The low‐temperature phase of 1,3‐di­bromo‐2,4,6‐tri­methyl­benzene: a single‐crystal neutron diffraction study at 120 and 14 K

In the low‐temperature phase of di­bromo­mesityl­ene (1,3‐di­bromo‐2,4,6‐tri­methyl­benzene), C₉H₁₀Br₂, the mol­ecule deviates significantly from the C_3h molecular symmetry encountered in tri­bromo­mesityl­ene (1,3,5‐tri­bromo‐2,4,6‐tri­methyl­benzene), even for the endocyclic bond angles. An apparent C_2v molecular symmetry is observed. The angle between the normal to the molecular plane and the normal to the (100) plane is ∼20°. The overall displacement was analysed at 120 K with rigid‐body‐motion tensor analysis. The methyl group located intermediate between the two Br atoms is rotationally disordered at both temperatures. This disorder was treated using two different approaches at 14 K, viz. the conventional split‐atom model and a model using the special annular shapes of the atomic displacement parameters that are available in CRYSTALS [Watkin, Prout, Carruthers & Betteridge (1999). Issue 11. Chemical Crystallography Laboratory, Oxford, England], but only through the latter approach at 120 K. The disorder locally breaks the C_2v molecular symmetry at 14 K only. Intra‐ and intermolecular contacts are described and discussed in relation to this methyl‐group disorder. The bidimensional pseudo‐hexagonal structural topology of tri­halogeno­mesityl­enes is altered in di­bromo­mesityl­ene insofar as the (100) molecular layers are undulated and are not coplanar as a result of an alternating tilt angle of ∼34° propagating along the [011] and [01] directions between successive antiferroelectric molecular columns oriented roughly along the a axis.     

Bis(2,5‐dimethoxy‐4‐methylphenyl)methane and bis(2,5‐dimethoxy‐3,4,6‐trimethylphenyl)methane

Bis(2,5‐di­methoxy‐4‐methyl­phenyl)­methane, C₁₉H₂₄O₄, (IIa), was obtained and characterized as a minor product from the reaction of tolu­hydro­quinone di­methyl ether (1,4‐dimethoxy‐2‐methylbenzene) with N‐(hydroxy­methyl)­tri­fluoro­acet­amide. Similarly, bis(2,5‐di­methoxy‐3,4,6‐tri­methyl­phenyl)­methane, C₂₃H₃₂O₄, (IIb), was prepared from the corresponding reaction of tri­methyl­hydro­quinone di­methyl ether (2,5‐dimethoxy‐1,3,4‐trimethylbenzene). The mol­ecules of (IIa) and (IIb) each lie on a twofold axis passing through the methyl­ene group. The dihedral angle between the planar phenyl rings is 73.4 (1)° in (IIa) and 77.9 (1)° in (IIb). The external bond angles around the bridging methyl­ene group are 116.6 (2) and 117.3 (2)° for (IIa) and (IIb), respectively. In (IIa), the methoxy substituents lie in the plane of the ring and are conjugated with the aromatic system, whereas in (IIb), they are almost perpendicular to the phenyl ring and are positioned on opposite sides.     

1‐(4‐Chloro­phenyl­sulfanyl)‐2‐nitro‐4‐(tri­fluoro­methyl)­benzene and 1‐(4‐chloro­phenyl­sulfanyl)‐4‐nitro‐2‐(tri­fluoro­methyl)­benzene

Two chemical isomers of 3‐nitro­benzotrifluoride, namely 1‐(4‐chloro­phenyl­sulfanyl)‐2‐nitro‐4‐(tri­fluoro­methyl)­benzene, C₁₃H₇ClF₃NO₂S, (I), and 1‐(4‐chloro­phenyl­sulfanyl)‐4‐nitro‐2‐(tri­fluoro­methyl)­benzene, C₁₃H₇ClF₃NO₂S, (II), have been prepared and their crystal structures determined with the specific purpose of forming a cocrystal of the two. The two compounds display a similar conformation, with dihedral angles between the benzene rings of 83.1 (1) and 76.2 (1)°, respectively, but (I) packs in P while (II) packs in P2₁/c, with C—H⋯O interactions. No cocrystal could be formed, and it is suggested that the C—H⋯O associations in (II) prevent intermolecular mixing and promote phase separation.     

Model porphyrin precursors: 1,2,4,5‐tetrakis(cyanomethyl)­benzene,methyl 3,4,5‐triacetoxy­benzoate and 2‐(N‐phthalimidomethyl)benzoic acid

In the crystalline state, the centrosymmetric mol­ecule 1,2,4,5‐tetrakis­(cyano­methyl)­benzene, C₁₄H₁₀N₄, has one cyano­methyl group in the benzene plane and one cyano­methyl group rotated 67.2 (2)° out of the benzene plane. Molecules of methyl 3,4,5‐tri­acetoxy­benzoate, C₁₄H₁₄O₈, form chains with each mol­ecule twisted 89.6 (1)° from the preceding mol­ecule. In this orientation, a close C—H?O contact is formed, with an H?O distance of 2.34 Å. The structure of 2‐(N‐phthalimido­methyl)­benzoic acid, C₁₆H₁₁NO₄, reveals hydrogen‐bonded dimers linked by the carboxyl groups of adjacent mol­ecules. The O4?O3 distance is 2.636 (2) Å and the O4—H?O3 angle is 171 (2)°.     

Three 5H‐indeno­[1,2‐c]­pyridazin‐5‐one derivatives,potent type‐B mono­amine oxidase inhibitors

The structures of three compounds, namely 7‐methoxy‐2‐[3‐(tri­fluoro­methyl)­phenyl]‐9H‐indeno­[1,2‐c]­pyridazin‐9‐one, C₁₉H₁₁F₃N₂O₂, (Id), 6‐methoxy‐2‐[3‐(tri­fluoro­methyl)­phenyl]‐9H‐indeno­[1,2‐c]­pyridazin‐9‐one, C₁₉H₁₁F₃N₂O₂, (IId), and 2‐methyl‐6‐(4,4,4‐tri­fluoro­butoxy)‐9H‐indeno­[1,2‐c]­pyridazin‐9‐one, C₁₆H₁₃F₃N₂O₂, (IIf), which are potent reversible type‐B mono­amine oxidase (MAO‐B) inhibitors, are presented and discussed. Compounds (Id) and (IId) crystallize in a nearly planar conformation. The crystal structures are stabilized by weak C—H⋯O hydrogen bonds. The packing is dominated by π–π stacking interactions between the heterocyclic central moieties of centrosymmetrically related mol­ecules. In compound (IIf), the tri­fluoro­ethyl termination is almost perpendicular to the plane of the ring.     

2,3,3′,6‐Tetra‐O‐acetyl‐4,1′,6′‐trichloro‐4,1′,4′,6′‐tetradeoxygalactosucrose

At 160 K, one of the Cl atoms in the furanoid moiety of 3‐O‐acetyl‐1,6‐di­chloro‐1,4,6‐tri­deoxy‐β‐d ‐fructo­furan­osyl 2,3,6‐tri‐O‐acetyl‐4‐chloro‐4‐deoxy‐α‐d ‐galacto­pyran­oside, C₂₀H₂₇­Cl₃O₁₁, is disordered over two orientations, which differ by a rotation of about 107° about the parent C—C bond. The conformation of the core of the mol­ecule is very similar to that of 3‐O‐acetyl‐1,4,6‐tri­chloro‐1,4,6‐tri­deoxy‐β‐d ‐tagato­furanos­yl 2,3,6‐tri‐O‐acetyl‐4‐chloro‐4‐deoxy‐α‐d ‐galacto­pyran­oside, particularly with regard to the conformation about the glycosidic linkage.     

Phenyl‐ and mesitylglyoxylic acids: catemeric hydrogen bonding in two α‐keto acids

α‐Oxo­benzene­acetic (phenyl­glyoxy­lic) acid, C₈H₆O₃, adopts a transoid di­carbonyl conformation in the solid state, with the carboxyl group rotated 44.4 (1)° from the nearly planar benzoyl moiety. The heterochiral acid‐to‐ketone catemers [O?O = 2.686 (3) and H?O = 1.78 (4) Å] have a second, longer, intermolecular O—H?O contact to a carboxyl sp³ O atom [O?O = 3.274 (2) and H?O = 2.72 (4) Å], with each flat ribbon‐like chain lying in the bc plane and extending in the c direction. In α‐oxo‐2,4,6‐tri­methyl­benzene­acetic (mesityl­glyoxy­lic) acid, C₁₁H₁₂O₃, the ketone is rotated 49.1 (7)° from planarity with the aryl ring and the carboxyl group is rotated a further 31.2 (7)° from the ketone plane. The solid consists of chiral conformers of a single handedness, aggregating in hydrogen‐bonding chains whose units are related by a 3₁ screw axis, producing hydrogen‐bonding helices that extend in the c direction. The hydrogen bonding is of the acid‐to‐acid type [O?O = 2.709 (6) and H?O = 1.87 (5) Å] and does not formally involve the ketone; however, the ketone O atom in the acceptor mol­ecule has a close polar contact with the same donor carboxyl group [O?O = 3.005 (6) and H?O = 2.50 (5) Å]. This secondary hydrogen bond is probably a major factor in stabilizing the observed cisoid di­carbonyl conformation. Several intermolecular C—H?O close contacts were found for the latter compound.     

1‐Chloro‐3,6‐di­methoxy‐2,5‐di­methyl­benzene and 1‐chloro‐3,6‐di­methoxy‐2,4‐di­methyl­benzene

The title compounds, 1‐chloro‐3,6‐di­methoxy‐2,5‐di­methyl­benzene, (IIIa), and 1‐­chloro‐3,6‐di­methoxy‐2,4‐di­methyl­benzene, (IIIb), both C₁₀H₁₃ClO₂, were obtained from 2,5‐ and 2,6‐di­methyl‐1,4‐benzo­quinone, respectively, and are intermediates in the synthesis of ammonium quinone derivatives. The isomers have different substituents around the methoxy groups and crystallize in different space groups. In both mol­ecules, the methoxy groups each have different orientations with respect to the benzene ring. In both cases, one methoxy group lies in the plane of the ring and can participate in conjugation with the aromatic system, while the second is almost perpendicular to the plane of the aromatic ring. The C—O—C bond angles around these substituents are also different: 117.5 (4) and 118.2 (3)° in (IIIa) and (IIIb), respectively, when the methoxy groups lie in the plane of the ring, and 114.7 (3) and 113.6 (3)° in (IIIa) and (IIIb), respectively, when they are out of the plane of the ring.     

Redetermination of 1,3,5‐tri­chloro‐2,4‐di­nitro­benzene

The title compound, C₆HCl₃N₂O₄, is an intermediate in the synthesis of 1,3,5‐tri­chloro‐2,4,6‐tri­nitro­benzene. The crystal structure at 153 K shows no major deviations from the previously reported structure at 295 K other than the expected contraction of the a and c axes and, correspondingly, the β angle.     

4‐Vinyl­benzoic acid and 9‐vinyl­anthracene

The crystal structures of two styrene analogues, 4‐vinyl­benzoic acid, C₉H₈O₂, (I), and 9‐vinyl­anthracene, C₁₆H₁₂, (II), were determined by X‐ray analyses at 108 and 293 K for (I) and at 123 and 293 K for (II). In (I), a pair of mol­ecules around an inversion center form a dimer connected by two carboxyl groups. The anthracene planes of two mol­ecules in (II) are antiparallel to each other around an inversion center. The vinyl group of (I) is almost coplanar with the phenyl ring, whereas the vinyl group of (II) is nearly perpendicular to the anthracene plane. In (I), the bond length of the vinyl group at 293 K is significantly shorter than that at 108 K [1.288 (2) versus 1.3248 (14) Å] suggesting a bias of the thermal motion, whereas the bond lengths are not so different between the two temperatures in (II) [1.3266 (15) versus 1.310 (2) Å].     

cis‐Di­chloro(5,8‐dioxa‐2,11‐dithia[12]‐o‐cyclo­phane)­palladium(II)

The preparation and crystal structure of the title compound, cis‐di­chloro­[6,9‐dioxa‐3,12‐di­thia­bi­cyclo­[12.4.0]­octadeca‐14,‐16,­18(1)‐tri­ene‐S,S′]­palladium(II), [PdCl₂(C₁₄H₂₀O₂S₂)], are described. The Pd atom has a square‐planar environment, coordinated to two S atoms of the di­thia­dioxa macrocycle and to two Cl^? ions. The non‐coordinating O atoms are oriented away from the metal coordination plane. Upon complexation, a bicyclic chelate structure, which consists of a seven‐ and an eleven‐membered ring, is formed.     

cis‐ and trans‐2‐(4‐tert‐Butylcyclohexyloxy)‐1,3,5‐trinitrobenzene

The structures of cis‐ and trans‐2‐(4‐tert‐butyl­cyclo­hexyl­oxy)‐1,3,5‐tri­nitro­benzene, C₁₆H₂₁N₃O₇, (I) and (II), respectively, were determined at low temperature in order to obtain accurate structural parameters for comparison purposes. The C_alkyl—O_ether bond distances are 1.497 (2) and 1.491 (2) Å for (I) and (II), respectively.     

9‐(Tri­chloro­acetyl­imino)­acridine monohydrate

The title compound, alternatively called N‐acridin‐9(10H)‐yl­idene‐2,2,2‐tri­chloro­acet­amide mono­hydrate, C₁₅H₉Cl₃N₂O·H₂O, crystallizes in space group P2₁/c with Z = 4. The acridine moieties are arranged in layers, tilted at an angle of 15.20 (4)° relative to the ac plane, while adjacent mol­ecules pack in a head‐to‐tail manner. Acridine and water mol­ecules form columns along the b axis held in place by a network of hydrogen bonds, which is the major factor stabilizing the lattice. The acridine mol­ecule exhibits structural features of both the amino and imino forms, which could be due to the presence of the strong electronegative tri­chloro­acetyl substituent at the exocyclic N atom.     

Precursor of a β‐lactamase inhibitor: allyl (4S,8S,9R)‐10‐[(E)‐ethyl­idene]‐4‐methoxy‐11‐oxo‐1‐aza­tri­cyclo­[7.2.0.03,8]­undec‐2‐ene‐2‐carboxyl­ate

The molecular structure of the title tricyclic compound, C₁₇H₂₁NO₄, which is the immediate precursor of a potent synthetic inhibitor {Lek157: sodium (8S,9R)‐10‐[(E)‐ethyl­idene]‐4‐methoxy‐11‐oxo‐1‐aza­tri­cyclo­[7.2.0.0^3,8]­undec‐2‐ene‐2‐carboxyl­ate} with remarkable potency, provides experimental evidence for the previously modelled relative position of the fused cyclo­hexyl ring and the carbonyl group of the β‐lactam ring, which takes part in the formation of the initial tetrahedral acyl–enzyme complex. In this hydro­phobic mol­ecule, the overall geometry is influenced by C—H?O intramolecular hydrogen bonds [3.046 (4) and 3.538 (6) Å, with corresponding normalized H?O distances of 2.30 and 2.46 Å], whereas the mol­ecules are interconnected through intermolecular C—H?O hydrogen bonds [3.335 (4)–3.575 (5) Å].     

Chiral and meso‐bis([2.2]­para­cyclo­phan‐4‐yl)­methane and meso‐bis­([2.2]­para­cyclo­phan‐4‐yl) sulfide

The [2.2]­para­cyclo­phane groups of the title compounds, chiral and meso‐bis­(tri­cyclo­[8.2.2.2^4,7]­hexa­deca‐4,6,10,12,13,15‐hexa­en‐5‐yl)­methane (the former as a racemate), C₃₃H₃₂, and meso‐bis­(tri­cyclo­[8.2.2.2^4,7]­hexa­deca‐4,6,10,12,13,15‐hexa­en‐5‐yl) sulfide, C₃₂H₃₀S, show the characteristic structural features of the parent compound [2.2]­para­cyclo­phane and the related compound di­methylbis([2.2]­para­cyclo­phan‐4‐yl)­silane, C₃₄­H₃₆­Si: the aromatic rings are puckered, resulting in a boat conformation. The planes of the four coplanar C atoms are slightly twisted with respect to each other. The Csp³—Csp³ bond lengths of the ethyl­ene bridges are elongated by the electronic and steric effects of the skeleton.     

4,5,9,10‐Tetrahydro‐4‐methyl‐2‐phenyl‐9,10‐epoxy‐3H,10aH‐cyclobuta[a]benzo[2,3,4‐de]isoquinoline‐3,5‐dione

In the title compound, C₂₁H₁₅NO₃, which is one of the photoreaction products of N‐methyl‐1,8‐naphthalene­dicar­box­imide with phenyl­acetyl­ene, the cyclo­butene and epoxy rings are trans to each other across the cyclo­hexene ring of the tetralin moiety. The dihedral angle between the mean planes of the cyclo­butene and cyclo­hexene rings is 112.80 (2)°, while the latter makes a dihedral angle of 103.70 (9)° with the epoxy ring. The crystal structure is stabilized by C—H⋯O intermolecular interactions.     

(Z)‐2‐Methylbuten‐1‐yl(aryl)iodonium trifluoromethanesulfonates containing electron‐withdrawing groups on the aryl moiety

The crystal structures of [(Z)‐2‐methyl­but‐1‐en‐1‐yl]­[4‐(tri­fluoro­methyl)­phenyl]­iodo­nium tri­fluoro­methane­sulfonate, C₁₂H₁₃F₃I⁺·CF₃O₃S^?, (I), (3,5‐di­chloro­phenyl)­[(Z)‐2‐methyl­but‐1‐en‐1‐yl]­iodo­nium tri­fluoro­methane­sulfonate, C₁₁H₁₂­Cl₂I⁺·CF₃O₃S^?, (II), and bis{[3,5‐bis­(tri­fluoro­methyl)­phenyl][(Z)‐2‐methyl­but‐1‐en‐1‐yl]­iodo­nium} bis­(tri­fluoro­methane­sulfonate) di­chloro­methane solvate, 2C₁₃H₁₂F₆I⁺·­2CF₃­O₃S^?·CH₂Cl₂, (III), are described. Neither simple acyclic β,β‐di­alkyl‐substituted alkenyl­(aryl)­idonium salts nor a series containing electron‐deficient aryl rings have been described prior to this work. Compounds (I)–(III) were found to have distorted square‐planar geometries, with each I atom interacting with two tri­fluoro­methane­sulfonate counter‐ions.     

trans‐Bis(3,5‐di­aza‐1‐azonia‐7‐phosphaadamantane‐κP)­bis­(thiocyanato‐κS)­palladium(II) bis­(thio­cyanate)

The crystal structure of the title compound, trans‐[Pd(NCS)₂(C₆H₁₃N₃P)₂](NCS)₂, is one of the few pal­ladium(II) complexes containing two protonated water‐soluble 1,3,5‐tri­aza‐7‐phos­pha­adamantane (PTA) ligands re­ported to date. The compound displays a distorted square‐planar geometry, with the Pd atom on an inversion centre and with the S atoms of the thio­cyanate counter‐ions occupying the axial positions above and below the equatorial plane described by the phosphine and thio­cyanate ligands. Geometric parameters for the formal coordination polyhedron include a Pd—P distance of 2.2940 (8) Å, a Pd—S distance of 2.3509 (8) Å and a P—Pd—S angle of 89.45 (3)°. The effective cone angle for the PTA ligands was calculated as 114.5°.     

3‐Germyl‐3,3‐di­methyl­propionic acid derivatives

The crystal structures of 3,3‐di­methyl‐3‐(tri­chloro­germyl)­propionic acid, [Ge(C₅H₉O₂)Cl₃], 3,3‐di­methyl‐3‐(tri­phenyl­germyl)­propionic acid, [Ge(C₆H₅)₃(C₅H₉O₂)], and 3,3‐di­methyl‐3‐(tri‐p‐toly­lgermyl)­propionic acid, [Ge(C₇H₇)₃(C₅H₉O₂)], have slightly distorted tetrahedral geometries about the Ge atoms. All the structures form dimers via strong O—H·O hydrogen bonds, resulting in eight‐membered rings that can be best described in terms of graph‐set notation (8).     

Exo Diels–Alder adducts between ortho‐ and para‐N‐acetoxy­phenyl­male­imides and furan

In exo‐2‐(3,5‐dioxo‐10‐oxa‐4‐aza­tri­cyclo­[5.2.1.0^2,6]­dec‐8‐en‐4‐yl)­phenyl acetate, C₁₆H₁₃NO₅, the plane of the acetoxy group lies almost perpendicular to that of the phenyl ring [dihedral angle = 89.8 (1)°], in contrast with the smaller deviations found in the para isomer exo‐4‐(3,5‐dioxo‐10‐oxa‐4‐aza­tri­cyclo­[5.2.1.0^2,6]­dec‐8‐en‐4‐yl)­phenyl acetate, C₁₆H₁₃NO₅, these being 63.6 (1) and 37.0 (1)° for the two crystallographically independent mol­ecules. Irrespective of the position of the acetoxy group, both compounds pack through soft C—H⋯X (X is O or phenyl) interactions, forming interlinked centrosymmetric tetramers in the bc plane.