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1.  Monohalogenated ferrocenes C5H5FeC5H4 X (X = Cl, Br and I) and a second polymorph of C5H5FeC5H4I 
The structures of the three title monosubstituted ferrocenes, namely 1-chloro­ferrocene, [Fe(C5H5)(C5H4Cl)], (I), 1-bromo­ferrocene, [Fe(C5H5)(C5H4Br)], (II), and 1-iodo­ferrocene, [Fe(C5H5)(C5H4I)], (III), were determined at 100 K. The chloro- and bromo­ferrocenes are isomorphous crystals. The new triclinic polymorph [space group P , Z = 4, T = 100 K, V = 943.8 (4) Å3] of iodo­ferrocene, (III), and the previously reported monoclinic polymorph of (III) [Laus, Wurst & Schottenberger (2005 ▶). Z. Kristallogr. New Cryst. Struct. 220, 229–230; space group Pc, Z = 4, T = 100 K, V = 924.9 Å3] were obtained by crystallization from ethanolic solutions at 253 and 303 K, respectively. All four phases contain two independent mol­ecules in the unit cell. The relative orientations of the cyclo­penta­dienyl (Cp) rings are eclipsed and staggered in the independent mol­ecules of (I) and (II), while (III) demonstrates only an eclipsed conformation. The triclinic and monoclinic polymorphs of (III) contain nonbonded inter­molecular I⋯I contacts, causing different packing modes. In the triclinic form of (III), the mol­ecules are arranged in zigzag tetra­mers, while in the monoclinic form the mol­ecules are arranged in zigzag chains along the a axis. Crystallographic data for (III), along with the computed lattice energies of the two polymorphs, suggest that the monoclinic form is more stable.
PMCID: PMC2773730  PMID: 19893225
2.  Insight into the structures of [M(C5H4I)(CO)3] and [M 2(C12H8)(CO)6] (M = Mn and Re) containing strong I⋯O and π(CO)–π(CO) inter­actions 
The compounds tricarbonyl(η5-1-iodo­cyclo­penta­dienyl)­man­gan­ese(I), [Mn(C5H4I)(CO)3], (I), and tricarbonyl(η5-1-iodo­cyclo­penta­dienyl)rhenium(I), [Re(C5H4I)(CO)3], (III), are isostructural and isomorphous. The compounds [μ-1,2(η5)-acetyl­enedicyclo­penta­dienyl]bis­[tricarbonyl­manganese(I)] or bis­(cymantrenyl)acetyl­ene, [Mn2(C12H8)(CO)6], (II), and [μ-1,2(η5)-acetyl­enedicyclo­penta­dienyl]bis­[tri­carbonyl­rhenium(I)], [Re2(C12H8)(CO)6], (IV), are isostructural and isomorphous, and their mol­ecules display inversion symmetry about the mid-point of the ligand C C bond, with the (CO)3 M(C5H4) (M = Mn and Re) moieties adopting a transoid conformation. The mol­ecules in all four compounds form zigzag chains due to the formation of strong attractive I⋯O [in (I) and (III)] or π(CO)–π(CO) [in (I) and (IV)] inter­actions along the crystallographic b axis. The zigzag chains are bound to each other by weak inter­molecular C—H⋯O hydrogen bonds for (I) and (III), while for (II) and (IV) the chains are bound to each other by a combination of weak C—H⋯O hydrogen bonds and π(Csp 2)–π(Csp 2) stacking inter­actions between pairs of mol­ecules. The π(CO)–π(CO) contacts in (II) and (IV) between carbonyl groups of neighboring mol­ecules, forming pairwise inter­actions in a sheared anti­parallel dimer motif, are encountered in only 35% of all carbonyl inter­actions for transition metal–carbonyl compounds.
PMCID: PMC2773731  PMID: 19893226
3.  3-[(E)-(3-tert-Butyl-1-phenyl-1H-pyrazol-5-yl)imino­methyl]quinolin-2(1H)-one: chains built by π-stacking of hydrogen-bonded R 2 2(8) dimers 
In the title compound, C23H22N4O, there is evidence for some bond fixation in the aryl component of the quinolinone unit. Pairs of mol­ecules related by inversion are linked into R 2 2(8) dimers by almost linear N—H⋯O hydrogen bonds, and dimers related by inversion are linked into chains by a single aromatic π–π stacking inter­action.
PMCID: PMC2758068  PMID: 19805879
4.  Pseudomerohedrally twinned monoclinic structure of unfolded ‘free’ nona­ctin: comparative analysis of its large conformational change upon encapsulation of alkali metal ions 
The title compound, C40H64O12, crystallizes in a pseudo­merohedrally twinned primitive monoclinic cell with similar contributions of the two twin components. There are two symmetry-independent half-mol­ecules of nona­ctin in the asymmetric unit. Each mol­ecule has a pseudo-S 4 symmetry and resides on a crystallographic twofold axis; the axes pass through the mol­ecular center of mass and are perpendicular to the plane of the macrocycle. The literature description of the room-temperature structure of nona­ctin as an order–disorder structure in an ortho­rhom­bic unit cell is corrected. We report a low-temperature high-precision ordered structure of ‘free’ nona­ctin that allowed for the first time precise determination of its bond distances and angles. It possesses an unfolded and more planar geometry than its complexes with encapsulated Na+, K+, Cs+, Ca2+ or NH4 + cations that exhibit more isometric overall conformations.
PMCID: PMC2816929  PMID: 19805886
5.  5-Nitro-N 4,N 6-diphenyl­pyrimidine-4,6-diamine: polarized mol­ecules linked into π-stacked chains via three-centre C—H⋯(O)2 hydrogen bonds 
Mol­ecules of the title compound, C16H13N5O2, have no inter­nal symmetry despite the symmetric pattern of substitution in the pyrimidine ring. The intra­molecular distances indicate polarization of the electronic structure. There are two intra­molecular N—H⋯O hydrogen bonds and mol­ecules are linked into centrosymmetric dimers by pairs of three-centre C—H⋯(O)2 hydrogen bonds. These dimers are linked into chains by means of a π–π stacking inter­action.
PMCID: PMC2737422  PMID: 19726856
6.  2-Amino-3-methyl-6-[meth­yl­(phen­yl)­amino]-5-nitro­pyrimidin-4(3H)-one: polarized mol­ecules within hydrogen-bonded sheets 
The pyrimidinone ring in the title compound, C12H13N5O3, is effectively planar, despite the presence of five substituents. The bond distances provide evidence for significant polarization of the electronic structure, with charge separation, and the mol­ecules are linked into sheets by a combination of N—H⋯O and N—H⋯π(arene) hydrogen bonds. Comparisons are made with the mol­ecular and supra­molecular structures of the precursor compound 2-amino-6-[meth­yl(phen­yl)amino]-5-nitro­pyrimidin-4(3H)-one.
PMCID: PMC2737423  PMID: 19726857
7.  (E)-3-(4-Methyl­phen­yl)-2-(2-thien­yl)­acrylonitrile has Z′ = 0.75 in the space group C2/m: fourfold disordered mol­ecules lie in channels enclosed by fully ordered mol­ecules 
The title compound, C14H11NS, crystallizes with Z′ = 0.75 in the space group C2/m. Two independent mol­ecules are present, one of which lies with all the non-H atoms on a mirror plane, while the other is fourfold disordered across a site of 2/m symmetry. The ordered mol­ecules are stacked such that they enclose continuous channels running along twofold rotation axes, and the disordered mol­ecules are positioned within these channels.
PMCID: PMC2737424  PMID: 19726858
8.  Four differently substituted 2-aryl-2,3,4,5-tetra­hydro-1H-1,4-ep­oxy-1-benzazepines: hydrogen-bonded structures in one, two and three dimensions 
In (2RS,4SR)-7-chloro-2-exo-(2-chloro-6-fluoro­phen­yl)-2,3,4,5-tetra­hydro-1H-1,4-epoxy-1-benzazepine, C16H12Cl2FNO, (I), mol­ecules are linked into chains by a single C—H⋯π(arene) hydrogen bond. (2RS,4SR)-2-exo-(2-Chloro-6-fluoro­phen­yl)-2,3,4,5-tetra­hydro-1H-1,4-ep­oxy-1-benzazepine, C16H13ClFNO, (II), is isomorphous with compound (I) but not strictly isostructural with it, as the hydrogen-bonded chains in (II) are linked into sheets by an aromatic π–π stacking inter­action. The mol­ecules of (2RS,4SR)-7-methyl-2-exo-(4-methyl­phenyl)-2,3,4,5-tetra­hydro-1H-1,4-ep­oxy-1-benzazepine, C18H19NO, (III), are linked into sheets by a combination of C—H⋯N and C—H⋯π(arene) hydrogen bonds. (2S,4R)-2-exo-(2-Chloro­phen­yl)-2,3,4,5-tetra­hydro-1H-1,4-ep­oxy-1-benzazepine, C16H14ClNO, (IV), crystallizes as a single enantiomer and the mol­ecules are linked into a three-dimensional framework structure by a combination of one C—H⋯O hydrogen bond and three C—H⋯π(arene) hydrogen bonds.
PMCID: PMC2737425  PMID: 19726863
9.  Sterically shielded pyramidal amino groups in two 4,4′-(aryl­methyl­ene)bis­(6-allyl-3-chloro-2-methyl­aniline) derivatives 
4,4′-(Phenyl­methyl­ene)bis­(6-allyl-3-chloro-2-methyl­aniline), C27H28Cl2N2, (I), and 4,4′-(2-thienylmethyl­ene)bis­(6-allyl-3-chloro-2-methyl­aniline), C25H26Cl2N2S, (II), adopt similar mol­ecular conformations, although the thienyl group in (II) exhibits orientational disorder over two sets of sites with occupancies of 0.614 (3) and 0.386 (3). The amino groups in both compounds are pyramidal. A single N—H⋯N hydrogen bond links the mol­ecules of (I) into cyclic centrosymmetric dimers. Mol­ecules of (II) are linked by an ordered C—H⋯π(arene) hydrogen bond to form cyclic centrosymmetric dimers, and these dimers are linked into statistically inter­rupted chains by a second C—H⋯π(arene) hydrogen bond involving a donor in the minor component of the disordered thienyl unit.
PMCID: PMC2737426  PMID: 19726866
10.  2-{2-[2-(4-Methoxy­benzoyl)ethyl­amino]-4-nitro­anilino}ethyl acetate: complex sheets built from five independent hydrogen bonds 
The mol­ecules of the title compound, C20H23N3O6, are almost completely planar, apart from the H atoms bonded to tetra­hedral C atoms. A combination of five hydrogen bonds, one of the N—H⋯O type and two each of the C—H⋯O and C—H⋯π(arene) types, links the mol­ecules into complex sheets.
PMCID: PMC2737427  PMID: 19726867
11.  Different hydrogen-bonded structures in three 2-thienyl-substituted tetra­hydro-1,4-ep­oxy-1-benzazepines 
The mol­ecules of (2RS,4SR)-2-exo-(5-bromo-2-thienyl)-7-chloro-2,3,4,5-tetra­hydro-1H-1,4-ep­oxy-1-benzazepine, C14H11BrClNOS, (I), are linked into cyclic centrosymmetric dimers by C—H⋯π(thienyl) hydrogen bonds. Each such dimer makes rather short Br⋯Br contacts with two other dimers. In (2RS,4SR)-2-exo-(5-methyl-2-thienyl)-2,3,4,5-tetra­hydro-1H-1,4-ep­oxy-1-benzazepine, C15H15NOS, (II), a com­bination of C—H⋯O and C—H⋯π(thienyl) hydrogen bonds links the mol­ecules into chains of rings. A more complex chain of rings is formed in (2RS,4SR)-7-chloro-2-exo-(5-methyl-2-thienyl)-2,3,4,5-tetra­hydro-1H-1,4-ep­oxy-1-benzazepine, C15H14ClNOS, (III), built from a combination of two independent C—H⋯O hydrogen bonds, one C—H⋯π(arene) hydrogen bond and one C—H⋯π(thienyl) hydro­gen bond.
PMCID: PMC2737428  PMID: 19726868
12.  Polymorphism and phase transition behavior of 6,6′-bis­(chloro­meth­yl)-1,1′,4,4′-tetra­methyl-3,3′-(p-phenyl­enedimethyl­ene)bis­(piperazine-2,5-dione) 
A crystallographic investigation of the title compound, C22H28Cl2N4O4, using crystals obtained under different crystallization conditions, revealed the presence of two distinct polymorphic forms. The mol­ecular conformation in the two polymorphs is very different: one adopts a ‘C’ shape, whereas the other adopts an ‘S’ shape. In the latter, the molecule lies across a crystallographic twofold axis. The ‘S’-shaped polymorph undergoes a reversible ortho­rhom­bic-to-monoclinic phase transition on cooling, whereas the structure of the ‘C’-shaped polymorph is temperature insensitive.
PMCID: PMC2720150  PMID: 19652319
13.  Eight 7-benzyl-3-tert-butyl-1-phenyl­pyrazolo[3,4-d]oxazines, encompassing structures containing no inter­molecular hydrogen bonds, and hydrogen-bonded structures in one, two or three dimensions 
7-Benzyl-3-tert-butyl-1-phenyl-6,7-dihydro-1H,4H-pyrazolo[3,4-d][1,3]oxazine, C22H25N3O, (I), and 3-tert-butyl-7-(4-methyl­benz­yl)-1-phenyl-6,7-dihydro-1H,4H-pyrazolo[3,4-d][1,3]oxazine, C23H27N3O, (II), are isomorphous in the space group P21, and mol­ecules are linked into chains by C—H⋯O hydrogen bonds. In each of 3-tert-butyl-7-(4-methoxy­benz­yl)-1-phenyl-6,7-dihydro-1H,4H-pyrazolo[3,4-d][1,3]oxazine, C23H27N3O2, (III), which has cell dimensions rather similar to those of (I) and (II), also in P21, and 3-tert-butyl-1-phenyl-7-[4-(trifluoro­meth­yl)benz­yl]-6,7-dihydro-1H,4H-pyrazolo[3,4-d][1,3]oxazine, C23H24F3N3O, (IV), there are no direction-specific inter­actions between the mol­ecules. In 3-tert-butyl-7-(4-nitro­benz­yl)-1-phenyl-6,7-dihydro-1H,4H-pyrazolo[3,4-d][1,3]oxazine, C22H24N4O3, (V), a combination of C—H⋯O and C—H⋯N hydrogen bonds links the mol­ecules into complex sheets. There are no direction-specific inter­actions between the mol­ecules of 3-tert-butyl-7-(2,3-dimethoxy­benz­yl)-1-phenyl-6,7-dihydro-1H,4H-pyrazolo[3,4-d][1,3]oxazine, C24H29N3O3, (VI), but a three-dimensional framework is formed in 3-tert-butyl-7-(3,4-methyl­enedioxy­benz­yl)-1-phenyl-6,7-dihydro-1H,4H-pyrazolo[3,4-d][1,3]oxazine, C23H25N3O3, (VII), by a combination of C—H⋯O, C—H⋯N and C—H⋯π(arene) hydrogen bonds, while a combination of C—H⋯O and C—H⋯π(arene) hydrogen bonds links the mol­ecules of 3-tert-butyl-1-phenyl-7-(3,4,5-trimethoxy­benz­yl)-6,7-dihydro-1H,4H-pyrazolo[3,4-d][1,3]oxazine, C25H31N3O4, (VIII), into complex sheets. In each compound, the oxazine ring adopts a half-chair conformation, while the orientations of the pendent phenyl and tert-butyl substituents relative to the pyrazolo[3,4-d]oxazine unit are all very similar.
PMCID: PMC2720151  PMID: 19652329
14.  3-[1-(4-Sulfamoylphen­yl)-5-p-tolyl-1H-pyrazol-3-yl]propanoic acid and 3-[5-(4-bromo­phen­yl)-1-(4-sulfamoyl­phen­yl)-1H-pyrazol-3-yl]­propanoic acid–dichloro­methane–diethyl ether–water (2/0.72/1/1) 
The syntheses of 3-[1-(4-sulfamoylphenyl)-5-p-tolyl-1H-pyra­zol-3-yl]propanoic acid, C19H19N3O4S, (I), and 3-[5-(4-bromo­phen­yl)-1-(4-sulfamoyl­phen­yl)-1H-pyrazol-3-yl]­propanoic acid–dichloro­methane–diethyl ether–water (2/0.72/1/1), 2C18H16BrN3O4S·0.72CH2Cl2·C4H10O·H2O, (II), are regio­specific. However, correct identification by spectroscopic techniques of the regioisomer formed is not trivial and single-crystal X-ray analysis provided the only means of unambiguous structure determination. Both structures make extensive use of hydrogen bonding and while compound (I) forms a straightforward unsolvated Z′ = 1 structure, compound (II) crystallizes as an unusual mixed solvate, with two crystallographically unique mol­ecules of the pyrazole derivative present in the asymmetric unit. The structure of (II) also features Br⋯Br inter­actions.
PMCID: PMC2724996  PMID: 19498242
15.  A diketiminate-bound diiron complex with a bridging carbonate ligand 
Reduction of carbon dioxide by a diiron(I) complex gives μ-carbonato-κ3 O:O′,O′′-bis­{[2,2,6,6-tetra­methyl-3,5-bis­(2,4,6-triisopropyl­phenyl)heptane-2,5-diiminate(1−)-κ2 N,N′]iron(II)} toluene disolvate, [Fe2(C41H65N)2(CO3)]·2C7H8, a diiron(II) species with a bridging carbonate ligand. The asymmetric unit contains one diiron complex and two cocrystallized toluene solvent mol­ecules that are distributed over three sites, one with atoms in general positions and two in crystallographic sites. Both FeII atoms are η2-coordinated to diketiminate ligands, but η1- and η2-coordinated to the bridging carbonate ligand. Thus, one FeII center is three-coordinate and the other is four-coordinate. The bridging carbonate ligand is nearly perpendicular to the iron–diketiminate plane of the four-coordinate FeII center and parallel to the plane of the three-coordinate FeII center.
PMCID: PMC2675934  PMID: 19407402
16.  Diastereomers (R C,S P)- and (R C,R P)-S-methyl P-(3-azido­prop­yl)-N-[(1R)-1-phenyl­ethyl]phospho­namido­thio­ate 
Diastereoisomers of the title organophospho­rus compound, C12H19N4OPS, denoted R C S P, (I), and R C R P, (II), were structurally characterized and compared. Asymmetric phosphorus compounds are of interest with regard to the use of these systems as possible protein probes via the stereoselective delivery of an azide group tethered to the P atom into key protein regions. The diastereomers were produced in a 1:1 mixture and isolated by chromatography. Although both isomers crystallize in the same space group with superficially similar cell constants, conformational and packing differences are pronounced. Despite the conformational differences, strong inter­molecular hydrogen bonding links both isomers into chains parallel to the a axis [N⋯O = 2.8609 (18) and 2.966 (3) Å in (I) and (II), respectively], with C—H⋯π inter­chain inter­actions of ca 3.5 Å.
PMCID: PMC2724995  PMID: 19346618
17.  3-[5-(4-Chloro­phen­yl)-1-(4-methoxy­phen­yl)-1H-pyrazol-3-yl]propionic acid and the corresponding methyl ester 
The synthesis of 3-[5-(4-chloro­phen­yl)-1-(4-methoxy­phen­yl)-1H-pyrazol-3-yl]propionic acid, C19H17ClN2O3, (I), and its corresponding methyl ester, methyl 3-[5-(4-chloro­phen­yl)-1-(4-methoxy­phen­yl)-1H-pyrazol-3-yl]propionate, C20H19ClN2O3, (II), is regiospecific. However, correct identification of the regioisomer formed by spectroscopic techniques is not trivial and single-crystal X-ray analysis provided the only means of unambiguous structure determination. Compound (I) crystallizes with Z′ = 2. The propionic acid groups of the two crystallographically unique mol­ecules form a hydrogen-bonded dimer, as is typical of carboxylic acid groups in the solid state. Conformational differences between the meth­oxy­benzene and pyrazole rings give rise to two unique mol­ecules. The structure of (II) features just one mol­ecule in the asymmetric unit and the crystal packing makes greater use than (I) of weak C—H⋯A inter­actions, despite the lack of any functional groups for classical hydrogen bonding.
PMCID: PMC2724994  PMID: 19346614
18.  From small structural modifications to adjustment of structurally dependent properties: 1-methyl-3,5-bis­[(E)-2-thienyl­idene]-4-piperidone and 3,5-bis­[(E)-5-bromo-2-thienyl­idene]-1-methyl-4-piperidone 
The mol­ecules of the title compounds, C16H15NOS2, (I), and C16H13Br2NOS2, (II), are E,E-isomers and consist of an extensive conjugated system, which determines their mol­ecular geometries. Compound (I) crystallizes in the monoclinic space group P21/c. It has one thio­phene ring disordered over two positions, with a minor component contribution of 0.100 (3). Compound (II) crystallizes in the noncentrosymmetric ortho­rhom­bic space group Pca21 with two independent mol­ecules in the unit cell. These mol­ecules are related by a noncrystallographic pseudo-inversion center and possess very similar geometries. The crystal packings of (I) and (II) have a topologically common structural motif, viz. stacks along the b axis, in which the mol­ecules are bound by weak C—H⋯O hydrogen bonds. The noncentrosymmetric packing of (II) is governed by attractive inter­molecular Br⋯Br and Br⋯N inter­actions, which are also responsible for the very high density of (II) (1.861 Mg m−3).
PMCID: PMC2665971  PMID: 19346612

Results 1-18 (18)