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K+ Cations (k+ + cation)

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Chemistry100%

Selected Abstracts

The twinned crystal structure of tripotassium benzene-1,3,5-tris(trifluoroborate)

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2010
Daniel Franz
The title compound, 3K+·C6H3B3F93,, crystallizes as discrete anions and cations which are connected by K...F and K..., interactions. Two of the ,BF3 residues attached to the aromatic ring adopt a conformation with all F atoms out of the plane of the aromatic ring, whereas the third residue has an almost synperiplanar conformation for one of the F,B,C,C torsion angles. It is remarkable that only one of the K+ cations interacts with the arene ring and that only one side of the aromatic ring coordinates to a K+ cation. As a result, a sandwich structure does not occur. All K+ ions show a coordination mode that cannot be conveniently described with a polyhedron. The anions are located in the (102) planes with the K+ cations located between these planes. The investigated crystal was a nonmerohedral twin with the fractional contribution of the minor twin component being 0.405,(4). The title compound is the first example of a structure containing a benzene ring substituted with three ,BF3 groups. Only eight other structures have been reported in which a benzene ring carries at least one ,BF3 group. Just five of these contain a K+ ion, but in none of these is the K+ ion coordinated to the aromatic ring. [source]

K2[O(HgSO3)3], a new sulfitomercurate with an [OHg3] core

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2008
Matthias Weil
The structure of dipotassium ,3 -oxido-tris[sulfitomercurate(II)], K2[O(HgSO3)3], is characterized by segregation of the K+ cations and complex [O(HgSO3)3]2, anions into layers parallel to (010). The anion has m symmetry and is a new example of a ,3 -oxido-trimercurate complex with a central [OHg3] core. This unit adopts the shape of a flat, almost trigonal, pyramid (mean O,Hg = 2.072,Å and mean Hg,O,Hg = 110.8°). The two independent Hg,S bonds have nearly the same length (mean Hg,S = 2.335,Å). Due to intermolecular O...Hg donor,acceptor interactions greater than 2.65,Å, the O,Hg,S fragments are slightly bent. The [KO9] coordination polyhedron of the K+ cation approaches a distorted tricapped trigonal prism with a [6+1+2] coordination. [source]

Using Diffusion NMR To Characterize Guanosine Self-Association: Insights into Structure and Mechanism

CHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2005
Mark S. Kaucher
Abstract This paper presents results from a series of pulsed field gradient (PFG) NMR studies on lipophilic guanosine nucleosides that undergo cation-templated assembly in organic solvents. The use of PFG-NMR to measure diffusion coefficients for the different aggregates allowed us to observe the influences of cation, solvent and anion on the self-assembly process. Three case studies are presented. In the first study, diffusion NMR confirmed formation of a hexadecameric G-quadruplex [G,1]16,4,K+,4,pic, in CD3CN. Furthermore, hexadecamer formation from 5,-TBDMS-2,,3,-isopropylidene G,1 and K+ picrate was shown to be a cooperative process in CD3CN. In the second study, diffusion NMR studies on 5,-(3,5-bis(methoxy)benzoyl)-2,,3,-isopropylidene G,4 showed that hierarchical self-association of G8 -octamers is controlled by the K+ cation. Evidence for formation of both discrete G8 -octamers and G16 -hexadecamers in CD2Cl2 was obtained. The position of this octamer,hexadecamer equilibrium was shown to depend on the K+ concentration. In the third case, diffusion NMR was used to determine the size of a guanosine self-assembly where NMR signal integration was ambiguous. Thus, both diffusion NMR and ESI-MS show that 5,- O -acetyl-2,,3,- O -isopropylidene G,7 and Na+ picrate form a doubly charged octamer [G,7]8,2,Na+,2,pic,9 in CD2Cl2. The anion's role in stabilizing this particular complex is discussed. In all three cases the information gained from the diffusion NMR technique enabled us to better understand the self-assembly processes, especially regarding the roles of cation, anion and solvent. [source]

Alkali Metal (Li+,Cs+) Salts with Hexafluorochromate(V), Hexafluorochromate(IV), Pentafluorochromate(IV), and Undecafluorodichromate(IV) Anions

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2008
Zoran Mazej
Abstract The compounds ACrF6 (A = Li,Cs) were prepared by photochemical reactions of AF/CrF3 mixtures in anhydrous HF with elemental F2 at ambient temperature. The crystal structures of compounds ACrF6 (A = K,Cs) are analogous to that of KOsF6, and NaCrF6 exhibits polymorphism. The trigonal phase (II) can be classified to have the well-known LiSbF6 type of structure, while the crystal structure of the orthorhombic modification (I) appears to be a new structure-type. Thermal decomposition of the ACrF6 salts produce ACrF5(A = Rb, Cs), ACrF5/A2CrF6 (A = K), or A2CrF6 (A = Li, Na). These compounds undergo partial solvolysis in anhydrous HF with precipitation of CrF4. From the remaining solutions of the [CrF6]2, anions and dissolved AF (A = Li,Cs), single crystals of ACrF5 (A = K,Cs), A2CrF6·2HF (A = Na, K), A2CrF6·4HF (A = Rb, Cs), Li2CrF6, and K3Cr2F11·2HF were grown, and their crystal structures determined. The main structural feature of the ACrF5 compounds is the infinite zig-zag [CrF5]nn, chain of distorted [CrF6] octahedra joined by cis vertices. The crystal structures of A2CrF6·2HF (A = Na, K) and A2CrF6·4HF (A = Rb, Cs) consist of distorted [CrF6]2, octahedra involved in moderate to strong hydrogen bonding with HF molecules, while two A+ cations compensate the negative charge of each octahedron. In Na2CrF6·2HF, two neighboring HF molecules are involved in moderate to strong hydrogen bonding with each other. (HF)2 dimers with a parallelogram structure are formed. The mutual interactions in the crystal structure of K2CrF6·2HF differ from those found in Na2CrF6·2HF. In the former, each HF molecule interacts with the [CrF6]2, anion and three K+ cations. A2CrF6·4HF compounds of Rb and Cs are isostructural. Their structures consist of A+ cations and [CrF6]2, anions involved in hydrogen bonding with two sets of HF molecules in the trans position. The crystal structure of K3Cr2F11·2HF reveals a rare case of the [M2F11]3, anion. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Treating [K4(H2O)0.5][SnTe4] with PPh4+ or AsPh4+: Formation of a Highly Air-Stable Tellurostannate Salt, a Tellurolate with One-Coordinate Te Atoms, and a Polytelluride Salt with ,1[Te4(H2O)2]2, Chains,

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 28 2007
Eugen Ruzin
Abstract In reactions of potassium orthotellurostannates with EPh4Cl (E = P, As), different single-crystalline products are obtained. An air-stable dimeric tellurostannate forms by partial replacement of strongly interacting K+ cations by weakly interacting or noninteracting [PPh4]+ ions. For E = As, an equally air-stable tellurophenolate, in which Te has the rare coordination number 1, results upon As,C bond cleavage at a tetraphenylarsonium cation. Oxidation of the air-sensitive [Sn2Te6]4, anion and Te2, by O2 (air) affords a tetratelluride salt with strands of H2O-bridged [Te4]2, anions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

The synthesis of novel crown ethers, part X,, 4-propyl-and 3-ethyl-4-methylchromenone-crown ethers

JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2004
Esra Tiftikçi
Starting from ethyl propionylacetate, and ethyl 2-ethylacetoacetate we prepared 4-propyl-7,8-, 4-propyl-6,7-, 3-ethyl-4-methyl-7,8- and 3-ethyl-4-methyl-6,7-dihydroxy-2H -chromenones which were allowed to react with the bis-dihalides or ditosylates of glycols in DMF/Na2CO3 to afford the 6,7- and 7,8-chromenone derivatives of 12-crown-4, 15-crown-4 and 18-crown-6. The products were identified using ir, 13C and 1H nmr, ms and high resolution mass spectroscopy. The cation selectivities of chromenone crown ethers with Li+, Na+ and K+ cations were estimated from the steady state emission fluorescence spectra of free and cation complexed chromenone macrocyclic ethers in acetonitrile. [source]

The twinned crystal structure of tripotassium benzene-1,3,5-tris(trifluoroborate)

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2010
Daniel Franz
The title compound, 3K+·C6H3B3F93,, crystallizes as discrete anions and cations which are connected by K...F and K..., interactions. Two of the ,BF3 residues attached to the aromatic ring adopt a conformation with all F atoms out of the plane of the aromatic ring, whereas the third residue has an almost synperiplanar conformation for one of the F,B,C,C torsion angles. It is remarkable that only one of the K+ cations interacts with the arene ring and that only one side of the aromatic ring coordinates to a K+ cation. As a result, a sandwich structure does not occur. All K+ ions show a coordination mode that cannot be conveniently described with a polyhedron. The anions are located in the (102) planes with the K+ cations located between these planes. The investigated crystal was a nonmerohedral twin with the fractional contribution of the minor twin component being 0.405,(4). The title compound is the first example of a structure containing a benzene ring substituted with three ,BF3 groups. Only eight other structures have been reported in which a benzene ring carries at least one ,BF3 group. Just five of these contain a K+ ion, but in none of these is the K+ ion coordinated to the aromatic ring. [source]

CdZn2KB2O6F, a new fluoride borate crystal

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2010
Fan Zhang
During an attempt to grow crystals of the nonlinear optical material Cd3Zn3B4O12 using a KBF4 flux, crystals of a new cadmium dizinc potassium borate fluoride compound, CdZn2KB2O6F, were unexpectedly isolated. The structure consists of layers constructed of distorted corner-sharing ZnO3F tetrahedra and BO3 triangles. Both Zn and B reside on threefold rotation axes, while the F, anion is located at a site of 3.2 symmetry. The CdII (site symmetry ) and K+ (site symmetry 3.2) ions occupy six- and nine-coordinate interlayer sites, respectively. The BO3 triangles and ZnO3 pyramids from the ZnO3F tetrahedra share bridging O atoms with each other to form an extended [ZnBO3] layer parallel to (001). Although these layers are similar to the [MBO3] layers seen in other compounds, they are uniquely bridged here by the Cd centres and F, anions to form a three-dimensional framework. In so doing, a series of channels is formed along the [010] direction and the K+ cations are found in these channels. [source]

K2[O(HgSO3)3], a new sulfitomercurate with an [OHg3] core

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2008
Matthias Weil
The structure of dipotassium ,3 -oxido-tris[sulfitomercurate(II)], K2[O(HgSO3)3], is characterized by segregation of the K+ cations and complex [O(HgSO3)3]2, anions into layers parallel to (010). The anion has m symmetry and is a new example of a ,3 -oxido-trimercurate complex with a central [OHg3] core. This unit adopts the shape of a flat, almost trigonal, pyramid (mean O,Hg = 2.072,Å and mean Hg,O,Hg = 110.8°). The two independent Hg,S bonds have nearly the same length (mean Hg,S = 2.335,Å). Due to intermolecular O...Hg donor,acceptor interactions greater than 2.65,Å, the O,Hg,S fragments are slightly bent. The [KO9] coordination polyhedron of the K+ cation approaches a distorted tricapped trigonal prism with a [6+1+2] coordination. [source]

Potassium silver tin selenide, K2Ag2Sn2Se6

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2001
Jing Li
The title compound was synthesized by a reactive salt reaction at 773,K over a period of 5,d. It has a one-dimensional chain structure consisting of K+ cations and one-dimensional [Ag2Sn2Se6]2, anions. The chain is constructed by edge-sharing bitetrahedral [Sn2Se6] units connected in a 1:2 ratio via linear Ag+ ions. [source]