Search results for "geometry."
showing 10 items of 4386 documents
Points massiques, espace des sphères et « hyperbole »
2015
The use of massic points permits to define a branch of a hyperbola in the Euclidean plane using a Rational Quadratic Bézier Curve. In the space of spheres, a circular cone, a circular cylinder, a torus, a pencil of spheres or a Dupin cyclide is represented by a conic. If the kind of the pencil is Poncelet or if the canal surface is a circular cone, a spindle torus, a spindle or a horned Dupin cyclide, the curve is a circle which is seen as a hyperbole. The limit points of the pencil or the singular points of the Dupin cyclide can be determined using the asymptotes of this circle. In this article, we show that the use of massic points simplifies the modelization of these pencils or these Dup…
Crystal structure of bis{μ2-3-(pyridin-2-yl)-5-[(1,2,4-triazol-1-yl)methyl]-1,2,4-triazolato}bis[aquanitratocopper(II)] dihydrate
2016
The title complex is a centrosymmetric dimer with a copper–copper distance of 4.0408 (3) Å. The Cu ions in the dimer are bridged by two triazole rings and oxygen donor ligands from water molecules and nitrate anions in a distorted octahedral coordination geometry.
Crystal structures of organoplatinum complexes containing alkyleugenoxyacetate and p-chloroaniline
2016
In the title trans-dichloridoplatinum(II) complexes, the central PtII atom is further coordinated by the p-chloroaniline N atom and ethylenic double bond of alkyleugenoxyacetate.
Bis{3,5-di-tert-butyl-N-[(4-dimethylamino)phenyl]salicylaldiminato}cobalt(II)
2017
In the title complex [systematic name: bis(2,4-di-tert-butyl-6-{N-[4-(dimethylamino)phenyl]carboximidoyl}phenolato)cobalt(II)], [Co(C23H31N2O)2], the cobalt(II) atom is coordinated by pairs of O and N atoms in a distorted tetrahedral coordination geometry. The dihedral angles formed by the aromatic rings of the same ligand are 51.99 (11) and 36.58 (9)°. The molecular conformation features weak intramolecular C—H...O hydrogen bonds. In the crystal, inversion-related pairs of complex molecules are linked into dimers by weak C—H...π interactions. The methyl C atoms oftert-butyl groups have rotational disorder, with site occupancies of 0.647 (7) and 0.617 (6) for the major components and 0.353 …
Bis(4,6-di-tert-butyl-2-{N-[4-(diethylamino)phenyl]carboximidoyl}phenolato)cobalt(II)
2017
In the title complex, [Co(C25H35N2O)2], the cobalt(II) atom has a distorted tetrahedral geometry provided by pairs of O and N atoms. The dihedral angles between the benzene rings of the same ligand are 52.39 (9) and 34.96 (9)°. The molecular structure is stabilized by weak intramolecular C—H...O hydrogen bonds. The crystal packing is stabilized mainly by van der Waals forces. The structure contains a solvent-accessible void of 276 Å3which was treated using the SQUEEZE routine fromPLATON[Spek (2015).Acta Cryst.C71, 9–18]. The methyl C atoms of thetert-butyl groups are rotationally disordered, with site occupancies of 0.802 (3) and 0.548 (9) for the major components and 0.198 (3) and 0.452 (9…
Crystal structure of chlorido(2-{1-[2-(4-chlorophenyl)hydrazin-1-ylidene-κN]ethyl}pyridine-κN)(η5-pentamethylcyclopentadienyl)rhodium(III) chloride
2015
The title compound, [Rh(η5-C5Me5)Cl(C13H12ClN3)]Cl, is chiral at the metal and crystallizes as a racemate. Upon coordination, the hydrazinylidenepyridine ligand is non-planar, an angle of 54.42 (7)° being observed between the pyridine ring and the aromatic ring of the [2-(4-chlorophenyl)hydrazin-1-ylidene]ethyl group.
Crystal structure of catena-poly[[[(2-ethoxypyrazine-κN)copper(I)]-di-μ2-cyanido] [copper(I)-μ2-cyanido]]
2019
The title compound, {[Cu(EtOpz)(CN)2][CuCN]}n, where EtOpz is 2-ethoxypyrazine, is a two-dimensional polymeric copper complex with different coordination environments of the two CuI ions. One Cu atom is coordinated to the 2-ethoxypyrazine molecule and two bridging cyanide ligands, equally disordered over two sites. The second Cu atom is coordinated by two disordered over two sites bridging cyanide groups. Two copper–cyanide chains are connected through Cu⋯Cu contact.
Crystal structures of three mercury(II) complexes [HgCl2L] where L is a bidentate chiral imine ligand
2015
Three complexes synthesized by coordination of chiral imines to HgCl2 have been characterized, in which the tetrahedral HgII centre has a geometry strongly distorted towards the disphenoidal geometry.
Geometrical and conformational preferences of the 9‐fluorenylmethoxycarbonyl‐amino moiety
2004
Structural parameters, originating from x-ray crystallographic data, have been compiled for 13 derivatives of amino acids, peptides and related compounds, which contain a total of 14 Fmoc-NH- moieties. For these moieties, molecular geometries and conformations--described by the omegao, theta1, theta2 and theta3' torsion angles--were analysed and compared with the corresponding parameters for the Z-NH- and Boc-NH-moieties (290 and 553, respectively). To gain a deeper insight into the conformational features of the Fmoc-NH- moiety, ab initio free molecule calculations were performed for fully relaxed minima. Also the potential energy surface as a function of the torsion angles (theta3', theta…
Crystal structure of bis(cyclohexylammonium) diphenyldioxalatostannate(IV)
2015
In the title salt, (CyNH3)2[Sn(Ph2)(C2O4)2] (Cy is cyclohexyl and Ph is phenyl), the SnPh2 moiety is chelated by two oxalate anions, leading to a cis arrangement within the distorted octahedral coordination sphere of the SnIV atom.