Hydrogen bonding in labdane diterpenoids, labda-7,12(E),14-triene-17-oic acid and labda-12(Z),14,17-triene-18-oic acid

Two labdane diterpenoids, labda-7,12(E),14-triene-17-oic acid (1) and labda-12(Z),14,17-triene-18-oic acid (2), C₂₀H₃₀O₂, have been isolated from Croton oblongifolius. Both 1 and 2 crystallized in the monoclinic system, space group C2, with cell dimensions of a = 21.912(1) Å, b = 7.4002(4) Å, c = 11.5079(7) Å, = 101.999(1)^o and a = 21.308(2) Å, b = 11.9067(9) Å, c = 7.5606(6) Å, = 100.763(1)^o, respectively. Compound 1, a rare example of carboxylic group bound to a cyclohexene ring, forms an infinite intermolecular hydrogen-bonded polymer [O1 O2(–x + 1/2, y + 1/2, –z + 2) 2.697(2) Å], whereas molecules of compound 2 are linked to form an asymmetric hydrogen-bonded dimer [O1 O2(–x, y, –z) 2.657(3) Å].     

Reaction of ethyl diazoacetate with Co3(CO)9(μ3-CCl): Isolation and X-ray structures of Co3(CO)9(μ3-CCO2Et), Co3(CO)9(μ3-CCH2CO2Et), and [Co3(CO)9(μ3-CCHCO2Et)]2

The reaction between the tricobalt cluster Co₃(CO)₉(₃-CCl) (1) and AlCl₃, followed by treatment with ethyl diazoacetate, N₂CHCO₂Et, affords a complex mixture of products in low yields. Column chromatography has allowed the isolation of the four cluster compounds Co₃(CO)₉(₃-CH) (2), Co₃(CO)₉(₃-CCO₂Et) (3), Co₃(CO)₉(₃-CCH₂CO₂Et) (4), and [Co₃(CO)₉(₃-CCHCO₂Et)]₂ (5). Clusters 4 and 5 are new and have been fully characterized in solution by IR and ¹H NMR spectroscopy. The molecular structures of clusters 3–5 have also been determined by single-crystal X-ray diffraction analysis. Co₃(CO)₉(₃-CCO₂Et) crystallizes in the triclinic space group P , a = 8.8393(5), b = 14.727(1), c = 15.272(1) Å, = 93.361(6), = 105.509(5)°, = 100.336(6)°, V = 1872.6(2) ų, Z = 4, and d _calc = 1.823 g/cm³. Co₃(CO)₉(₃-CCH₂CO₂Et) crystallizes in the monoclinic space group P2₁/n, a = 9.3806(7), b = 9.2617(8), c = 22.455(2) Å, = 94.483(7)°, V = 1944.9(3) ų, Z = 4, and d _calc = 1.803 g/cm³. [Co₃(CO)₉(₃-CCHCO₂Et)]₂ crystallizes in the monoclinic space group C2/c, a = 21.585(2), b = 8.7977(7), c = 20.784(1) Å, = 104.807(6)°, V = 3815.8(5) ų, Z = 4, and d _calc = 1.835 g/cm³. Plausible pathways leading to the formation of clusters 2, 4, and 5 are discussed.     

Synthesis and structural studies of <Emphasis Type="Italic">tris</Emphasis>-2-chlorobenzylamine and <Emphasis Type="Italic">tris</Emphasis>-2-bromobenzylamine

The tris-2-chloro and 2-bromotribenzylamines are prepared from aqueous ammonia and 2-chlorobenzyl chloride and 2-bromobenzyl bromide, respectively, in ethanol. Recrystallization yielded colorless cubes of each product. The crystal structures are each solved in space group P , and are isostructural. The tris-2-chloro compound, 1, has a = 7.4226(5) Å, b = 9.0825(7) Å, c = 14.529(1) Å, = 78.279(1), = 82.389(1), = 84.661(1), and V = 948.41(12) ų with Z = 2, and d_calc = 1.368 Mg/m³. The tris-2-bromo analog, 2, has a = 7.6569(11) Å, b = 9.0922(13) Å, c = 14.614(2) Å, = 79.286(2), = 81.777(2), = 85.401(2), and V = 987.9(2) ų with Z = 2, and d_calc = 1.762 Mg/m³. Lithium–halogen exchange experiments conducted in tetrahydrofuran at –78C using n-butyl lithium revealed that no exchange occurred for the tris-2-chloro compound, but did occur for the tris-2-bromo analog to yield tribenzylamine upon quench and work-up.     

Synthesis and X-ray structural analysis of (2<Emphasis Type="Italic">Z</Emphasis>)-3(4-hydroxyphenyl)-2-pyridin-4-ylacrylonitrile and (2<Emphasis Type="Italic">Z</Emphasis>)-3-(3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-hydroxyphenyl)2-pyridin-4-ylacrylonitrile

Synthesis and X-ray structural investigations have been carried out for the two title compounds C₁₄H₁₀N₂O (3a) and C₂₂H₂₆N₂O (3b). Compound 3a crystallizes in the monoclinic space group P2₁/c, with a = 3.843(1) Å, b = 24.618(5) Å, c = 11.318(2) Å, = 92.61(3), V = 1069.7(4) Å,³ and Z = 4. Compound 3b crystallizes in the triclinic space group P-1, with a = 9.004(2) Å, b = 9.447(2) Å, c = 11.713(2) Å, = 76.70(3), = 83.12(3), = 82.16(3), V = 956.5(3) Å,³ and Z = 2. Both stilbazole derivatives have Z-geometry about the ethylene bridge which links the heterocyclic and aromatic rings. The molecular skeleton of 3a is slightly non-planar: the dihedral angles between the acrylonitrile linkage and the pyridine ring, and between this linkage and the p-hydroxyphenyl ring are 7.2(2) and 4.1(2), respectively. The molecular skeleton of 3b is less planar: the values of similar dihedral angles are 17.0(2) and 20.8(2), respectively. In the crystal of 3a, the molecules are packed in stacks along the a axis with head-to-head orientation. Intermolecular hydrogen bonds O=H s N and C=H s N link molecules into sheets parallel to (100) plane. In the crystals of 3b, the molecules have a head-to-tail orientation and intermolecular hydrogen bonds O=H s N link the molecules into infinite chains along [01-1] direction.     

Reactions of [Mn2(μ-pyS)2(CO)6] with bidentate N-donor ligands: Crystal structure of [Mn(η1-pyS)(bipy)(CO)3] (bipy = 2,2′-bipyridyl, pySH = pyridine-2-thiol)

The dimeric complex [Mn₂(-pyS)₂(CO)₆] (1) reacted with 2 equivalents of 2,2-bipyridyl (bipy), 1,10-phenanthroline (phen), and ethylenediamine (en) to give the corresponding monomeric complexes [Mn(¹-pyS)(bipy)(CO)₃] (2), [Mn(¹-pyS)(phen)(CO)₃] (3), and [Mn( ¹-pyS)(en)(CO)₃] (4). The pyS ligand in these complexes acts as a monodentate, two-electron donor ligand, which coordinates to manganese through the sulfur atom. This is confirmed by an X-ray structure determination of 2, which contains two structural isomers in the asymmetric unit. Crystals of this compound are the monoclinic, space group P2 ₁/c, a = 21.593(4), b = 10.463(2), c = 16.385(3) Å, = 102.468(13)°, V = 3614.5(12) ų, and Z = 8. The three CO groups are facially distributed in both isomers, but the relative positions of the pyS and bipy ligands are different.     

Synthesis and structural characterization of five new coordination polymer chain structures using a new,Z-shaped ligand, 2,2′-bis-(4-pyridylethynyl)tolane

Using the new ligand, 2,2-bis-(4-pyridylethynyl)tolane we have synthesized five new coordination polymers: HgBr₂[2,2-bis-(4-pyridylethynyl)tolane] (1), HgI₂[2,2-bis-(4-pyridylethynyl)tolane] (2), Ni(acetylacetonate)₂[2,2-bis-(4-pyridylethynyl)tolane] (3), Zn(acetylacetonate)₂[2,2-bis-(4-pyridylethynyl)tolane] (4), and Cu(hexafluoro acetylacetonate)₂[2,2-bis-(4-pyridylethynyl)tolane]CHCl₃ (5). 2,2-Bis-(4-pyridyl ethynyl)tolane is a rigid ligand with a Z-shape that promotes the formation of zig-zag chains. Compounds 1– 5 were characterized by single crystal X-ray diffraction; and compounds 1– 3 were additionally characterized by IR, elemental analysis, and thermogravimetric analysis. Compound 1 crystallizes in the monoclinic space group C2/c with a = 29.761(3) Å, b = 5.0531(5) Å, c = 16.7823(15) Å, = 104.090(2), V = 2447.9(4) ų, Z = 4. Each mercury is bound to two tolane ligands and two bromine anions, resulting in a tetrahedral coordination environment. Compound 2 crystallizes in the monoclinic space group P2/c, with a = 20.3061(17) Å, b = 5.6303(5) Å, c = 24.5459(19) Å, = 110.338(2), V = 2631.4(4) ų, Z = 4. Here also, each mercury is bound to two tolane ligands and two iodine anions in a tetrahedral coordination environment. The ligand orientation differs in compounds 1 and 2 being trans oriented in 1 and cis oriented in 2. Compound 3 crystallizes in the monoclinic space group P2₁/c with a = 14.5947(14) Å, b = 6.3082(6) Å, c = 18.3939(18) Å, = 112.112(2), V = 1568.9(3) ų, Z = 2. Each nickel is bound to two tolane ligands and two bidentate AcAc anions, resulting in an octahedral coordination environment. Compound 4, which is isostructural with 3, also crystallizes in the monoclinic space group P2₁/c with a = 14.6990(9) Å, b = 6.2724(4) Å, c = 18.6433(11) Å, = 112.8610(10), V = 1583.86(17) ų, Z = 2. Compound 5 crystallizes in the triclinic space group P-1 with a = 6.5487(4) Å, b = 11.6471(7) Å, c = 14.3225(9) Å, = 70.1360(10), = 89.3990(10), = 88.7680(10), V = 1027.18(11) ų, Z = 1. Each copper in 5 is bound to two tolane ligands and two bidentate hfAcAc anions, resulting in an octahedral coordination environment identical to that found in 3 and 4.     

Thermodynamic vs. kinetic control in the Diels-Alder cycloaddition of cyclopentadiene to 2,3-dicyano-p-benzoquinone

Diels-Alder cycloaddition of cyclopentadiene (1a) to 2,3-dicyano-p-benzoquinone (2a), when performed in methanol solvent at ambient temperature, proceeds with kinetic control to afford 1,4,4a,8a-tetrahydro-5,8-dioxo-1,4-methanonaphthalene-4a,8a-dicarbonitrile (7, 77% yield). However, when this cycloaddition is performed by refluxing an equimolar solution of1a and2a in benzene for 3 h, the product of thermodynamic control, i.e., 1,4,4a,8a-tetrahydro-5,8-dioxo-1,4-methanonaphthalene-6,7-dicarbonitrile (3a) is obtained in 64% yield. The structure of3a was confirmed by an analysis of the reduced intramolecular photocyclization product,9.     

Synthesis and crystal structure of 1D 2,3-naphtho 15-crown-5 complex [Na(N15C5)]<Subscript>2</Subscript>[Ni(i-mnt)<Subscript>2</Subscript>] containing S⋅<Emphasis Type="Italic">s</Emphasis>C and S⋅<Emphasis Type="Italic">s</Emphasis>π interactions

The reaction of 2,3-naphtho-15-crown-5 (N15C5) with Na₂[Ni(i-mnt)₂] [i-mn = 1,1-dicyanoethylene-2,2-dithiolate] affords the title complex [Na(N15C5)]₂[Ni(i-mnt)₂] (1), which is characterized by elemental analysis, FT-IR, UV-visible spectra and single crystal X-ray diffraction. 1 crystallizes in the triclinic, space group P with a = 8.291(4), b = 12.833(7), c = 12.913(6) Å, = 115.732 (7), = 105.030(7), = 90.912(8), V = 1182.2(10) ų, Z = 1 and R₁(wR₂) = 0.0422(0.1001). The single crystal X-ray analysis shows that the [Na(N15C5)]⁺ complex cations act as the bridges linking the [Ni(i-mnt)₂]^2– anions into a 1D infinite chain through Na–N interactions and SsC and Ss interactions are observed in the chain with the shortest SsC distance of 3.433 Å.     

Crystal structure of 1,5,8-trihydroxyl-3-methoxy xanthone from Swertia chirayita

In order to study the relationship between biological and pharmacological activities with their structures, a series of tri-, tetra-oxygenated xanthones including 1-hydroxyl-2,3,4,7-tetramethoxy xanthone 1, 1-hydroxyl-2,3,4,5-tetramethoxyl xanthone 2, 1-hydroxyl-3,5-dimethoxy xanthone 3, 1,8-dihydroxyl-3,5-dimethoxyl xanthone 4, 1,5,8-trihydroxyl-3-methoxy xanthone 5 has been isolated from Swertia chirayita. Their structures were established on the basis of spectral and chemical evidence. The crystal structure of 5 was also investigated by single crystal X-ray diffraction analysis. It crystallizes in the triclinic system, space group P , with a = 7.1540(10) Å, b = 7.520(2) Å, c = 10.671(2) Å, V = 562.7(2) ų, = 86.50(3), = 80.06(3), = 85.00(3), Z = 2, D_c = 1.618 g m^–3, R_int = 0.0230, wR(F²) = 0.1028, F(000) = 284. The molecular structure is nearly plane and four substituents are much closer to the plane of the molecule. Compound 5 also shows three intermolecular hydrogen bonds. A recent study shows that phenolic hydroxyls in xanthones are the main active groups capable of scavenging OH and O₂.     

Crystal and molecular structure of 3-(4-chlorobenzoylimino)-5,6-dihydro-3H-imidazo[2,1-c]-1,2,4-dithiazole

Crystal structure of the title compound belonging to the group of-acylimino derivatives of sulfur(II) compounds has been determined by X-ray structure analysis. The crystals are monoclinic, P2₁/c,a=11.210(2),b=8.197(1),c=13.659(2) Å,=102.36(2)°,V=1226.0(3) ų,Z=4,D _x =1.61 g cm^–3, (MoK)=0.71069 Å,=6.3 cm^–1. The structure has been refined to a finalR value of 0.035 for 1401 observed reflexions.The molecule is nearly planar with symmetrym. The title compound contains a very short intramolecular C=OS contact of 2.328(3) Å, suggesting a bond-non-bond resonance interaction.     

X-ray crystal structure of 2-hydroxy-2′-(1,4-bisoxo-6-hexanol)-1,1′-biphenyl

The X-ray crystal structure of 2-hydroxy-2-(1,4-bisoxo-6-hexanol)-1,1-biphenyl, 3, is presented. This molecule crystallizes in the monoclinic space group P2₁/n (a = 9.440(2), b = 12.679(3), c = 11.679(3) Å = 94.60(2)° V = 1382.5(5) ų; Z = 4). One of the unique features of the X-ray structure of 3 is the intramolecular hydrogen bonding. The hydrogens of the phenolic and hydroxy groups occupies bridging positions via hydrogen bonding to an ether oxygen (O₁) and a phenolic oxygen (O₄), respectively. This hydrogen bonding does not affect the interplanar angle between phenyl rings (49.34°), which is in the range expected for ortho-disubstituted biphenyl compounds. The hydrogen bonding of this type explains why it is difficult to alkylate both phenoxy groups of 2,2-biphenol with tetrahydropyranyl protected 2-(2-chloroethoxy)ethanol.     

Crystal structures of 3,5,5′-trichloro-2,2′-bithiophene and 3,3′,5,5′-tetrachloro-2,2′-bithiophene

The crystal structures of 3,5,5-trichloro-2,2-bithiophene (I) and 3,3,5,5-tetrachloro-2,2-bithiophene (II) have been determined by single crystal X-ray diffraction techniques. BothI andII crystallize in the monoclinic crystal system. ForI,a=3.895(2),b=11.928(2),c=10.701(2)Å,=97.70(1)°, space groupP2₁,Z=2 and forII,a=8.942(2),b=3.900(2),c=15.180(2)Å,=92.30(1)°, space groupP2₁/n,Z=2. The structures have been solved by direct methods and all nonhydrogen atoms refined with anisotropic thermal parameters. ForI the final residual is 0.035 (all 1185 independent reflections, MoK radiation) and forII, 0.034 (all 1209 independent reflections, MoK radiation). BothI andII have theanti conformation butI has a torsion angle of 3.4(5)° between the two thiophene rings whileII is completely planar.     

Crystal structures of five policyclic compounds related to the natural product forskolin

(3(Z),4,6a,9a,9b)-(±)-3a,4,6a,7,8,9,9a,9b-octahydro-4,7,7, 9b-tetramethyl-3a-[3-(methoxymethyloxy)-3-methyl-1-butenyl]-5H-naphto[1,8-de]-1,3-dioxin-6-one (I), C₂₂H₃₆O₅,M _r=378.51, monoclinic,P2₁/n,a=6.330(1),b=14.576(2),c=22.837(2)Å,=93.04(1)°,V=2104.1(2)ų,Z=4,D _c=1.19 Mg/m³, (MoK)=0.71069Å,=0.8 cm^–1,F(000)=832,T=298 K,R=0.054 for 1971 observed reflections; (7a,10a,10b,12)-(±)-7a,9, 10,10a,10b,11,12,12a-octahydro-2,2,10,10,10b,12a-hexamethyl-2H,8H-1-benzopyrano[4a,5,6,-de][1,3,2]-benzodioxin-11-one (II), C₂₀H₂₉O₄,M _r=334.5, triclinic,P-1,a=10.595(2),b=12.152(1),c=8.073(1)Å,=106.53(1),=105.65(1), =66.29(1)°,V=897.9(2)ų,Z=2,D _c=1.24 Mg/m³, (MoK)=0.71069Å,=0.8 cm^–1,F(000)=362,T=298 K,R=0.046 for 2848 observed reflections; (7a,10a,10b,12, 12a)-(±)-7a,9,10,10a,10b,11,12,12a-octahydro-2,2,10,10,10b,12a-hexamethyl-2H,8H-1-benzopyrano[4a,5,6-de][1,3,2]-benzodioxin-11, 12-diol (III), C₂₀H₃₂O₅ (two molecules in the asymmetric unit),M _r=352.2, triclinic,P-1,a=12.948(3),b=13.615(3),c=12.197(4)Å,=101.16(2),=111.88(2), =69.48(2)°,V=1863.8(9)ų,Z=2,D _C=1.26 Mg/m³,(MoK)=0.71069 Å,=0.8 cm^–1,F(000)=768,T=298 K,R=0.060 for 4570 observed reflections; 4-acetoxy-4-[[(4a,5,8a)-(±)-hexahydro-4a,6,6-trimethyl-4H-1,3-benzodioxin-4-one]-5-yl]butan-2-one (IV), C₁₇H₂₆O₆,M _r=326.4, monoclinic,P2₁/c,a=10.495(2),b=12.050(2),c=14.216(2)Å,=108.51(1)°,V=1704.8(5)ų,Z=4,D _c=1.27 Mg/m³,(MoK)=0.71069 Å,=0.9 cm^–1,F(000)=704,T=298 K,R=0.049 for2455 observed reflections; (3a,4,5,6,6a,9a,9b)-(±)-4,5-epoxy-decahydro-3, 3a-dihydroxy-2-ethoxy-4,7,7,9b-tetramethyl-naphto-[1,8-bc]-pyran-6-ol-acetate (V), C₂₀H₃₂O₇,M _r=383.5, monoclinic,C2/c,a=10.353(2),b=17.975(3),c=21.188(3)Å,=91.29(1)°,V=3942(1)ų,Z=8,D _c=1.29 Mg/m³,(MoK)=0.71069 Å,=0.8 cm^–1,F(000)=1664,T=298 K,R=0.051 for 2120 observed reflections. We report here the complete structures of four decalin derivatives (compoundsI, II, III, V) and one related compound (compoundIV) synthetized in order to find an efficient synthetic approach for the natural productforskolin.     

Dinuclear complex of rhodium(III) with an amine-phenol ligand: synthesis and X-ray crystal structure

A new rhodium(III) complex of an amine-phenol ligand N,NN-bis-(2-hydroxybenzyl)1,3-diaminopropane was synthesized and characterized by X-ray diffraction studies. Diffraction data were collected by the-2 scan method using MoK. radiation. The structure was solved by conventional methods resulting in a final R factor of 0.037 for 1954 independent reflections (F _o >2(F _o )). The structure consists of a dinuclear complex with two -hydroxy bridges between the two Rh atoms. The overall charge of the molecule is neutral due to deprotonation of all phenolic groups. Crystal data: triclinic, space groupP¯1,a=7.308(3)Å;b=9.586(3)Å,c=12.686(5)Å, =87.51(2), =88.28(2), =71.70(3)°,V=866.6(6)ų;Z=2.     

Crystal structure and spectroscopy of the high-spin compound: Tris-(2,2′-bipyridine-1,1′-dioxide)Iron(III) tris(perchlorate) bis(acetonitrile), [Fe(bpdo)3](ClO4)3(CH3CN)2

The first high-spin iron(III) compound with the ligand 2,2-bipyridine-1,1-dioxide (abbreviated as bpdo) is reported. The compound [Fe(bpdo)₃](ClO₄)₃(CH₃CN)₂ crystallizes in the space group P , with a = 11.767(3), b = 13.166(4), c = 15.951(4) Å, = 104.62(3), = 101.66(3), = 112.14(3)°, and Z = 2. The Fe(III) atom is octahedrally surrounded by six oxygen atoms of three bpdo ligands. In the far-infrared region the Fe—O vibration is observed at 411 cm^–1. The magnetic susceptibility reveals a of 6.04 ± 0.04 BM in the 10–280 K region, typical of high-spin Fe(III).     

Structure of 2,2′-bis(3-allyl-4-cyanatophenyl)isopropylidene

The structure of the title compound (I) was determined by direct methods using MoK diffractometer data, and refined by full-matrix least squares toR=0.066 for 1536 reflections (I3 (I)). The structure shows a central tetrahedral carbon atom surrounded by two methyl and two 3-allyl-4-cyanatophenyl groups. The geometry of the cyanato group in this molecule compares well with those in 2,2-bis(4-cyanatophenyl)isopropylideneII) and 4-chloro-3,5-dimethyl-phenylcyanate (III), the only other examples of organic compounds bearing the cyanato moiety in the Cambridge Crystallographic Database (V.3).     

Molecular structure of 1-phenyl-1-dimethylamino-4,4-bis(trimethylsilyl)-2-aza-3λ3-phosphabutadiene-1,3

The crystal and molecular structure of 1-phenyl-1-dimethylamino-4,4-bis(trimethylsilyl)-2-aza-3³-phosphabutadiene-1,3, Me₂N(Ph)C=N—P=C(SiMe₃)₂ (1), has been determined. Crystal data: triclinic, P1¯, a = 8.975(4), b = 10.001(5), c = 12.440(6) Å, = 79.04(4), = 77.98(4), = 73.07(4)°, V = 1034.7 ų, Z = 2, and D _c = 1.08 g cm^–3. The main geometrical parameters of 1 as well as ab initio (HF/6-31+G**) calculations of the model systems show no clear evidence of high efficiency of the (C=N)— (P=C) conjugation.     

Energetic materials: The preparation and structural characterization of melaminium dinitramide and melaminium nitrate

Two energetic salts of the melaminium cation have been prepared and structurally characterized from room temperature X-ray single crystal diffraction data. Melaminium dinitramide (I), triclinic, P1¯, a = 6.6861(11), b = 6.9638(16), c = 10.447(2) Å , = 99.07(3), = 98.30(3), = 108.50(3)°, V = 445.6(2) ų, and Z = 2. Melaminium nitrate (II), monoclinic, P2₁/c, a = 3.5789(7), b = 20.466(4), c = 10.060(2) Å, = 94.01(2)°, V = 735.0(3) ų, and Z = 4. The crystal structures of both salts show distinct monoprotonated melaminium cations and dinitramide- or nitrate anions, respectively. Efficient packing in the solid state is achieved by extensive hydrogen bonding between two-dimensional zigzag ribbons of the melaminium cations and the respective anions resulting in high densities of the solid state structures of 1.74 (I) and 1.71 g/cm³ (II).     

Crystal structures of two substituted key intermediates of phenothiazine derivatives

The key intermediates, in the synthesis of phenothiazines, 5-hydroxy-5-methyl 3(phenyl) 2,4-N-dimethylcarbamoyl cyclohexanone, C₁₇H₂₂O₄N₂ (I), and 5-hydroxy-5-methyl 3(2-methylphenyl) 2,4-N-dimethylcarbamoyl cyclohexanone, C₁₈H₂₄O₄N₂ (II), contain essentially substituted cyclohexanone rings in chair conformation with approximately perpendicular oriented phenyl rings. The carbamoyl groups are aligned in opposite directions to facilitate the formation of intramolecular C–HO interaction and O–HO hydrogen bonding. The molecules are linked in helical fashion by an N–HO type intermolecular hydrogen bonding framework. Crystal data: [I], orthorhombic, space group Pbca, a = 9.278(1), b = 19.094(2), c = 19.802(2) Å, V = 3508.0(6) ų, Z = 8 and d = 1.206 Mg m^–3, R = 0.074 (wR = 0.137) for 208 parameters and 1190 observed reflections with I 2 (I); [II], monoclinic, space group P2₁/n, a = 10.523(1), b = 9.005(1), c = 19.771(2) Å, = 94.96(6)°, V = 1866.5(3) ų, Z = 4 and d = 1.183 Mg m^–3, R = 0.062 (wR = 0.131) for 217 parameters and 2276 observed reflections with I 2 (I).     

C−Cl...π(Ar)...Cl−C,Cl...Cl and other interactions in the structures of two 6-substituted-2,4-bis(trichloromethyl)-1,3-benzdioxin's: (I) 6-carboxymethyl; (II) 6-propionyl,an antimethanogenesis food additive

C₁₂H₃Cl₆O₄, (I),M _r=428.91, triclinic, ,a=9.197(1),b=9.336(2),c=9.830(1) Å, =79.29(1), =83.33(1), =85.38(1)°,V=822.16,Z=2,D _x=1.73 Mg m^–3,F(000)=428, (MoK)=0.71069 Å, =10.62 cm^–1, room temperature, finalR=0.033 for 2573 unique counter reflections withF _o>4(F _o). C₁₃H₁₀Cl₆O₃, (II),M _r=426.94, triclinic, ,a=9.374(2),b=9.503(1),c=9.888(4) Å, =79.26(2), =82.10(3), =84.43(1)°,V=854.88,Z=2,D _c=1.66 Mg m^–3,F(000)=428, =0.71069 Å, =10.17 cm^–1, room temperature, finalR=0.030 for 2609 unique counter reflections withF _o>4(F _o). Compounds I and II are isostructural. Centrosymmetric dimers are formed by hydrogen bonds from the two methine hydrogen atoms to the carbonyl oxygen atom. The dimers are linked by Cl...(Ar)...Cl, Cl...O and Cl...Cl interactions to form a three-dimensional pattern. The geometry associated with these interactions is discussed in terms of the electrophile: nucleophile model.