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author:("Al-Far, rahi")
1.  Bis(2,4-dimethyl­pyridinium) tetra­bromido­mercurate(II) 
The asymmetric unit of the title compound, (C7H10N)2[HgBr4], consists of one cation and one half-anion, bis­ected by a twofold rotation axis passing through the metal atom. The anion exhibits a distorted tetra­hedral arrangement about the HgII atom. In the crystal, the cations and anions are linked by N—H⋯Br hydrogen-bonding inter­actions along [010]. Cation–cation π–π stacking and Br⋯Br inter­molecular inter­actions are absent.
doi:10.1107/S1600536812046788
PMCID: PMC3588751  PMID: 23468716
2.  Bis(2,4,6-trimethyl­pyridinium) tetra­bromidozincate 
In the title compound, (C8H12N)2[ZnBr4], the coordination geometry of the anion is approximately tetra­hedral. The Zn—Br bond lengths range from 2.3901 (19) to 2.449 (2) Å and the Br—Zn—Br angles range from 107.09 (8) to 112.48 (8)°. In the crystal, each [ZnBr4]2− anion is connected to four cations through two N—H⋯Br and two C—H⋯Br hydrogen bonds, forming two-dimensional ⋯(cation)2⋯anion⋯(cation2)⋯ sheets parallel to the bc plane. Within each sheet, the anions are arranged in stacks with no significant inter-anion Br⋯Br inter­actions [the shortest being > 4.3 Å], while the cations are in chains, with weak π–π stacking inter­actions [centroid–centroid distance = 3.991 Å] between cations inter­acting with the same anion.
doi:10.1107/S1600536812040925
PMCID: PMC3515090  PMID: 23284317
3.  3-(Ammonio­meth­yl)pyridinium dibromide 
In the title salt, C6H10N2 2+·2Br−, the non-H atoms of the 3-methyl­pyridinium unit of the cation are almost coplanar (r.m.s. deviation = 0.0052 Å). In the crystal, the dications and Br anions are linked by a combination of six hydrogen bonds, viz. one Npy—H⋯Br, two C—H⋯Br and three H2N–H⋯Br, into supra­molecular layers, parallel to the bc plane, composed of alternating R24(10) and R24(8) loops. Weak π–π inter­actions between cationic rings with centroid–centroid distances of 3.891 (2) Å are also observed.
doi:10.1107/S1600536812040937
PMCID: PMC3515173  PMID: 23284400
4.  Redetermination of 2,2′-bipyridine-1,1′-diium dibromide 
In the title mol­ecular salt, C10H10N2 2+·2Br−, the dihedral angle between the aromatic rings is 20.83 (14)° and the N—H groups have a transoid conformaton [N—C—C—N = 158.5 (3)°]. In the crystal, the cations are linked to the anions by two N—H⋯Br and five C—H⋯Br hydrogen bonds, generating corrugated sheets incorporating R 2 1(7), R 4 2(10), R 4 2(11) and two different R 4 2(12) loops. This structure was originally reported by Nakatsu et al. [Acta Cryst (1972), A28, S24], but no atomic coordinates are available.
doi:10.1107/S1600536812040214
PMCID: PMC3470387  PMID: 23125800
5.  2,6-Dimethyl­pyridinium bromide 
The asymmetric unit of the title salt, C7H10N+·Br−, comprises two 2,6-dimethyl­pyridinium cations and two bromide anions. One cation and one anion are situated in general positions, while the other cation and the other anion lie on a crystallographic mirror plane parallel to (010). Each pair of ions inter­act via N—H⋯Br and C—H⋯Br hydrogen bonding, generating motifs depending on the cation and anion involved. Thus, the cation and the anion on the mirror plane generate infinite chains along the c axis, while the other ionic pair leads to sheets parallel to the ac plane. In the overall crystal packing, both motifs alternate along the b axis, with a single layer of the chain motif sandwiched between two double layers of the sheet motif. The sheets and chains are further connected via aryl π–π inter­actions [centroid–centroid distances = 3.690 (2) and 3.714 (2) Å], giving a three-dimensional network.
doi:10.1107/S1600536812039578
PMCID: PMC3470347  PMID: 23125760
6.  2-Amino-5-methyl­pyridinium dibromo­iodate 
In the title salt, C6H9N2 +·Br2I−, the cation is essentially planar (r.m.s. deviation = 0.0062 Å for the non-H atoms) while the anion is almost linear with a Br—I—Br angle of 177.67 (2)°. The crystal packing shows two anions and two cations connected via N—H⋯Br and (pyridine)N—H⋯Br hydrogen-bonding inter­actions, forming centrosymmetric tetra­mers with R44(16) ring motifs. Very weak offset aromatic π–π stacking interactions [centroid-centroid separation = 4.038 (4), slippage = 1.773 Å] also occur.
doi:10.1107/S1600536812036136
PMCID: PMC3435817  PMID: 22969663
7.  Bis(2,6-dimethyl­pyridinium) dibromo­iodate bromide 
In the title salt, 2C7H10N+·IBr2 −·Br−, each of the anions, viz. [IBr2]− and Br−, lie on a twofold axis. The IBr2 − anion is almost linear, with a Br—I—Br angle of 178.25 (3)°. The cation is essentially planar (r.m.s. deviation = 0.0067 Å). In the crystal, each Br− anion links two cations via N—H⋯Br⋯H—N hydrogen-bonding inter­actions.
doi:10.1107/S1600536812035702
PMCID: PMC3435755  PMID: 22969626
8.  Bis(2,6-dimethyl­pyridinium) tetra­bromido­zincate(II) 
In the crystal structure of the title compound, (C7H10N)2[ZnBr4], the coordination geometry of the anion is approximately tetra­hedral and a twofold rotation axis passes through the Zn atom. The Zn—Br bond lengths range from 2.400 (2) to 2.408 (3) Å and the Br—Zn—Br angles range from 108.14 (6) to 115.15 (15)°. In the crystal structure, the [ZnBr4]2− anion is connected to two cations through N—H⋯Br and H2C—H⋯Br hydrogen bonds, forming two-dimensional cation–anion–cation layers normal to the b axis. No significant Br⋯Br inter­actions [the shortest being 4.423 (4) Å] are observed in the structure.
doi:10.1107/S1600536809015219
PMCID: PMC2977623  PMID: 21583809
9.  Bis(2,6-diamino-3,5-dibromo­pyridinium) hexa­bromidostannate(IV) 
The asymmetric unit of the title compound, (C5H6Br2N3)2[SnBr6], contains one cation and one half-anion in which the Sn atom is located on a crystallographic centre of inversion and is in a quasi-octa­hedral geometry. The crystal structure is assembled via hydrogen-bonding inter­actions of two kinds, N(pyridine/amine)—H⋯Br—Sn, along with C—Br⋯Br—Sn interactions [3.4925 (19) Å]. The cations are involved in π–π stacking, which adds an extra supra­molecularity as it presents a strong case of offset-face-to-face motifs [centroid–centroid distance = 3.577 (3) Å]. The inter­molecular hydrogen bonds, short Br⋯Br inter­actions and π–π stacking result in the formation of a three-dimensional supra­molecular architecture.
doi:10.1107/S1600536809015189
PMCID: PMC2977624  PMID: 21583810
10.  2,5-Dibromo­pyridine 
In the title compound, C5H3Br2N, C—H⋯N hydrogen-bonding inter­actions and Br⋯Br inter­actions [3.9418 (3) and 3.8986 (3) Å] connect the mol­ecules into planar sheets stacked perpendicular to the b axis. In addition, pyrid­yl–pyridyl inter­sheet π–π stacking inter­actions [centroid–centroid distance = 4.12 (1) Å] result in a three-dimensional network.
doi:10.1107/S160053680900974X
PMCID: PMC2969055  PMID: 21582562
11.  Bis(2-amino-4-methyl­pyridinium) tetra­chloridocuprate(II) 
The asymmetric unit of the title compound, (C6H9N2)2[CuCl4], consists of one cation and one half-anion, bis­ected by a twofold rotation axis through the metal center. The anion exhibits a geometry that is inter­mediate between a Td and D 4h arrangement about the Cu atom. The crystal structure contains chains of cations alternating with stacks of anions. The cationic groups inter­act via offset face-to-face π–π stacking, forming chains running along the c axis. The anion stacks are parallel to the cation chains, with no significant inter- nor intra­stack Cl⋯Cl inter­actions. There are several anion–cation hydrogen-bonding inter­actions of the (N—H)pyridine⋯Cl and (N—H)amino⋯Cl types, connecting the chains of cations to the stacks of anions. Both the N—H⋯Cl and π–π stacking inter­actions [centroid–centroid distances 3.61 (8) and 3.92 (2) Å] contribute to the formation of a three-dimensional supra­molecular architecture.
doi:10.1107/S1600536808041652
PMCID: PMC2967911  PMID: 21581540
12.  3-Ammonio­pyridinium tetra­bromido­mercurate(II) monohydrate 
The asymmetric unit of the title compound, (C5H8N2)[HgBr4]·H2O, consists of one cation, one anion and one water mol­ecule. The anion exhibits a distorted tetra­hedral arrangement about the Hg atom. The crystal structure contains alternating sheets of cations (in the ac plane) and stacks of anions. Several strong hydrogen-bonding inter­actions (pyN—H⋯Br and C—H⋯Br; py is pyridine), along with O—H⋯Br inter­actions, connect the sheets of cations to the stacks of anions. Cation–cation π–π stacking is also present (C⋯C distances in the range 3.424–3.865 Å). The shortest Br⋯Br distance is 3.9527 (9) Å.
doi:10.1107/S1600536808012336
PMCID: PMC2961581  PMID: 21202445
13.  Bis(2-bromo­pyridinium) hexa­bromido­stannate(IV) 
The asymmetric unit of the title compound, (C5H5BrN)2[SnBr6], contains one cation and one half-anion. The [SnBr6]2− anion is located on an inversion center and forms a quasi-regular octa­hedral arrangement. The crystal structure consists of two-dimensional supra­molecular layers assembled via hydrogen-bonding inter­actions of N—H⋯Br—Sn [D⋯A = 3.375 (13)–3.562 (13) Å and D—H⋯A = 127–142°, along with C—Br⋯Br synthons [3.667 (2) and 3.778 (3) Å]. These layers are parallel to the bc plane and built up from anions inter­acting extensively with the six surrounding cations.
doi:10.1107/S1600536808012129
PMCID: PMC2961614  PMID: 21202444
14.  Bis­(2-amino-6-methyl­pyridinium) tetra­bromido­cuprate(II) 
In the crystal structure of the title compound, (C6H9N2)2[CuBr4], the geometry around the Cu atom is inter­mediate between tetra­hedral (Td) and square planar (D4h). Each [CuBr4]2− anion is connected non-symmetrically to four surrounding cations through N—H⋯X (pyridine and amine proton) hydrogen bonds, forming chains of the ladder-type running parallel to the crystallographic b axis. These layers are further connected by means of offset face-to-face inter­actions (parallel to the a axis), giving a three-dimensional network. Cation π–π stacking [centroid separations of 3.69 (9) and 3.71 (1) Å] and Br⋯aryl inter­actions [3.72 (2) and 4.04 (6) Å] are present in the crystal structure. There are no inter­molecular Br⋯Br inter­actions.
doi:10.1107/S1600536808010647
PMCID: PMC2961314  PMID: 21202225
15.  Bis(2-bromo­pyridinium) hexa­chlorido­stannate(IV) 
The asymmetric unit of the title compound, (C5H5BrN)2[SnCl6], contains one cation and one half-anion. The [SnCl6]2− anion is located on an inversion center and forms a quasi-regular octa­hedral arrangement. Hydrogen-bonding inter­actions of two kinds, viz. N—H⋯Cl—Sn and C—H⋯Cl—Sn, along with Cl⋯Br inter­actions [3.4393 (15) Å], connect the ions in the crystal structure into two-dimensional supra­molecular arrays. These supra­molecular arrays are arranged in layers approximately parallel to (110) built up from anions inter­acting with six symmetry-related surrounding cations.
doi:10.1107/S160053680800901X
PMCID: PMC2961104  PMID: 21202188
16.  Bis(2,6-dimethyl­pyridinium) tetra­bromido­cobaltate(II) 
In the crystal structure of the title compound, (C7H10N)2[CoBr4], the [CoBr4]2− anion is connected to two cations through N—H⋯Br and H2C—H⋯Br hydrogen bonds to form two-dimensional cation–anion–cation layers normal to the crystallographic b axis. Inter­actions of the π–π type are absent between cations in the stacks [centroid–centroid separation = 5.01 (5) Å]. Significant inter­molecular Br–aryl inter­actions are present in the structure, especially an unusually short Br–ring centroid inter­action of 3.78 (1) Å. The coordination geometry of the anion is approximately tetrahedral and a twofold rotation axis passes through the Co atom.
doi:10.1107/S160053680800439X
PMCID: PMC2960811  PMID: 21201870

Results 1-16 (16)