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author:("Ng, seek Weng")
1.  A second monoclinic polymorph of 3,5-di-tert-butyl-2-hy­droxy­benzaldehyde 
In the title mol­ecule, C15H22O2, there is an intra­molecular hydrogen bond involving the hy­droxy and aldehyde groups and forming an S(6) ring. The mean plane of the non-H atoms of this ring [(H)O—C C—C=O, with a maximum deviation of 0.013 (1) Å] are essentially coplanar with the benzene ring, forming a dihedral angle of 2.29 (8)°.
PMCID: PMC3884484  PMID: 24427059
2.  Tetra­kis(triphenyl­phosphane-κP)silver(I) trifluoro­acetate ethanol monosolvate 
In the title solvated salt, [Ag(C18H15P)4](CF3CO2)·C2H5OH, the AgI atom is coordinated by four P atoms from triphenyl­phosphane ligands in a distorted tetra­hedral geometry. The anion and solvent are engaged in weak O—H⋯O hydrogen bonds. Of the four triphenyl­phosphane ligands, two each have an equally disordered phenyl ring while the AgI atom is disordered over two positions in a 0.9595 (15):0.0405 (15) ratio and the trifluoro­acetate anion is equally disordered over two positions with respect to the lattice ethanol mol­ecule.
PMCID: PMC3588779  PMID: 23468744
3.  Tetra­kis(triphenyl­arsane-κAs)silver(I) trifluoro­acetate hemihydrate methanol hemisolvate 
The AgI atom in the title hydrated solvated salt, [Ag(C18H15As)4](CF3CO2)·0.5CH3OH·0.5H2O, is coordinated by four As atoms from triphenyl­arsane ligands in a distorted tetra­hedral geometry. In the crystal, O—H⋯O hydrogen bonding occurs between carboxyl­ate groups of anions and lattice solvent mol­ecules. Of the four triphenyl­arsane ligands in the Ag complex cation, two each have an equally disordered phenyl ring while the trifluoro­acetate anion is disordered over two positions with respect to the lattice methanol and water mol­ecules which both show half-occupyncy. The crystal studied was a non-merohedral twin with a 13.6 (1)% contribution of the minor twin component.
PMCID: PMC3588780  PMID: 23468745
4.  Di-μ3-acetato-bis­{μ-6,6′-dieth­oxy-2,2′-[propane-1,2-diylbis(nitrilo­methanylyl­idene)]diphenolato}dicadmiumdisodium ethanol 0.67-solvate 
In the crystal of the title compound, [Cd2Na2(C2H3O2)2(C21H24N2O4)2]·0.67C2H6O, the doubly deprotonated Schiff base ligand N,N′,O,O′-chelates to the CdII cation, which is also O,O′-chelated by the acetate ion. Two Cd–Schiff base units are connected to two Na+ atoms to form the tetra­nuclear complex, in which the Cd2+ and Na+ cations show distorted octa­hedral coordinations. The asymmetric unit consists of half a tetra­nuclear mol­ecule (lying on an inversion center) and a full tetra­nuclear mol­ecule (lying on a general position) along with a lattice ethanol mol­ecule, which links to the coordinating acetate ion via an O—H⋯O hydrogen bond. In the crystal, the propyl and ethyl groups of the complex mol­ecule are disordered over two positions in a 1:1 ratio; the ethyl group of the lattice ethanol mol­ecule is also equally disordered over two positions.
PMCID: PMC3588789  PMID: 23468754
5.  A second polymorph of 2,4,6-tris­(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazine 
The mol­ecule of the title compound, C18H21N9, is nearly planar, with the three pyrazole rings aligned at 2.40 (5), 9.27 (5) and 9.71 (5)° with respect to the triazine ring. The triazine ring is planar (r.m.s. deviation = 0.005 Å), the distortion from a hexa­gonal arrangement arising from the angles at the N [112.4 (1)–113.1 (1)°] and C [127.1 (1)–127.6 (1)°] atoms deviating from 120°. The crystal studied was an inversion twin.
PMCID: PMC3515290  PMID: 23284510
6.  (R)-(3-Carb­oxy-2-hy­droxy­prop­yl)tri­methyl­aza­nium chloride 
In the title salt (common name l-carnitine hydro­chloride), C7H16NO3 +·Cl−, the organic cation features a carb­oxy­lic part (–CO2H) having unambigous single- and double-bonds [1.336 (2), 1.211 (2) Å]. There is a large N—C—C bond angle [115.9 (1)°] for the C atom connected to the bulky trimethyl­amino substituent. In the crystal, the acid H atom forms a hydrogen bond to the chloride anion, whereas the hydroxyl H atom forms a longer hydrogen bond to the anion, generating a helical chain running along [001].
PMCID: PMC3344540  PMID: 22590302
7.  A triclinic modification of 3,4-dihy­droxy­benzoic acid monohydrate 
The unit cell of the title compound, C7H6O4·H2O, features four independent formula units; the individual carb­oxy­lic acid mol­ecules themselves are nearly planar (r.m.s. deviations = 0.0189, 0.0334, 0.0356 and 0.0441 Å). Two independent mol­ecules each form two hydrogen bonds by acid–carbonyl O—H⋯O inter­actions and the dimers are also nearly planar (r.m.s. deviations = 0.039 and 0.049 Å). The two independent dimers are aligned at 44.5 (1)°. Other O—H⋯O inter­actions involving the hy­droxy groups and water mol­ecules give rise to a three-dimensional network.
PMCID: PMC3200807  PMID: 22059032
8.  Triclinic modification of tetra­kis­(triethyl­ammonium) dihydrogeno­deca­vanadate(V) 
In the title ammonium polyoxometallate salt, (C6H16N)4[H2V10O28], the anion features O atoms engaged in μ6-, μ3- and μ2-bridging of adjacent VV atoms, confering an octa­hedral coordination at each of the twenty unique metal atoms. Two anions are linked by μ3- and μ2-bridged OH units across a center of inversion, forming a dimer which is linked to the cations by N—H⋯O hydrogen bonds. The cation is disordered over two positions in a 0.776 (4):0.224 (4) ratio in one of the two independent ion pairs in the asymmetric unit, and 0.627 (10):0.373 (10) in the other.
PMCID: PMC3120463  PMID: 21754685
9.  Monoclinic modification of bis­(μ2-pyridine-2,6-dicarboxyl­ato)-κ4 O 2,N,O 6:O 6;κ4 O 2:O 2,N,O 6-bis­[aqua­dibutyl­tin(IV)] 
The SnIV atom in the centrosymmetric dinuclear title compound, [Sn2(C4H9)4(C7H3NO4)2(H2O)2], exists in a trans-C2SnNO4 penta­gonal–bipyramidal geometry. There are two half-mol­ecules in the asymmetric unit that are completed by inversion symmetry. The crystal studied was a non-merohedral twin with a ratio of 47.3 (1)% for the minor twin component. Bond dimensions are similar to those found in the tetra­gonal polymorph [Huber et al. (1989 ▶). Acta Cryst. C45, 51–54]. O—H⋯O hydrogen-bonding interactions stabilize the crystal packing.
PMCID: PMC3051593  PMID: 21522924
10.  Monoclinic modification of di-n-butyl­dichlorido(1,10-phenanthroline-κ2 N,N′)tin(IV) 
The Sn(IV) atom in the title compound, [Sn(C4H9)2Cl2(C12H8N2)], is chelated by the N-heterocycle; the n-butyl groups are trans to each other whereas the Cl atoms are cis to each other. The crystal studied was a non-merohedral twin with the minor domain being in a 15.8 (1)% proportion.
PMCID: PMC3011636  PMID: 21589329
11.  4-Chloro-2,6-dinitro­phenol 
The aromatic ring of the title compound, C6H3ClN2O5, is almost planar (r.m.s. deviation = 0.007 Å); one nitro substituent is nearly coplanar with the ring [dihedral angle = 3(1)°], whereas the other is twisted [dihedral angle = 36 (1)°]. The phenol OH group is intra­molecularly hydrogen bonded to the nitro group that is coplanar with the ring, generating an S(6) graph-set motif.
PMCID: PMC3011538  PMID: 21589498
12.  Monoclinic modification of aquadi-n-butyl­bis­(pyrazine-2-carboxyl­ato-κ2 N 1,O)tin(IV) 
The asymmetric unit of the title organotin(IV) compound, [Sn(C4H9)2(C5H3N2O2)2(H2O)], contains one-and-a-half mol­ecules. The half-mol­ecule is completed by crystallographic twofold symmetry, with its Sn and water O atoms lying on the rotation axis. Both mol­ecules feature seven-coordinate Sn atoms in trans-C2SnN2O3 penta­gonal-bipyramidal coordination environments. The carboxyl­ate anions N,O-chelate to the Sn atom. In the crystal, the carboxyl­ate O atoms not involved in coordination serve as acceptors for O—H⋯O hydrogen bonds from adjacent water mol­ecules, generating a three-dimensional network.
PMCID: PMC3008135  PMID: 21588539
13.  Redetermination of 4-(dimethyl­amino)­pyridinium tribromide 
In the title salt, C7H11N2 +·Br3 −, the essentially planar cation (r.m.s. deviation = 0.006 Å) forms an N—H⋯Br hydrogen bond to one of the Br atoms of the almost linear anion [Br—Br—Br = 179.31 (2)°]. The crystal studied was found to be a racemic twin. The whole-mol­ecule disorder of the cation and anion about a twofold rotation axis described earlier [Ng (2009). Acta Cryst. E65, o1276] is an artifact of halving one of the axes of the ortho­rhom­bic unit cell.
PMCID: PMC3008028  PMID: 21588594
14.  4,4′-Diphenyl-2,2′-bi-1,3-thia­zole 
In the centrosymmetric title compound, C18H12N2S24, the five- (r.m.s. deviation = 0.002 Å) and six-membered (r.m.s. deviation = 0.002 Å) rings are essentially coplanar [dihedral angle between rings = 1.9 (1)°].
PMCID: PMC3007272  PMID: 21588340
15.  (Quinoline-2-carboxyl­ato-κO)(quinoline-2-carb­oxy­lic acid-κO)bis­(quinoline-2-carb­oxy­lic acid-κ2 N,O)potassium 
The K atom in the title complex, [K(C10H6NO2)(C10H7NO2)3], lies on a twofold rotation axis that relates one N,O-chelating quinoline-2-carb­oxy­lic acid to the other; their N and O atoms are cis to each other in the distorted octa­hedral coordination geometry. The K atom is also coordinated by another monodentate quinoline-2-carb­oxy­lic acid; the acid is disordered with respect to a monodentate quinoline-2-carboxyl­ate anion; the acid and anion are linked by an O—H⋯O hydrogen bond. An O—H⋯N hydrogen bond links adjacent mol­ecules into a linear chain structure along the a axis.
PMCID: PMC3007487  PMID: 21588178
16.  2-Chloro-3-nitro­pyridine 
In the title compound, C5H3ClN2O2, the nitro group is twisted by 38.5 (2)° with respect to the pyridine ring. In the crystal, adjacent mol­ecules are linked by non-classical C—H⋯N and C—H⋯O hydrogen bonds, forming a layer motif.
PMCID: PMC2979275  PMID: 21579084
17.  2-Chloro-5-nitro­pyridine 
The non-H atoms of the title compound, C5H3ClN2O2, almost lie in a common plane (r.m.s. deviation = 0.090 Å). In the crystal, adjacent mol­ecules feature a short Cl⋯O contact [3.068 (4) Å], forming a chain; these chains are consolidated into a layer structure by non-classical C—H⋯O inter­actions.
PMCID: PMC2983943  PMID: 21580672
18.  4-(Methyl­amino)pyridine 
The non-H atoms of the title compound, C6H8N2, lie in a common plane (r.m.s. deviation = 0.034 Å). In the crystal, adjacent mol­ecules are linked by inter­molecular N—H⋯N hydrogen bonds into a zigzag chain running along the c axis.
PMCID: PMC2983869  PMID: 21580654
19.  (E)-2,4-Dihydroxy­benzaldehyde 4-ethyl­thio­semicarbazone–4,4′-bipyridine–water (4/7/2) 
The asymmetric unit of the title compound, 7C10H8N2·4C10H13N3O2S·2H2O, contains two independent 2,4-hydroxy­benzaldehyde 4-ethyl­thio­semicarbazone mol­ecules, three and a half 4,4′-bipyridine mol­ecules and one water mol­ecule. Two of the 4,4′-bipyridine mol­ecules lie on general positions and the other three on centers of inversion. The two 4,4′-bipyridine mol­ecules on general positions and one of the three on special positions are disordered over two positions each with an occupancy of 0.50. The –NH—C(=S)—NH—NC fragment is close to planar in the two 2,4-hydroxy­benzaldehyde 4-ethyl­thio­semicarbazone mol­ecules (r.m.s. deviations = 0.04 and 0.05 Å). In the crystal, the Schiff base, N-heterocycle and water mol­ecules engage in O—H⋯O, O—H⋯N and N—H⋯O hydrogen-bonding inter­actions, generating a layer structure.
PMCID: PMC2969953  PMID: 21577541
20.  Ortho­rhom­bic modification of (E)-4-benzyl­idene-2-phenyl-1,3-oxazol-5(4H)-one: whole mol­ecule disorder 
The title mol­ecule, C16H11NO2, is disordered about a pseudo-twofold rotation axis that approximately bis­ects the mol­ecule along the C=O double bond. The two overlapping components are planar [r.m.s. deviation = 0.10 Å in the major 0.537 (4) component and 0.07 Å in the minor component]. The two components are aligned at 1.8 (3)°.
PMCID: PMC2977315  PMID: 21583555
21.  Tripotassium bis­(acetato-κ2 O,O′)(thio­cyanato-κN)plumbate(II) dithio­cyanate 
In the crystal structure of the title salt, K3[Pb(CH3COO)2(NCS)](NCS)2, the [Pb(CH3COO)2(NCS)]− anion exists as a covalently bonded entity in which the acetate anions chelate in an anisobidentate manner. The Pb atom shows a distorted ψ-octa­hedral coordination to four acetate O atoms and one isocyanate N atom, with the stereochemically active lone pair occupying one of the six sites. When the three longer Pb⋯S inter­actions are considered, the eight-coordinate geometry is based on a dodeca­hedron. The Pb(CH3COO)2(NCS)]− anion has mirror symmetry. The potassium cations connect the other constituents into a three-dimensional network through electrostatic K⋯N and K⋯S inter­actions.
PMCID: PMC2969246  PMID: 21582691
22.  5-Chloro-8-hydroxy­quinolinium nitrate 
The 5-chloro-8-hydroxy­quinolinium cation in the the title ion pair, C9H7ClNO+·NO3 −, is approximately coplanar with the nitrate anion [dihedral angle = 16.1 (1)°]. Two ion pairs are hydrogen bonded (2 × O—H⋯O and 2 × N—H⋯O) about a center of inversion, generating an R 4 4(14) ring.
PMCID: PMC2969641  PMID: 21583288
23.  A second monoclinic modification of triphenyl­phosphine oxide hemihydrate 
In the crystal of the title compound, C18H15OP·0.5H2O, a water molecule links to two adjacent triphenylphosphine molecules by way of O—H⋯O hydrogen bonds. The crystal is twinned, the minor twin component being 36%.
PMCID: PMC2969812  PMID: 21583272
24.  Low-temperature redetermination of benzofurazan 1-oxide 
In the six-membered ring of the low-temperature crystal structure of benzofurazan 1-oxide, C6H4N2O2, the two C atoms adjacent to the N atoms are linked by a delocalized aromatic bond [1.402 (2) Å]; each is connected to its neighbour by a longer, more localized, bond [1.420 (2), 1.430 (2) Å]. However, the next two bonds in the ring approximate double bonds [1.357 (2), 1.366 (2) Å]. As such, the six-membered ring is better described as a cyclo­hexa­diene system, in contrast to the description in the room-temperature structure reported by Britton & Olson (1979 ▶) [Acta Cryst. B35, 3076–3078].
PMCID: PMC2969705  PMID: 21583137
25.  4-(Dimethyl­amino)pyridinium tribromide: whole mol­ecule disorder of cation and anion 
In the title salt, C7H11N2 +·Br3 −, the cation and the near-linear anion [Br—Br—Br = 179.41 (8)°] both show whole-mol­ecule disorder about crystallographic twofold rotation axes. The cation is weakly hydrogen-bonded to the anion by an N—H⋯Br inter­action. The crystal studied was found to be a racemic twin, with a twin component of nearly 50%.
PMCID: PMC2969780  PMID: 21583138

Results 1-25 (1237)