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Independent Cations (independent + cation)

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Chemistry100%

Selected Abstracts

More examples of the 15-crown-5...H2O,M,OH2...15-crown-5 motif, M = Al3+, Cr3+ and Pd2+

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2010
Maxime A. Siegler
Five structures of co-crystals grown from aqueous solutions equimolar in 15-crown-5 (or 15C5) and [M(H2O)6](NO3)n, M = Al3+, Cr3+ and Pd2+, are reported. The hydrogen-bonding patterns in all are similar: metal complexes including the fragment trans -H2O,M,OH2 alternate with 15C5 molecules, to which they are hydrogen bonded, to form stacks. A literature survey shows that this hydrogen-bonding pattern is very common. In each of the two polymorphs of the compound [Al(H2O)6](NO3)3·15C5·4H2O there are two independent cations; one forms hydrogen bonds directly to the 15C5 molecules adjacent in the stack, while the other cation is hydrogen-bonded to two water molecules that act as spacers in the stack. These stacks are then crosslinked by hydrogen bonds formed by the three nitrate counterions and the three lattice water molecules. The hydrogen-bonded stacks in [Cr(H2O)5(NO3)](NO3)2·1.5(15C5)·H2O are discrete rather than infinite; each unit contains two Cr3+ complex cations and three 15C5 molecules. These units are again crosslinked by the uncoordinated nitrate ions and a lattice water molecule. In [Pd(H2O)2(NO3)2]·15C5 the infinite stacks are electrically neutral and are not crosslinked. In [Pd(H2O)2(NO3)2]·2(15C5)·2H2O·2HNO3 a discrete, uncharged unit containing one Pd complex and two 15C5 molecules is `capped off' at either end by a lattice water molecule and an included nitric acid molecule. In all five structures the infinite stacks or discrete units form an array that is at least approximately hexagonal. [source]

A new modification of thallium chromate related to the ,-K2SO4 family

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2010
Jan Fábry
The title structure is a new modification of Tl2CrO4. There are four independent Tl+ cations and two [CrO4]2, anions in the structure. It is closely related to the already known modification, which belongs to the ,-K2SO4 family with two independent cations and one anion. In both modifications, the cations and anions are situated on crystallographic mirror planes. The volume of the asymmetric unit of the title structure is ,0.4% smaller than that of the known modification belonging to the ,-K2SO4 family. The other difference between the two modifications is seen in the environment of the cations. In the title structure, none of the Tl+ cations is underbonded, in contrast with the modification isostructural with ,-K2SO4. In the ,-K2SO4 family with simple cations, underbonding of one of the constituent cations is typical. The dependence of the unit-cell parameters on temperature does not indicate a phase transition in the interval 90,300,K. [source]

A three-dimensional hydrogen-bonded network in bis(4-hydroxyanilinium) selenate(VI) dihydrate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2009
Jan Janczak
The title compound, 2C6H8NO+·SeO42,·2H2O, contains 4-hydroxyanilinium cations, selenate(VI) anions and water molecules. One of the two independent cations is nearly planar (excluding the ammonium H atoms), while the other is markedly nonplanar, with the hydroxy and ammonium groups displaced from the plane of the benzene ring. This results from the antiparallel orientation of the cations, which interact through oppositely polarized ammonium and hydroxy groups. Ionic and hydrogen-bonding interactions join the oppositely charged units into a three-dimensional network. This work demonstrates the usefulness of 4-aminophenol in the crystal engineering of organic,inorganic hybrid compounds. [source]

A polymorph of tetrakis(acetonitrile-,N)copper(I) tetrafluoridoborate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2009
Jan W. Bats
A P212121 polymorph of the title compound, [Cu(CH3CN)4]BF4, is reported. The crystal structure is very similar to the structure of the Pna21 polymorph reported by Jones & Crespo [Acta Cryst. (1998), C54, 18,20]. The anions and one of the three independent cations occupy similar positions in both polymorphs. Two of the four symmetry-related positions of the other two cations are also identical in the two polymorphs, and the other two positions are related by mirror symmetry. The crystal used for the structure determination contained a volume fraction of 0.088,(7) of the Pna21 polymorph. [source]