New polydentate sulfide ligands: Synthesis, redox properties, and molecular structure of 4,5-bis(p-tolylthio)-4-cyclopenten-1,3-dione

The reaction of p-toluenethiol with 4,5-dichloro-4-cyclopenten-1,3-dione in 1,2-dichloroethane with added DBU affords good yields of the new bidentate sulfide ligand 4,5-bis(p-tolylthio)-4-cyclopenten-1,3-dione. The title compound was isolated by column chromatography and characterized in solution by IR and NMR spectroscopies. The solid-state structure of RC=CRC(O)CH₂C(O) (where R = p-tolylthio) was solved by X-ray crystallography. 4,5-Bis(p-tolylthio)-4-cyclopenten-1,3-dione crystallizes in the monoclinic space group P2 ₁/c, a = 14.203(3) Å, b = 6.181(1) Å, c = 20.372(4) Å, = 106.111(3)°, V = 1718.1(6) ų, Z = 4, and d _calc = 1.316 mg/m³; R = 0.0743, R _w = 0.1693 for 3958 reflections with I > 2(I). The redox properties of 4,5-bis(p-tolylthio)-4-cyclopenten-1,3-dione have been examined by cyclic voltammetry in CH₂Cl₂ solution, where a quasireversible reduction wave at –1.10 V was found. The reduction behavior is discussed relative to the nature of the LUMO level, which has been determined by extended Hückel MO calculations. The redox chemistry and the LUMO of our bidentate sulfide ligand are contrasted with the known redox chemistry and the LUMO composition of the corresponding bidentate phosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd).     

Chlorine-atom abstraction and cluster fragmentation in the reaction of H3Re3(CO)10(MeCN)2 with the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd): X-ray diffraction structure of fac-ClRe(CO)3(bpcd)

Treatment of the activated trirhenium cluster H₃Re₃(CO)₁₀(MeCN)₂ with the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) in CH₂Cl₂ does not afford the expected cluster product H₃Re₃(CO)₁₀(bpcd) but rather the mononuclear complex fac-ClRe(CO)₃(bpcd). The identity of fac-ClRe(CO)₃(bpcd) was determined in solution by IR and NMR (¹H and ³¹P) spectroscopies and the solid-state structure was established by X-ray diffraction analysis. fac-ClRe(CO)₃(bpcd) crystallizes in the triclinic space P-1, a = 9.958(2) Å, b = 11.991(3) Å, c = 13.676(3) Å, α = 73.230(4)°, β = 73.806(4)°, γ = 77.409(4)°, V = 1484.6(6) ų, Z = 2, and d _calc = 1.723 Mg/m³; R = 0.0367, R _w  = 0.0857 for 4253 reflections with I > 2σ(l).     

CO replacement in the tetrahedrane cluster MeC(O)CCo3(CO)9 by the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-l,3-dione (bpcd): Diphosphine ligand isomerization and X-ray structure of the bridged cluster MeC(O)CCo3(CO)7(bpcd)

The tricobalt cluster MeC(O)CCo₃(CO)₉ reacts with the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-l,3-dione (bpcd) in the presence of added Me₃NO to furnish the disubstituted cluster MeC(O)CCo₃(CO)₇(bpcd) in good yield. MeC(O)CCo₃(CO)₇(bpcd) has been characterized in solution by IR and NMR (¹H and ³¹P) spectroscopies, and the solid-state structure determined by X-ray crystallography. MeC(O)CCo₃(CO)₇(bpcd) crystallizes in the monoclinic space group P2₁/c, a=14.8421(8), b=16.6162(9), c=14.9363(8) ?, β=99.705(1)°, V=3630.9(3) ?³, Z=4, D _cacl=1.632 Mg/m³; R=0.0288, R _w=0.0683 for 8618 observed reflections with I > 2σ(I). The bridging of adjacent cobalt atoms by the bpcd ligand in MeC(O)CCo₃(CO)₇(bpcd) is crystallographically established, and the facile isomerization of the bridging bpcd to the chelating isomer at low temperature is confirmed by VT ³¹P NMR measurements.     

Syntheses and X-ray structures of the bridging and chelating isomers of Os3(CO)10(dmpe)

The substitution chemistry of the activated clusters Os₃(CO)₁₀(MeCN)₂ (1) and Os₃(CO)₁₀(1,5-cod) (2) has been investigated with the bidentate ligand 1,2-bis(dimethylphosphino)ethane (dmpe). Both starting clusters react rapidly with dmpe at room temperature to give the corresponding substitution product Os₃(CO)₁₀(dmpe) (3), whose isomeric composition is shown to depend on the nature of the starting cluster. Whereas the bridged cluster 1,2-Os₃(CO)₁₀(dmpe) (3b) was formed almost exclusively upon reaction with Os₃(CO)₁₀(MeCN)₂, a near statistical mixture of bridging (3b) and chelating (3c) isomers of Os₃(CO)₁₀(dmpe) was found in the reaction employing Os₃(CO)₁₀(1,5-cod). Both dmpe isomers have been characterized in solution by 3iP NMR spectroscopy and their solid-state structures established by X-ray crystallography. The bridged cluster 1,2-Os₃(CO)₁₀(dmpe) crystallizes in the monoclinic space group P2₁/n, a = 9.867(2) Å, b = 17.081(3) Å, c = 14.198(2) Å, β = 95.902(3)°, V = 2380.4(6) ų, Z = 4, and d _calc = 2.793 Mg/m³; R = 0.0435, R _w = 0.0466 for 3519 reflections with I > 2σ(I). The chelated cluster 1,1-Os₃(CO)₁₀(dmpe) crystallizes in the orthorhombic space group C222(1), a = 8.329(3) Å, b = 19.028(6) Å, c = 15.008(5) Å, V = 2379(1) ų, Z = 4, and d _calc = 2.795 Mg/m³; R = 0.0390, R _w = 0.0718 for 2360 reflections with I > 2σ(I).     

Synthesis and crystal structure of 5-amino-4-cyano-1-[(5-methyl-1-t-butyl-4-pyrazolyl)carbonyl]-3-methylthio-1H-pyrazole

The title compound, 5-amino-4-cyano-1-[(5-methyl-1-t-butyl-4-pyrazolyl)carbonyl]-3-methylthio-1H-pyrazole 5, was synthesized by the treatment of 4 (5-methyl-1-t-butylpyrazole-4-carbohydrazide) with 2-cyano-3, 3-dimethylthio-acrylonitrile, and its crystal structure was determined by X-ray diffraction method. The crystal belongs to monoclinic, space group P2₁/c with unit cell parameters a = 13.566(4) Å, b = 10.833(3) Å, c = 11.202(3) Å, α = 90°, β = 98.073(5)°, γ = 90°, V = 1629.9(8) ų, Z = 4, D _c = 1.298, M _r = 318.40, μ = 0.210 mm⁻¹, F(000) = 672, R ₁ = 0.0488 and wR ₂ = 0.1250.     

Synthesis, crystal structures, and properties of two manganese(II)-nitroprusside complexes

Two new manganese(II)-1,10-phenanthroline-nitroprusside complexes, [Mn(phen)₃][Fe (CN)₅(NO)]⋯2H₂O⋯0.25CH₃OH (1) and [Mn(phen)₂(H₂O)₂][Fe(CN)₅(NO)]⋯H₂O (2) (where phen is 1,10-phenanthroline) have been synthesized and characterized by X-ray diffraction, electronic paramagnetic resonance (E.P.R.) and IR analyses. Complex 1 crystallizes in the monoclinic space group P2₁/n, with lattice parameters a = 10.0441(15) Å, b = 19.668(2) Å, c = 19.938(3) Å,  β =100.427(14)°, V = 3873.7(10) ų, Z = 4; complex (2) crystallizes in the monoclinic space group C2/c, with a = 17.120(2) Å, b = 13.7925(19) Å, c = 14.4362(17) Å, β = 107.962(12)°, V = 3242.6(7) ų, Z = 4. In the two compounds, three phen ligands 1, or two phen ligands and two cis-related aqua molecules 2, are in a distorted octahedral arrangement around the Mn(II) ion. The nitroprusside anion, [Fe(CN)₅(NO)]²⁻, acts as a counterion. It is intriguing that in complex 2 no cyano bridges are present with two water molecules coordinated to the Mn(II) ion considering that usually the cyano nitrogen atoms are strong donors and could readily replace the coordinating solvent water molecules. Abundant hydrogen bond interactions and π–π stacking between the phen rings in two complexes lead to three-dimensional supramolecular networks.     

Crystal structure analyses of bis(triphenyl- phosphoranyliden)ammonium bis(pentafluoroethyl) argentate, [Ph3P=N=PPh3][Ag(C2F5)2] and bis[bis(triphenylphosphoranyliden)ammonium] tetrachloro-diargentate, [Ph3P=N=PPh3]2[ClAg(μ-Cl)2AgCl]

Bis(triphenylphosphoranyliden)ammonium bis(pentafluoroethyl)argentate, [Ph₃P=N= PPh₃][Ag(C₂F₅)₂] (1) and bis[bis(triphenylphosphoranyliden)ammonium]tetrachloro-diargentate, [Ph₃P=N=PPh₃]₂[ClAg(μ-Cl)₂AgCl] (2) were crystallized from the reaction mixture of pentafluoroethylsilver(I) and bis(triphenylphosphoranyliden)ammonium chlo-ride. Crystallization of 1 occurs in the centrosymmetric monoclinic space group P2₁/c (No. 14) with a = 17.083(2) Å, b = 11.600(2) Å, c = 19.833(2) Å, β = 109.66(1)°, V = 3700.8(7) ų, Z = 4. 2 crystallizes in the centrosymmetric orthorhombic space group Pbca (No. 61) with a = 19.540(1) Å, b = 15.926(1) Å, c = 20.160(1) Å, V = 6273.6(3) ų, Z = 8.     

Organometallic derivatives of N-phenylmaleimidetriazoles and quinonetriazoles

The syntheses, properties, and structures of Mn, Cr, Re, and W organometallic derivatives of N-phenyl-1,2,3-triazoles and quinone-1,2,3-triazoles are described. The X-ray structures of eleven compounds are described. 9, a = 11.588(2), b = 11.904(2), 14.179(2) Å, α = 69.407(3)°, β = 70.879(3)°, γ = 78.627(3)°, P-1, R = 0.0739. 10, a = 7.643(1), 9.375(1), 13.077(2) Å, α = 74.292(2)°, β = 74.763(2)°, γ = 71.694(2)°. P-1, R = 0.0415. 11, a = 14.325(4) Å, b = 17.508(5) Å, c = 15.465(5), β = 99.282(5)°, P2/n, R = 0.0610. 17, a = 7.679(2) Å, b = 9.273(2) Å, c = 13.084(3) Å, α = 75.166(3)°, β = 74.651(3)°, γ = 71.613(3)°, P-1, R = 0.0428. 18, a = 5.757(1), 13.470(3), 23.056(4) Å, P2₁2₁2₁, R = 0.0697. 19, a = 8.118(1) Å, b = 10.471(2), 15.027(2) Å, α = 72.848(2)°, β = 82.237(2)°, γ = 71.829(2)°, P-1, R = 0.0597. 23, a = 7.993(1), 9.302(1) Å. C = 13.318(2) Å, α = 94.471(2)°, β = 105.269(2)°, γ = 109.523(2)°, P-1, R = 0.0271. 24, a = 7.583(4), 9.595(5), 13.030(6) Å, α = 76.389(7)°, β = 74.883(7)°, γ = 71.102(7)°, P-1, R = 0.0502. 26, a = 32.757(5) Å, b = 6.7083(9) Å, c = 26.033(4) Å, β = 128.895(5)°, C2/c, R = 0.0489. 31, a = 8.302(2), 8.347(2), 13.794(4) Å, α = 85.749(4)°, β = 81.176(4)°, γ = 74.849(4)°, P-1, R = 0.0400. 32, a = 11.321(2) Å, b = 12.110(2), 18.179(3) Å, β = 103.951(3)°, P2₁/c, R = 0.0318.     

Crystal structure of 2,8,14,20-tetranaphthylpyrogallol[4]arene

The aromatic derivative 2,8,14,20-tetranaphthylpyrogallol[4]arene was synthesized by the acid catalyzed condensation of 2-naphthaldehyde and pyrogallol in refluxing aqueous ethanol. Single crystal X-ray analysis revealed that the molecule crystallizes in a triclinic space group P1(bar) No. 2, with a = 11.3396(7) Å, b = 15.9942(10) Å, c = 26.3653(17) Å, α = 94.309(2)°, β = 91.765(2)°, γ = 93.892(2)°, D _calc = 1.298 g/m³ for Z = 1. Within the unit cell, six methanol molecules of crystallization plus one molecule of pyrazine were found to accompany the pyrogallol macrocycle. In the solid state, the macrocycle is found to adopt the chair conformation.     

Synthesis and characterization of carboxylate-bridged copper(II) dinuclear complex

The dinuclear copper(II) complex {[Cu(pmea)Cl][Cu(H₂O)₃Cl]}(Cl)·H₂O (1) (pmea =bis(2-pyridylmethyl)amino-2-ethanoic acid) has been synthesized and characterized. It crystallizes in the monoclinic system P2₁/c, a = 9.0057(11), b = 28.031(3), c = 8.5669(10) Å, β = 104.267(2)°, V = 2095.9(4) ų, Z = 4. Crystal structure of 1 reveals a syn-anti carboxylate-bridged dinuclear complex, in which the coordination environment around each copper atom exhibits a distorted square-pyramid. Magnetic susceptibility measurement for 1 exhibits a weak intermolecular antiferromagnetic exchange interaction with 2J = −1.17(9) cm⁻¹. The cyclic voltammogram of 1 gives one oxidation and two reduction processes.     

Crystal structure of cis-[Rh(biq)2Cl2]Cl·3H2O: Solid-state characterization and crystal packing analysis

The title compound, cis-[Rh(biq)₂Cl₂]Cl·3H₂O (biq = 2,2′-biquinoline) crystallized in the monoclinic space group P2 ₁ /n with a = 11.231(2) Å, b = 20.895(4) Å, c = 14.081(3) Å, β = 94.76(3)°, V = 3293.0(11) ų, D _c = 1.565 g cm⁻³, μ = 0.806 mm⁻¹, F(000) = 1576 and Z = 4. It contains a monomeric [Rh(biq)₂Cl₂]⁺ cation, a chloride ion and three molecules of H₂O. The rhodium(III) ion is hexa coordinated forming a distorted octahedral arrangement. The mean Rh(III)–N distance for the four Rh(III)–N bonds is 2.0625 Å. The two chloride atoms are bonded in a cis configuration [Rh(III)–Cl bond distances are 2.329(3) and 2.341(4) Å]. The structure shows a curling stacks of cationic complexes interacting via offset-face-to-face (OFF) π–π aryl interaction motif. Water molecules and chloride ions are hydrogen bonded (H₂O···H–OH and Cl···H–OH) and links the curling stacks by hydrogen bonding via Rh–Cl···H–OH interactions.     

Crystal structures and packing motifs of 2,3-diphenylquinoxaline and 2,3-diphenylbenzo[g]quinoxaline

White plates of 2,3-diphenylquinoxaline crystallize in the monoclinic space group P2₁/n with Z = 4 and a = 6.0325(3) Å, b = 10.9516(6) Å, c = 22.5985(13) Å, and β = 95.107(2)°. The phenyl rings in 2,3-diphenylquinoxaline form torsion angles of 36.88(5)° and 53.32(4)° with the plane defined by the quinoxaline moiety. Yellow plates of 2,3-diphenylbenzo[g]quinoxaline crystallize in the monoclinic space group C2/c with Z = 8 and a = 25.0621(16) Å, b = 7.7190(5) Å, c = 21.2225(14) Å, and β = 123.674(2)°. The phenyl rings in 2,3-diphenylbenzo[g]quinoxaline form torsion angles of 46.89(3)° and 43.42(3)° with the plane defined by the benzo[g]quinoxaline moiety. Packing in 2,3-diphenylquinoxaline can best be described as following the herringbone motif; whereas the packing in 2,3-diphenylbenzo[g]quinoxaline crystals can also be described as herringbone—albeit a herringbone pattern made up of head-to-tail oriented neighbors.     

Crystal structure of bis 4-benzyl piperidinium bis dihydrogenmonophosphate trihydrogenmonophosphate

The salt bis 4-benzyl piperidinium bis dihydrogenmonophosphate trihydrogenmonophosphate (bis 4-BPP bis DPT) is monoclinic with the following unit cell dimensions: a = 13.132(2) Å, b = 8.755(2) Å, c = 13.643(2) Å, β = 92.40(2)°, space group P2₁ with Z = 2. The structure was solved by the Patterson method and refined to final R value of 0.0430. The structure consists of infinite parallel two-dimensional planes built of mutually H₂PO₄ ⁻, H₃PO₄ tetrahedra and cations connected by strong O–H···O and N–H···O hydrogen bonding. There are no contacts other than van der Waals interactions between the layers.     

Synthesis and characterization of Bis(μ-sulfido)bis[{O,O-dimethyldithiophosphato}oxomolybdenum(V)]. Crystal structure of Mo2O2(Φ-S2)[S2P(OMe)2]2.C6H6

Bis(μ-sulfido)bis[{O,O-dimethyldithiophosphato}oxomolybdenum(V) was prepared by dropwise addition of an ethanolic solution of the ammonium salt of O,O-dimethyldithio-phosphoric acid to a hot aqueous solution of MoCl₅. The X-ray structure of Mo₂O₂(Φ-S₂)[S₂P(OMe)₂]₂.C₆H₆ was determined. Crystal data: Monoclinic, P2₁/n, a = 6.9788(6), b = 22.616(3), c = 14.633(1) Å, β = 101.193(9)°, V = 2265.5(4) Å⁻³, Z = 4. The immediate environment around the two molybdenum atoms is essentially square pyramidal if the Mo—Mo interaction is ignored. The terminal oxygen atoms are in the syn conformation.     

π–π Interactions in diimine Pt(II) complexes with thiacrown ligands: The crystal structure of (1,4,7-trithiacyclononane)(3,4,7,8-tetramethyl-1, 10-phenanthroline)platinum(II) hexafluorophosphate

We wish to report the crystal structure for the heteroleptic platinum(II) complex with the crown thioether 1,4,7-trithiacyclononane (9S3) and the diimine ligand 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen), [Pt(9S3)(tmphen)](PF₆)₂ (1). The Pt(II) center is surrounded by a cis-S₂N₂ ligand environment formed by the bidentate diimine and two of the three sulfur atoms from the 9S3 ligand. These two sulfurs are positioned 2.2665(10) and 2.2612(11) Å from the Pt(II), but the third sulfur shows a long distance interaction at 2.8849(13) Å to form an elongated square pyramidal structure. An examination of the structure reveals π–π-intermolecular stacking of the phen groups with alternating distances of 3.53 and 3.62 Å between the planes of the phen ligands. A detailed survey of 12 other divalent Pt(II) and Pd(II) diimine complexes of 9S3 reveals three different stacking motifs involving π–π interactions in the solid state. Crystal Data for (1): P-1, a = 10.868(2) Å, b = 11.292(2) Å, c = 11.513(2) Å, α = 93.76(3)°, β = 90.82(3)°, γ = 92.28(3)°, V = 1408.5(5) Å³, Z = 2.

Knoevenagel condensation of the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione with 9-anthracenecarboxaldehyde: Synthesis of the second-generation ligand 2-(anthracen-9-ylidene)-4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione

The Knoevenangel condensation between 9-anthracenecarboxaldehyde and the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione (bpcd) takes place rapidly in CH₂Cl₂/MeOH solution in the presence of molecular sieves (4 ?) to produce the functionalized ligand 2-(anthracen-9-ylidene)-4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione. The title compound has been isolated and characterized in solution by IR, NMR, and UV-vis spectroscopies, and the solid-state structure has been established by X-ray diffraction analysis. 2-(anthracen-9-ylidene)-4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione crystallizes in the triclinic space group P−1, a=10.227(2) ?, b=13.865(2) ?, c=15.905(2) ?, α=112.157(2)°, β=101.424(2)°, γ=100.065(3)°, V=1968.5(5) ?³, Z=2, and d _calc=1.101 Mg/m³; R=0.0873, R _w=0.2604 for 7452 reflections with I>2σ(I). The cyclic voltammetric behavior for 2-(anthracen-9-ylidene)-4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione has been studied, and the observed redox data and results from extended Hückel MO calculations are discussed relative to the parent ligand bpcd.

Synthesis and crystal structure of 5,7-diallyloxy-4-methylcoumarin

The title compound, 5,7-diallyloxy-4-methyl-2H-[1]-benzopyran-2-one, (C₁₆H₁₆O₄), was prepared by condensation of ethyl acetoacetate with phloroglucinol followed by allylation of the 5,7-dihydroxy-4-methylcoumarin thus obtained. The compound crystallizes into monoclinic space group P2₁/c with unit cell parameters a = 7.531(1) Å, b = 22.596(4) Å, c = 8.090(1) Å, β = 92.74(2)°, Z = 4. The crystal structure was solved by direct methods using single crystal X-ray diffraction data and refined to R = 0.0596 for 2166 observed reflections. The coumarin moiety is perfectly planar, with dihedral angle between the two fused rings of 0.46(5)°. The two allyloxy groups have different behaviour, one of them being disordered. Molecules form chains of weak C–HO and C–Hπ hydrogen bonds.     

Synthesis and crystal structure of the copper(I) complex with 2-[(o-pyridyl)-sulfanylmethyl]-pyrimidine ligand

The reaction of a flexible monothioether ligand, 2-[(o-pyridyl)-sulfanylmethyl]-pyrimidine (L), with CuI leads to the formation of a novel complex [Cu₄I₄(L)₂] (1), which has been characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction analysis: monoclinic, space group P2₁/n, with a = 10.921(5), b = 10.824(5), c = 13.128(6) Å, β = 109.333(5)° and Z = 2. Single-crystal X-ray analyses show that complex 1 is tetranuclear structure with a distorted chair-like Cu₄I₄ skeleton. Cu···Cu interactions are found to exist in this tetranuclear molecule. In the packing mode of complex 1, there exist N⋯⋯⋯I weak interactions and intermolecular π–π contacts. These weak interactions not only stabilize the structure of complex, but also further link the tetranuclear molecules into a high-dimensional supramolecular architecture.     

X-ray crystal structures ofcis-bis(diphenylphosphinamide)tetracarbonylmolybdenum(0) andtrans-bis(N-methyl diphenylphosphinamide)tetracarbonylmolybdenum(0)

The X-ray crystal structures ofcis-Mo(CO)₄(Ph₂PNH₂)₂,I, andtrans-Mo(CO)₄(Ph₂PNHMe)₂,II, are presented. ComplexI crystallizes in the monoclinic space groupP2₁/c(a=13.433(1),b=12.2719(8),c=17.318(2)Å;=109.79(1)°;V=2686.1(8)ų;Z=4). ComplexII crystallizes in the triclinic space groupP¯1 (a=6.9986(8),b=10.328(1),c=11.241(2)Å,=107.58(1)°,=91.76(1)°, =101.28(1)°,V=756.1(4)ų,Z=1). The molybdenum coordination geometry in each complex is a slightly distorted octahedron. The molybdenum-carbon bond lengths for the carbonyls trans to phosphorus in complexI are shorter than those the carbonyls trans to other carbonyls. The average molybdenum-phosphorus distance inI (2.525(5)Å) is similar to those in other diphenylphosphinamide complexes and longer than the molybdenum-phosphorus distance inII in 2.4585(7)Å). The distance between two nitrogen atoms incis Mo(CO)₄(Ph₂PNH₂)₂ (3.74(3)Å) is significantly larger than the sum of their van der Waals radii (3.10 Å) indicating that the two nitrogens are not hydrogen bonded.     

6α,7α-epoxy-5α,17α,dihydroxy-1-oxo-22R-witha-2,24-dienolide in leaves of Withania somnifera: Isolation and its crystal structure

6α,7α-epoxy-5α,17α,dihydroxy-1-oxo-22R-witha-2,24-dienolide (C₂₈H₃₈O₆) was isolated from Withania somnifera leaves. The structure of the withanolide was established by spectral analysis and X-ray diffraction studies as withanone. The compound crystallizes in the orthorhombic space group P2₁2₁2₁ with unit cell parameters: a = 9.191(10) Å, b = 12.858(6) Å, c = 21.400(16) Å, Z = 4. The crystal structure was solved by direct methods and refined to R = 0.0603 for 1742 observed reflections. There is positional disorder of the H atom in a hydroxy group (O5), resulting in two possible hydrogen-bond linkages. All the rings of the steroid skeleton are trans connected. Ring A exists in a half-chair conformation, ring B is intermediate between a half-chair and a sofa, ring C a distorted chair, and five-membered ring D is intermediate between a half-chair and an envelope. The δ-lactone ring E adopts a sofa conformation. The twist along the length of the steroid nucleus is negligible [C19–C10…C13–C18=1.8°]. Both the hydroxy groups are involved in hydrogen bonding.