Hansjürgen Mattausch

B and B–C as interstitials in reduced rare earth halides

Abstract In this review we describe a variety of rare earth metal boride halides and boride carbide halides. In boride halides boron atoms occur either as discrete atoms octahedrally coordinated by rare earth metal atoms or as chains of interconnected B 4 rhomboids in rods of fused metal atom bisphenoids. Characteristic building units in boride carbide halides are quasi-molecular B–C, C–B–C, C–B–B–C, and C 2 –B–B–C 2 entities. In these compounds B centers trigonal prisms of rare earth metal atoms, and C is located in tetragonal pyramids. Owing to the electropositive character of rare earth metals, B atoms, B 4 units, and C n B m groups tend to be anions. Band structure calculations as well as electrical and magnetic measurements have been performed. The compounds show semiconducting or metallic behavior, depending on whether excess electrons according to the Zintl–Klemm formalism are localized or delocalized. La 9 Br 5 (CBC) 3 is superconducting with T c ∼6 K. Ce and Gd compounds are paramagnetic. In most cases anti-ferromagnetic ordering is observed at low temperature.

Metalloktaederdoppel in den Clusterverbindungen Gd10I16(C2)2 und Gd10Br15B2/Tb10Br15B2

Aus Gd-Metall, GdI3 und Graphitpulver entsteht bei 950u200a°C die Verbindung Gd10I16(C2)2. Sie kristallisiert in P1 mit au200a=u200a10.463(4)u200aA, bu200a=u200a16.945(6)u200aA, cu200a= 11.220(4)u200aA, αu200a=u200a99.15(3)°, βu200a=u200a92.68(3)° und γu200a=u200a88.06(3)°. Gd10Br15B2 bildet sich zwischen 900 und 950u200a°C, Tb10Br15B2 zwischen 900 und 930u200a°C aus stochiometrischen Mengen Metall, Metallbromid und Bor. Beide Verbindungen sind isotyp und kristallisieren in P1 fur Gd10Br15B2 mit au200a=u200a8.984(2)u200aA, bu200a=u200a9.816(2)u200aA, cu200a=u200a10.552(2)u200aA, αu200a=u200a91.14(3)°, βu200a=u200a114.61(3)° und γu200a=u200a110.94(3)° und fur Tb10Br15B2 mit au200a=u200a8.939(4)u200aA, bu200a=u200a9.788(3)u200aA, cu200a=u200a10.502(5)u200aA, αu200a=u200a91.19(3)°, βu200a=u200a114.51(3)° und γu200a=u200a111.10(2)°. In den Kristallstrukturen liegen Seltenerdmetallcluster mit kantenverknupften Ln10-Oktaederdoppeln vor. In Gd10I16(C2)2 befinden sich im Gd6-Oktaeder C2-Gruppen mit einem C–C-Abstand von 1.43(7)u200aA und in Ln10Br15B2 (Lnu200a=u200aGd, Tb) isolierte B-Atome. Die Oktaederdoppel sind uber die Halogenatome zu Ketten [Ln10(Z)2XXX] verkupft und daruberhinaus dreidimensional durch II beim Gd-Iodidcarbid und durch BrBr bei den Bromidboriden. Interessanterweise findet man das identische Verknupfungsmuster zu Strangen bei reduzierten Oxomolybdaten wie PbMo5O8. n n n nGd10I16(C2)2 and Gd10Br15B2/Tb10Br15B2 Cluster Compounds with M10 Twin Octahedra n n n nThe compound Gd10I16(C2)2 can be prepared from Gd metal, GdI3 and C at 950u200a°C. It crystallizes in P1 with au200a=u200a10.463(4)u200aA, bu200a=u200a16.945(6)u200aA, cu200a=u200a11.220(4)u200aA, αu200a= 99.15(3)°, βu200a=u200a92.68(3)° und γu200a=u200a88.06(3)°. Gd10Br15B2 is formed between 900 und 950u200a°C, Tb10Br15B2 between 900 und 930u200a°C from stoichiometric amounts of the rare earth metals, tribromide and boron. Both compounds crystallize in the space group P1 for Gd10Br15B2 with au200a=u200a8.984(2)u200aA, bu200a=u200a9.816(2)u200aA, cu200a=u200a10.552(5)u200aA, αu200a=u200a91.14(3)°, βu200a=u200a114.61(3)° and γu200a=u200a110.94(3)° and for Tb10Br15B2 with au200a=u200a8.939(4)u200aA, bu200a=u200a9.788(3)u200aA, cu200a=u200a10.502(2)u200aA, αu200a=u200a91.19(3)°, βu200a=u200a114.51(3)° and γu200a=u200a111.10(2)°. In the crystal structures of all three compounds the rare earth metals form edge-shared Ln10 twin octahedra. In Gd10I16(C2)2 the Gd octahedra are centered with C2 groups (dC–Cu200a=u200a1.43(7)u200aA). In Ln10Br15B2 (Lnu200a=u200aGd, Tb) the octahedra contain single boron atoms. The clusters arexa0connected through halide atoms to chains [Ln10(Z)2XXX]. Adjacent chains are fused threedimensionally via II for the Gd iodide carbide and via BrBr for the bromide borides of Gd und Tb. It is interesting to see an identical pattern of connection between the chains for the reduced oxomolybdates, e.u200ag. PbMo5O8.

Tb16Br23B4: Endohedrale Bor-Atome in tetrameren Terbiumclustern

Wir berichten uber die neue Clusterverbindung Tb16Br23B4, die durch Tempern stochiometrischer Mengen von Tb-Metall, TbBr3 und Bor unter Ar-Atmosphare in verschweisten Ta-Ampullen bei 920–950u200a°C dargestellt wird und monoklin in C2/m mit au200a=u200a17.523(4)u200aA, bu200a= 12.008(2)u200aA, cu200a=u200a11.901(2)u200aA und βu200a=u200a103.95(3)° kristallisiert. In der Struktur liegen Tb-Oktaeder vor, die uber gemeinsame Kanten zu tetrameren Einheiten verknupft sind. Die Tb-Oktaeder werden durch B-Atome zentriert. Die Br-Atome koordinieren die Tb16B4-Cluster uber allen freien Kanten und Ecken der Oktaeder und verknupfen sie dreidimensional. Tb16Br23B4 ist ein Halbleiter mit einer Energielucke von Egu200a=u200a0.4u200aeV und zeigt Curie-Weiss-Verhalten mit einem magnetischen Moment von μeffu200a=u200a9.55u200aμB und ordnet antiferromagnetisch unterhalb 20u200aK. n n n nTb16Br23B4: Tetrameric Terbium Clusters with Endohedral Boron Atoms n n n nThe new cluster compound Tb16Br23B4 was prepared from a stoichiometric mixture of Tb-metal, TbBr3 and B-powder under Ar-atmosphere in sealed Ta ampoules at 920–950u200a°C. It crystallizes monoclinic in the space group C2/m with au200a=u200a17.523(4)u200aA, bu200a=u200a12.008(2)u200aA, cu200a=u200a11.901(2)u200aA und βu200a=u200a103.95(3)°. In the crystal structure B-centered Tb6 octahedra are connected via common edges to form tetrameric units. The Br atoms connect the Tb16B4-clusters 3-dimensionally coordinating the unoccupied edges and corners of the octahedra. Tb16Br23B4 is a semiconductor with an electrical band gap of Egu200a=u200a0.4u200aeV. The magnetic susceptibility follows a Curie-Weiss law corresponding to an effective magnetic moment μeffu200a=u200a9.55u200aμB at high temperatures with an antiferromagnetic ordering below 20u200aK.

Si6, Si14, and Si22 Rings in Iodide Silicides of Rare Earth Metals

A new class of compounds containing layers of Sin Zintl polyanions is represented by the silicides MISi (M=La, Ce, Pr), La4 I3 Si4 , and La5 I3 Si5 (a section of the structure is shown below). Their structures contain Si6 and the previously unknown Si14 and Si22 rings, which are condensed into layers. The Si atoms are coordinated in a trigonal-prismatic fashion by M atoms to give M-(SiSi)-M slabs that are bonded to one another through I atoms. An extensive chemistry of halide silicides similar to that of the carbide halides of the rare earth metals can be expected.

A five-membered Ru5 ring in a hexagonal La14 cage: the La14Cl20Ru5 structure.

The title compound features a five-membered Ru(5) ring embedded in a La(14) hexagonal wheel-like cage, an incommensurate combination of the two building units. A formal electron partition of (La(3+))(14)(Cl(-))(20)(Ru(5))(22-) results in a (Ru(5))(22-) ring isoelectronic to (Cd(5))(2-). However, computational studies show that there is significant electron back-donation from the Ru(5) ring to the La(14) wheel. This interaction strongly stabilizes the Ru(5) ring. The resistivity and magnetic susceptibility of the compound have also been investigated.

Neue reduzierte Halogenide der Lanthanoide mit kondensierten Clustern: Tb6Br7 und Er6I7 / New Reduced Halides of Rare Earth Metals with Condensed Clusters: Tb6Br7 and Er6I7

Abstract The new compounds Tb6Br7 and Er6I7 are formed from the trihalides with an excess of metal in sealed tantalum containers. X-ray structure investigations [space group C2/m; Tb6Br7 (Er6I7): a = 2057.1 (2137.5), b = 379.3 (386.9), c = 1180.0 (1231.9) pm, β = 124.59° (123.50°)] show one-dimensional regions connected by Ln-Ln bonds. The structure type can be described in terms of Ln6X12-clusters which are linked via edges of Ln6-octahedra to form double strings. The structure is derived from an FCC arrangement of halogen atoms part of which is systematically substituted by Ln6-octahedra.

Reliability of Monte Carlo simulations of disordered structures optimized with evolutionary algorithms exemplified with diffuse scattering from La0.70(1)(Al0.14(1)I0.86(1)).

Complex disorder and corresponding diffuse scattering from La(0.70(1))(Al(0.14(1))I(0.86(1))) was taken as basis for investigating the reliability, reproducibility and influence of the refinement parameters of evolutionary algorithm refinements of Monte Carlo simulations. Using the same diffuse-scattering data set, a model relying on reasonable a priori knowledge about the real structure was used, as well as one that includes no presumptions except the average structure and the chemical composition. To strengthen the complementary character of the approaches, different evolutionary algorithms (differential and cooperative evolution) were employed. It was found that the resulting structures are qualitatively and quantitatively in good agreement independent of the strategy used. It is shown that the method of population averaging (applicable only in differential evolution refinements) allows reasonable estimates about uncertainties of structure parameters if proper refinement parameters are chosen, which makes differential evolution the method of choice for quantitative refinements. Recommendations for the best choices of the parameters are given. The disordered structure of La(0.70(1))(Al(0.14(1))I(0.86(1))) contains clusters including differently interconnected La(6)Al units. The modes of interconnection and local distortions are discussed in detail.

Y7I12C2N: Eine Verbindung aus Einheiten zweier Y6(C2)-Oktaeder und eines Y6N2-Tetraederdoppels / Y7I12C2N: A Compound with Units of Two Y6(C2) Octahedra and a Y6N2 Double Tetrahedron

The new compounds Y7I12C2N and Ho7I12C2N have been prepared by reaction of stoichiometric amounts of the metals (RE), REI3, REN and C in closed Ta capsules at 1150 and 1120K, respectively. Pure samples of the compounds were obtained after 5 days annealing time. The crystals with xenomorphic shape are olive-green (Y7I12C2N) or red-brown (Ho7I12C2N) in colour and sensitive to air and moisture. Y7I12C2N crystallizes in the space group P 1̄ (No. 2) with lattice constants a = 971.24(7), b = 1030.38(7), c = 1673.58(11) pm and α = 101.366(5), β = 92.758(5), γ = 112.799(5)°. According to Guinier photographs Ho7I12C2N is isotypic with the lattice consiants u - 968.8(3), b = 1028.7(3), r. = 1667.8(5) pm and α = 101.31(2), β = 92.78(2), γ = 112.80(1)°. In the structure the C atoms are present as C2 units with a C -C distance of 144 pm. These C2 units are octahedrally coordinated by Y atoms (o1). The N atoms are in the center of Y4 tetrahedra, which are linked via a common edge to form double tetrahedra (t2). By condensation of N-centered double tetrahedra (t2) with a C2-centered Y octahedron (o1) the characteristic units o1t2o1 are formed. The I atoms coordinate all free edges and corners of these units and connect them via Ii - Ia contacts parallel [100] and [001]. The compounds are semiconducting. Ho7I12C2N exhibits Curie-Weiss behaviour with θ = 15(1) K and μeff = 10.5(1) μB.

Notizen: Y7I6C3O: Ein Carbidoxid mit kondensierten Y6C-Oktaedern und Y4O-Tetraedern / Y7I6C3O: A Carbide Oxide with Condensed Y6C-Octahedra and Y4O-Tetrahedra

The new compound Y7I6C3O is prepared by reaction of stoichiometric amounts of Y, YI3, Y2O3 and C in closed Ta capsules at 1370 K. Y7I6C3O forms bronze coloured, metallic, air and moisture sensitive crystals. It crystallizes in the space group Pmma (No. 51) with the lattice constants a = 2249.4(4), b = 383.7(1), c = 1079.1(1) pm. Within the crystal structure the C atoms and the O atoms are surrounded by Y atoms octahedrally and tetrahedrally, respectively. The Y6C octahedra and Y4O tetrahedra are condensed to form ondulated layers, which are separated by double layers of I atoms.

Synthesis, structure and properties of Nd2BC containing the trans-dibora–(1,3)-butadiene [C=B–B=C]8–-unit

Abstract The crystal structure of Nd2BC, synthesized by arc melting of the element mixture, repeated in a high frequency furnace and subsequent annealing at 1070 K, has been determined from single crystal X-ray diffraction data. It crystallizes in a new structure type in the monoclinic space group C2/m (a = 12.732(2) Å, b = 3.6848(4) Å, c = 9.398(2) Å, β = 130.43(1)°, R1 = 0.038 (wR2 = 0.091) for 596 reflections with Io > 2σ (Io)). Characteristic building units are C—B—B—C entities with the distances dC—B = 1.51(2) Å and dB—B = 1.65(2) Å. These units are embedded in a framework of neodymium atoms resulting from the stacking of slightly corrugated two-dimensional square nets of Nd. Within the ionic limit Nd2BC can be described as (Nd2+)4[C—B—B—C]8– or (Nd3+)4[CBBC]8– · 4 e– with [C=B—B=C]8– units, which are isoelectronic to 1,3-butadiene. The measured magnetic moment of 3.65μB per Nd atom in Nd2BC is in good agreement with the expected value of 3.62μB for 4f3 configuration. LMTO band structure calculations show that Nd2BC is metallic and the extra electrons occupy mainly bonding Nd-5d and antibonding π* states within the C—B—B—C units.