoclinic, space group P2(1), a = 6.9169(6) A, b = 13.943(1) A, c = 7.0170(6) A, beta = 114.542(1) degrees, Z = 2.     

Structures and physical properties of rare-earth zinc antimonides Pr6Zn(1+x)Sb(14+y) and RE6Zn(1+x)Sb14 (RE = Sm, Gd-Ho)

A new series of isostructural ternary rare-earth zinc antimonides RE(6)Zn(1+x)Sb(14+y) (RE = Pr, Sm, Gd-Ho) has been obtained by direct reaction of the elements at 1050-1100 degrees C. Single-crystal X-ray diffraction studies revealed that these compounds adopt an orthorhombic structure type (space group Immm (no. 71), Z = 2, a = 4.28-4.11 A, b = 15.15-14.73 A, c = 19.13-18.56 A in the progression from RE = Pr to Ho) that may be regarded as stuffed variants of a (U(0.5)Ho(0.5))(3)Sb(7)-type host structure. Columns of face-sharing RE(6) trigonal prisms, centered by Sb atoms, occupy channels defined by an extensive polyanionic Sb network. This network is constructed from three-atom-wide and four-atom-wide Sb strips, the latter being linked together by single Sb atoms in RE(6)Zn(1+x)Sb(14) (RE = Sm, Gd-Ho; y = 0), but also by additional Sb-Sb pairs in a disordered fashion in Pr(6)Zn(1+x)Sb(14+y) (y = approximately 0.6). Interstitial Zn atoms then partially fill tetrahedral sites (occupancy of 0.5-0.7) and, to a lesser extent, square pyramidal sites (occupancy of 0.04-0.12), accounting for the observed nonstoichiometry with variable x. Except for the Gd member, these compounds undergo antiferromagnetic ordering below T(N) < 9 K, with the magnetic susceptibilities of the Tb, Dy, and Ho members following the Curie-Weiss law above T(N). For the Ho member, the thermal conductivities are low and the Seebeck coefficients are small and positive, implying p-type character consistent with the occurrence of partial Zn occupancies. At low temperatures (down to 5 K), electrical resistivity measurements for the Tb, Dy, and Ho members indicated metallic behavior, which persists at high temperatures (up to 560 K) for the Ho member. Band structure calculations on an idealized "Gd(6)Zn(2)Sb(14)" model revealed the existence of a pseudogap near the Fermi level.     

Polygallide RE2MGa9Ge2 (RE = Ce, Sm; M = Ni, Co) phases grown in molten gallium

The quaternary intermetallics Ce2CoGa9Ge2, Ce2NiGa9Ge2, and Sm2NiGa9Ge2 were prepared by reacting elemental metals in excess of gallium at 850 degrees C. The title compounds crystallize in the tetragonal space group P4/nmm in the Sm2Ni(Si(1-x)Ni(x))Al4Si6 structure type with cell parameters a = 5.9582(5) A, c = 15.0137(18) A, and a = 5.9082(17) A, c = 14.919(6) A, Z = 2, for Ce2CoGa9Ge2 and Sm2NiGa9Ge2, respectively. The structures are composed of covalently bonded three-dimensional networks of [CoGa9Ge2] in which the rare-earth metals fill the voids forming a 2D square net. The structures of RE2MGa9Ge2 are Ga-rich and possess extensive Ga-Ga bonding even though the Ga atoms do not form a network on their own. Magnetic susceptibility measurements for Ce2CoGa9Ge2 and Ce2NiGa9Ge2 show Curie-Weiss paramagnetism, consistent with presence of Ce(3+) ions. Magnetocrystalline anisotropy was observed for Ce2NiGa9Ge2, with the magnetically easy axis lying along the [001] crystallographic direction. A transition to an antiferromagnetic state was observed below 4 K in the easy direction of magnetization. In the magnetically hard direction of the basal plane, paramagnetic behavior was observed down to 1.8 K.     

Structure and properties of Gd3Ge4: the orthorhombic RE3Ge4 structures revisited (RE = Y, Tb-Tm)

The new binary compound Gd(3)Ge(4) has been synthesized and its structure has been determined from single-crystal X-ray diffraction. Gd(3)Ge(4) crystallizes in the orthorhombic space group Cmcm (No. 63) with unit cell parameters a = 4.0953(11) A, b = 10.735(3) A, c = 14.335(4) A, and Z = 4. Its structure can be described as corrugated layers of germanium atoms with gadolinium atoms enclosed between them. The bonding arrangement in Gd(3)Ge(4) can also be derived from that of the known compound GdGe (CrB type) through cleavage of the (infinity)(1)[Ge(2)] zigzag chains in GdGe and a subsequent insertion of an extra germanium atom between the resulting triangular fragments. Formally, these characteristics represent isotypism with the Er(3)Ge(4) type (Pearson's oC28). However, re-examination of the crystallography in the whole RE(3)Ge(4) series (RE = Y, Tb-Tm) revealed discrepancies and called into question the accuracy of the originally determined structures. This necessitated a new rationalization of the bonding, which is provided in the context of a comparative discussion concerning both the original and revised structure models, along with an analysis of the trends across the series. The temperature dependence of the magnetic susceptibility of Gd(3)Ge(4) shows that it is paramagnetic at room temperature and undergoes antiferromagnetic ordering below 29 K. Magnetization, resistivity, and calorimetry data for several other members of the RE(3)Ge(4) family are presented as well.     

Chemical Manipulation of Magnetic Ordering in Mn(1-x)Sn(x)Bi(2)Se(4) Solid-Solutions

Several compositions of manganese-tin-bismuth selenide solid-solution series, Mn(1-x)Sn(x)Bi(2)Se(4) (x = 0, 0.3, 0.75), were synthesized by combining high purity elements in the desired ratio at moderate temperatures. X-ray single crystal studies of a Mn-rich composition (x = 0) and a Mn-poor phase (x = 0.75) at 100 and 300 K revealed that the compounds crystallize isostructurally in the monoclinic space group C2/m (no.12) and adopt the MnSb(2)Se(4) structure type. Direct current (DC) magnetic susceptibility measurements in the temperature range from 2 to 300 K indicated that the dominant magnetic ordering within the Mn(1-x)Sn(x)Bi(2)Se(4) solid-solutions below 50 K switches from antiferromagnetic (AFM) for MnBi(2)Se(4) (x = 0), to ferromagnetic (FM) for Mn(0.7)Sn(0.3)Bi(2)Se(4) (x = 0.3), and finally to paramagnetic (PM) for Mn(0.25)Sn(0.75)Bi(2)Se(4) (x = 0.75). We show that this striking variation in the nature of magnetic ordering within the Mn(1-x)Sn(x)Bi(2)Se(4) solid-solution series can be rationalized by taking into account: (1) changes in the distribution of magnetic centers within the structure arising from the Mn to Sn substitutions, (2) the contributions of spin-polarized free charge carriers resulting from the intermixing of Mn and Sn within the same crystallographic site, and (3) a possible long-range ordering of Mn and Sn atoms within individual {M}(n)Se(4n+2) single chain leading to quasi isolated {MnSe(6)} octahedra spaced by nonmagnetic {SnSe(6)} octahedra.     

New layered germanide halides RE2GeX2 (RE = Y, Gd; X = Br, I)

The title compounds were synthesized from RE, REX3, and Ge under an Ar atmosphere at 1200-1370 K. Y2GeI2 and Gd2GeI2 crystallize in space group Rm with lattice constants a = 4.2135(3) and 4.2527(1) A and c = 31.480(2) and 31.657(1) A, respectively. Gd2GeBr2 crystallizes in two modifications, the 1T-type (space group Pm1; a = 4.1668(2) A, c = 9.8173(6) A) and the 3R-type (space group Rm; a = 4.1442(9) A, c = 29.487(7) A). The structural motifs of RE2GeX2 compounds are Ge-centered slightly distorted RE6 octahedra connected via their common edges and extending in the a and b directions. The resulting close-packed double layers are separated by halogen atoms. The electrical resistivity measurements revealed semiconductor behavior for Y2GeI2 and Gd2GeI2 and a metal-semiconductor transition for 1T-Gd2GeBr2. Magnetic susceptibility and heat capacity measurements show long-range magnetic ordering for Gd2GeI2 and 1T-Gd2GeBr2 at approximately 15 and approximately 13 K, respectively.     

REMGa3Ge and RE3Ni3Ga8Ge3 (M = Ni, Co; RE = rare-earth element): new intermetallics synthesized in liquid gallium. X-ray, electron, and neutron structure determination and magnetism

New quaternary intermetallic phases REMGa(3)Ge (1) (RE = Y, Sm, Tb, Gd, Er, Tm; M = Ni, Co) and RE(3)Ni(3)Ga(8)Ge(3) (2) (RE = Sm, Gd) were obtained from exploratory reactions involving rare-earth elements (RE), transition metal (M), Ge, and excess liquid Ga the reactive solvent. The crystal structures were solved with single-crystal X-ray and electron diffraction. The crystals of 1 and 2 are tetragonal. Single-crystal X-ray data: YNiGa(3)Ge, a = 4.1748(10) A, c = 23.710(8) A, V = 413.24(2) A(3), I4/mmm, Z = 4; Gd(3)Ni(3)Ga(8)Ge(3), a = 4.1809(18) A, c = 17.035(11) A, V = 297.8(3) A(3), P4/mmm, Z = 1. Both compounds feature square nets of Ga atoms. The distribution of Ga and Ge atoms in the REMGa(3)Ge was determined with neutron diffraction. The neutron experiments revealed that in 1 the Ge atoms are specifically located at the 4e crystallographic site, while Ga atoms are at 4d and 8g. The crystal structures of these compounds are related and could be derived from the consecutive stacking of disordered [MGa](2) puckered layers, monatomic RE-Ge planes and [MGa(4)Ge(2)] slabs. Complex superstructures with modulations occurring in the ab-plane and believed to be associated with the square nets of Ga atoms were found by electron diffraction. The magnetic measurements show antiferromagnetic ordering of the moments located on the RE atoms at low temperature, and Curie-Weiss behavior at higher temperatures with the values of mu(eff) close to those expected for RE(3+) free ions.     

Synthesis and Crystal Structure of a One-dimensional Azido-bridged Manganese (II) Compound [Mn(N_3)_2(H_2O)_3·C_6H_(12)N_4]_n

1 INTRODUCTION The azide anion is a good bridging ligand for di- valent metal ions to form discrete, one-dimensional, two-dimensional or three-dimensional complexes. In recent years, these complexes have drawn consider- able attentions for their interesting magnetic charace- ristics which attribute to the efficient magnetic coup- ling ability of the azido bridges[1]. When the azide anion acts as a bridging ligand, two typical modes are adopted: end-to-end (EE, μ1, 3) or end-on (EO, μ1…     

RE(Et2dtc)3(phen)(RE=La，Pr，Nd，Sm)的恒容燃烧能测定(英)

Four ternary solid complexes were synthesized with sodium diethyldithiocarbamate (NaEt₂dtc)(b), 1,10-phenanthroline (o-phen) (c) and hydrated lanthanide chlorides in absolute ethanol by an improved reported method. The complexes were identified as the general formula of RE(Et₂dtc)₃(phen) (RE=La, Pr, Nd, Sm) by chemical and elemental analyses. IR spectra of the complexes showed that the RE³⁺ was coordinated with sulfur atoms of NaEt₂dtc and nitrogen atoms of o-phen. The constant-volume combustion energies of complexes, Δ_cU, were determined by a precise rotating-bomb calorimeter at 298.15 K. The standard enthalpies of combustion, Δ_cH_m^?, and standard enthalpies of formation, Δ_fH_m^?, were calculated for these complexes, respectively.     

Cubic aluminum silicides RE8Ru12Al49Si9(Al(x)Si12-x) (RE = Pr, Sm) from liquid aluminum. Empty (Si,Al)12 cuboctahedral clusters and assignment of the Al/Si distribution with neutron diffraction.

Two new quaternary aluminum silicides, RE8Ru12Al49Si9(Al(x)Si12-x) (x approximately 4; RE = Pr, Sm), have been synthesized from Sm (or Sm2O3), Pr, Ru, and Si in molten aluminum between 800 and 1000 degrees C in sealed fused silica tubes. Both compounds form black shiny crystals that are stable in air and NaOH. The Nd analog is also stable. The compounds crystallize in a new structural type. The structure, determined by single-crystal X-ray diffraction, is cubic, space group Pm3m with Z = 1, and has lattice parameters of a = 11.510(1) A for Sm8Ru12Al49Si9(Al(x)Si12-x) and a = 11.553(2) A for Pr8Ru12Al49Si9(Al(x)Si12-x) (x approximately 4). The structure consists of octahedral units of AlSi6, at the cell center, Si2Ru4Al8 clusters, at each face center, SiAl8 cubes, at the middle of the cell edges, and unique (Al,Si)12 cuboctohedral clusters, at the cell corners. These different structural units are connected to each other either by shared atoms, Al-Al bonds, or Al-Ru bonds. The rare earth metal atoms fill the space between various structural units. The Al/Si distribution was verified by single-crystal neutron diffraction studies conducted on Pr8Ru12Al49Si9(Al(x)Si12-x). Sm8Ru12Al49Si9(Al(x)Si12-x) and Pr8Ru12Al49Si9(Al(x)Si12-x) show ferromagnetic ordering at Tc approximately 10 and approximately 20 K, respectively. A charge of 3+ can be assigned to the rare earth atoms while the Ru atoms are diamagnetic.     

Synthesis, crystal chemistry, and magnetic properties of RE7Li8Ge10 and RE11Li12Ge16 (RE = La-Nd, Sm): new members of the [REGe2](n)[RELi2Ge](m) homologous series

Eight new rare-earth metal-lithium-germanides belonging to the [REGe(2)](n)[RELi(2)Ge](m) homologous series have been synthesized and structurally characterized by single-crystal X-ray diffraction. The structures of the title compounds can be rationalized as linear intergrowths of imaginary RELi(2)Ge (MgAl(2)Cu structure type) and REGe(2) (AlB(2) structure type) slabs. The compounds with general formula RE(7)Li(8)Ge(10) (RE = La-Nd, Sm), i.e., [REGe(2)](3)[RELi(2)Ge](4), crystallize in the orthorhombic space group Cmmm (No. 65) with a new structure type. Similarly, the compounds with general formula RE(11)Li(12)Ge(16) (RE = Ce-Nd), i.e., [REGe(2)](5)[RELi(2)Ge](6), crystallize in the orthorhombic space group Immm (No. 71) also with its own structure type. Temperature-dependent DC magnetization measurements indicate Curie-Weiss paramagnetism in the high-temperature regime and hint at complex magnetic ordering at low temperatures. The measured effective moments are consistent with RE(3+) ground states in all cases. The experimental results have been complemented by tight-binding linear muffin-tin orbital (TB-LMTO) electronic structure calculations.     

Ternary Rare Earth (RE) Gold Compounds REAuCd and RE2Au2Cd

New intermetallic rare earth compounds REAuCd (RE = Y, La–Nd, Sm–Yb) and RE₂Au₂Cd (RE = La, Pr, Nd, Sm) were prepared by reaction of the elements in sealed tantalum tubes in a high‐frequency furnace. The compounds were investigated by X‐ray diffraction both on powders and single crystals. The equiatomic REAuCd compounds with RE = Y, La–Nd, Sm, and Gd–Tm adopt the ZrNiAl type structure with space group P62m. Single crystal X‐ray data yielded a = 786.2(2), c = 415.9(1) pm, wR2 = 0.0337, 402 F² values for LaAuCd and a = 782.91(9), c = 410.01(5) pm, wR2 = 0.0653, 395 F² values for CeAuCd with 14 parameters for each refinement. Geometrical motifs in CeAuCd are two types of gold centered tricapped trigonal prisms: [Au1Cd₃Ce₆] and [Au2Cd₆Ce₃]. The gold and cadmium atoms form a three‐dimensional [AuCd] polyanion in which the cerium atoms fill distorted hexagonal channels. EuAuCd and YbAuCd crystallize with a TiNiSi type structure, space group Pnma: a = 755.2(1), b = 450.59(5), c = 878.6(1) pm, wR2 = 0.0904, 500 F² values for EuAuCd, and a = 731.64(3), b = 432.94(2), c = 875.80(4) pm, wR2 = 0.1192, 457 F² values for YbAuCd with 20 parameters for each refinement. In these structures the europium(ytterbium) and cadmium atoms form zig‐zag chains of egde‐ and face‐sharing trigonal prisms which are centered by the gold atoms. Also in EuAuCd and YbAuCd a three‐dimensional [AuCd] polyanion occurs in which the europium(ytterbium) atoms are embedded. Europium and ytterbium are divalent in EuAuCd and YbAuCd. Susceptibility measurements show Pauli paramagnetism for YbAuCd and Curie‐Weiss behavior above 100 K for EuAuCd with an experimental magnetic moment of 7.86(6) μ_B/Eu. Ferromagnetic ordering is detected at 28 K. The saturation magnetic moment is 7.1(1) μ_B/Eu at 1.9 K. ¹⁵¹Eu Mössbauer spectra show an isomer shift of –9.2(2) mm/s and full magnetic hyperfine field splitting at 4.2 K with an internal hyperfine field of 19.5(4) T at the europium nuclei. The RE₂Au₂Cd compounds crystallize with the Mo₂FeB₂ structure, a ternary ordered version of the U₃Si₂ type. These structures may be considered as an intergrowth of distorted CsCl and AlB₂ related slabs of compositions RECd and REAu₂. Chemical bonding in REAuCd and RE₂Au₂Cd is briefly discussed.     

Formation of gallium dimers in the intermetallic compounds R(5)Ga(3) (R = Sc, Y, Ho, Er, Tm, Lu). Deformation of the Mn(5)Si(3)-type structure

The R(5)Ga(3) (R = Sc, Y, Ho, Er, Tm, Lu) phases were prepared by high-temperature solid-state techniques. The structure of monoclinic Sc(5)Ga(3) was determined by single-crystal X-ray diffraction means (C2/m, No. 12, Z = 4, a = 8.0793(5) A, b = 14.003(1) A, c = 5.9297(3) A, beta = 90.994(5) degrees ), and those of the isotypic R(5)Ga(3), R = Y, Ho, Er, Tm, Lu, were determined by Guinier powder diffraction. The new Sc(5)Ga(3) structure is a deformation of the hexagonal Mn(5)Si(3) type (P6(3)/mcm) and contains two types of gallium dimers with d(Ga-Ga) = 2.91 and 3.14 A. The closely spaced Sc1 chains in the parent Mn(5)Si(3) type transform to zigzag chains in concert with displacements of the uniformly spaced gallium atoms to form dimers within distorted confacial square antiprisms of Sc. Matrix effects appear important in the different Ga(2) bond lengths. Electronic calculations reveal that the transformation from the hypothetical Mn(5)Si(3) to the Sc(5)Ga(3) type is aided by antibonding Ga-Ga interactions between the dimers that are pushed above E(F) and Ga-Ga and Ga-Sc bonding states just below E(F) that are stabilized. Sc(5)Ga(3) is appropriately metallic. Except for R = Sc, Lu, the arc-melted R(5)Ga(3) compounds above slowly transform on annealing at 1150 degrees C and below into tetragonal Ba(5)Si(3)-type structures.     

Two series of novel rare earth complexes with dicyanamide [Ln(dca)2(phen)2(H2O)3][dca].(phen), (Ln = Pr, Gd, and Sm) and [Ln(dca)3(2,2'-bipy)2(H2O)]n, (Ln = Gd, Sm, and La): syntheses, crystal structures, and magnetic properties

Two series of novel complexes, [Ln(dca)(2)(Phen)(2)(H(2)O)(3)](dca).(phen) (Ln = Pr (1), Gd (2), and Sm (3), dca = N(CN)(-), phen = 1,10-phenanthroline) and [Ln(dca)(3)(2,2'-bipy)(2)(H(2)O)](n), (Ln = Gd (4), Sm (5), and La (6), 2,2'-bipy = 2,2'-bipydine), have been synthesized and structurally characterized by X-ray crystallography. The crystal structures of the first series (1-3) are isomorphous and consist of discrete [Ln(dca)(2)(Phen)(2)(H(2)O)(3)]+ cations, dca anions, and lattice phen molecules; whereas the structures of the second series (4-6) are characterized by infinite chains [Ln(dca)(3)(2,2'-bipy)(2)(H(2)O)](n). The Ln(III) atoms in all complexes are nine-coordinated and form a distorted tricapped trigonal prism environment. The three-dimensional frameworks of 1-6 are constructed by intermolecular hydrogen bond interactions. Variable-temperature magnetic susceptibility measurements for complexes 1, 2, 4, and 5 indicate a Curie-Weiss paramagnetic behavior over 5-300 K.