Band 225, Heft 4

The orthotellurates (VI) of strontium and barium were synthesized at 1373 K in air by oxidation of TeO 2 in a melt of SrBr 2 and BaBr 2 , respectively. Their unprecedented structures were determined from room temperature single crystal X-ray diffraction data. Sr 3 TeO 6 , [ F -1, Z = 32, a = 16.5338(2) Å, b = 16.6308(2) Å, c = 16.7112(3) Å, α = 90.031(2)°, β = 90.035(2)°, γ = 90.1370(10)°, R [ F 2 > 2 σ ( F 2 )] = 0.035, 19195 F 2 data, 375 variable parameters] and Ba 3 TeO 6 [ I 4 1 / a , Z = 80, a = 19.3878(10) Å, c = 34.909(2) Å, R [ F 2 > 2 σ ( F 2 )] = 0.034, 19576 F 2 data, 453 variable parameters] are eight- and 40-fold superstructures which can be described as a pseudo-cubic close-packing of [TeO 6 ] 6– octahedra with M 2+ ( M = Ba, Sr) atoms located in the tetrahedral and octahedral voids. Sr 3 TeO 6 and Ba 3 TeO 6 are hettotypes of the cubic aristotype with the double perovskite structure crystallizing in space group Fm -3 m . A comparative discussion of the crystal structures and their group-subgroup relations are given, including different approaches for the structure descriptions.

A simple method for preparing monoclinic single crystals of ZSM-5 is developed. The ZSM-5 crystals are pressed with a weight of 50 g at an angle of 45° relative to the b and c crystallographic axes of twin ZSM-5 crystals while the temperature is simultaneously increased to 573 K. The temperature is then slowly reduced to 313 K, and these steps are repeated three times. The monoclinic structure of the single crystals of ZSM-5 produced using this method is then determined.

The high-pressure room temperature behavior of PbCO 3 was investigated by angle-dispersive synchrotron powder diffraction up to 16.16(5) GPa. A phase transition to a high-pressure polymorph II of lead carbonate was observed at a pressure of approximately p c = 8.7 GPa. Thereby, the symmetry is reduced from orthorhombic Pmcn to monoclinic P 12 1 / c 1. The cell parameters at p = 8.90(5) GPa are a = 5.101(1) Å, b = 8.303(3) Å, c = 5.602(2) Å, β = 89.51(4)°, Z = 4. The transformation is supposed to be of 2 nd order.

Crystallography reveals that the title compound, n Bu 3 SnL(LH) features a neutral n Bu 3 SnL species complexed to the neutral form of the carboxylic acid, where LH is 2-[( E )-2-(4-hydroxy-3-methylphenyl)diazen-1-yl]benzoic acid. The resulting trigonal bipyramidal coordination geometry is based on a trans -C 3 O 2 donor set; O–Sn–O = 167.59(13)°. As such, a new structural motif is found for triorganotin carboxylates. In the crystal structure, two n Bu 3 SnL(LH) molecules self assemble via O–HO hydrogen bonding leading to the formation of 48-membered macrocyclic rings. Crystal data for C 40 H 50 N 4 O 6 Sn: triclinic, P -1, a = 11.792(7), b = 12.887(7), c = 13.708(7) Å, α = 71.61(3), β = 78.39(3), γ = 82.80(4)°, V = 1932.0(18) Å 3 , Z = 2, R = 0.066.

The crystal structures of six (pyrazinecarbonyl)hydrazone di-substituted benzaldehyde derivatives [N 2 C 4 H 3 CONHN = CHC 6 H 3 XY: X,Y = 2,3-Cl 2 ; 2,3-(MeO) 2 ; 2,4-F 2 ; 2,4-Me 2 ; 3-HO—4-MeO; 3-MeO—4-HO] and one tri-substituted benzaldehyde derivative, [N 2 C 4 H 3 CONHN = CHC 6 H 2 X 3 : X 3 = 3,4,5-(MeO) 3 ] are reported. In all cases extensive intermolecular C—H···X (X = O, N or π-ring) hydrogen-bonding is present in which the the oxygen atoms of OH and OMe substituents act as hydrogen-bond acceptors and C—H bonds of methyl groups act as hydrogen-bond donors. The connectivity attained is one-dimensional in chains or ribbons in the 2,3-(OMe) 2 and 2,4-Me 2 derivatives, three dimensional only in the case of the 3-MeO—4-HO derivative and two dimensional in layers of molecules otherwise. It is concluded, therefore, that the bulky nature of the substituents limits the connectivity attainable in this series of compounds.