Volume 77, Issue 10

The stannide YbRhSn 2 has been synthesized. An arc-melted Rh 25 Sn 48 precursor sample was reacted with ytterbium in a sealed tantalum ampoule in an induction furnace. The structure of YbRhSn 2 was refined from single-crystal X-ray diffractometer data: MgCuAl 2 type, Cmcm , a  = 433.10(3), b  = 1076.63(8), c  = 739.36(5) pm, wR 2 = 0.0676, 444 F 2 values and 16 variables. The rhodium and tin atoms form a three-dimensional [RhSn 2 ] δ− polyanionic network with short Rh–Sn (271–273 pm) and Sn–Sn (301–324 pm) distances. The tin substructure is an orthorhombically distorted lonsdaleite network. YbRhSn 2 shows paramagnetic behavior with a reduced magnetic moment of 2.2(1) µ B per ytterbium atom, classifying it as an intermediate-valent compound.

The rare earth intermetallic compounds RE 2 Ga 2 Mg with RE  = Tb–Tm and Lu were synthesized from the elements in sealed tantalum ampoules in a high-frequency furnace. These rare earth-rich phases crystallize with the tetragonal Mo 2 B 2 Fe-type structure, space group P 4/ mbm and Z  = 2. The polycrystalline samples were characterized through their Guinier powder patterns. The structures of Er 2 Ga 2.092(1) Mg 0.908(1) , Tm 2 Ga 2.037(1) Mg 0.963(1) and Lu 2 Ga 2.176(1) Mg 0.824(1) have been refined from single crystal X-ray diffractometer data. The refinements revealed small homogeneity ranges (small degrees of Mg/Ga mixing on the 2 a sites). The magnesium atoms show square planar coordination by Ga 2 dumbbells (282 pm Mg–Ga and 257 pm Ga–Ga in the lutetium compound). Geometrically one can describe the RE 2 Ga 2 Mg phases as 1:1 intergrowth structures of CsCl and AlB 2 -related slabs of compositions RE Mg and RE Ga 2 . From DFT based calculations, charge transfer from the rare earth and magnesium atoms towards gallium can be illustrated in electron localization function ELF slice planes showing strong localization around gallium in the basal plane as well as along the tetragonal c axis signaling Ga–Ga pair interactions. The site-projected density of states DOS and COOP data further quantify this observation. Temperature dependent magnetic susceptibility measurements show Pauli paramagnetism for Sc 2 Ga 2 Mg and Lu 2 Ga 2 Mg with low room temperature susceptibility values of 2.1(1) × 10 −4 and 1.1(1) × 10 −4  emu mol −1 , respectively. Ho 2 Ga 2 Mg, Er 2 Ga 2 Mg and Tm 2 Ga 2 Mg are Curie-Weiss paramagnets with stable trivalent rare earth ground states. Antiferromagnetic ordering was detected below the Néel temperatures of T N  = 18.6(1) ( RE  = Ho), 11.9(1) ( RE  = Er) and 6.4(1) K ( RE  = Tm). The three compounds show metamagnetic transitions in their 3 K magnetization isotherms. Tm 2 Ga 2 Mg exhibits a square loop behavior with small hysteresis.

Three new cyanide-bridged heterometallic complexes {{[Cu( S , S -Chxn) 2 ][Fe(bbp)(CN) 3 ]} 2 ·2 H 2 O} n ( 1 ), {{[Cu( R , R -Chxn) 2 ][Fe(bbp)(CN) 3 ]} 2 ·2 H 2 O} n ( 2 ) and {{[Cu(Cycam)][Fe(bbp)(CN) 3 ]}·CH 3 OH·2 H 2 O} n ( 3 ) (bbp = bis(2-benzimidazolyl)pyridine dianion, Chxn = 1,2-diaminocyclo hexane, cyclam = 1,4,8,11-tetraazacyclodecane) have been assembled from the rarely used mer -tricyanidoiron(III) building block [PPh 4 ] 2 [Fe(bbp)(CN) 3 ] and three copper(II) compounds. The complexes have been characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. For the chiral enantiomers 1 and 2 , the circular dichroism (CD) spectrum was also investigated. X-ray structural analyses revealed that the structures of the cyanide-bridged Fe-Cu complexes 1 and 2 are characterized by two crystallographically independent but structurally very similar homochiral neutral chains, each consisting of the repeating units {[Cu( S,S -Chxn) 2 ][Fe(bbp)(CN) 3 ]} ( 1 ) or {[Cu( R,R -Chxn) 2 ][Fe(bbp)(CN) 3 ]} ( 2 ). The crystal structure of 3 likewise is build up of chains consisting of {[Cu(Cyclam)][Fe(bbp)(CN) 3 ]} building blocks. The temperature-dependent magnetic susceptibility and field dependent magnetization of the complexes showed antiferromagnetic interactions in complex 1 between the Fe(III) and Cu(II) ions, while complex 3 is ferromagnetic, indicating that the magnetic coupling through cyanide linkage is very sensitive to the structure parameters around the paramagnetic metal ions. These results have been further confirmed by fitting of the experimental data using a uniform chain model, leading to the coupling constants J  = −6.35 cm −1 , g  = 2.08, R  = 4.42 × 10 −4 and J  = 1.24 cm −1 , g  = 2.09, R  = ∑( χ obsd T  −  χ cald T ) 2 /∑( χ obsd T ) 2  = 4.67 × 10 −4 for complexes 1 and 3 , respectively.

The isothermal section of the Sc–Co–In system at T  = 870 K has been constructed using X-ray powder diffraction and SEM/EDX data. At the studied temperature, nine ternary compounds are formed: Sc 50 Co 12.5 In 3.5 (Ag 7+ x Mg 24− x -type structure, space group Fm 3 ‾ $\overline{3}$ , a  = 17.7411 Å), Sc 14 Co 3.10 In 2.59 (Lu 14 Co 3 In 3 type, P 4 2 / nmc , a  = 8.8913, c  = 21.387 Å), Sc 6 Co 2.18 In 0.82 (Ho 6 Co 2 Ga type, Immm , a  = 8.867, b  = 8.780, c  = 9.321 Å), Sc 2 CoIn (Pt 2 ZnCd type, P 4/ mmm , a  = 3.2887, c  = 7.1642 Å), Sc 11 Co 4 In 9 (Nd 11 Pd 4 In 9 type, Cmmm , a  = 13.836, b  = 20.758, c  = 3.351 Å), Sc 5 Co 2 In 4 (Lu 5 Ni 2 In 4 type, Pbam , a  = 17.3400, b  = 7.5940, c  = 3.3128 Å), Sc 3 Co 1.64 In 4 (Lu 3 Co 2− x In 4 type, P 6 ‾ $\overline{6}$ , a  = 7.6702, c  = 3.3595 Å), Sc 10 Co 9 In 20 (Ho 10 Ni 9 In 20 type, P 4/ nmm , a  = 12.8331, c  = 9.0226 Å), Sc 0.5 In 0.5 Co 2 (ternary non-centrosymmetric derivative of the Laves phase MgNi 2 , P 6 3 mc , a  = 4.8910, c  = 16.0166 Å, with a homogeneity range from 12.3 to 16.7 at% of indium). The cubic phase ScCo 4 In (MgCu 4 Sn type, F 4 ‾ $\overline{4}$ 3 m , a  = 6.9230(8) Å) is evidently present in the cast samples and disappears after the annealing procedure. A Sc/In substitution was observed for the solid solution Sc 1− x In x Co 2 ( x  = 0–0.26) with the structure of the cubic Laves phase (MgCu 2 type) and also for the hexagonal Sc 0.5 In 0.5 Co 2 -type phase.

The orthorhombic nitrate-boracites with the sum formula M 3 B 7 O 13 NO 3 ( M  = Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ ) were synthesized in a Walker-type multianvil apparatus under high-pressure/high-temperature conditions of 6 GPa and 800 °C, respectively. The crystal structures of the five isotypic substances, which crystallize in the space group Pca 2 1 , were determined via single-crystal X-ray diffraction and the structural features of the incorporated nitrate anions are discussed.

The Laves phase Mg 2 MnGa 3 was synthesized from the elements by arc-melting and subsequent annealing in a silica ampoule at T  = 670 K. The structure of Mg 2 MnGa 3 was refined from single-crystal X-ray diffractometer data: URe 2 type, Cmcm , a  = 543.24(1), b  = 869.59(3), c  = 858.58(2) pm, wR 2 = 0.0556, 273 F 2 values and 24 variables. The manganese and gallium atoms form a three-dimensional network of corner- and face-sharing MnGa 3 tetrahedra that derive as a ternary ordering variant from the hexagonal Laves phase MgZn 2 . The structures of the distortion and coloring variants, i.e., MgZn 2 , URe 2 , Mg 2 Cu 3 Si and Mg 2 MnGa 3 are discussed on the basis of a Bärnighausen tree. The electronic structure calculation data indicate that in addition to the metallic type of bonding an additional covalent interaction appears between the Ga–Ga and Mn–Ga atoms.

Several Lu 26 T 17− x In x ( T  = Rh, Ir, Pt) phases with varying x values were obtained by induction-melting reactions of the elements in sealed tantalum ampoules. All samples were characterized through their X-ray powder diffraction patterns. These compounds crystallize with the tetragonal Sm 26 Co 11 Ga 6 -type structure, space group P 4/ mbm and Z  = 2. The structure of Lu 26 Pt 7.55 In 9.45 has been refined from single-crystal X-ray diffractometer data: a  = 1165.32(5), c  = 1547.46(6) pm, w R 2 = 0.0895, 2173 F 2 values and 70 variables. The Lu 26 T 17− x In x phases are the first indium representatives of the Sm 26 Co 11 Ga 6 type. They belong to the n  = 4 members of Parthé’s A 5 n +6 B 3 n +5 series, which show different stacking sequences of square prisms and antiprisms. Lu 26 Pt 7.55 In 9.45 as a lutetium-rich intermetallic compound exhibits a broader range of shorter Lu–Lu distances (341–375 pm). Temperature dependent magnetic susceptibility measurements show Pauli paramagnetism for Lu 26 Ir 8.5 In 8.5 and Lu 26 Rh 7 In 10 with room temperature values of the magnetic susceptibility of χ  = 1.53 × 10 −3  emu mol −1 for Lu 26 Rh 7 In 10 and χ  = 6.54 × 10 −4  emu mol −1 for Lu 26 Ir 8.5 In 8.5 .

Orthoamides of alkynecarboxylic acids 10 react with 2-thienyl-acetonitrile under condensation to give ketene aminals. In the reaction of orthoamides 10 with 2-benzimidazolyl-acetonitrile tricyclo[1,2- a ]benzimidazol-4-carbonitriles are formed under similar conditions. From 2-methyl-1,3-disubstituted-triazin-2,4-diones and orthoamides 10 the ketene aminals result at room temperature.