Martin Schlüter

The Ternary Stannides MgRuSn4 and MgxRh3Sn7—x (x = 0.98—1.55)

The magnesium transition metal stannides MgRuSn4 and MgxRh3Sn7—x (x = 0.98—1.55) were synthesized from the elements in glassy carbon crucibles in a water-cooled sample chamber of a high-frequency furnace. They were characterized by X-ray diffraction on powders and single crystals. MgRuSn4 adopts an ordered PdGa5 type structure: I4/mcm, a = 674.7(1), c = 1118.1(2) pm, wR2 = 0.0506, 515 F2 values and 12 variable parameters. The ruthenium atoms have a square-antiprismatic tin coordination with Ru—Sn distances of 284 pm. These [RuSn8/2] antiprisms are condensed via common faces forming two-dimensional networks. The magnesium atoms fill square-prismatic cavities between adjacent [RuSn4] layers with Mg—Sn distances of 299 pm. The rhodium based stannides MgxRh3Sn7—x crystallize with the cubic Ir3Ge7 type structure, space groupe Im3m. The structures of four single crystals with x = 0.98, 1.17, 1.36, and 1.55 have been refined from X-ray diffractometer data. With increasing tin substitution the a lattice parameter decreases from 932.3(1) pm for x = 0.98 to 929.49(6) pm for x = 1.55. The rhodium atoms have a square antiprismatic tin/magnesium coordination. Mixed Sn/Mg occupancies have been observed for both tin sites but to a larger extend for the 12d Sn2 site. Chemical bonding in MgRuSn4 and MgxRh3Sn7—x is briefly discussed. Die ternaren Stannide MgRuSn4 und MgxRh3Sn7—x (x = 0.98—1.55) Die Magnesium-Ubergangsmetall-Stannide MgRuSn4 and MgxRh3Sn7—x (x = 0.98—1.55) wurden aus den Elementen in Glaskohlenstofftiegeln in einer wassergekuhlten Probenkammer im Hochfrequenzofen synthetisiert. Sie wurden uber Rontgen-Beugungsexperimente an Pulvern und Einkristallen charakterisiert. MgRuSn4 kristallisiert mit einen geordneten Variante der PdGa5-Struktur: I4/mcm, a = 674, 7(1); c = 1118, 1(2) pm; wR2 = 0, 0506; 515 F2-Werte und 12 variable Parameter. Die Rutheniumatome haben eine quadratisch-antiprismatische Zinnkoordination mit Ru—Sn-Abstanden von 284 pm. Diese [RuSn8/2]-Antiprismen sind uber gemeinsame Flachen zu zweidimensionalen Netzwerken kondensiert. Die Magnesiumatome besetzen quadratisch-prismatische Lucken zwischen benachbarten [RuSn4]-Schichten mit Mg—Sn-Abstanden von 299 pm. Die Rhodiumstannide MgxRh3Sn7—x kristallisieren mit der kubischen Ir3Ge7-Struktur, Raumgruppe Im3m. Von vier Einkristallen mit x = 0, 98; 1, 17; 1, 36 und 1, 55 wurden die Strukturen anhand von Rontgen-Diffraktometerdaten verfeinert. Mit steigender Zinnsubstitution verkleinert sich der Gitterparameter a von 932, 3(1) pm fur x = 0, 98 zu 929, 49(6) pm fur x = 1, 55. Die Rhodiumatome haben eine quadratisch-antiprismatische Zinn/Magnesium-Koordination. Sn/Mg-Mischbesetzungen wurden fur beide Zinnlagen beobachtet, jedoch mit einem hoheren Wert fur die 12d Sn2-Position. Die chemische Bindung in MgRuSn4 und MgxRh3Sn7—x wird diskutiert.

The ternary rare earth ruthenium gallides R3Ru4Ga15 (R=Y, Tb–Er) with a new structure type, a further example of a recently recognized large family of structures

Abstract The title compounds were prepared by reaction of the elemental components at high temperature. They crystallize with a new orthorhombic structure type which was determined from single-crystal diffractometer data of Ho3Ru4Ga15: Pnma, a=871.7(1) pm, b=956.4(1) pm, c=1765.9(3) pm, Z=4, R=0.040 for 1039 structure factors and 114 variable parameters. The structure may be viewed as consisting of two kinds of atomic layers, although atomic bonding within and between the layers is comparable strength, as can be judged from the near-neighbor environments, where all of the 15 atomic sites have high coordination numbers. One kind of atomic layers (A) contains all of the holmium and additional gallium atoms in the ratio Ho:Ga=3:5 with a unit mesh content of 2Ho3Ga5; these layers are flat. The other layers (B) consist of sheets of corner- and edge-sharing condensed RuGa6 octahedra, which are extremely compressed resulting in a hexagonal close-packed, puckered net with a Ru:Ga ratio of 2:5 and a unit mesh content of 4Ru2Ga5. These nets alternate in the sequence ABAB, ABAB, thus yielding the formula 4Ho3Ga5·8Ru2Ga5=4Ho3Ru4Ga15. Similar layers are observed in the structures of Y2Co3Ga9, Gd3Ru4Al12, Er4Pt9Al24, CeOsGa4, CaCr2Al10, and the four stacking variants with the compositions TbRe2Al10, DyRe2Al10, YbFe2Al10, and LuRe2Al10.

Preparation and Crystal Structures of Ternary Rare Earth Osmium Gallides LnOsGa3 (Ln = Gd—Tm) and LnOsGa3 (Ln = La—Nd)Dedicated to Professor Welf Bronger on the Occasion of his 70th Birthday

The title compounds were prepared from the elemental components at high temperatures. The compounds LnOsGa3 crystallize with the cubic TmRuGa3 type structure which was refined from four-circle X-ray diffractometer data of TbOsGa3: Pm3¯m, Z = 3, a = 640.8(1) pm, R = 0.014 for 173 structure factors and 10 variable parameters. The other gallides crystallize with a new structure type which was determined from single-crystal X-ray data of CeOsGa4: Pmma, Z = 6, a = 963.9(2) pm, b = 880.1(1) pm, c = 767.0(1) pm, R = 0.030 for 744 F values and 56 variables. The structure may be considered as consisting of two kinds of alternating layers, although bonding within and between the layers is of similar strength. One kind of layers (A) is slightly puckered, two-dimensionally infinite, hexagonal close packed, with the composition OsGa3; the other kind of layers (B) is planar with the composition CeGa. The structure is closely related to that of Y2Co3Ga9 where the corresponding layers have the compositions Co3Ga6 (A) and Y2Ga3 (B). Praparation und Kristallstruktur ternarer Seltenerdmetall-Osmium-Gallide LnOsGa3 (Ln = Gd—Tm) und LnOsGa3 (Ln = La—Nd) Die im Titel genannten Verbindungen wurden bei hohen Temperaturen aus den elementaren Komponenten hergestellt. Die Verbindungen LnOsGa3 kristallisieren in der kubischen TmRuGa3-Struktur, die anhand von Rontgen-Vierkreis-Diffraktometerdaten von TbOsGa3 verfeinert wurde: Pm3¯m, Z = 3, a = 640, 8(1) pm, R = 0, 014 fur 173 Strukturfaktoren und 10 variable Parameter. Die anderen Gallide kristallisieren mit einer neuen orthorhombischen Kristallstruktur, welche mittels Einkristall-Rontgendaten der Verbindung CeOsGa4 bestimmt wurde: Pmma, Z = 6, a = 963, 9(2) pm, b = 880, 1(1) pm, c = 767, 0(1) pm, R = 0, 030 fur 744 Strukturfaktoren und 56 Variable. Die Struktur kann aufgefasst werden als eine Abfolge zweier alternierender unterschiedlicher Schichten, wobei die Bindungen innerhalb und zwischen den Schichten vergleichbar sind. Die eine Schicht (A) ist gewellt, zwei-dimensional-unendlich hexagonal dicht gepackt mit der Zusammensetzung OsGa3. Die andere Schicht (B) ist planar mit der Zusammensetzung CeGa. Die Struktur ist nahe verwandt mit der von Y2Co3Ga9, in der die entsprechenden Schichten die Zusammensetzung Co3Ga6 (A) bzw. Y2Ga3 (B) haben.

The Lanthanoid Osmium Gallides Er2Os3Ga10 and Tm2Os3Ga10 with Yb2Ru3Ga10-type Structure

The title compounds were prepared by melting and annealing of stoichiometric mixtures of the elemental components in a high-frequency furnace. They are isotypic with Yb2Ru3Ga10 (P4/mbm, Z = 2). Their lattice constants were determined from X-ray powder data, and their crystal structures were refined from single-crystal X-ray data. Er2Os3Ga10: a = 883.4(1), c = 636.7(1) pm, R = 0.025 for 506 Fo values, and Tm2Os3Ga10: a = 883.2(1), c = 633.6(1) pm, R = 0.023 for 568 Fo values and 25 variable parameters each. The crystal structures of these intermetallic compounds are briefly discussed. Graphical Abstract The Lanthanoid Osmium Gallides Er2Os3Ga10 and Tm2Os3Ga10 with Yb2Ru3Ga10-type Structure

Transition Metal-Gallium Ordering in HfCoGa2 and HfNiGa2

Abstract The gallides HfCoGa2 and HfNiGa2 were synthesized by arc-melting of the elements and subsequent annealing in glassy carbon crucibles. Their structures have been reinvestigated by X-ray diffraction on powders and single crystals: I4mm, a = 1222.4(1), c = 812.0(1) pm, wR2 = 0.0766, 1464 F2 values, 64 variables, BASF = 0.41(2) for HfCoGa2 and a = 1224.0(2), c = 809.3(2) pm, wR2 = 0.0609, 1499 F2 values, 63 variables for HfNiGa2. In contrast to a previous investigation (Dopov. Akad. Nauk Ukr. RSR, Ser. A, 51 (1988)) we observe a fully ordered arrangement of the transition metal and gallium atoms. The crystal chemistry of these gallides is briefly discussed.