The first crystal structure of a Meisenheimer complex with organic cation

The structure of the Meisenheimer complex 2′,4′,6′-trinitro-3′,5′-dihydrospiro(1,3-dioxolane-2,8′-cyclohexadienide) C₈H₆N₃O₈(?) 1^? with tetra-n-butyl-ammonium C₁₆H₃₆ N(+) has been determined by X-ray crystallography. The compound 1 crystallizes in the space group P2₁ with two molecules (Z′ = 2) in the asymmetric unit. The unit cell parameters are a = 8.728(3) Å, b = 13.760(4) Å, c = 22.882(7) Å, β = 96.17(3)^°. Interactions between the Meisenheimer complex and organic cation in 1 involve only a number of weak to moderate C–H?sO bonds. Thus, it has been concluded that the structure 1 represents the geometry of the Meisenheimer complex minimally influenced by the cation. Comparison the structure 1 and the compound 2 (1^? K⁺?H₂O) studied previously reveals an interesting structural effect attributed to coordination of potassium cations with the nitro groups of 1^?. It leads to notable shortening of the C–N bond lengths of the nitro groups only, while changes of other bond lengths in the Meisenheimer complex are not significant.     

Crystal structure of strontium Di[bis(iminodiacetato)cobaltate(III)] pentahydrate,Sr[<Emphasis Type="Italic">cis</Emphasis>(N)-Co(<Emphasis Type="Italic">Ida</Emphasis>)<Subscript>2</Subscript>]<Subscript>2</Subscript> · 5H<Subscript>2</Subscript>O

Compound Sr[cis(N)-Co(Ida)₂]₂ · 5H₂O (I) is synthesized and its crystal structure is determined. The crystals are built of [Co(Ida)₂]^? anionic complexes, [Sr(H₂O)₃]²⁺ hydrated cations, and crystallization water molecules. Two independent anions are located on rotation axis 2 and have close structures. A distorted octahedral coordination of Co³⁺ atoms is formed by two N atoms and four O atoms of two Ida ^2? ligands [Co-N, 1.932(3) and 1.940(3) Å; Co-O, 1.879–1.899(3) Å]. [Sr(H₂O)₃]²⁺ cations randomly occupy half of the positions in the vicinity of centers of inversion. In addition to three water molecules, the environment of the Sr²⁺ atom includes five O atoms of five Ida ^2? ligands [Sr-O, 2.487(3)-2.889(5) Å]. Because of the disordering of [Sr(H₂O)₃]²⁺ cations, the structural function of the Ida ^2- ligands varies from tridentate chelate to pentadentate bridging chelate. Sr-O and hydrogen bonds connect structural elements into a three-dimensional framework. The structure of I is compared with that of a related compound Sr[CoEdta]₂·9H₂O (II). It is shown that the formation of N-H…O hydrogen bonds, which connect [Co(Ida)₂]^? anionic complexes in I into compact chains, is an important factor leading to the difference between packings I and II.     

Crystal structures of copper(II) nitrate,copper(II) chloride,and copper(II) perchlorate complexes with 2-formylpyridine semicarbazone

Compounds dinitrato(2-formylpyridinesemicarbazone)copper (I), dichloro(2-formylpyridinesemicarbazone) copper hemihydrate (II), and bis(2-formylpyridinesemicarbazone)copper(2+) perchlorate hydrate (III) are synthesized and their crystal structures are determined. In compounds I–III, the neutral 2-formylpyridine semicarbazone molecule (L) is tridentately attached to the copper atom via the N,N,O set of donor atoms. In compounds I and II, the Cu: L ratio is equal to 1: 1, whereas, in III, it is 1: 2. In complex I, the coordination sphere of the copper atom includes two nitrate ions with different structural functions in addition to the L ligand. The structure is built as a one-dimensional polymer in which the NO₃ bidentate group fulfills a bridging function. The coordination polyhedron of the copper(2+) atom can be considered a distorted tetragonal bipyramid (4 + 1 + 1). Compound II has an ionic structure in which the main element is the [CuLCl₂ · Cu(H₂O)LCl]⁺ dimer. In the dimer, the copper atoms are linked via one of the μ₂-bridging chlorine atoms. The coordination polyhedra of the central atoms of the Cu(H₂)LCl and CuLCl₂ complex fragments are tetragonal bipyramid and tetragonal pyramid, respectively. In compound III, the copper atom is octahedrally surrounded by two L ligands in the mer configuration.     

Crystal structures of dioxonium hexafluorotantalate and dioxonium hexafluoroniobate complexes with tetrabenzo-30-crown-10

Two isostructural complexes of dioxonium [H₅O₂]⁺ with tetrabenzo-30-crown-10 of the compositions [(tetrabenzo-30-crown-10 · H₅O₂)][TaF₆] (I) and [(tetrabenzo-30-crown-10 · H₅O₂)][NbF₆] (II) are studied using X-ray diffraction. The complexes crystallize in the monoclinic crystal system (space group C2/c, Z = 4). The unit cell parameters of these compounds are as follows: a = 15.6583(12) Å, b = 15.2259(13) Å, c = 16.4473(13) Å, and β = 99.398(6)° for complex I and a = 15.7117(12) Å, b = 15.2785(15) Å, c = 16.5247(15) Å, and β = 99.398(7)° for complex II. These complexes belong to the ionic type. The dioxonium cation [H₅O₂]⁺ in the form of the two-unit cluster [H₃O · H₂O]⁺ is stabilized by the strong hydrogen bond OH?O [O?O, 2.353(4) Å] and encapsulated by the crown ether. Each oxygen atom of the dioxonium cation also forms two oxygen bonds O?O(crown). The crown ether adopts an unusual two-level (pocket-like) conformation, which provides a complete encapsulation of the oxonium associate. The interaction of the cationic complex with the anion in the crystal occurs through contacts of the C-H?F type.     

Unclassical hydrogen bonds of C—H⋅<Emphasis Type="Italic">s</Emphasis>O and C—H⋅<Emphasis Type="Italic">s</Emphasis>N in the crystals of 2-amino-3-cyano-4-(3,4-dichlorophenyl)-5-oxo-1,4,5,6-tetrahydro-4H-pyrano[2,3-<Emphasis Type="Italic">d</Emphasis>]pyrimidine

The 2-amino-3-cyano-4-(3,4-dichlorophenyl)-5-oxo-1,4,5,6-tetrahydro-4H-pyrano[2,3-d] pyrimidine (1, C₁₇H₁₅Cl₂N₅O₃) was synthesized and characterized by IR,¹H NMR and elemental analysis. The molecular structure of1 was further studied by using X-ray crystallography. The crystals of compound1 are triclinic, space groupP-1,a = 6.0090(4) Å,b = 10.4056(7) Å,c = 15.6021(11) Å, α = 70.983(4), β = 84.056(6), γ = 84.611(6),Z = 2,V = 915.47(11) ų. Two types of unclassical hydrogen bonds C–H?sO and C–H?sN were presented in the crystals. In addition, there were classical hydrogen bonds in the crystal structure.     

Synthesis,antityrosinase activity of curcumin analogues,and crystal structure of (1<Emphasis Type="Italic">E</Emphasis>,4<Emphasis Type="Italic">E</Emphasis>)-1,5-bis(4-ethoxyphenyl)penta-1,4-dien-3-one

Five derivatives of curcumin analogue (R = OCH₂CH₃ (1), R = N(CH₃)₂ (2), R = 2,4,5-OCH₃ (3), R = 2,4,6-OCH₃ (4), and R = 3,4,5-OCH₃ (5)) were synthesized and characterized by ¹H NMR, FT-IR and UV–Vis spectroscopy. The synthesized derivatives were screened for antityrosinase activity, and found that 4 and 5 possess such activity. The crystal structure of 1 was determined by single crystal X-ray diffraction: monoclinic, sp. gr. P2₁/c, a = 17.5728(15) Å, b = 5.9121(5) Å, c = 19.8269(13) Å, β = 121.155(5)°, Z = 4. The molecule 1 is twisted with the dihedral angle between two phenyl rings being 15.68(10)°. In the crystal packing, the molecules 1 are linked into chains by C?H···π interactions and further stacked by π···π interactions with the centroid–centroid distance of 3.9311(13) Å.     

X-ray crystal structures of two polymorphic forms,monoclinic and triclinic,of: 1-[(<Emphasis Type="Italic">E</Emphasis>)-2-(4-bromophenyl)1-diazenyl]-3-({3-[(<Emphasis Type="Italic">E</Emphasis>)-2-(4-bromophenyl)-1-diazenyl]-6-ethylhexahydro-1-pyrimidinyl}methyl)-4-ethylhexahydropyrimidine

1-[(E)-2-(4-bromophenyl)-1-diazenyl]-3-({3-[(E)-2-(4-bromophenyl)-1-diazenyl]-6-ethylhexahydro-1-pyrimidinyl}methyl)-4-ethylhexahydropyrimidine (1) has been synthesized by reaction of a mixture of formaldehyde and 1,3-pentanediamine{DYTEK^®EPdiamine} with p-bromobenzenediazonium chloride. This compound crystallizes in two polymorphic forms 1-α and 1-β whose crystal structures have been determined by single crystal X-ray diffraction analysis. Both polymorphs 1-α and 1-β display crystallographic disorder within the hexahydropyrimidine rings. The molecule of 1 is built up of two equivalent 3-(aryldiazenyl)-6-ethylhexahydro-1-pyrimidinyl groups in the s-trans orientation around the central methylene group (C13). In both structures the triazene moieties adopt the anti configuration around the N=N bonds, displaying significant π-conjugation. The crystal packings are determined only by van der Waals interactions. The crystal structures of 1-α and 1-β are compared with the previously reported structure of the 5,5-dimethylhexahydropyrimidine analogue 3. Compounds 1 and 3 are isomeric with respect to the hexahydropyrimidine moiety. The structures of 1 and 3 are very different in one respect; in 1 the aryldiazenyl-hexahydropyrimidinyl groups are in the s-trans orientation around the central methylene group, whereas in 3 the arrangement of the aryldiazenylhexahydropyrimidinyl groups is the s-cis orientation. Crystal data: 1-α C₂₅H₃₄N₈Br₂, monoclinic, space group P2(1)/c, a = 9.2150(3), b = 19.4059(6), c = 15.4324(5) Å, β = 98.738(1)^°, V = 2727.7(2) ų, for Z = 4; 1-β C₂₅H₃₄N₈Br₂, triclinic, space group P-1, a = 9.6009(3), b = 10.7509(4), c = 14.2169(5) Å, α = 99.830(2), β = 105.973(3), γ = 95.578(1)^°, V = 1373.9(1) ų, for Z = 2.     

Synthesis and structure of Cs[UO<Subscript>2</Subscript>(SeO<Subscript>4</Subscript>)(OH)] · <Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O (<Emphasis Type="Italic">n</Emphasis> = 1.5 or 1)

The synthesis and single-crystal X-ray diffraction study of Cs[UO₂(SeO₄)(OH)] · 1.5H₂O (I) and Cs[UO₂(SeO₄)(OH)] · H₂O (II) are performed. Compound I crystallizes in the monoclinic crystal system, a = 7.2142(2) Å, b = 14.4942(4) Å, c = 8.9270(3) Å, β = 112.706(1)°, space group P2₁/m, Z = 4, and R = 0.0222. Compound II is monoclinic, a = 8.4549(2) Å, b = 11.5358(3) Å, c = 9.5565(2) Å, β = 113.273(1)°, space group P2₁/c, Z = 4, and R = 0.0219. The main structural units of crystals I and II are [UO₂(SeO₄)(OH)]^? layers which belong to the AT ³ M ² crystal chemical group of uranyl complexes (A = UO ₂ ²⁺ , T ³ = SeO₄ ^2?, and M ² = OH^?). In structure I, johannite-like layers are found. Structure II is a topological isomer of I. The two structures differ in the number of U(VI) atoms bound to the central atom by all bridging ligands.     

Synthesis and X-ray diffraction study of new uranyl malonate and oxalate complexes with carbamide

Two new malonate-containing uranyl complexes with carbamide of the formulas [UO₂(C₃H₂O₄)(Urea)₂] (I) and [UO₂(C₃H₂O₄)(Urea)₃] (II), where Urea is carbamide, and one uranyl oxalate complex of the formula [UO₂(C₂O₄)(Urea)₃] (III) were synthesized, and their crystals were studied by X-ray diffraction. The main structural units in crystals I are the electroneutral chains [UO₂(C₃H₂O₄)(Urea)₂]_∞ belonging to the crystal-chemical group AT¹¹M₂¹ (A = UO₂²⁺, T¹¹ = C₃H₂O₄^2-, M¹ = Urea) of uranyl complexes. Crystals II and III are composed of the molecular complexes [UO₂(L)(Urea)₃], where L = C₃H₂O₄^2- or C₂O₄^2-, belonging to the crystal-chemical group AB⁰¹M₃¹ (A = UO₂²⁺, B⁰¹ = C₃H₂O₄^2- or C₂O₄^2-, M¹ = Urea). The characteristic features of the packing of the uranium-containing complexes are discussed in terms of molecular Voronoi–Dirichlet polyhedra. The effect of the Urea: U ratio on the structure of uranium-containing structural units is considered.     

Synthesis,Spectroscopy, and α-Glucosidase Inhibitory Activity of 3-Substituted Hydrazone Derivatives and Crystal Structure of (1<Emphasis Type="Italic">E</Emphasis>,2<Emphasis Type="Italic">E</Emphasis>)-1,2-Bis[1-(3-methoxyphenyl)ethylidene]hydrazone

Six 3-substituted hydrazone derivatives [R = ?OCH₃ (1), ?NH₂ (2), ?NO₂ (3), ?F (4), ?Cl (5), and ?Br (6)] were synthesized by condensation reaction. Their structures were elucidated by ¹H NMR, FT-IR and UV-Vis spectroscopy. The synthesized compounds were further evaluated for their α-glucosidase inhibitory activity. Strong activity was found for 1 and 3. The crystal structure of 1 was determined by single crystal X-ray diffraction: a = 6.9743(1) Å, b = 18.3627(3) Å, c = 12.0207(2) Å, β = 96.087(1)o, sp. gr. P2₁/c, Z = 4. The molecule of 1 is twisted with the dihedral angle between the two phenyl rings being 51.91(4)°. In the crystal packing, the molecules are linked into chains by C–H···π interactions.     

Synthesis and structure of oxovanadium(IV) complexes [VO(<Emphasis Type="Italic">Acac</Emphasis>)<Subscript>2</Subscript>] and [VO(<Emphasis Type="Italic">Sal</Emphasis>: <Emphasis Type="Italic">L</Emphasis>-alanine)(H<Subscript>2</Subscript>O)]

Bis(acetylacetonato)oxovanadium C₁₀H₁₄O₅V (I) and (S)-[2-(N-salicylidene)aminopropionate]oxovanadium monohydrate C₁₀H₉NO₅V (II) are synthesized. The crystal structures of compounds I and II are determined using single-crystal X-ray diffraction. Crystals of compound I are triclinic, a = 7.4997(19) Å, b = 8.2015(15) Å, c = 11.339(3) Å, α = 91.37(2)°, β = 110.36(2)°, γ = 113.33(2)°, Z = 2, and space group \(P\bar 1\). Crystals of compound II are monoclinic, a = 8.5106(16) Å, b = 7.373(2) Å, c = 9.1941(16) Å, β = 101.88(1)°, Z = 2, and space group P2₁. The structures of compounds I and II are solved by direct methods and refined to R₁ = 0.0382 and 0.0386, respectively. The oxovanadium complexes synthesized are investigated by vibrational spectroscopy.     

Synthesis,Crystal Structure,Antioxidant, and α-Glucosidase Inhibitory Activities of Methoxy-substituted Benzohydrazide Derivatives

Eight methoxy substituted at the benzylidene moiety benzohydrazide derivatives [R = 2-OCH₃ (1), 3-OCH₃ (2), 4-OCH₃ (3), 2,3-(OCH₃)₂ (4), 3,4-(OCH₃)₂ (5), 2,4,5-(OCH₃)₃ (6), 2,4,6-(OCH₃)₃ (7), and 3,4,5-(OCH₃)₃ (8)] were synthesized and characterized by ¹H NMR, FT-IR and UV-Vis spectroscopy. The crystal structure of 4 was determined by single crystal X-ray diffraction (sp. gr. Pbca, Z = 8). The molecule is slightly twisted with the dihedral angle between the two phenyl rings being 9.33(14)°. The methoxy group at the ortho position is twisted [C–O–C–C angle is–109.2(3)°] whereas the other at meta position is co-planar with the attached benzene ring. In the crystal packing, the molecules are linked into two-dimensional network parallel to the (001) plane by O–H···O, O–H···N, and N–H···O hydrogen bonds. Compounds 1–8 were evaluated for an antioxidant and α-glucosidase inhibitory activities and the results suggested that the ?OCH₃ substituent was ineffective for bioactivity enhancement.     

The synthesis and crystal structure of (4<Emphasis Type="Italic">E</Emphasis>)-5(3-chlorophenyl)-<Emphasis Type="Italic">N</Emphasis>-(4-chlorophenyl)-2-diazo3-oxopent-4-enoic acid amide

(4E)-5-(3-Chlorophenyl)-N-(4-chlorophenyl)-2-diazo-3-oxopent-4-enoic acid amide (5) was synthesized from p-chloroaniline to N-(4-chlorophenyl)-2-diazo-3-oxo-butyramide (4) with 3-chlorobenzaldehyde. The yielded product 5 was investigated with X-ray crystallographic, NMR, MS, and IR techniques. Compound 5 (C₁₇H₁₁Cl₂N₃O₂, Formula wt = 360.19), crystallizes in the monoclinic space group P21/c with unit cell parameters a = 10.516(2), b = 17.996(4), c = 8.902(2) Å, α = 90.00, β = 105.36(3), γ = 90.00^°. V = 1624.5(6) ų, Z = 4, D _x = 1.473 Mg m^?3. The final R was 0.0511.     

X-ray mapping in heterocyclic design: 18. X-ray diffraction study of a series of derivatives of 3-cyanopyridine-2-one with annelated heptane and octane cycles

Seven new, previously unknown, bicyclic and tricyclic heterocycles based on derivatives of 3-cyanopyrid-2-ones are obtained: 2-oxo-2,5,6,7,8,9-hexahydro-1H-cyclohepta[b]pyridine-3-carbonitrile, C₁₁H₁₂N₂O (1a); 2-[2-(4-chlorophenyl)-2-oxoethoxy]-6,7,8,9-tetrahydro-5Н-cyclohepta[b]pyridine-3-carbonitrile, C₁₉H₁₇ClN₂O₂ (2a); (3-amino-6,7,8,9-tetrahydro-5H-cyclohepta[b]furo[3,2-e]pyridin-2-yl)(4- chlorophenyl)methanone, C₁₉H₁₇ClN₂O₂ (3); 2-oxo-1,2,5,6,7,8,9,10-octahydrocycloocta[b]pyridine-3-carboxamide, C₁₂H₁₆N₂O₂ (4); 2-[2-(4-chorophenyl)-2-oxoethoxy]-5,6,7,8,9,10-hexahydrocycloocta[b]pyridine-3-carboxamide, C₂₀H₂₁ClN₂O₃ (5a); 1-[2-(4-chlorophenyl)-2-oxoethyl]-2-oxo-1,2,5,6,7,8,9,10-octahydrocycloocta[b]pyridine-3-carboxamide, C₂₀H₂₁ClN₂O₃ (5b); and 2-[2-(4-chlorophenyl)-2-oxoethoxy]-5,6,7,8,9,10-hexahydrocycloocta[b]pyridine-3-carbonitrile, C₂₀H₁₉ClN₂O₂, (6). All compounds are characterized by ¹H NMR spectroscopy, and their crystal structures are determined by X-ray diffraction.     

Crystal and molecular structure of 2-(2-pyridyl)-indandione-1,3 and a zinc(II) complex with this ligand

The crystal structures of 2-(2-pyridyl)-indandione-1,3 C₁₄H₉NO₂ (HL, I) and the zinc complex ZnL ₂(Dmso) (II) (where Dmso is dimethyl sulfoxide) with this ligand are determined. The specific features of the crystal structures of both compounds are considered. A comparative analysis of the supramolecular aggregates in crystals of these compounds is performed. It is demonstrated that the supramolecular dimers retain their structure in the crystals of compounds I and II. These dimers are involved in weak secondary interactions (usually of one type) with the formation of spatially more complex supramolecular associates, such as chains, ribbons, and layers.     

Crystal and molecular structures of dimethyl 4-phenylthiosemicarbazidediacetate and its adduct with rhodium(II) acetate

The crystal structures of dimethyl 4-phenylthiosemicarbazidediacetate C₁₃H₁₇N₃O₄S (I) and its adduct [C₈H₁₂O₈Rh₂ (C₁₃H₁₇N₃O₄S)₂] (II) with rhodium(II) acetate are determined by X-ray diffraction analysis. The unit cell parameters of crystals I are as follows: a = 8.066(6) Å, b = 15.812(6) Å, c = 24.977(8) Å, β = 94.88(3)°, space group P2₁/n, and Z = 8. The unit cell parameters of crystals II are a = 8.513(1) Å, b = 16.055(1) Å, c = 16.071(3) Å, β = 104.99(1)°, space group P2₁/c, and Z = 2. In structure I, two crystallographically independent molecules considerably differ from each other in the mutual orientation of the structural fragments containing the ester groups. In the centrosymmetric dimeric complex II, the organic molecule I acts as a monodentate thio ligand and adopts only one conformation.     

Triosmium and triruthenium clusters containing morpholine ligand: X-ray structure of Os<Subscript>3</Subscript>(CO)<Subscript>10</Subscript>(μ-η<Superscript>2</Superscript>-NC<Subscript>4</Subscript>H<Subscript>6</Subscript>O)(μ-H)

Treatment of the labile cluster Os₃(CO)₁₀(CH₃CN)₂ with morpholine in benzene at 60^°C afforded Os₃(CO)₁₀(μ-η²-NC₄H₆O)(μ-H) (1). Decarbonylation of 1 at 128^°C gave Os₃(CO)₉(μ₃-η²-NC₄H₆O)(μ-H) (2), which reacts with PPh₃ at ambient temperature to give an addition product Os₃(CO)₉(μ-η²-NC₄H₆O)(PPh₃)(μ-H) (3). Compound 1 reacted with PPh₃ at 98^°C to give the substitution product 4 which is an isomer of 3. The reaction of Ru₃(CO)₁₂ with morpholine in the presence of Me₃NO in refluxing benzene at 80^°C afforded Ru₃(CO)₉(μ₃-η²-NC₄H₆O)(μ-H) (5). Compounds 1– 5 have been characterized by elemental analysis, infrared, ¹H NMR, and mass spectroscopic data. The molecular structure of 1 has been determined by single crystal X-ray diffraction analysis. Compound 1 crystallizes in the monoclinic space group P2/c with a = 29.598(8) Å, b = 9.202(2) Å, c = 14.496(4) Å, β = 93.19(3)^°, Z = 8, and V = 3942(2) ų. Compound 1 consists of an isosceles triangle of osmium atoms with one elongated Os–Os edge, which is bridged by the hydride and the morpholine ligand.     

Crystal structures of complexes of the <Emphasis Type="Italic">cys-syn-cys</Emphasis> isomer of dicyclohexano-18-crown-6 with oxonium hexafluorotantalate and oxonium hexafluoroniobate

The crystal structures of [(cys-syn-cys-dicyclohexano-18-crown-6 · H₃O)][TaF₆] and [(cys-syn-cys-dicyclohexano-18-crown-6 · H₃O)][NbF₆] complex compounds are determined using X-ray diffraction analysis. The tantalum complex has two polymorphic modifications, namely, the monoclinic (I) and triclinic (II) modifications. The unit cell parameters of these compounds are as follows: a = 8.507(4) Å, b = 11.947(5) Å, c = 27.392(12) Å, β = 93.11(1)°, Z = 4, and space group P2₁/n for modification I; and a = 10.828(1) Å, b = 11.204(1) Å, c = 12.378(1) Å, α = 72.12(1)°, β = 79.40(1)°, γ = 73.70(1)°, Z = 2, and space group P-1 for modification II. The triclinic niobium complex [(cys-syn-cys-dicyclohexano-18-crown-6 · H₃O)][NbF₆] (III) with the unit cell parameters a = 10.796(3) Å, b = 11.183(3) Å, c = 12.352(3) Å, α = 72.364(5)°, β = 79.577(5)°, γ = 73.773(4)°, Z = 2, and space group P-1 is isostructural with tantalum complex II. The structures of all three complexes are ionic in character. The oxonium cation in complexes I–III is encapsulated by the crown ether and thus forms one ordinary and two bifurcated hydrogen bonds with the oxygen atoms of the crown ether. This macrocyclic cation is bound to the anions through the C-H...F contacts (H...F, 2.48–2.58 Å). The conformation of the macrocycle in complex I differs substantially from that in complex II (III).     

X-ray mapping in heterocyclic design: VI. X-ray diffraction study of 3-(isonicotinoyl)-2-oxooxazolo[3,2-<Emphasis Type="Italic">a</Emphasis>]pyridine and the product of its hydrolysis

The structure of 3-(isonicotinoyl)-2-oxooxazolo[3,2-a]pyridine, C₁₃H₈N₂O₃, (I) is determined by X-ray powder diffraction analysis. Crystals I are orthorhombic, a = 16.610(2) Å, b = 3.853(1) Å, c = 16.431(2) Å, Z = 4, and space group Pna2₁. The structure is solved by the grid search procedure and refined by the Reitveld method (R_p = 0.086, R_wp = 0.115, R_e = 0.030, and χ² = 11.138). The structure of the product of hydrolysis of compound I, C₁₂H₁₀N₂O₂, (II) is determined by the single-crystal X-ray diffraction technique. Crystals II are orthorhombic, a = 8.755(4) Å, b = 10.526(17) Å, c = 23.088(6) Å, Z = 8, and space group Pc2₁b. The structure is solved by the direct method and refined by the full-matrix least-squares procedure to R = 0.0464. A fragment of two fused heterocycles in I is planar. The dihedral angle between the plane of the pyridine ring in the isonicotinoyl fragment and the plane of the bicyclic system is 51.2(2)°. Both exocyclic CO groups that are adjacent to the five-membered fragment contain double bonds. The structures of two crystallographically independent molecules II are almost identical to each other, and the isonicotinoyl fragment is nearly perpendicular to the plane of the pyridone fragment [84.3(1)° and 87.0(1)°].     

X-ray diffraction investigation of <Emphasis Type="Italic">trans</Emphasis>-2,8-dihydroxy-2,4,4′, 6,6′,8,10,10′,12,12′-decamethyl-5,11-dicarbacyclohexasiloxane and <Emphasis Type="Italic">trans</Emphasis>-1,4-dihydroxy-1,4-dimethyl-1,4-disilacyclohexane

The crystal structures of two organosilicon compounds are studied by X-ray diffraction. Crystals of trans-2,8-dihydroxy-2,4,4′,6,6′,8,10,10′,12,12′-decamethyl-5,11-dicarbacyclohexasiloxane, C₁₂H₃₆O₆Si₆, (I) are studied at 293 K [a = b = 16.310(4) Å, c = 9.849(3) Å, V = 2620(1) ų, d_calcd = 1.128 g/cm³, space group P4(2)/n, Z = 4, 3370 reflections, wR2 = 0.1167, R1 = 0.0472 for 2291 reflections with F > 4σ(F)]. Crystals of trans-1,4-dihydroxy-1,4-dimethyl-1,4-disilacyclohexane, C₆H₁₆O₂Si₂, (II) are studied at 110 K [a = 6.8253(5) Å, b = 9.5495(8) Å, c = 12.0064(10) Å, α = 101.774(2)°, β = 102.203(2)°, γ = 95.068(2)°, V = 741.8(1) ų, d_calcd = 1.184 g/cm³, space group \(P\bar 1\), Z = 3, 6267 reflections, wR2 = 0.1052, R1 = 0.0421 for 3299 reflections with F > 4σ(F)]. It is found that the conformation of the ring in compound I, which contains two methylene groups in the cyclohexasiloxane ring, differs from those in its analogues containing only oxygen atoms or one methylene group in the ring. The noticeable difference between the SiCSi angle [123.0(2)°] and the tetrahedral angle is characteristic of cyclohexasiloxanes. Structure II contains three independent molecules with very close conformations. The cyclohexane rings adopt a chair conformation. The methylene groups in II, in distinction to those in I, are characterized by a standard tetrahedral coordination.