Use of intensity quotients and differences in absolute structure refinement

Crystal structure of 3β-acet-oxy-androsta-5,16-dien-17-yl tri-fluoro-methane-sulfon-ate

The title compound, C22H29F3O5S [systematic name: (3S,8R,9S,10R,13S,14S)-10,13-dimethyl-17-(tri-fluoro-methylsulfon-yloxy)-2,3,4,7,8,9,10,11,12,13,14,15-dodeca-hydro-1H-cyclo-penta-[a]phenanthren-3-yl acetate], contains a fused four-ring steroidal system. Rings A and C adopt a chair conformation, while rings B and D adopt half-chair and envelope (with the fused CH atom as the flap) conformations, respectively. In the crystal, weak inter-molecular C-H⋯O inter-actions link the mol-ecules into layers parallel to the ab plane.

Crystal structures of five (2-chloro-quinolin-3-yl)methyl ethers: supra-molecular assembly in one and two dimensions mediated by hydrogen bonding and π-π stacking

In the mol-ecules of the title compounds, methyl 5-bromo-2-[(2-chloro-quinolin-3-yl)meth-oxy]benzoate, C18H13BrClNO3, (I), methyl 5-bromo-2-[(2-chloro-6-methyl-quinolin-3-yl)meth-oxy]benzoate, C19H15BrClNO3, (II), methyl 2-[(2-chloro-6-methyl-quinolin-3-yl)meth-oxy]benzoate, C19H16ClNO3, (III), which crystallizes with Z' = 4 in space group P212121, and 2-chloro-3-[(naphthalen-1-yl-oxy)meth-yl]quinoline, C20H14ClNO, (IV), the non-H atoms are nearly coplanar, but in {5-[(2-chloro-quinolin-3-yl)meth-oxy]-4-(hy-droxy-meth-yl)-6-methyl-pyridin-3-yl}methanol, C18H17ClN2O3, (V), the planes of the quinoline unit and of the unfused pyridine ring are almost parallel, although not coplanar. The mol-ecules of (I) are linked by two independent π-π stacking inter-actions to form chains, but there are no hydrogen bonds present in the structure. In (II), the mol-ecules are weakly linked into chains by a single type of π-π stacking inter-action. In (III), three of the four independent mol-ecules are linked by π-π stacking inter-actions but the other mol-ecule does not participate in such inter-actions. Weak C-H⋯O hydrogen bonds link the mol-ecules into three types of chains, two of which contain just one type of independent mol-ecule while the third type of chain contains two types of mol-ecule. The mol-ecules of (IV) are linked into chains by a C-H⋯π(arene) hydrogen bond, but π-π stacking inter-actions are absent. In (V), there is an intra-molecular O-H⋯O hydrogen bond, and mol-ecules are linked into sheets by a combination of O-H⋯N hydrogen bonds and π-π stacking inter-actions.

Crystal structures of five 1-alkyl-4-aryl-1,2,4-triazol-1-ium halide salts

The asymmetric units for the salts 4-(4-fluoro-phen-yl)-1-isopropyl-1,2,4-triazol-1-ium iodide, C11H13FN3 (+)·I(-), (1), 1-isopropyl-4-(4-methyl-phen-yl)-1,2,4-triazol-1-ium iodide, C12H16N3 (+)·I(-), (2), 1-isopropyl-4-phenyl-1,2,4-triazol-1-ium iodide, C11H14N3 (+)·I(-), (3), and 1-methyl-4-phenyl-1,2,4-triazol-1-ium iodide, C9H10N3 (+)·I(-), (4), contain one cation and one iodide ion, whereas in 1-benzyl-4-phenyl-1,2,4-triazol-1-ium bromide monohydrate, C15H14N3 (+)·Br(-)·H2O, (5), there is an additional single water mol-ecule. There is a predominant C-H⋯X(halide) inter-action for all salts, resulting in a two-dimensional extended sheet network between the triazolium cation and the halide ions. For salts with para-substitution on the aryl ring, there is an additional π-anion inter-action between a triazolium carbon and iodide displayed by the layers. For salts without the para-substitution on the aryl ring, the π-π inter-actions are between the triazolium and aryl rings. The melting points of these salts agree with the predicted substituent inductive effects.

Crystal structure of (4Z)-4-[(2E)-3-(2-chloro-phen-yl)-1-hy-droxy-prop-2-en-1-yl-idene]-3-methyl-1-phenyl-1H-pyrazol-5(4H)-one

In the title compound, C19H15ClN2O2, the pyrazole ring is almost planar (r.m.s. deviation = 0.002 Å) and subtends dihedral angles of 5.31 (16) and 1.86 (16)° with the phenyl and chloro-benzene rings, respectively. An intra-molecular O-H⋯O hydrogen bond closes an S(6) ring and a short C-H⋯O contact is also observed. In the crystal, mol-ecules are linked by weak C-H⋯O inter-actions to generate (001) sheets. Weak aromatic π-π inter-actions between the chloro-benzene and pyrazole rings, with a centroid-centroid distance of 3.7956 (17) Å are also observed.

Two reversible enantiotropic phase transitions in a pentacoordinate silicon complex with an O,N,O'-tridentate valinate ligand

Dimethyl[N-(4-oxidopent-3-en-2-ylidene)valinato-κ(3)O,N,O']silicon(IV), C12H21NO3Si, (II), crystallizes in the orthorhombic space group P2₁2₁2₁. The chiral compound undergoes two sharp enantiotropic phase transitions upon cooling. The first transformation occurs at 163 K to yield a unit cell with one axis having double length. This intermediate-temperature form has the monoclinic space group P2₁. The second transition takes place at 142 K and converts the single crystal into the low-temperature form in the orthorhombic space group P2₁2₁2₁. This transition proceeds under tripling of the a axis of the high-temperature form. Both phase transitions are fully reversible and correspond to order-disorder transitions of the isopropyl group of the valine unit in the ligand backbone. The phase transitions presented here raise questions, since they do not fit into the rules of group-subgroup relationships.

A structural study of (1RS,2SR,3RS,4SR,5RS)-2,4-dibenzoyl-1,3,5-triphenylcyclohexan-1-ol chloroform hemisolvate and (1RS,2SR,3RS,4SR,5RS)-2,4-dibenzoyl-1-phenyl-3,5-bis(2-methoxyphenyl)cyclohexan-1-ol

(1RS,2SR,3RS,4SR,5RS)-2,4-Dibenzoyl-1,3,5-triphenylcyclohexan-1-ol or (4-hydroxy-2,4,6-triphenylcyclohexane-1,3-diyl)bis(phenylmethanone), C38H32O3, (1), is formed as a by-product in the NaOH-catalyzed synthesis of 1,3,5-triphenylpentane-1,5-dione from acetophenone and benzaldehyde. Single crystals of the chloroform hemisolvate, C38H32O3·0.5CHCl3, were grown from chloroform. The structure has triclinic (P1) symmetry. One diastereomer [as a pair of (1RS,2SR,3RS,4SR,5RS)-enantiomers] of (1) has been found in the crystal structure and confirmed by NMR studies. The dichoromethane hemisolvate has been reported previously [Zhang et al. (2007). Acta Cryst. E63, o4652]. (1RS,2SR,3RS,4SR,5RS)-2,4-Dibenzoyl-3,5-bis(2-methoxyphenyl)-1-phenylcyclohexan-1-ol or [4-hydroxy-2,6-bis(2-methoxyphenyl)-4-phenylcyclohexane-1,3-diyl]bis(phenylmethanone), C40H36O5, (2), is also formed as a by-product, under the same conditions, from acetophenone and 2-methoxybenzaldehyde. Crystals of (2) have been grown from chloroform. The structure has orthorhombic (Pca2₁) symmetry. A diastereomer of (2) possesses the same configuration as (1). In both structures, the cyclohexane ring adopts a chair conformation with all bulky groups (benzoyl, phenyl and 2-methoxyphenyl) in equatorial positions. The molecules of (1) and (2) both display one intramolecular O-H···O hydrogen bond.

L-Argininium phosphite - a new candidate for NLO materials

In order to investigate the possibility of salt formation in the L-Arg-H3PO3-H2O system, single crystals of L-argininium phosphite, C6H15N4O2(+)·H2PO3(-), were prepared by evaporation of an aqueous solution containing equimolar quantities of L-arginine and phosphorous acid. The asymmetric unit contains one L-argininium(+) cation and one phosphite [HPO2(OH)](-) anion. The phosphite anions form chains parallel to [010] by O-H...O hydrogen bonding, with an O...O distance of 2.630 (3) Å. The protonated amine and guanidyl groups of the L-argininium(+) cations form N-H...O hydrogen bonds with the carboxylate groups and anions. The IR and Raman spectra are discussed in relation to the crystal structure. The salt displays nonlinear optical (NLO) properties. Another salt was obtained from a solution with a 1:2 molar ratio of components, but was characterized by vibrational spectra only.

The first structurally analysed nucleic acid building block containing the Reese protecting group: 2'-O-[1-(2-fluorophenyl)-4-methoxypiperidin-4-yl]-β-D-(1'R,2'R,3'R,4'R)-uridine

The title compound, C21H26FN3O7, is assembled by N-H...O and O-H...O hydrogen bonds into well-separated two-dimensional layers of about 15 Å thickness. The crescent conformation of the molecules is stabilized by weak intramolecular C-H...O and C-H...F hydrogen bonds. The uridine moiety adopts an anti conformation. The ribofuranose ring exists in an envelope conformation. All the endocyclic uracil bonds are shorter than normal single C-N and C-C bonds, and five of them have comparable lengths, which implies a considerable degree of delocalization of the electron density within this ring.

Crystal structure of (2S)-3-methyl-2-[(naphthalen-1-ylsulfon-yl)amino]-butanoic acid

The title compound, C15H17NO4S, was synthesized from l-valine and naphthalene-1-sulfonyl chloride. The hydrogen-bonded carb-oxy-lic acid groups form a catemer C(4) motif extending along [100]. The catemer structure is reinforced by a rather long N-H⋯O hydrogen bond, between the sulfamide N-H group and a carb-oxy-lic acid O atom [H⋯O = 2.52 (2) Å], and a C-H⋯O hydrogen bond.

Crystal structure of the co-crystalline adduct 1,3,6,8-tetra-aza-tri-cyclo-[4.4.1.1(3,8)]dodecane (TATD)-4-bromo-phenol (1/2)

The structure of the 1:2 co-crystalline adduct C8H16N4·2C6H5BrO, (I), from the solid-state reaction of 1,3,6,8-tetra-aza-tri-cyclo-[4.4.1.1(3,8)]dodecane (TATD) and 4-bromo-phenol, has been determined. The asymmetric unit of the title co-crystalline adduct comprises a half mol-ecule of aminal cage polyamine plus a 4-bromo-phenol mol-ecule. A twofold rotation axis generates the other half of the adduct. The primary inter-species association in the title compound is through two inter-molecular O-H⋯N hydrogen bonds. In the crystal, the adducts are linked by weak non-conventional C-H⋯O and C-H⋯Br hydrogen bonds, giving a two-dimensional supra-molecular structure parallel to the bc plane.

Crystal structure of 5,5'-di-bromo-3,3'-di-tert-butyl-6,6'-di-methyl-biphenyl-2,2'-diol

The whole mol-ecule of the title compound, C22H28Br2O2, is generated by twofold rotation symmetry. The dihedral angle of the biphenyl moiety is 85.05 (11)°. The hy-droxy groups show intra-molecular O-H⋯π inter-actions without any other hydrogen-bond acceptors. In the crystal, there are no other significant inter-molecular inter-actions present.

Crystal structure of anagyrine perchlorate

The title mol­ecular salt, C₁₅H₂₁N₂O⁺·ClO₄⁻, crystallizes with four cations (A, B, C and D) and four anions in the chiral unit cell (space group P2₁). The alkaloid was isolated from the aerial parts of Genista Hispanica collected in the Samarkand region of Uzbekistan. Each cation is protonated at the N atom that bridges the alkaloid rings C and D. In each cation, ring A is almost planar and ring B adops a sofa conformation with the methyl­ene group bridging to the C ring as the flap. Rings C and D adopt chair conformations with a cis ring junction in all four cations. In the crystal, A+B and C+D dimeric pairs linked by pairs of N—H⋯O hydrogen bonds are observed, which generate R₂²(16) loops in each case. The dimers are consolidated by weak aromatic π–π stacking inter­actions between the A rings [centroid–centroid distances = 3.913 (3) and 3.915 (3) Å].

Crystal structures of 1-(4-chloro-phen-yl)-2-(di-phenyl-phosphor-yl)ethan-1-one and 1-(di-phenyl-phosphor-yl)-3,3-di-methyl-butan-2-one

The title compounds, C20H16ClO2P, (I), and C18H21O2P, (II), were synthesized via an Arbuzov reaction between an α-bromo-ketone and isopropoxydi-phenyl-phosphane. In the crystals of both compounds, mol-ecules are linked via bifurcated C-H⋯(O,O) hydrogen bonds, forming chains propagating along [100] for (I) and along [010] for (II). The chains are linked via C-H⋯π inter-actions, leading to the formation of sheets lying parallel to (010) for (I) and (001) for (II). The absolute structure of compound (II) was determined by resonant scattering [Flack parameter = 0.088 (14)].

Crystal structure of 2-chloro-3-(di-meth-oxy-meth-yl)-6-meth-oxy-quinoline

The title compound, C13H14ClNO3, crystallizes with Z' = 2 in the space group Pca21, but a search for possible additional crystallographic symmetry found none. However, the crystal structure exhibits pseudosymmetry as the two independent mol-ecules are related by an approximate but non-crystallographic inversion located close to (0.38, 0.26, 1/2) in the selected asymmetric unit, and the structure exhibits partial inversion twinning. The approximate inversion relationship between the two mol-ecules in the selected asymmetric unit is clearly shown by comparison of the relevant torsion angle in the two mol-ecules; the corresponding torsion angles have similar, although not identical magnitudes but with opposite signs. The mean planes of the quinoline rings in the two independent mol-ecules are almost parallel, with a dihedral angle of only 0.16 (3)° between them, and the mutual orientation of these rings permits significant π-π stacking inter-actions between them [centroid-centroid distances = 3.7579 (15) and 3.7923 (15) Å]. In addition, the bimolecular aggregates which are related by translation along [010] are linked by a further π-π stacking inter-action [centroid-centroid distance = 3.7898 (15) Å], so forming a π-stacked chain running parallel to [010]. However, there are no C-H⋯N hydrogen bonds in the structure nor, despite the number of independent aromatic rings, are there any C-H⋯π hydrogen bonds; hence there are no direction-specific inter-actions between adjacent π-stacked chains.

Evaluation of New Dihydrophthalazine-Appended 2,4-Diaminopyrimidines against Bacillus anthracis: Improved Syntheses Using a New Pincer Complex

The synthesis and evaluation of ten new dihydrophthalazine-appended 2,4-diaminopyrimidines as potential drugs to treat Bacillus anthracis is reported. An improved synthesis utilizing a new pincer catalyst, dichlorobis[1-(dicyclohexylphosphanyl)-piperidine]palladium(II), allows the final Heck coupling to be performed at 90 °C using triethylamine as the base. These milder conditions have been used to achieve improved yields for new and previously reported substrates with functional groups that degrade or react at the normal 140 °C reaction temperature. An analytical protocol for separating the S and R enantiomers of two of the most active compounds is also disclosed. Finally, the X-ray structure for the most active enantiomer of the lead compound, (S)-RAB1, is given.

A three-dimensional cadmium(II) coordination polymer with unequal homochiral double-stranded concentric helical chains

A homochiral helical three-dimensional coordination polymer, poly[[(μ2-acetato-κ(3)O,O':O)(hydroxido-κO)(μ4-5-nicotinamido-1H-1,2,3,4-tetrazol-1-ido-κ(5)N(1),O:N(2):N(4):N(5))(μ3-5-nicotinamido-1H-1,2,3,4-tetrazol-1-ido-κ(4)N(1),O:N(2):N(4):N(5))dicadmium(II)] 0.75-hydrate], {[Cd2(C7H5N6O)2(CH3COO)(OH)]·0.75H2O}n, was synthesized by the reaction of cadmium acetate, N-(1H-tetrazol-5-yl)isonicotinamide (H-NTIA), ethanol and H2O under hydrothermal conditions. The asymmetric unit contains two crystallographically independent Cd(II) cations, two deprotonated 5-nicotinamido-1H-1,2,3,4-tetrazol-1-ide (NTIA(-)) ligands, one acetate anion, one hydroxide anion and three independent partially occupied water sites. The two Cd(II) cations, with six-coordinated octahedral and seven-coordinated pentagonal bipyramidal geometries are located on general sites. The tetrazole group of one symmetry-independent NTIA(-) ligand links one of the independent Cd(II) cations into 61 helical chains, while the other NTIA(-) ligand links the other independent Cd(II) cations into similar but unequal 61 helical chains. These chains, with a pitch of 24.937 (5) Å, intertwine into a double-stranded helix. Each of the double-stranded 61 helices is further connected to six adjacent helical chains through an acetate μ2-O atom and the tetrazole group of the NTIA(-) ligand into a three-dimensional framework. The helical channel is occupied by the isonicotinamide groups of NTIA(-) ligands and two helices are connected to each other through the pyridine N and carbonyl O atoms of isonicotinamide groups. In addition, N-H···O and O-H···N hydrogen bonds exist in the complex.

Evidence for stereoelectronic effects in the N-C-N group of 8,10,12-triaza-1-azoniatetracyclo[8.3.1.1(8,12).0(2,7)]pentadecane 4-nitrophenolate 4-nitrophenol monosolvate from the protonation of aminal (2R,7R)-1,8,10,12-tetraazatetracyclo[8.3.1.1(8,12).0(2,7)]pentadecane: X-ray and natural bond orbital analysis

The title molecular salt, C11H21N4(+)·C6H4NO3(-)·C6H5NO3, (II), crystallizes with two independent three-component aggregates in the asymmetric unit. In the cations, the cyclohexane rings fused to the cage azaadamantane systems both adopt a chair conformation. In the crystal structure, the aggregates are connected by C-H···O hydrogen bonds, forming a supramolecular unit enclosing an R4(4)(24) ring motif. These units are linked via C-H···O and C-H···N hydrogen bonds, forming a three-dimensional network. Even hydrogen-bond formation to one of the N atoms is enough to induce structural stereoelectronic effects in the normal donor→acceptor direction. The C-N bond distances provide structural evidence for a strong anomeric effect. The structure also displays O-H···O and N-H···O hydrogen bonding. Geometric optimization and natural bond orbital (NBO) analysis of (II) were undertaken by utilizing DFT/B3LYP with the 6-31+G(d,p) basis set. NBO second-order perturbation theory calculations indicate donor-acceptor interactions between nitrogen lone pairs and the antibonding orbital of the C-C and C-N bonds for the protonated polyamine, in agreement with the occurrence of bond-length and bond-angle changes within the aminal cage structure.

The crystal structures of three clozapinium salts: different mol-ecular configurations, and supra-molecular assembly in one, two and three dimensions

The structures of three salts derived from clozapine, 8-chloro-11-(4-methyl-piperazin-1-yl)-5H-dibenzo[b,e][1,4]diazepine, are reported, namely, clo-za-pin-ium 3,5-di-nitro-benzoate dimethyl sulfoxide monosolvate, C18H20ClN4 (+)·C7H3N2O6 (-)·C2H6OS, (I), where the dimethyl sulfoxide component is disordered over two sets of atomic sites having occupancies 0.627 (2) and 0.373 (2); clo-za-pin-ium hydrogen maleate 0.21-hydrate, C18H20ClN4 (+)·C4H3O4 (-)·0.21H2O, (II), and clozapinium 2-hy-droxy-benzoate, C18H20ClN4 (+)·C7H5O3 (-), (III). In all three salts, the protonation site is the methyl-ated N atom of the piperazine ring, and the dimensions and conformations of the fused tricyclic system are very similar. However, differences are apparent in the piperazine component: in both compounds (II) and (III), the unprotonated N atom of this ring has a pyramidal geometry, but in compound (I) this atom has a planar geometry. In compound (III), both N-substituents in this ring occupy equatorial sites, but in compound (II) the fused tricyclic system occupies an axial site of the piperazine ring. The independent components of compound (I) are linked within the selected asymmetric unit by a combination of N-H⋯O and C-H⋯O hydrogen bonds, and these hydrogen-bonded aggregates are linked into chains by an aromatic π-π stacking inter-action. In compound (II), the components are linked into sheets by a combination of O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds, and in compound (III), a combination of N-H⋯O, C-H⋯O and C-H⋯N hydrogen bonds links the components into a three-dimensional framework structure. Comparisons are made with some similar compounds.

Crystal structures of the water and acetone monosolvates of bis-[4'-(pyridin-4-yl)-2,2':6',2''-terpyridine]-manganese(II) bis-(hexa-fluorido-phosphate)

The crystal structures of bis-[4'-(pyridin-4-yl)-2,2':6',2''-terpyridine]-man-gan-ese(II) bis-(hexa-fluorido-phosphate) monohydrate, [Mn(C20H14N4)2](PF6)2·H2O, (1), and bis-[4'-(pyridin-4-yl)-2,2':6',2''-terpyridine]-manganese(II) bis(hexa-fluorido-phosphate) acetone monosolvate, (2), [Mn(C20H14N4)2](PF6)2·CH3COCH3, are described. At 150 K, (1) and (2) have monoclinic (P21/c) and ortho-rhom-bic (C2221) symmetries, respectively. Both structures exhibit octahedrally coordinated Mn(II) atoms and disorder. They display weak inter-actions, such as C-H⋯F, C-H⋯N, C-H⋯π, F⋯π and π-π. The twofold rotation axis in the molecule of (2) is coincident with a twofold rotation axis of the crystal.

Crystal structures of {[Cu(Lpn)2][Fe(CN)5(NO)]·H2O} n and {[Cu(Lpn)2]3[Cr(CN)6]2·5H2O} n [where Lpn = (R)-propane-1,2-di-amine]: two heterometallic chiral cyanide-bridged coordination polymers

The title compounds, catena-poly[[[bis-[(R)-propane-1,2-di-amine-κ(2) N,N']copper(II)]-μ-cyanido-κ(2) N:C-[tris-(cyanido-κC)(nitroso-κN)iron(III)]-μ-cyanido-κ(2) C:N] monohydrate], {[Cu(Lpn)2][Fe(CN)5(NO)]·H2O} n , (I), and poly[[hexa-μ-cyanido-κ(12) C:N-hexa-cyanido-κ(6) C-hexa-kis-[(R)-propane-1,2-di-amine-κ(2) N,N']dichromium(III)tricopper(II)] penta-hydrate], {[Cu(Lpn)2]3[Cr(CN)6]2·5H2O} n , (II) [where Lpn = (R)-propane-1,2-di-amine, C3H10N2], are new chiral cyanide-bridged bimetallic coordination polymers. The asymmetric unit of compound (I) is composed of two independent cation-anion units of {[Cu(Lpn)2][Fe(CN)5)(NO)]} and two water mol-ecules. The Fe(III) atoms have distorted octa-hedral geometries, while the Cu(II) atoms can be considered to be penta-coordinate. In the crystal, however, the units align to form zigzag cyanide-bridged chains propagating along [101]. Hence, the Cu(II) atoms have distorted octa-hedral coordination spheres with extremely long semicoordination Cu-N(cyanido) bridging bonds. The chains are linked by O-H⋯N and N-H⋯N hydrogen bonds, forming two-dimensional networks parallel to (010), and the networks are linked via N-H⋯O and N-H⋯N hydrogen bonds, forming a three-dimensional framework. Compound (II) is a two-dimensional cyanide-bridged coordination polymer. The asymmetric unit is composed of two chiral {[Cu(Lpn)2][Cr(CN)6]}(-) anions bridged by a chiral [Cu(Lpn)2](2+) cation and five water mol-ecules of crystallization. Both the Cr(III) atoms and the central Cu(II) atom have distorted octa-hedral geometries. The coordination spheres of the outer Cu(II) atoms of the asymmetric unit can be considered to be penta-coordinate. In the crystal, these units are bridged by long semicoordination Cu-N(cyanide) bridging bonds forming a two-dimensional network, hence these Cu(II) atoms now have distorted octa-hedral geometries. The networks, which lie parallel to (10-1), are linked via O-H⋯O, O-H⋯N, N-H⋯O and N-H⋯N hydrogen bonds involving all five non-coordinating water mol-ecules, the cyanide N atoms and the NH2 groups of the Lpn ligands, forming a three-dimensional framework.

Redetermination and absolute configuration of berkeleydione

The crystal structure of the title compound, berkeleydione [systematic name; (5aS,7R,9S,11R,11aS)-methyl 9-hy-droxy-1,1,5,7,9,11a-hexa-methyl-14-methyl-idene-3,8,10-trioxo-1,3,4,5a,6,7,8,9,10,11,11a,12-dodeca-hydro-7,11-methano-cycloocta-[4,5]cyclo-hepta-[1,2-c]pyran-11-carboxyl-ate], C26H32O7, has been reported previously [Stierle et al. (2004 ▶). Org. Lett. 6, 1049-1052]. However, the absolute configuration could not be determined from the data collected with Mo Kα radiation and has now been determined by refinement of the Flack parameter with data collected using Cu Kα radiation. It is in agreement with the previous circular dichroism assignment, and the crystal packing is similar to that described previously.

Serendipitous preparation of fac-(aceto-nitrile-κN)tri-chlorido-[(1,2,5,6-η)-cyclo-octa-1,5-diene]iridium(III)

An octa­hedral complex of iridium(III) with a chelating cyclo­octa-1,5-diene ligand, a facial arrangement of three chloride ligands and one aceto­nitrile ligand was isolated serendipitously from an attempted reaction between indene, the chlorido­cyclo­octa­dieneiridium dimer and HCl. Work-up that included use of aceto­nitrile solvent led to the formation of a few crystals of the title compound.

A reaction between [(COD)IrCl]₂ (COD is cyclo­octa-1,5-diene), HCl and indene failed to provide the hoped for chlorido­indenyliridium dimer, but instead produced the title compound, [IrCl₃(CH₃CN)(C₈H₁₂)], which is an octa­hedral complex of iridium(III) with a chelating cyclo­octa-1,5-diene ligand, three chloride ligands in a fac arrangement, and one aceto­nitrile ligand. Attempts to devise a rational synthesis for the title compound were unsuccessful.

Crystal structure of the co-crystal fac-tri-aqua-tris(thio-cyanato-κN)iron(III)-2,3-di-methyl-pyrazine (1/3)

In the crystal of the title compound, [Fe(NCS)3(H2O)3]·3C6H8N2, the Fe(III) cation is located on a threefold rotation axis and is coordinated by three N atoms of the thiocyanate anions and three water mol-ecules in a fac arrangement, forming a slightly distorted N3O3 octa-hedron. Stabilization within the crystal structure is provided by O-H⋯N hydrogen bonds; the H atoms from coordinating water mol-ecules act as donors to the N atoms of guest 2,3-di-methyl-pyrazine mol-ecules, leading to a three-dimensional supra-molecular framework.

Four oxoindole-linked α-alkoxy-β-amino acid derivatives

Four structures of oxoindolyl α-hydroxy-β-amino acid derivatives, namely, methyl 2-{3-[(tert-butoxycarbonyl)amino]-1-methyl-2-oxoindolin-3-yl}-2-methoxy-2-phenylacetate, C24H28N2O6, (I), methyl 2-{3-[(tert-butoxycarbonyl)amino]-1-methyl-2-oxoindolin-3-yl}-2-ethoxy-2-phenylacetate, C25H30N2O6, (II), methyl 2-{3-[(tert-butoxycarbonyl)amino]-1-methyl-2-oxoindolin-3-yl}-2-[(4-methoxybenzyl)oxy]-2-phenylacetate, C31H34N2O7, (III), and methyl 2-[(anthracen-9-yl)methoxy]-2-{3-[(tert-butoxycarbonyl)amino]-1-methyl-2-oxoindolin-3-yl}-2-phenylacetate, C38H36N2O6, (IV), have been determined. The diastereoselectivity of the chemical reaction involving α-diazoesters and isatin imines in the presence of benzyl alcohol is confirmed through the relative configuration of the two stereogenic centres. In esters (I) and (III), the amide group adopts an anti conformation, whereas the conformation is syn in esters (II) and (IV). Nevertheless, the amide group forms intramolecular N-H···O hydrogen bonds with the ester and ether O atoms in all four structures. The ether-linked substituents are in the extended conformation in all four structures. Ester (II) is dominated by intermolecular N-H···O hydrogen-bond interactions. In contrast, the remaining three structures are sustained by C-H···O hydrogen-bond interactions.

Inversion twinning in a second polymorph of the hydrochloride salt of the recreational drug ethylone

A second polymorph of the hydrochloride salt of the recreational drug ethylone, C12H16NO3(+)·Cl(-), is reported [systematic name: (±)-2-ethylammonio-1-(3,4-methylenedioxyphenyl)propane-1-one chloride]. This polymorph, denoted form (A), appears in crystallizations performed above 308 K. The originally reported form (B) [Wood et al. (2015). Acta Cryst. C71, 32-38] crystallizes preferentially at room temperature. The conformations of the cations in the two forms differ by a 180° rotation about the C-C bond linking the side chain to the aromatic ring. Hydrogen bonding links the cations and anions in both forms into similar extended chains in which any one chain contains only a single enantiomer of the chiral cation, but the packing of the ions is different. In form (A), the aromatic rings of adjacent chains interleave, but pack equally well if neighbouring chains contain the same or opposite enantiomorph of the cation. The consequence of this is then near perfect inversion twinning in the structure. In form (B), neighbouring chains are always inverted, leading to a centrosymmetric space group. The question as to why the polymorphs crystallize at slightly different temperatures has been examined by density functional theory (DFT) and lattice energy calculations and a consideration of packing compactness. The free energy (ΔG) of the crystal lattice for polymorph (A) lies some 52 kJ mol(-1) above that of polymorph (B).

Exoconformers ofN-(pyridin-2-yl)- andN-(pyridin-3-yl)norbornene-5,6-dicarboximide crystals

Two isomeric pyridine-substituted norbornenedicarboximide derivatives, namelyN-(pyridin-2-yl)-exo-norbornene-5,6-dicarboximide, (I), andN-(pyridin-3-yl)-exo-norbornene-5,6-dicarboximide, (II), both C14H12N2O4, have been crystallized and their structures unequivocally determined by single-crystal X-ray diffraction. The molecules consist of norbornene moieties fused to a dicarboximide ring substituted at the N atom by either pyridin-2-yl or pyridin-3-yl in ananticonfiguration with respect to the double bond, thus affordingexoisomers. In both compounds, the asymmetric unit consists of two independent molecules (Z′ = 2). In compound (I), the pyridine rings of the two independent molecules adopt different conformations,i.e. synandanti, with respect to the methylene bridge. The intermolecular contacts of (I) are dominated by C—H...O interactions. In contrast, in compound (II), the pyridine rings of both molecules have ananticonformation and the two independent molecules are linked by carbonyl–carbonyl interactions, as well as by C—H...O and C—H...N contacts.

Crystal structure of catena-poly[silver(I)-μ-l-tyrosinato-κ(2) O:N]

The title compound, [Ag(C₉H₁₀NO₃)]_n, is a polymeric silver(I) complex of l-tyrosine. The Ag^I atom is connected to N and O atoms of two different l-tyrosine ligands in an almost linear arrangement, with an Nⁱ—Ag—O1 bond angle of 173.4 (2)° [symmetry code: (i) x + 1, y, z]. The Ag—Nⁱ and Ag—O bond lengths are 2.156 (5) and 2.162 (4) Å, respectively. The polymeric chains extend along the crystallographic a axis. Strong hydrogen bonds of the N—H⋯O and O—H⋯O types and additional C—H⋯O inter­actions connect these chains into a double-layer polymeric network in the ab plane.

Crystal structure of the di-Mannich base 4,4'-di-chloro-3,3',5,5'-tetra-methyl-2,2'-[imidazolidine-1,3-diylbis(methyl-ene)]diphenol

The title compound, C21H26Cl2N2O2, was prepared in a solvent-free microwave-assisted synthesis, and crystallizes in the ortho-rhom-bic space group Pna21. The imidazolidine ring adopts an envelope conformation and its mean plane is almost perpendicular to the two pendant aromatic rings [dihedral angles = 84.61 (9) and 86.54 (9)°]. The mol-ecular structure shows the presence of two intra-molecular O-H⋯N hydrogen bonds between the phenolic hy-droxy groups and imidazolidine N atoms. The two 3-chloro-6-hy-droxy-2,4-di-methyl-benzyl groups are located in a cis orientation with respect to the imidazolidine fragment. As a result, the lone pairs of electrons on the N atoms are presumed to be disposed in a syn conformation. This is therefore the first example of an exception to the 'rabbit-ears' effect in such 2,2'-[imidazolidine-1,3-diylbis(methyl-ene)]diphenol derivatives.

Captopril and its dimer captopril disulfide: comparative structural and conformational studies

The crystal structures of captopril {systematic name: (2S)-1-[(2S)-2-methyl-3-sulfanylpropanoyl]pyrrolidine-2-carboxylic acid}, C(9)H(15)NO(3)S, (1), and its dimer disulfide metabolite, 1,1'-{disulfanediylbis[(2S)-2-methyl-1-oxopropane-3,1-diyl]}bis-L-proline, C(18)H(28)N(2)O(6)S(2), (2), were determined by single-crystal X-ray diffraction analysis. Compound (1) crystallizes in the orthorhombic space group P2(1)2(1)2(1), while compound (2) crystallizes in the monoclinic space group P2(1), both with one molecule per asymmetric unit. The molecular geometries of (1) and (2) are quite similar, but certain differences appear in the conformations of the five-membered proline rings and the side chains containing the sulfhydryl group. The proline ring adopts an envelope conformation in (1), while in (2) it exists in envelope and slightly deformed half-chair conformations. The conformation adopted by the side chain is extended in (1) and folded in (2). A minimum-energy conformational search using Monte Carlo methods in the aqueous phase reveals that the optimized conformations of the title compounds differ from those determined crystallographically, which depend on their immediate environment. Intermolecular O-H...O and relatively weak C-H...O interactions seem to be effective in both structures and, together with S-H...O and C-H...S contacts, they create three-dimensional networks.

Solid-state supramolecular architecture of carbenoxolone – comparative studies with glycyrrhetinic and glycyrrhizic acids

Carbenoxolone (CBXH2), a pharmaceutically relevant derivative of glycyrrhetinic acid, was studied by X-ray crystallography. The crystal structures of its unsolvated form, propionic acid and dimethoxyethane solvates and a solvated cocrystal of the free acid with its monobasic sodium salt CBXH2·CBXHNa·(butan-2-one)2·2H2O reveal that the recurring motif of supramolecular architecture in all crystal forms is a one-dimensional ribbon with closely packed triterpene fragments. It does not result from strong specific interactions but solely from van der Waals interactions. The ribbons are further arranged into diverse layer-type aggregates with a hydrophobic interior (triterpene skeletons) and hydrophilic surfaces covered with carboxylic/carboxylate groups. Solvent molecules included at the interface between the layers influence hydrogen-bonding interactions between the carbenoxolone molecules and organization of the ribbons within the layer. Comparison of crystal structures of carbenoxolone, glycyrrhizic acid and its aglycone-glycyrrhetinic acid have shown the impact of the size and hydrophilic character of the substituent at the triterpene C3 atom on the supramolecular architecture of these three closely related molecules.

Crystal structure of catena-poly[[cadmium(II)-di-μ2-bromido-μ2-l-proline-κ(2) O:O'] monohydrate]

In the title coordination polymer, {[CdBr2(C5H9NO2)]·H2O} n , the Cd(II) ion is coordinated by four bromido ligands and two carboxyl-ate oxygen atoms of two symmetry-related proline ligands, which exist in a zwitterionic form, in a distorted octa-hedral geometry. There is an intra-molecular N-H⋯O hydrogen bond between the amino group and the carboxyl-ate fragment. Each coordinating ligand bridges two Cd(II) atoms, thus forming polymeric chains running along the c-axis direction. The water mol-ecules of crystallization serve as donors for the weak inter-molecular O-H⋯O and O-H⋯Br hydrogen bonds that link adjacent polymeric chains, thus forming a three-dimensional structure. N-H⋯O and N-H⋯Br hydrogen bonds also occur.

Crystal structure of (E)-1-[4-({4-[(4-meth-oxy-benzyl-idene)amino]-phen-yl}sulfan-yl)phen-yl]ethan-1-one

The title Schiff base compound, C22H19NO2S, crystallized with two independent mol-ecules (A and B) in the asymmetric unit. Both mol-ecules have an E conformation about the C=N bond. The two mol-ecules differ in the orientation of the aromatic rings with respect to each other. The outer 4-meth-oxy-benzene ring is inclined to the central benzene ring and the outer 4-acetyl-benzene ring by 1.80 (19) and 63.73 (19)°, respectively, in mol-ecule A, and by 6.72 (18) and 68.53 (19)°, respectively, in mol-ecule B. The two outer benzene rings are inclined to one another by 63.77 (18) and 63.19 (18)° in mol-ecules A and B, respectively. In the crystal, the individual mol-ecules stack in columns along [010], and are linked by a number of C-H⋯π inter-actions, forming slabs lying parallel to (001).

A structural study of 4-aminoantipyrine and six of its Schiff base derivatives

Six derivatives of 4-amino-1,5-dimethyl-2-phenyl-2,3-dihydro-1H-pyrazol-3-one (4-aminoantipyrine), C11H13N3O, (I), have been synthesized and structurally characterized to investigate the changes in the observed hydrogen-bonding motifs compared to the original 4-aminoantipyrine. The derivatives were synthesized from the reactions of 4-aminoantipyrine with various aldehyde-, ketone- and ester-containing molecules, producing (Z)-methyl 3-[(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)amino]but-2-enoate, C16H19N3O3, (II), (Z)-ethyl 3-[(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)amino]but-2-enoate, C17H21N3O3, (III), ethyl 2-[(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)amino]cyclohex-1-enecarboxylate, C20H25N3O3, (IV), (Z)-ethyl 3-[(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)amino]-3-phenylacrylate, C22H23N3O3, (V), 2-cyano-N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)acetamide, C14H14N4O2, (VI), and (E)-methyl 4-{[(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)amino]methyl}benzoate, C20H19N3O3, (VII). The asymmetric units of all these compounds have one molecule on a general position. The hydrogen bonding in (I) forms chains of molecules via intermolecular N-H...O hydrogen bonds around a crystallographic sixfold screw axis. In contrast, the formation of enamines for all derived compounds except (VII) favours the formation of a six-membered intramolecular N-H...O hydrogen-bonded ring in (II)-(V) and an intermolecular N-H...O hydrogen bond in (VI), whereas there is an intramolecular C-H...O hydrogen bond in the structure of imine (VII). All the reported compounds, except for (II), feature π-π interactions, while C-H...π interactions are observed in (II), C-H...O interactions are observed in (I), (III), (V) and (VI), and a C-O...π interaction is observed in (II).

Facile redox state manipulation in Cu(i) frameworks by utilisation of the redox-active tris(4-(pyridin-4-yl)phenyl)amine ligand

Two Cu(i) frameworks were synthesised with the NPy₃ ligand and Cu(ii) salts to yield electroactive Cu(i) frameworks whose spectral properties varied as a function of the redox state.

Crystal structure of (S)-4-carbamoyl-4-(1,3-dioxo-isoindolin-2-yl)butanoic acid

The title compound is a one of the first-step hydrolysis products of thalidomide. In the crystal, each mol­ecule is linked via six neighbouring mol­ecules into a three-dimensional network through N—H⋯O and O—H⋯O hydrogen bonds.

In the title compound, C₁₃H₁₂N₂O₅, the phthalimide ring system is essentially planar, with a maximum deviation of 0.0479 (14) Å. In the crystal, each mol­ecule is linked via six neighbouring mol­ecules into a three-dimensional network through N—H⋯O and O—H⋯O hydrogen bonds, which form an R₃²(8) ring motif.

Crystal structure of [(2R,3R,4S)-3,4-bis(acet-yloxy)-5-iodo-3,4-di-hydro-2H-pyran-2-yl]methyl acetate

In the title compound, C12H15IO7, the 3,4-di-hydro-2H-pyran ring is in a distorted half-boat conformation with the atom bearing the acet-yloxy group adjacent to the C atom bearing the methyl-acetate group lying 0.633 (6) Å above the plane of the remaining ring atoms (r.m.s. deviation = 0.0907 Å). In the crystal, mol-ecules are linked into a supra-molecular chain along the a axis through two C-H⋯O inter-actions to the same acceptor carbonyl O atom; these chains pack with no specific inter-molecular inter-actions between them.

Analysis of rapidly synthesized guest-filled porous complexes with synchrotron radiation: practical guidelines for the crystalline sponge method

A detailed set of synthetic and crystallographic guidelines for the crystalline sponge method based upon the analysis of expediently synthesized crystal sponges using third-generation synchrotron radiation are reported. The procedure for the synthesis of the zinc-based metal-organic framework used in initial crystal sponge reports has been modified to yield competent crystals in 3 days instead of 2 weeks. These crystal sponges were tested on some small molecules, with two being unexpectedly difficult cases for analysis with in-house diffractometers in regard to data quality and proper space-group determination. These issues were easily resolved by the use of synchrotron radiation using data-collection times of less than an hour. One of these guests induced a single-crystal-to-single-crystal transformation to create a larger unit cell with over 500 non-H atoms in the asymmetric unit. This led to a non-trivial refinement scenario that afforded the best Flack x absolute stereochemical determination parameter to date for these systems. The structures did not require the use of PLATON/SQUEEZE or other solvent-masking programs, and are the highest-quality crystalline sponge systems reported to date where the results are strongly supported by the data. A set of guidelines for the entire crystallographic process were developed through these studies. In particular, the refinement guidelines include strategies to refine the host framework, locate guests and determine occupancies, discussion of the proper use of geometric and anisotropic displacement parameter restraints and constraints, and whether to perform solvent squeezing/masking. The single-crystal-to-single-crystal transformation process for the crystal sponges is also discussed. The presented general guidelines will be invaluable for researchers interested in using the crystalline sponge method at in-house diffraction or synchrotron facilities, will facilitate the collection and analysis of reliable high-quality data, and will allow construction of chemically and physically sensible models for guest structural determination.

Crystal structure of (2S,4R)-ethyl 4-nitromethyl-1-[(S)-1-phenylethyl]-6-sulfanylidenepiperidine-2-carboxylate

In the title compound, C₁₇H₂₂N₂O₄S, a thio­piperidine derivative, the piperidine ring has an envelope conformation with the methyl­ene C atom opposite to the C=S bond as the flap. The nitro­methyl substituent is equatorial while the eth­oxy­carbonyl group is axial. The mean planes of the nitro­methyl group, the carb­oxy group and phenyl ring are inclined to the mean plane through the five planar atoms of the piperidine ring [maximum deviation = 0.070 (4) Å] by 56.8 (2), 83.8 (5) and 87.1 (2)°, respectively. There is an intra­molecular C—H⋯O hydrogen bond involving an H atom of the eth­oxy­carbonyl group and a nitro O atom. In the crystal, mol­ecules are linked by C—H⋯O hydrogen bonds, forming chains along [100]. The chains are linked by further C—H⋯O hydrogen bonds, forming corrugated layers lying parallel to (001).

Crystal structure of γ-methylL-glutamateN-carboxy anhydride

In the title compound, C7H9NO5, alternative nameN-carboxy-L-glutamic anhydride γ-methyl ester, the oxazolidine ring is essentially planar with a maximum deviation of 0.020 (3) Å. In the crystal, molecules are linked by N—H...O hydrogen bonds between the imino group and the carbonyl O atom in the methyl ester group, forming a tape structure along thea-axis direction. The tapes are linked by C—H...O interactions into a sheet parallel to theacplane. The tapes are also stacked along thebaxis with short contacts between the oxazolidine rings [C...O contact distances = 2.808 (4)–3.060 (4) Å], so that the oxazolidine rings are arranged in a layer parallel to theabplane. This arrangement of the oxazolidine rings is very preferable for the polymerization of the title compound in the solid state.

SHELXT - integrated space-group and crystal-structure determination

The new computer program SHELXT employs a novel dual-space algorithm to solve the phase problem for single-crystal reflection data expanded to the space group P1. Missing data are taken into account and the resolution extended if necessary. All space groups in the specified Laue group are tested to find which are consistent with the P1 phases. After applying the resulting origin shifts and space-group symmetry, the solutions are subject to further dual-space recycling followed by a peak search and summation of the electron density around each peak. Elements are assigned to give the best fit to the integrated peak densities and if necessary additional elements are considered. An isotropic refinement is followed for non-centrosymmetric space groups by the calculation of a Flack parameter and, if appropriate, inversion of the structure. The structure is assembled to maximize its connectivity and centred optimally in the unit cell. SHELXT has already solved many thousand structures with a high success rate, and is optimized for multiprocessor computers. It is, however, unsuitable for severely disordered and twinned structures because it is based on the assumption that the structure consists of atoms.

Crystal structure of (1S,2R,4S)-1-[(morpholin-4-yl)meth-yl]-4-(prop-1-en-2-yl)cyclo-hexane-1,2-diol

Besides intra­molecular O—H⋯N hydrogen bonds, the crystal structure displays inter­molecular O—H⋯O and C—H⋯O hydrogen bonds linking the mol­ecules into undulating layers parallel to the (01) plane.

The asymmetric unit of the title compound, C₁₄H₂₅NO₃, contains two independent mol­ecules with similar geometry. The morpholine and cyclo­hexane rings of both mol­ecules adopt a chair conformation. Intra­molecular O—H⋯N hydrogen bonds are observed. In the crystal, mol­ecules are linked by O—H⋯O hydrogen bonds into chains parallel to the [101] direction. The chains are further connected through C—H⋯O hydrogen bonds forming undulating layers parallel to the (-101) plane. The absolute configuration was assigned by reference to an unchanging chiral centre in the synthetic procedure.

Crystal structure refinement with SHELXL

The improvements in the crystal structure refinement program SHELXL have been closely coupled with the development and increasing importance of the CIF (Crystallographic Information Framework) format for validating and archiving crystal structures. An important simplification is that now only one file in CIF format (for convenience, referred to simply as `a CIF') containing embedded reflection data and SHELXL instructions is needed for a complete structure archive; the program SHREDCIF can be used to extract the .hkl and .ins files required for further refinement with SHELXL. Recent developments in SHELXL facilitate refinement against neutron diffraction data, the treatment of H atoms, the determination of absolute structure, the input of partial structure factors and the refinement of twinned and disordered structures. SHELXL is available free to academics for the Windows, Linux and Mac OS X operating systems, and is particularly suitable for multiple-core processors.

Crystal structure of 2-meth-oxy-2-[(4-methyl-phen-yl)sulfan-yl]-1-phenyl-ethan-1-one

In the title β-thio­carbonyl compound, C₁₆H₁₆O₂S, the carbonyl and meth­oxy O atoms are approximately coplanar [O—C—C—O torsion angle = −18.2 (5)°] and syn to each other, and the tolyl ring is orientated to lie over them. The dihedral angle between the planes of the two rings is 44.03 (16)°. In the crystal, supra­molecular chains are formed along the c axis mediated by C—H⋯O inter­actions involving methine and methyl H atoms as donors, with the carbonyl O atom accepting both bonds; these pack with no specific inter­molecular inter­actions between them.

SHELXT - integrated space-group and crystal-structure determination

The new computer program SHELXT employs a novel dual-space algorithm to solve the phase problem for single-crystal reflection data expanded to the space group P1. Missing data are taken into account and the resolution extended if necessary. All space groups in the specified Laue group are tested to find which are consistent with the P1 phases. After applying the resulting origin shifts and space-group symmetry, the solutions are subject to further dual-space recycling followed by a peak search and summation of the electron density around each peak. Elements are assigned to give the best fit to the integrated peak densities and if necessary additional elements are considered. An isotropic refinement is followed for non-centrosymmetric space groups by the calculation of a Flack parameter and, if appropriate, inversion of the structure. The structure is assembled to maximize its connectivity and centred optimally in the unit cell. SHELXT has already solved many thousand structures with a high success rate, and is optimized for multiprocessor computers. It is, however, unsuitable for severely disordered and twinned structures because it is based on the assumption that the structure consists of atoms.

Crystal structure of (2S,4S)-5,5-dimethyl-2-(pyridin-2-yl)-1,3-thiazolidine-4-carboxylic acid

In the title compound, C₁₁H₁₄N₂O₂S, the thia­zolidine ring has an envelope conformation with the C atom bonded to the carb­oxy­lic acid group at the flap. Two C atoms of the thia­zolidine ring adopt S conformations. In the crystal, O—H⋯N hydrogen bonds between the amine and carb­oxy­lic acid groups construct a helical chain structure along the a-axis direction. The chains are further connected via weak C—H⋯π contacts, forming a layer parallel to the ac plane.

About the polymorphism of [Li(C4H8O)3]I: crystal structures of trigonal and tetra-gonal polymorphs

Two new polymorphs of the ion pair LiI(C₄H₈O)₃ (trigonal, space group P; tetra­gonal, space group I4₁cd) show different three-dimensional arrangements in the crystal structure and co-exist at the same temperature.

Two new trigonal and tetra­gonal polymorphs of the title compound, iodido­tris­(tetra­hydro­furan-κO)lithium, are presented, which both include the isolated ion pair Li(THF)₃⁺·I⁻. One Li—I ion contact and three tetra­hydro­furan (THF) mol­ecules complete the tetra­hedral coordination of the lithium cation. The three-dimensional arrangement in the two polymorphs differs notably. In the trigonal structure, the ion pair is located on a threefold rotation axis of space group P-3 and only one THF mol­ecule is present in the asymmetric unit. In the crystal, strands of ion pairs parallel to [001] are observed with an eclipsed conformation of the THF mol­ecules relative to the Li⋯I axis of two adjacent ion pairs. In contrast, the tetra­gonal polymorph shows a much larger unit cell in which all atoms are located on general positions of the space group I4₁cd. The resulting three-dimensional arrangement shows helical chains of ion pairs parallel to [001]. Apart from van der Waals contacts, no remarkable inter­molecular forces are present between the isolated ion pairs in both structures.

Crystal structure of (4R,5S)-4-methyl-3-methyl-sulfinyl-5-phenyl-1,3-oxazolidin-2-one

The absolute structure of the chiral asymmetric indole precursor title compound, C₁₁H₁₃NO₃S, was confirmed by refinement of the Flack and Hooft parameters and is that expected based on the starting materials for the synthesis. The phenyl group subtends a dihedral angle of 56.40 (5)° with the mean plane of the oxazolidinone ring, which adopts an envelope conformation, with the C atom bearing the methyl group as the flap. In the crystal, no significant directional inter­actions beyond van der Waals contacts are observed.

Crystal structure of (-)-(2R,3S,4R,5R)-5-(1,3-di-thian-2-yl)-3-methyl-1-(triiso-propyl-sil-yloxy)hexane-2,4-diol

The title compound, C20H42O3S2Si, crystallized with two independent mol-ecules (A and B) in the asymmetric unit. They consist of syn,anti,anti-stereo-tetrads with a 1,3-di-thiane motif and a primary alcohol protected as the triisopropyl silyl ether. The 1,3-di-thiane ring adopts a chair conformation, while the rest of each mol-ecule displays a common zigzag conformation. There is an intra-molecular O-H⋯O hydrogen bond in each mol-ecule. In the crystal, the A and B mol-ecules are linked via O-H⋯O hydrogen bonds, forming -A-B-A--B-- chains along [010]. The absolute structure was determined by resonant scattering (anomalous scattering) [Flack parameter = 0.035 (8)].