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Main group element nets to a T
No full textT-shaped nets (three-coordinated nets with an angular metric, bond angles near 90°, 90°, 180°) are found in a number of extended structures. We explore in this paper the geometrical and electronic consequences of a stricter T-shape metric, where the distances between the vertices of the net are approximately equal and in the range of
a chemical bond. Every atom in such a net has a T-shaped environment. One can think of these nets as extensions of BrF3 or of substructures of various extended tellurium compounds. Several construction principles are found which allow an enumeration of a variety of one-, two-, and three-dimensional T-shape nets; not every threecoordinated
net lends itself to the stricter geometrical and distance metric. Not everything is possible; there are no zero-dimensional T-nets, and none made entirely of three atom segments. Previous ideas on electron-rich multicenter bonding lead to a simple way of calculating the magic electron counts for each net; these lie in the range of 6 to
6.67
Studi EPR di radicali indotti per irraggiamento gamma di solidi porosi modulari dello Zn contenenti molecole guest
No full textLigand dependent topology changes in six zinc coordination polymers
No full textUsing 4,4'-(hexafluoroisopropylidene)bis(benzoic acid) (H2hfipbb) and different pyridyl-containing additional ligands, six novel zinc coordination polymers have been obtained under hydrothermal conditions, and structurally characterized. The frame topology of the obtained compounds is discussed
An Unusual Three-Dimensional Coordination Network Formed by Parallel Polycatenation of Two-Fold Interpenetrated (6,3) Layers Based on a Novel Three-Connecting Ligand
No full textThe novel tridentate ligand 1,3,5-tris(4-cyano-phenoxymethyl)-2,4,6-trimethylbenzene (1) together with silver-(I) triflate has afforded the interesting coordination polymer [Ag(1)(CF3SO3)].0.5H2O, containing undulated (6,3) layers of hexagonal meshes, with alternating Ag and (1) triconnected centers, entangled into 2-fold parallely interpenetrated sheets, which, furthermore, are polycatenated to generate an unique three-dimensional array
Ortho-metalated pyridine derivatives of the unsaturated anion [Re3(μ-H)4(CO)10]-. Syntheses and X-ray crystal structures of the tetraethylammonium salts of the anions [Re3(μ-H)3(μ-η2-NC5H 4)(CO)10]- and [Re3(μ-H)3
No full textFull title: Ortho-metalated pyridine derivatives of the unsaturated anion [Re3(μ-H)4(CO)10]-. Syntheses and X-ray crystal structures of the tetraethylammonium salts of the anions [Re3(μ-H)3(μ-η2-NC5H 4)(CO)10]- and [Re3(μ-H)3(μ-η2-NC5H 4)(CO)9(NC5H5)]-. The unsaturated cluster anion [Re3(μ-H)4(CO)10]- (1) reacts overnight in pyridine solution, at room temperature, giving the μ-pyridyl derivative [Re3(μ-H)3(μ-η2-NC5H 4)(CO)10]- (2). The ortho-metalation proceeds with H2 evolution, which derives from the elimination of two hydrides of the parent cluster, as shown on performing the reaction with NC5D5. When the above reaction, in pyridine solution, is accomplished at 85°C, within 2 h another product is obtained, namely [Re3(μ-H)3(μ-η2-NC5H 4)(CO)9(NC5H5)]- (3), containing the μ-pyridyl ligand and a pyridine molecule replacing a carbonyl ligand. On the contrary, in tetrahydrofuran solution, in the presence of only a moderate excess of pyridine (∼5 equiv), the reaction at 85°C gives the unsaturated anion [Re3(μ-H)4(CO)9(NC5H 5)]- (4), previously known. This species has been proven to be unable to further react with pyridine, and therefore the formation of 3 from compound 1 occurs via intermediate 2 and not 4. Both complexes 2 and 3, as their NEt4+ salts, have been investigated by X-ray analysis. Complex 2 gives orthorhombic crystals, space group Pbca (No. 61), with a = 13.297 (4) Å, b = 18.343(7) Å, c = 24.432(12) Å, and Z = 8; the structure was refined to R = 0.028 for 1829 significant observed reflections. Complex 3 crystallizes in the monoclinic space group P21/c (No. 14), with a = 13.363(1) Å, b = 13.143(1) Å, c = 18.955(3) Å, β = 100.09(1)°, and Z = 4; the refinements, based on 3924 significant observed data, gave a final R value of 0.027. Both the anions contain an isosceles triangle of metal atoms, with the two longer edges bridged by a hydrido ligand and the shorter one by a hydride and a μ-pyridyl ligand. In 3 an axial carbonyl of the Re(CO)4 unit of 2 has been substituted by a pyridine molecule whose aromatic ring faces that of the pyridyl group. 1H NMR analysis of 2 in solution at different temperatures reveals a fluxional behavior, leading to the exchange of the two hydrides bridging the longer triangular edges (Ea, = 72 ± 1 kJ/mol). © 1993 American Chemical Society
Synthesis and crystal structure of a new alkaline-earth metal chalcogenide: Barium ditelluride
No full textDuring our exploration of kinetically stable solid state materials, we have discovered a new binary material, BaTe2, the first alkaline earth metal dichalcogenide prepared using flux growth technique. The crystal structure of BaTe2 was determined by single-crystal X-ray diffraction methods. It belongs to the tetragonal space group I4/mcm (No. 140) with lattice constants a = 7.181(1) A ̊, c = 8.898(2) A ̊, V = 458.8(1) A ̊3 and Z=4. The final residual index is converged to R=1.5%, wR2=3.5%. BaTe2 is a Zintl type compound isostructural to SrS2. Pairs of tellurium atoms form dimeric units (Te2)2- with a Te-Te separation of 2.7722(8) Å. The synthesis of BaTe2 at relatively low temperature has provided an alternative and convenient route for preparing new compounds in this category. © 1994
The cation as a tool to get spin-canted three-dimensional iron(III) networks
No full textAlkyl-substituted ammonium cations (X) allow the preparation of a series of spin-canted oxo- and oxalato-bridged three-dimensional
iron(III) networks, exhibiting magnetic ordering at Tc values ranging from 40 to 56 K. The value of Tc varies with the cation despite the lack of significant structural modifications
Studi EPR di radicali indotti per irraggiamento gamma di solidi porosi dello Zn contenenti molecule guest.
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