A cobalt(III) compound of a 13‐membered cyclic tetra­amine: trans‐(12,12‐dimethyl‐1,4,7,10‐tetra­aza­cyclo­tetra­decane)diisothio­cyanato­cobalt(III) tetra­isothio­cyanato­zinc(II) ethanol solvate

The title compound, [Co(NCS)₂(C₁₁H₂₆N₄)]₂[Zn(NCS)₄]·C₂H₅OH, has two similar cations with the Co^III atom coordinated in a planar fashion by the 13‐membered cyclic tetra­amine, in the 1R,4S,7R,10S configuration, and with trans isothio­cyanate ligands. The six‐membered chelate ring is in a chair conformation, with one axially and one equatorially oriented methyl substituent [mean Co—N = 1.948 (2) Å]. The `opposite' chelate ring (N<sup>4</sup> and N<sup>7</sup>) is in an eclipsed conformation [mean Co—N = 1.928 (2) Å], and the `side' chelate rings have gauche conformations. The mean Co—N_NCS distance is 1.928 (2) Å. Both cations have one Co—N—C group nearly linear and the other appreciably bent, with mean Co—N—C angles of 178.7 (1) and 160.4 (1)°, respectively. The [Zn(NCS)₄]²⁻ anion is approximately tetra­hedral, with Zn—N = 1.951 (1)–1.986 (1) Å, N—Zn—N = 104.5 (1)–111.9 (1)° and Zn—N—C = 152.5 (1)–179.4 (1)°. One NH group is hydrogen bonded to the ethanol O atom and the other NH groups are bonded to thio­cyanate S atoms, forming a network.     

cis‐Dinitrito(1,4,8,11‐tetra­aza­cyclo­tetra­decane‐κ4N)­chromium(III) nitrite

In the title compound, [Cr(ONO)₂(cyclam)]NO₂ (cyclam is 1,4,8,11‐tetra­aza­cyclo­tetra­decane, C₁₀H₂₄N₂), the complex cation is located on a twofold symmetry axis. The central Cr atom has a distorted octahedral coordination, involving two Cr—O bonds, with the monodentate nitrite O atoms adopting a cis configuration, and four Cr—N bonds. The mean Cr—N and Cr—O distances are 2.0895 (14) and 1.9698 (14) Å.     

Tetra­phenyl­arsonium tetra­iodo­thallate(III)

The As and Tl atoms in title compound, (C₂₄H₂₀As)[TlI₄], sit on fourfold inversion centres, resulting in a [TlI₄]^? anion with D_2d symmetry and a Tl—I bond length of 2.7691 (3) Å. The tetrahedral anion is tetragonally distorted, being flattened in the direction of the c axis of the tetragonal unit cell, so that the two unique I—Tl—I angles differ by about 9°. In contrast, the cation has S₄ symmetry and the tetrahedral coordination geometry of the As atom is very slightly stretched in the direction of the c axis.     

Solvent extraction of gold(III) by octadecyldimethylbenzylammonium chloride (ODMBAC) from chloride solution

The mechanism of solvent extraction of gold(III) in hydrochloric acid media with quaternary ammonium salt octadecyl dimethyl benzyl ammonium chloride dissolved in chloroform was studied. The influences of temperature, NaCl and HCl concentraction on the extraction equilibrium were also investigated. The extraction reaction is exothermic (H° = -28.53±0.15 kJ/mol) and log K _ex = 5.47±0.04.     

Cyano­cobalt(III) complexes of penta‐ and tetra­dentate‐coordinated macrocyclic hexa­amines

The pendent‐arm macrocyclic hexa­amine trans‐6,13‐dimethyl‐1,4,8,11‐tetra­aza­cyclo­tetra­decane‐6,13‐diamine (L) may coordinate in tetra‐, penta‐ or hexa­dentate modes, depending on the metal ion and the synthetic procedure. We report here the crystal structures of two pseudo‐octa­hedral cobalt(III) complexes of L, namely sodium trans‐cyano­(trans‐6,13‐dimethyl‐1,4,8,11‐tetra­aza­cyclo­tetra­decane‐6,13‐diamine)cobalt(III) triperchlorate, Na[Co(CN)(C₁₃H₃₀N₆)](ClO₄)₃ or Na{trans‐[CoL(CN)]}(ClO₄)₃, (I), where L is coordinated as a penta­dentate ligand, and trans‐dicyano­(trans‐6,13‐dimethyl‐1,4,8,11‐tetra­aza­cyclo­tetra­decane‐6,13‐diamine)cobalt(III) trans‐dicyano­(trans‐6,13‐dimethyl‐1,4,8,11‐tetra­aza­cyclo­tetra­decane‐6,13‐diaminium)cobalt(III) tetra­perchlorate tetra­hydrate, [Co(CN)₂(C₁₄H₃₂N₆)][Co(CN)₂(C₁₄H₃₀N₆)](ClO₄)₄·4H₂O or trans‐[CoL(CN)₂]trans‐[Co(H₂L)(CN)₂](ClO₄)₄·4H₂O, (II), where the ligand binds in a tetra­dentate mode, with the remaining coordination sites being filled by C‐­bound cyano ligands. In (I), the secondary amine Co—N bond lengths lie within the range 1.944 (3)–1.969 (3) Å, while the trans influence of the cyano ligand lengthens the Co—N bond length of the coordinated primary amine [Co—N = 1.986 (3) Å]. The Co—CN bond length is 1.899 (3) Å. The complex cations in (II) are each located on centres of symmetry. The Co—N bond lengths in both cations are somewhat longer than in (I) and span a narrow range [1.972 (3)–1.982 (3) Å]. The two independent Co—CN bond lengths are similar [1.918 (4) and 1.926 (4) Å] but significantly longer than in the structure of (I), again a consequence of the trans influence of each cyano ligand.     

The hydrated and anhydrous gold(III) tetrachloride salts of l‐ecgonine,an important forensic toxicology marker for cocaine

The structure of the hydrated gold(III) tetrachloride salt of l ‐ecgonine {hydronium tetrakis[(1R,2R,3S,5S,8S)‐3‐hydroxy‐8‐methyl‐8‐azoniabicyclo[3.2.1]octane‐2‐carboxylate pentakis[tetrachloridoaurate(III)] hexahydrate}, (C₉H₁₆NO₃)₄(H₃O)[AuCl₄]₅·6H₂O, demonstrates an unprecedented stoichiometric relationship between the cations and anions in the unit cell. The previous tropane alkaloid structures, including the related hydrochloride salts, all have a cation–anion ratio of 1:1, as does the anhydrous salt described here, namely (1R,2R,3S,5S,8S)‐3‐hydroxy‐8‐methyl‐8‐azoniabicyclo[3.2.1]octane‐2‐carboxylate tetrachloridoaurate(III), (C₉H₁₆NO₃)[AuCl₄]. The hydrated salt, however, consists of four monopositive N‐protonated units of the alkaloid and five [AuCl₄]⁻ counter‐ions, plus seven solvent water molecules. The H atom required for change balance has been assigned to a water molecule. In addition, the hydrate has a novel arrangement, with all seven of the water molecules and all of the O atoms in the cations participating in an alternating arrangement of interleaved sheets of the anionic species. Both the hydrate and the anhydrous salt of the same toxicologically important marker for cocaine show that the cation and anion are in close proximity to each other, as was found in the gold(III) tetrachloride salt of l ‐cocaine.     

A second polymorph of 1,1,4,4‐tetra­methyl­piperazinium penta­bromo­thallate(III)

A new polymorph of the title compound, (C₈H₂₀N₂)[TlBr₅], contains cations located about crystallographic centres of inversion and trigonal‐bipyramidal anions which have a C₂ axis passing through the equatorial plane of the anion. The anion has the least distorted geometry seen so far in any structure possessing this anion and the axial Tl—Br bonds are about 0.13 Å longer than the equatorial Tl—Br bonds, consistent with related structures. The anion in the initially reported polymorph has lower symmetry and a greater distortion of the trigonal‐bipyramidal coordination.     

Polymeric tetra­aqua­tris­(malonato)­dilanthanum(III) monohydrate

The title compound, [La₂(C₃H₂O₄)₃(H₂O)₄]·H₂O, forms a layer‐type polymeric structure. The layers, which contain infinite puckered four‐membered La—O—La—O rings in a pseudo‐ternary symmetry, are formed by the lanthanum and one independent malonate group. They are interconnected by the second independent malonate group, giving a three‐dimensional framework in which wide channels accommodate one disordered water mol­ecule of crystallization. The La atom lies on a twofold axis and is ten‐coordinated by eight O atoms from carboxyl­ate groups and two water mol­ecules. One malonate group is monodentate and triply bridging chelating, whilst the other is doubly monodentate. The extensive network of hydrogen bonds and bridge bonds observed in this structure enhances the structural stability. Despite some identical subfeatures, this structure is quite different from that observed in [La₂(C₃H₂O₄)₃(H₂O)₃]·2H₂O.     

Tri‐μ2‐chloro‐tetra­chloro‐μ3‐oxo‐hexakis­(tetra­hydro­furan‐κO)­dititanium(III)­samarium(III): a novel trinuclear Sm–Ti mixed species

In the title compound, [SmTi₂Cl₇O(C₄H₈O)₆], the metal ions are linked by a central μ₃‐oxo ion and by three μ₂‐chloro ions, giving a planar moiety containing a binary crystallographic axis. The coordination spheres are completed by terminal chloro ligands and tetra­hydro­furan mol­ecules, with resulting pentagonal bipyramidal and octahedral environments for the Sm and Ti atoms, respectively.     

μ‐Oxo‐bis­[(2,3,12,13‐tetra­bromo‐5,10,15,20‐tetra­phenyl­porphyrinato)­iron(III)] bis­(di­chloro­methane) solvate

The precise structure of the title compound, [Fe₂O(C₄₄H₂₄Br₄N₄)₂]·2CH₂Cl₂, is reported. The Fe—N distances are non‐equivalent in pairs because of the asymmetric peripheral substitution; the values are 2.098 Å to the brominated rings and 2.041 Å to the other two rings. The Fe—O bond distance is 1.7583 (4) Å. The mol­ecule has required twofold symmetry so that there is one unique porphyrin macrocycle and one Fe—O bond length in contrast to a previous report on the same species.     

A 4‐ethyl­pyridine complex of tetra­chloro­molybdenum(III) and its oxidation product

The Mo atoms in the title compounds, i.e. triethyl­ammonium cis‐tetra­chloro­bis(4‐ethyl­pyridine‐N)­molybdate(III), cis‐(C₆H₁₆N)­[MoCl₄(C₇H₉N)₂], and trans‐tetra­chloro­bis(4‐ethyl­pyridine‐N)molybdenum(IV), trans‐[MoCl₄(C₇H₉N)₂], are six‐coordinate with octahedral geometry. The Mo atom in the latter complex lies on a site with crystallographic 2/m symmetry.     

Bis(1‐methyl­guanidinium) tetra­chloro­cuprate(II) and 4‐(2‐pyrimidin‐1‐io)­piperazinium tetra­chloro­cuprate(II)

The crystal structures of the title compounds, (C₂N₃H₈)₂[CuCl₄], (I), and (C₈H₁₄N₄)[CuCl₄], (II), have been studied by X‐ray diffraction. The structures consist of discrete [CuCl₄]^2? anions with two monoprotonated (C₂N₃H₈)⁺ cations for (I) and a diprotonated (C₈N₄H₁₄)²⁺ cation for (II). The [CuCl₄]^2? anions of both compounds have flattened tetrahedral geometries. There are several N—H?Cl weak bonds that join the [CuCl₄]^2? anions and the organic cations helping retain the pseudo‐tetrahedral geometries of the anions.     

Isothermal crystallization behavior of poly(L‐lactide) in poly(L‐lactide)‐block‐poly(ethylene glycol) diblock copolymers

The crystal unit‐cell structures and the isothermal crystallization kinetics of poly(L ‐lactide) in biodegradable poly(L ‐lactide)‐block‐methoxy poly(ethylene glycol) (PLLA‐b‐MePEG) diblock copolymers have been analyzed by wide‐angle X‐ray diffraction and differential scanning calorimetry. In particular, the effects due to the presence of MePEG that is chemically connected to PLLA as well as the PLLA crystallization temperature T_C are examined. Though we observe no variation of both the PLLA and MePEG crystal unit‐cell structures with the block ratio between PLLA and MePEG and T_C, the isothermal crystallization kinetics of PLLA is greatly influenced by the presence of MePEG that is connected to it. In particular, the equilibrium melting temperature of PLLA, T, significantly decreases in the diblock copolymers. When the T_C is high so that the crystallization is controlled by nucleation, because of the decreasing T and thereafter the nucleation density with decreasing PLLA molecular weight, the crystallinity of PLLA also decreases with a decrease in the PLLA molecular weight. While, for the lower crystallization temperature regime controlled by the growth mechanism, the crystallizability of PLLA in copolymers is greater than that of pure PLLA. This suggests that the activation energy for the PLLA segment diffusing to the crystallization site decreases in the diblocks. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2438–2448, 2006     

One‐dimensional structure of catena‐poly[tetra­ethyl­ammonium [tetra­cyano­iron(III)‐μ‐cyano‐[bis­(ethyl­ene­diamine)­cadmium(II)]‐μ‐cyano] tetra­hydrate]

The title compound, {(C₈H₂₀N)[CdFe(CN)₆(C₂H₈N₂)₂]·4H₂O}_n, was isolated from the aqueous system Cd²⁺/ethyl­ene­diamine (en)/[Fe(CN)₆]³⁻ in the presence of [Et₄N]Br. The crystal structure is dominated by a one‐dimensional motif, viz. a negatively charged 2,2‐CT (cis–trans) [–Cd(en)₂—NC—Fe(CN)₄—CN–]_nⁿ⁻ chain. The Cd and Fe atoms of the anion and the N atom of the cation all lie on twofold axes. The ethyl groups of the cation are equally disordered over two orientations. The cationic building block of the chain consists of a Cd^II atom coordinated by two chelating en ligands, and the distorted octa­hedral coordination is completed by two bridging cyano ligands in cis positions. The anionic building block is an [Fe(CN)₆]³⁻ anion in which the Fe^III atom is octa­hedrally coordinated by six cyano ligands; two of the cyano ligands, in trans positions, are bridging. The uncoordinated water mol­ecules link neighbouring chains through O—H⋯N and N—H⋯O hydrogen bonds.     

(12‐Hydro­xy­methyl‐5,5,7,12,14‐penta­methyl‐1,4,8,11‐tetra­aza­cyclo­tetra­decane‐N‐acetato‐N,N′,N′′,N′′′,O,O′)cobalt(III) chloride perchlorate monohydrate

In the title compound, [Co(C₁₈H₃₇N₄O₃)](ClO₄)Cl·H₂O, the Co^III ion has a distorted octahedral geometry, with four N atoms and two O atoms constituting the coordination sphere. The crystal structure is stabilized by a three‐dimensional network of hydrogen bonds.     

A square‐planar hydrated cationic tetrakis(methimazole)gold(III) complex

The cationic pseudo‐square‐planar complex tetrakis(1‐methyl‐2,3‐dihydro‐1H‐imidazole‐2‐thione‐κS)gold(III) trichloride sesquihydrate, [Au(C₄H₆N₂S)₄]Cl₃·1.5H₂O, was isolated as dark‐red crystals from the reaction of chloroauric acid trihydrate (HAuCl₄·3H₂O) with four equivalents of methimazole in methanol. The Au^III atoms reside at the corners of the unit cell on an inversion center and are bound by the S atoms of four methimazole ligands in a planar arrangement, with S—Au—S bond angles of approximately 90°.