Preparation and Crystal Structure of Rare Earth Rhenates: the Series Ln5Re2O12 with Ln = Y,Gd–Lu,and the Praseodymium Rhenates Pr3ReO8, Pr3Re2O10, and Pr4Re2O11

The crystal structure of the known compounds Ln₅Re₂O₁₂ (Ln = Y, Gd, Dy–Lu) and the new isotypic terbium rhenate Tb₅Re₂O₁₂ was determined from X‐ray data of a twinned crystal of Ho₅Re₂O₁₂: B2/m, a = 1236.5(4) pm, b = 748.2(2) pm, c = 563.8(1) pm, γ = 107.73(3)°, Z = 2, R = 0.034 for 379 structure factors and 37 variable parameters. The rhenium atoms (oxidation number +4.5) have octahedral oxygen coordination. These ReO₆ octahedra share edges, thus forming infinite strings with alternating short and long Re–Re distances: 243.6(2) and 320.1(2) pm. Of the three holmium positions two are surrounded by seven oxygen atoms and the third one has octahedral oxygen coordination. The crystal structure of Pr₃ReO₈ was refined from single‐crystal X‐ray data: P2₁/a, a = 1498.0(2) pm, b = 749.09(8) pm, c = 610.48(9) pm, γ = 110.39(1)°, R = 0.017 for 2082 F values and 110 variable parameters. It is isotypic with a structure first determined for Sm₃ReO₈. The new compounds Pr₃Re₂O₁₀ and Pr₄Re₂O₁₁ were prepared by reaction of elemental praseodymium with the metaperrhenate Pr(ReO₄)₃. They were characterized through their X‐ray powder diagrams. Pr₃Re₂O₁₀ was found to be monoclinic: a = 778.47(9) pm, b = 773.62(9) pm, c = 706.10(8) pm, β = 114.77(1)°. It is isotypic with La₃Os₂O₁₀ and La₃Re₂O₁₀. Pr₄Re₂O₁₁ crystallizes with Nd₄Re₂O₁₁ type structure with the tetragonal lattice constants a = 1272.49(3) pm, c = 562.29(2) pm. The compounds Nd₄Re₂O₁₁ and Sm₄Re₂O₁₁ are confirmed. The magnetic properties of Ho₅Re₂O₁₂, Tb₅Re₂O₁₂, Pr₃Re₂O₁₀, Pr₄Re₂O₁₁, Nd₄Re₂O₁₁, and Sm₄Re₂O₁₁ were investigated with a Faraday balance. None of these compounds shows magnetic order above 200 K.     

Investigations of the magnetic properties and structures of the pillared perovskites, La5Re3MO16 (M=Co, Ni)

La₅Re₃CoO₁₆ and La₅Re₃NiO₁₆ were synthesized by solid-state reaction and studied by SQUID magnetometry, heat capacity and powder neutron diffraction measurements. These two compounds belong to a series of isostructural Re-based pillared perovskites [Chi et al. J. Solid State Chem. 170 (2003) 165]. Magnetic susceptibility measurements indicate apparent short-range ferri or ferromagnetic correlations and possible long-range antiferromagnetic order for La₅Re₃CoO₁₆ at 35 K, and at 38 and 14 K for La₅Re₃NiO₁₆. Heat capacity measurements of the Co compound show a lambda anomaly, typical of long-range magnetic order, at 32 K. In contrast, the Ni compound displays a broader, more symmetric feature at 12 K in the heat capacity data, indicative of short-range magnetic order. Low-temperature powder neutron diffraction revealed contrasting magnetic structures. While both show an ordering wave vector, k=(0,0,1/2), in La₅Re₃CoO₁₆, the Co²⁺ and Re⁵⁺ moments are ordered ferrimagnetically within the corner-shared octahedral layers, while the layers themselves are coupled antiferromagnetically along the c-axis, as also found in La₅Re₃MnO₁₆ and La₅Re₃FeO₁₆. In the case of the Ni material, the Re⁵⁺ and Ni²⁺ moments in the perovskite layers couple ferromagnetically and are canted 30° away from the c-axis, angled 45° in the ab-plane. The layers then couple antiferromagnetically at low temperature, a unique magnetic structure for this series. The properties of the La₅Re₃MO₁₆ series, with M=Mn, Fe, Co, Ni and Mg are also reviewed.     

An investigation of polyhedral deformation in two mixed‐metal diarsenates: SrZnAs2O7 and BaCuAs2O7

Two isostructural diarsenates, SrZnAs₂O₇ (strontium zinc diarsenate), (I), and BaCuAs₂O₇ [barium copper(II) diarsenate], (II), have been synthesized under hydrothermal conditions and characterized by single‐crystal X‐ray diffraction. The three‐dimensional open‐framework crystal structure consists of corner‐sharing M2O₅ (M2 = Zn or Cu) square pyramids and diarsenate (As₂O₇) groups. Each As₂O₇ group shares its five corners with five different M2O₅ square pyramids. The resulting framework delimits two types of tunnels aligned parallel to the [010] and [100] directions where the large divalent nine‐coordinated M1 (M1 = Sr or Ba) cations are located. The geometrical characteristics of the M1O₉, M2O₅ and As₂O₇ groups of known isostructural diarsenates, adopting the general formula M1^IIM2^IIAs₂O₇ (M1^II = Sr, Ba, Pb; M2^II = Mg, Co, Cu, Zn) and crystallizing in the space group P2₁/n, are presented and discussed.     

Preparation and Crystal Structure of the Ternary Lanthanoid Nickel Arsenides Ln13Ni25As19 (Ln = Tm,Yb, and Lu)

The title compounds were prepared by reaction of the elemental components at high temperatures. They crystallize with a new structure type which was determined from single‐crystal X‐ray data of Tm₁₃Ni₂₅As₁₉: P 6, a = 1621.9(4) pm, c = 387.78(8) pm, Z = 1, R = 0.025 for 3164 structure factors and 119 variable parameters. The refinement of the occupancy parameters suggested a mixed Tm/Ni occupancy for one metal position and defects for one nickel site resulting in the composition Tm_12.57(1)Ni_25.22(2)As₁₉. These arsenides belong to a large structural family with a metal to metalloid ratio of 2 : 1.     

Ternary MIn2S4 (M = Mn,Fe, Co,Ni) Thiospinels – Crystal Structure and Thermoelectric Properties

A combined structural, magnetic and thermoelectric study of polycrystalline ternary MIn₂S₄ (M = Mn, Fe, Co, Ni) thiospinels is presented. All compounds crystallize with MgAl₂O₄-type structure. Rietveld refinement analysis confirmed that the preferred crystallographic position of transition metal element changes from mainly tetrahedral 8a for Mn to exclusively octahedral 16d for Ni (i.e. increase of the inversion parameter). Magnetic susceptibility measurements revealed M-elements to possess 2+ oxidation state in MIn₂S₄. All these compounds order antiferromagnetically with Néel temperatures T_N ranging from 5–13 K. The studied thiospinels are n-type semiconductors with large values of electrical resistivity ρ > 0.6 Ω · m at room temperature. An increase of the inversion parameter leads to a reduction of the determined activation energies, as well as to a more disorder-like behavior of thermal conductivity. The highest thermoelectric Figure of merit ZT was observed for MIn₂S₄ with M = Fe, Ni, which adopt inverse spinel structure.     

Synthesis, structure and magnetic properties of the pillared perovskites La5Re3MO16(M=Mg, Fe, Co, Ni)

Four new compounds La₅Re₃MgO₁₆ La₅Re₃FeO₁₆ La₅Re₃CoO₁₆ La₅Re₃NiO₁₆ have been prepared by solid-state reaction and characterized by X-ray and neutron powder diffraction and SQUID magnetometry. Rietveld refinement revealed that the four compounds are isostructural with La₅Re₃MnO₁₆ and crystallize in space group with cell parameters a=7.9370(3), 7.9553(5), 7.9694(7), and 7.9383(4) Å; b=7.9998(3), 7.9960(6), 8.0071(8), and 7.9983(5) Å; c=10.1729(4), 10.1895(7), 10.182(1), and 10.1732(6) Å; α=90.190(3)°, 90.270(3)°, 90.248(4) °, 90.287(3)°; β=94.886(2)°, 95.082(3)°, 94.980(4)°, 94.864(3)°; γ=89.971(4)°, 90.001(5)°, 89.983(6)°, 89.968(4)° for Mg, Fe, Co, and Ni, respectively. The structures are related to a layered perovskite. The layers of corner-sharing octahedra Re⁵⁺M²⁺O₆ (M²⁺=Mg, Fe, Co, Ni) are pillared by diamagnetic edge-sharing octahedra dimers, Re₂O₁₀, involving a Re=Re double bond. Three crystallographically independent lanthanum atoms occupy the three-dimensional interstices. All compounds obey the Curie-Weiss law at sufficiently high temperatures with Curie constants or effective magnetic moments near the expected values for the combination of Re⁵⁺(S=1) and M²⁺(S=0, 2, 3/2, 1 for Mg, Fe, Co, and Ni, respectively). Weiss constants, θ_C, are negative (−575, −84, −71, and −217 K for Mg, Fe, Co, and Ni, respectively) indicating the predominance of antiferromagnetic exchange coupling. The phases for M=Fe, Co and Ni show long-range order at 155, 33, 36 and 14 K, respectively. Neutron diffraction discloses a magnetic structure for the Fe series member consisting of ferrimagnetic perovskite layers coupled antiparallel along the stacking c-axis, direction which is consistent with the magnetic structure found recently for La₅Re₃MnO₁₆.     

Ternary K2Zn5As4‐type pnictides Rb2Cd5As4 and Rb2Zn5Sb4, and the solid solution Rb2Cd5(As,Sb)4

Dirubidium pentacadmium tetraarsenide, Rb₂Cd₅As₄, dirubidium pentazinc tetraantimonide, Rb₂Zn₅Sb₄, and the solid‐solution phase dirubidium pentacadmium tetra(arsenide/antimonide), Rb₂Cd₅(As,Sb)₄ [or Rb₂Cd₅As_3.00(1)Sb_1.00(1)], have been prepared by direct reaction of the component elements at high temperature. These compounds are charge‐balanced Zintl phases and adopt the orthorhombic K₂Zn₅As₄‐type structure (Pearson symbol oC44), featuring a three‐dimensional [M₅Pn₄]²⁻ framework [M = Zn or Cd; Pn is a pnicogen or Group 15 (Group V) element] built of linked MPn₄ tetrahedra, and large channels extending along the b axis which host Rb⁺ cations. The As and Sb atoms in Rb₂Cd₅(As,Sb)₄ are randomly disordered over the two available pnicogen sites. Band‐structure calculations predict that Rb₂Cd₅As₄ is a small‐band‐gap semiconductor and Rb₂Zn₅Sb₄ is a semimetal.     

Strukturelle Übergänge zwischen Phosphiden,Arseniden und Arsenophosphiden der ZusammensetzungM 2P,M 2As undM 2(P1—xAsx)

Zusammenfassung Phasen der ZusammensetzungM ₂P,M ₂As undM ₂(P_1-xAs_x) wurden untersucht. Dabei istM ein Übergangsmetall (M=Cr, Mn, Fe, Co, Ni) oder ein Gemisch solcher Metalle. Es treten tetragonale, hexagonale sowie orthorhombische Strukturtypen auf, die sich alle auf ein rhomboedrisches Grundelement zurückführen lassen, in dem die Metallatome pyramidal oder tetraedrisch von Metalloidatomen umgeben sind. Dabei zeigt sich, daß das Auftreten der Strukturen nicht mit der mittleren Zahl der 3d-Elektronen des Kationenanteils zusammenhängt. Ein Strukturwechsel tetragonal hexagonal orthorhombisch läßt sich hingegen auf steigende Wechselwirkung zwischen den Metallatomen zurückführen.

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Structural transitions between phosphides, arsenides and arsenophoshides of the composition M₂ P, M₂ As and M₂(P _1—xAs_x)

A study has been made of phases of the compositionM ₂P,M ₂As, andM ₂(P_1-xAs_x) whereM is a transition metal (Cr, Mn, Fe, Co, Ni) or a mixture of such metals. Tetragonal, hexagonal and orthorhombic structural types occur, which can all be referred to a rhombohedral primary structure, with metalloid atoms in a pyramidal or tetrahedral arrangement about the metal atoms. It is found that the occurrence of the structures is not related to the average number of 3d electrons of the cationic part, but that a structural variation tetragonal hexagonal orthorhombic can be ascribed to increasing interaction between the metal atoms.

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Mit 7 Abbildungen

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Gewidmet Herrn Prof. Dr.H. Nowotny in Bewunderung fü das Werk, das die Wiener Schule geschaffen hat.     

Neue Verbindungen mit Granatstruktur. IV. Arsenate des Typs {Na3}[M2III](As3)O12

The preparation and thermal behaviour of two garnets of the type {Na₃}[M^III₂]·(As₃)O₁₂ (M^III = Cr, Fe) are described. Both compounds undergo a reversible conversion into a high-temperature phase which, for the case of M^III = Ga, is found as the sole structure type. There is no mixed-crystal formation between {Y₃}[Fe₂](Fe₃)O₁₂ and {Na₃}[Fe₂] · (As₃)O₁₂ Preliminary investigations were performed on the possible mixed-crystal formation between the Ga compound and the Cr and Fe garnet structure, respectively.     

Isotype Borophosphate MII(C2H10N2)[B2P3O12(OH)] (MII = Mg,Mn, Fe,Ni, Cu,Zn): Verbindungen mit Tetraeder‐Schichtverbänden

Isotypic Borophosphates M^II(C₂H₁₀N₂)[B₂P₃O₁₂(OH)] (M^II = Mg, Mn, Fe, Ni, Cu, Zn): Compounds containing Tetrahedral Layers The isotypic compounds M^II(C₂H₁₀N₂) · [B₂P₃O₁₂(OH)] (M^II = Mg, Mn, Fe, Ni, Cu, Zn) were prepared under hydrothermal conditions (T = 170 °C) from mixtures of the metal chloride (chloride hydrate, resp.), Ethylenediamine, H₃BO₃ and H₃PO₄. The orthorhombic crystal structures (Pbca, No. 61, Z = 8) were determined by X‐ray single crystal methods (Mg(C₂H₁₀N₂)[B₂P₃O₁₂(OH)]: a = 936.81(2) pm, b = 1221.86(3) pm, c = 2089.28(5) pm) and Rietveld‐methods (M^II = Mn: a = 931.91(4) pm, b = 1234.26(4) pm, c = 2129.75(7) pm, Fe: a = 935.1(3) pm, b = 1224.8(3) pm, c = 2088.0(6) pm, Ni: a = 939.99(3) pm, b = 1221.29(3) pm, c = 2074.05(7) pm, Cu: a = 941.38(3) pm, b = 1198.02(3) pm, c = 2110.01(6) pm, Zn: a = 935.06(2) pm, b = 1221.33(2) pm, c = 2094.39(4) pm), respectively. The anionic part of the structure contains tetrahedral layers, consisting of three‐ and nine‐membered rings. The M^II‐ions are in a distorted octahedral or tetragonal‐bipyramidal [4 + 2] (copper) coordination formed by oxygen functions of the tetrahedral layers. The resulting three‐dimensional structure contains channels running along [010]. Protonated Ethylenediamine ions are fixed within the channels by hydrogen bonds.     

Über hexagonale Perowskite mit Kationenfehlstellen. XXVII. Die Systeme Ba4−xSrxBIIRe2□O12′, Ba4BCaxRe2□O12 und Ba4−xLaxBIIRe2−xWx□O12 mit BII = Co,Ni

On Hexagonal Perovskites with Cationic Vacancies. XXVII. Systems Ba_4?xSr_xB^IIRe₂□O₁₂, Ba₄B Ca_xRe₂□O₁₂, and Ba_4?xLa_xB^IIRe_2?xW_x□O₁₂ with B^II = Co, Ni In the systems Ba_4?xSr_xB^IIRe₂□O₁₂, Ba₄BCa_xRe₂□O₁₂ and Ba_4?xLa_xB^IIRe_2?xW_x□O₁₂ (B^II = Co, Ni) hexagonal perovskites with a rhombohedral 12 L structure (general composition A₄BM₂□O₁₂; sequence (hhcc)₃; space group R&3macr;m) are observed. With the exception of Ba₄NiRe₂□O₁₂ the octahedral net consists of BO₆ single octahedra and M₂□O₁₂ face connected blocks (type 1). In type 2 (Ba₄NiRe₂□O₁₂) the M ions are located in the single octahedra and in the center of the groups of three face connected octahedra. The two outer positions of the latter are occupied by B ions and vacancies in the ratio 1:1. The difference between type 1 and 2 are discussed by means of the vibrational and diffuse reflectance spectra.     

Synthesis and crystal structure of the octahedral cyano-bridged cluster complex β-[{Ni(NH3)5}2{Re6Te8(CN)6}]·4H2O

The rhenium cyano-bridged cluster complex with a composition of β-[{Ni(NH₃)₅}₂{Re₆Te₈(CN)₆}]−4H₂O is obtained and structurally characterized. The compound pound crystallizes in the P $ P\bar 1 $ P\bar 1 triclinic space group with the unit cell parameters: a = 9.997(2) ?, b = 10.423(2) ?, c = 11.714(2) ?, α = 100.92(3)°, β = 111.87(3)°, γ = 98.05(3)°, V = 1082.1(4) ?³, Z = 1, d _calc = 4.072 g/cm³. The rhenium atoms of the {Re₆Te₈} cluster core are coordinated by CN ligands to form the [Re₆Te₈(CN)₆]⁴⁻ cluster; two nitrogen atoms of CN ligands trans-positioned with respect to each other are coordinated to Ni atoms in the {Ni(NH₃)₅}²⁺ fragments to form the molecular complexes of [{Ni(NH₃)₅}₂}Re₆Te₈(CN)₆}]. The crystal structure is the H-bonded packing of these molecular complexes and crystallization water molecules.     

A Series of MAX Phases with MA‐Triangular‐Prism Bilayers and Elastic Properties

We report a new type of MAX phase (M=transition metals, A=main group elements, and X=C/N), Nb₃As₂C, designated as 321 phase. It differs from all the previous M_n+1AX_n phases in that it consists of an alternate stacking of one MX layer and two MA layers in its unit cell, while only one MA layer is allowed in usual MAX phases. The new 321 phase exhibits a bulk modulus of Nb₃As₂C up to 225(3) GPa as determined by high‐pressure synchrotron X‐ray diffraction, one of the highest values among MAX phases. Isostructural 321 phases V₃As₂C, Nb₃P₂C, and Ta₃P₂C are also found to exist. First‐principles calculations reveal the outstanding elastic stiffness in 321 phases. Among all 321 phases, Nb₃P₂C is predicted to have the highest elastic properties. These 321 phases, represented by a chemical formula M_n+1A_nX, were added as new members to the MAX family and their other properties deserve future investigations.     

Cyano-bridged complexes based on re tetrahedral cluster anions, Ni2+ cations, and polydentate amines

Interaction of the tetrahedral chalcocyanide cluster anionic complexes of Re, K₄[Re₄Q₄(CN)₁₂] (Q=S, Se, Te), with Ni²⁺ cationic complexes with polydentate amines, such as ethylenediamine (En), diethylenetriamine (Dien), or triethylenetetraamine (Trien) was used to synthesize six novel complexes: [Ni(NH₃)₄(En)][{Ni(NH₃)(En)₂}Re₄Te₄(CN)₁₂] · 2H₂O, [{Ni(En)₂}₂Re₄Se₄(CN)₁₂] · 3.5H₂O, [Ni(NH₃)₃(Dien)]₂[Re₄Se₄(CN)₁₂] · 5.5H₂O, [{Ni(NH₃)₂(Dien)}₂Re₄Te₄(CN)₁₂] · 2.5H₂O. [Ni(NH₃)₂(Trien)][{Ni(NH₃)(Trien)}Re₄Se₄(CN)₁₂] · 2.5H₂O, [{Ni(Trien)}₂Re₄S₄(CN)₁₂] · 3H₂O. The complexes were studied by single-crystal X-ray diffraction analysis.     

Crystal growth,properties, and structure refinements of some rhenium phosphides and arsenophosphides

Small single crystals of Re₂P and Re₃P₄ were grown in a tin flux. Their crystal structures were refined from single crystal diffractometer data to residuals of R = 0.055 and R = 0.049, respectively. The new compound ReP_2.3 was prepared. Re₆P₁₃ forms an extended solid solution with As up to Re₆As_10.7P_2.3. Re₃P₄ is diamagnetic. ReP₄ is a diamagnetic semiconductor with a band gap of 0.54 eV. Systematic trends in the structural chemistry of rhenium phosphides are discussed.     

New cyano-bridged complexes based on tetrahedral rhenium chalcocyanide clusters,Cu<Superscript>2+</Superscript> cations,and polydentate amines

Three new cyano-bridged compounds, viz., [{Cu(en)}{Cu(NH₃)(en)}Re₄Se₄(CN)₁₂]·{5H₂O (1), [{Cu(dien)}₂Re₄Te₄(CN)₁₂]·9H₂O (2), and [{Cu(trien)}₂Re₄Se₄(CN)₁₂]··5H₂O (3), were synthesized by the reactions of the tetrahedral rhenium chalcocyanide cluster complexes K₄[Re₄Q₄(CN)₁₂] ((Q = Se or Te) with copper(II) cations in aqueous solutions containing ethylenediamine (en), diethylenetriamine (dien), or triethylenetetraamine (trien), respectively. Complex 1 has a ladder-tubular-like polymeric structure, in which two infinite chains are linked to each other by Re-CN-Cu bridges, compound 2 has a polymeric chain structure, and compound 3 has a molecular structure. The structures of all complexes were established by X-ray diffraction analysis.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2040–2044, October, 2004.     

Die Undecaarsenide A3As11 (A = Rb,Cs) — Synthesen und Kristallstrukturen

Alkaline Metal Arsenides A₃As₁₁ (A = Rb, Cs): Preparation and Crystal Structures Rb₃As₁₁ and Cs₃As₁₁ were synthesized from the elements and the crystal structures of the ordered room temperature form were characterized via single crystal x‐ray studies. In the Zintl phases the As atoms form chiral ufosan‐anions As with As‐As distances ranging from 238 to 248 pm. Like K₃As₁₁ Rb₃As₁₁ crystallizes with the Na₃P₁₁ structure type (orthorhombic, space group Pbcn, a = 1108.2(2), b = 1533.5(3), c = 1060.1(2) pm, Z = 4), whereas the Cs compound (monoclinic, space group C2/c, a = 1324.5(7), b = 1524.5(9), c = 1937.2(11) pm, β = 95.29(1)°, Z = 8) forms a new structure type. The crystallographic relationship between the two structure types and the anion packings in the plastic crystalline high temperature forms are discussed.     

Ab initio pseudopotential study of M2As− and M2Br+ (M = Cu,Ag, Au)

The equilibrium geometries and the vibration frequencies of M₂As⁻ and M₂Br⁺ (M = Cu, Ag, Au) are calculated at the Hartree–Fock (HF) and the second‐order Møller–Plesset (MP2) levels with pseudopotentials. The calculated results indicate that the species have a bent structure (C_2v). The electron correlation corrections on the geometrical structure are investigated at the MP2 level, the bond angles are reduced by 10°–20° for considered species. The electron correlation effects on the geometry of the Au₂As⁻ are studied particularly at MP2, MP3, MP4, CCSD and CCSD(T) levels. Comparing the species containing Ag and Au, the relativistic effects slightly short the bond lengths of the species. The bonding possibility of the Au₂As⁻ is predicted. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 80: 38–43, 2000     

Darstellung,Eigenschaften und Molekülstrukturen von Komplexen des versteiften dreizähnigen Chelatliganden N,N′-Bis(diphenylphosphino)-2, 6-diaminopyridin mit MII - und M0-Übergangsmetallen [MII = Ni,Pd, Pt; M0 = Cr,Mo, W]

Preparation, Properties, and Molecular Structures of a Rigid Tridentate Chelate Ligand N, N′-Bis(diphenylphosphino)-2, 6-diaminopyridine with M^II and M⁰ Transition Metals [M^II = Ni, Pd, Pt; M⁰ = Cr, Mo, W] The reaction of chlorophenylphosphane and 2, 6-Diaminopyridine give N, N′-Bis-(diphenylphosphino)-2, 6-diaminopyridine (PNP). Two types of complexes [M(PNP)Cl]Cl · L (M = Ni, L = H₂O; M = Pd, L = C₂H₅OH; M = Pt) and mer-[M(PNP)(CO)₃] · 2 THF (M = Cr, Mo, W) have been prepared using PNP. These coordination compounds have been characterized by means of i.r., u.v., ³¹P and ¹H n.m.r. measurements. The determination of the molecular structure of the two triclinic substances mer-[Mo(PNP)(CO)₃] · 2 THF and [Ni(PNP)Cl]Cl · H₂O show that the octahedral Mo(d⁶) and the square planar nickel (d⁸) compounds contain a nearly planar tridentate chelate ring system (two fused five-membered rings of the type ) in which the observed bond distances are in accordance with a π electron delocalization effect. The observed gram susceptibility of the diamagnetic Ni(d⁸) compound remains unchanged between 293 and 410 K. The relative activation property for a homogenous catalytic standard hydrogenation reaction of styrene to ethylbenzene decreases in series of catalysts of type [M(PNP)Cl]Cl · L with M^II = Ni > Pd > Pt.     

Synthesis,Characterization, and Magnetic Properties of the New Boride Solid Solutions M0.5Ru6.5B3 (M = Cr,Mn, Co,Ni)

Powder samples and single crystals of the borides M_0.5Ru_6.5B₃ (M = Cr, Mn, Co, Ni) were synthesized by arc‐melting the elements in a water‐cooled copper crucible under argon. The new phases were structurally characterized by single‐crystal and powder X‐ray diffraction as well as EDX‐Analyses. They crystallize in the hexagonal Th₇Fe₃ structure type (space group P6₃mc, no. 186, Z = 2) and a pronounced site preferential M/Ru substitution is observed. Magnetic properties of the compounds were investigated and Pauli paramagnetism was observed in all cases. However, a strong temperature dependency is subsequently observed in Mn_0.5Ru_6.5B₃ below 250 K, but no hint of magnetic ordering was found.