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.     

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).     

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.     

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)°].     

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.     

Crystal structure analysis of two terpene derivatives

The crystal structures of two terpene derivatives, 2,4,5,6,7,7a-hexahydro-7a-hydroxy-3,6-dimethyl-2-benzofuranone (compound I) and β-cyclolavandulic acid (compound II), were determined by single-crystal diffractometry. Compound I, C₁₀H₁₄O₃, crystallizes in the orthorhombic space group P2₁2₁2₁ with the unit cell parameters a = 6.715(1) Å, b = 7.043(1) Å, c = 20.292(3) Å, and Z = 4. The six-membered ring has an ideal chair conformation. The five-membered ring is planar. Compound II, C₁₀H₁₆O₂, crystallizes in the monoclinic space group P2₁/n with the unit cell parameters a = 8.446(1) Å, b = 12.156(1) Å, c = 9.901(1) Å, β = 106.29(1)°, and Z = 4. The cyclohexene ring exhibits a half-chair conformation. Both the crystal structures are stabilized by intermolecular O-H?O hydrogen bonds.     

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.     

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 structures of thienyl-substituted 5-dipyrromethane isomers

The compounds 5(2-thienyl)-and 5(3-thienyl)-dipyrromethane (1 and2, respectively) have been synthesized and isolated from the acid-catalyzed reaction between thiophenes-carboxaldehyde and pyrrole. Characterization by X-ray diffraction confirms molecular structures involving twoortho-substituted pyrrolyl and one thienyl groups. Both the compounds1 and2 were crystallized in the monoclinic space groupP2₁/n with cell parametersa = 5.7149(16) Å,b = 17.338(6) Å, andc = 11.785(4) Å, β = 98.466(9)^°,V = 1155.0(6) ų for compound1; anda = 5.828(4) Å,b = 17.424(10) Å,c = 11.822(8) Å, β = 98.10(2)^°, andV = 1188.4(13) ų for compound2.     

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.     

Rare-earth and lead mixed anionic oxoborates

TheNd_4.5Pb_1.7(VO₄)_0.3(BO₃)O_6.42(I), Tb_4.5Pb_1.6(GeO₄)_0.4(BO₃)O_6.02(II), Dy_4.5Pb_1.68(GeO₄)_0.32(BO₃)O_6.28(III), and Ho_8.66(BO₃)₂(B₂O₅)O₈(IV) crystals were grown by spontaneous crystallization from flux and studied by the methods of X-ray diffraction analysis. The unit-cell parameters are a = 21.946, 21.590, 21.478, and 18.207 Å; b = 3.7881, 3.6565, 3.6333, and 3.6685 Å; c = 16.857, 16.618, 16.544, and 14.024 Å; β = 123.70°, 124.64°, 124.49°, and 119.81°; sp. gr. C2/m; and Z = 4, 4, 4, and 2 for I, II, III, and IV, respectively. In I–III compounds, Pb atoms, together with the atoms of group V, and Pb atoms and Ge atoms occupy the mixed positions. In structure IV, all the five independent Ho positions are occupied only partially.     

Crystal structures of bis{4-bromo-2-[(2-hydroxyethylimino)methyl]phenolato}copper and bis{4-chloro-2-[(2-hydroxyethylimino)methyl]phenolato}copper

The crystal structures of bis{4-bromo-2-[(2-hydroxyethylimino)methyl]phenolato}copper (I) and bis{4-chloro-2-[(2-hydroxyethylimino)methyl]phenolato}copper (II) are determined. Crystals I are monoclinic, space group P2₁/c, Z = 2, and R = 0.0732 (for all reflections). Crystals II are likewise monoclinic, space group P2₁/n, Z = 2, and R = 0.1106. In the structures of compounds I and II, the metal atom is situated at the center of symmetry and coordinated by two singly deprotonated bidentate 4-bromo-or 4-chloro-2-[(2-hydroxyethylimino)methylphenol molecules, respectively, through phenol oxygen and azomethine nitrogen atoms, which form a distorted planar square. In the structures of compound II, the coordination polyhedron of the central atom is completed to an elongated tetragonal bipyramid by the amino alcohol oxygen atoms of the adjacent complexes.     

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.     

Crystal Structures of Diphosphinated Chromium Fischer Amino Carbenes

The crystal structures of four new diphosphinated chromium Fischer amino carbenes with the compositions fac-[(P-P)(CO)₃Cr=C(NR₂′)(R)] (R = Me, NR₂′ = pyrrolidino, P-P = dppe, 1; R = Me, NR₂′ = pyrrolidino, P-P = dppp, 2; R = Me, R′ = Me, P-P = dppe, 3; R = Me, R′ = Me, P-P = dppp, 4) have been determined at 243 K. Compound 1 crystallizes in the monoclinic system, space group P2₁ /n with a = 12.1597(11) Å, b = 20.1556(17) Å, c = 14.0557(12) Å, β = 114.163(3)°, V = 3143.0(5) Å³, and Z = 4. Compound 2 crystallizes in the triclinic system, space group P ? 1 with a = 7.4424(3) Å, b = 10.8830(5) Å, c = 20.6040(9) Å, α = 100.9880(10)°, β = 91.7650(10)°, γ = 97.6610(10)°, V = 1620.90(12) Å³, and Z = 2. Compound 3 crystallizes in the monoclinic system as a mono-solvate of d⁵-pyridine, space group P2₁ /c with a = 11.485(2) Å, b = 22.825(5) Å, c = 14.092(3) Å, β = 108.53(3)°, V = 3502.7(12) Å³, and Z = 4. Compound 4 crystallizes in the orthorhombic system, space group P2 ₁ 2 ₁ 2 ₁ with a = 8.359(3) Å, b = 15.364(6) Å, c = 23.784(9) Å, V = 3055(2) Å³, and Z = 4. Steric repulsions with the diphosphine ligand favor a conformation with the amino moiety directed away from the diphosphine backbone in 1–4.     

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.     

Solvent-induced Polymorphism of 2-[(2-Amino-phenylimino)-phenyl-methyl]-phenol

The title compound C₁₉H₁₆N₂O crystallize as either triclinic or monoclinic polymorph depending on the solvent used. Polymorph [1] crystallizes from methanol in the space group P \( \mathop 1\limits^ - \) with unit cell dimensions: a = 8.723(2), b = 9.344(2), c = 10.544(2) Å, α = 71.54(2), ß = 78.74(2), γ = 74.15(2)°, and Z = 2. Polymorph [2] crystallizes from benzene with space group P2₁/n with unit cell dimensions: a = 10.230(3), b = 20.536(7), c = 14.563(4) Å, ß = 97.14(3)°, and Z = 8. The only similarity between molecules of [1] and two independent molecules of [2] can be found in almost co-planar phenyl moiety with chelate ring. Both structures are characterized with strong intramolecular O-H···N hydrogen bond. Whereas the molecular interconnections in [2] are based on van der Waals attractions between discrete molecules, molecules of [1] associate in dimers via intermolecular N-H···O hydrogen bonding by the operation of crystallographic centre of inversion.     

Bromination of 1,2,3,4-Tetrahydro-1,10-phenanthroline: Synthesis and Crystal Structure of 6-Bromo-1,2,3,4-tetrahydro-1,10-phenanthroline and Its Bromide Salt

The bromination reaction of 1,2,3,4-tetrahydro-1,10-phenanthroline (tphen) is investigated, which can afford a new heterocyclic compound, namely 6-bromo-1,2,3,4-tetrahydro-1,10-phenanthroline (1). The bromide salt of 1, i.e., 1 · (1H) · Br (2), can be isolated from the bromination system. The accurate structures of both compounds are confirmed and investigated by single-crystal X-ray diffraction. The result proves that the bromination reaction of tphen mainly affords its C6-substituted product. In compounds 1 and 2, the N?H···Br hydrogen bonds play an important role in intermolecular connection. Crystal data of 1: Monoclinic system, sp. gr. Pc, a = 4.6628(8) Å, b = 8.7980(15) Å, c = 13.1347(19) Å, β = 101.342(5)°, Z = 2, V = 528.31(15) ų. Crystal data of 2: Monoclinic system, sp. gr. P2₁/n, a = 16.6171(16) Å, b = 7.8323(8) Å, c = 18.6972(18) Å, β = 113.597(2)°, Z = 4, V = 2230.0(4) ų.     

Coordination dimers constructed from metal(II) halides and the organic ligand 1,2-dimethoxy- 4,5-bis(2-pyridylethynyl)benzene

A series of new coordination compounds has been synthesized using the organic ligand 1,2-dimethoxy-4,5-bis(2-pyridylethynyl)benzene (dmpeb). The compounds all form dimers consisting of two metal cations bridged by two ligand molecules. Charge balance is provided by halide ligands, and the four-coordinate metal centers are distorted from the ideal tetrahedral environment. [CoCl₂(dmpeb)]₂ (1) crystallizes in the monoclinic space group P2₁/n with a = 8.5272(6) Å, b = 18.3653(13) Å, c = 13.3493(9) Å, β = 103.574(2)^°, V = 2032.2(2) ų, Z = 2. [ZnCl₂(dmpeb)]₂ (2) is isostructural to 1 and has the cell parameters a = 8.5495(4) Å, b = 18.4049(8) Å, c = 13.3692(6) Å, β = 103.4460(10)^°, V = 2046.01(16) ų, Z = 2. [ZnBr₂(dmpeb)]₂ (3) is also isostructural to 1 with a = 8.7882(5) Å, b = 18.7260(12) Å, c = 13.3857(8) Å, β = 102.5990(10)^°, V = 2149.8(2) ų, Z = 2. Additionally, the compounds [ZnI₂(dmpeb)]₂ (4, cell parameters: a = 8.9650(5) Å, b = 19.1251(10) Å, c = 13.4160(7) Å, β = 101.1660(10)^°, V = 2256.7(2) ų, Z = 2), [HgCl₂(dmpeb)]₂ (5, cell parameters: a = 8.8457(7) Å, b = 18.4030(15) Å, c = 13.3711(11) Å, β = 104.246(2)^°, V = 2109.7(3) ų, Z = 2), and [HgBr₂(dmpeb)]₂ (6, cell parameters: a = 9.0576(5) Å, b = 18.8634(11) Å, c = 13.4535(8) Å, β = 102.9780(10)^°, V = 2239.9(2) ų, Z = 2) are also isostructural to 1. A seventh dimeric compound, [HgI₂(dmpeb)]₂, not isostructural to the others was also characterized by X-ray crystallography. [HgI₂(dmpeb)]₂ (7) crystallizes in the triclinic space group P-1 with a = 8.8028(5) Å, b = 12.0990(7) Å, c = 12.4082(7) Å, α = 109.7240(10)^°, β = 107.3680(10)^°, γ = 93.0880(10)^°, V = 1169.57(12) ų, Z = 1.     

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.     

Structural study of 2,4,6-triisopropylbenzenesulfonyl chloride

The structure of 2,4,6-triisopropylbenzenesulfonyl chloride (TPSCl) (I) was studied by X-ray diffraction. Compound I is a highly selective condensing agent first suggested by Khorana for the formation of the C3′–C5′ interribonucleotide linkage in the oligo- and polyribonucleotide synthesis. I crystals are orthorhombic. At ?120°C, the unit-cell parameters are a = 14.184(4) Å, b = 11.344(5) Å, c = 19.883(6) Å, V = 3199(2) ų, d _calc = 1.257 g/cm³, Z = 8, sp. gr. Pbca. Molecule I adopts a strongly flattened boat conformation with the carbon atoms C-SO₂Cl (C ₁) and C-i-Pr (C4) of the benzene ring deviating from the bottom of the boat by 0.065(1) and 0.032(1) Å, respectively. Molecule I is sterically overcrowded, resulting in an increase in the bond lengths and bond-angle distortions in the fragment containing the SO₂Cl group and two ortho-i-Pr groups. Nonbonded contacts that are present in the molecule can be considered weak intramolecular hydrogen bonds (for example, the (CH₃)₂C-H?O=S bond). There is no rotation of the SO₂Cl, ortho-i-Pr, and CH₃ groups. The above-mentioned facts are, apparently, responsible for the specific selectivity of TPSCl. New readily available sterically hindered arenesulfonyl chlorides were designed.