(E)‐2‐(2‐Adamantylidene)‐3‐(1‐ferrocenylethylidene)succinic anhydride

The title compound, [Fe(C₅H₅)(C₂₁H₂₁O₃)], was obtained from successive Stobbe condensations between ketones and di­methyl succinate. The succinic anhydride five‐membered ring is distorted significantly from planarity, with the buta­diene moiety being twisted by 49.3 (2)° from planarity and the C atoms at the succinic anhydride end of the alkene bonds showing significant pyramidalization. The cyclo­penta­diene rings of the ferrocenyl moiety adopt an almost eclipsed conformation.     

Di­chloro­(norborna­diene)­platinum(II): a comparison with di­chloro­(cyclo­octa­diene)­platinum(II)

The crystal structure of the title compound, (bi­cyclo­[2.2.1]­hepta‐2,5‐diene)­di­chloro­platinum(II), [PtCl₂(C₇H₈)], has been determined from single‐crystal X‐ray analysis. The coordination sphere about the Pt atom is pseudo‐square planar, with shorter Pt—C distances than in the corresponding di­chloro­(cyclo­octa­diene)­platinum(II) complex.     

The crystal and molecular structure of 1,1,4,4-tetraethyl-2,5-dimethyl-1,4-diphosphoniacyclohexadiene-1,4-dibromide

The structure of the title compound has been determined by a single-crystal, x-ray diffraction study. The compound crystallizes in a monoclinic unit cell (P2₁/c) with two molecules per unit cell. Least-squared lattice parameters are: a = 7.164 ± 0.001Å, b = 14.770 ± 0.001Å, c = 10.562 ± 0.001Å, and β = 124.95 ± 0.01°. The structure parameters refined to a value of R=0.06₂, excluding hydrogens, for the 1475 statistically significant reflections. The structure determination confirmed that the compound is indeed a diene and not a delocalized structure. The ring is planar but the ethyl groups extend over the ring in an unusual crab-like fashion.     

Acetic anhydride at 100 K: the first crystal structure determination

Acetic anhydride (ethanoic anhydride), (CH₃CO)₂O, is a widely used acetylation reagent in organic synthesis. The crystal and molecular structure, as determined by single‐crystal X‐ray analysis at 100 K, is reported for the first time. A crystal of the title compound (m.p. 200 K) suitable for X‐ray diffraction was grown from the melt at low temperature. The title compound crystallizes in the orthorhombic space group Pbcn, with Z = 4. In the crystal, the molecule adopts an exact C₂‐symmetric conformation about a crystallographic twofold axis. The molecules are densely packed. Two of the methyl H atoms form short intermolecular contacts to a neighbouring carbonyl O atom, which can be viewed as weak hydrogen bonds.     

The crystal and molecular structure of 3,5-Di-(t-butyl)-1-phenylphosphoryl-4-aza-2,5-cyclohexadiene

The crystal and molecular structure of the title compound (C₁₈H₂₆NOP) has been determined by a single crystal, x-ray diffraction study using Cu-Kα. radiation. The compound was found to crystallize in the orthorhombic space group Pnma with unit cell constants a = 12.686 ± .001 Å, b = 14.776 ± .001 Å, and c = 9.540 ± .001 Å. The structure was solved by the heavy atom method and refined by block-diagonal least-squares to a final R = 0.09₉ for the 696 statistically significant reflections. The compound exhibits orientational disorder in the crystalline state. Nevertheless, the planarity of this ring; the lengthening of the diene carbon-carbon bond to 1.41 Å the resultant shortening of both the carbon-nitrogen bond (1.43 Å) and the carbon-phosphorus bond (1.74 Å), and the CNC bond angle of 121° all strongly support the assumption of delocalization of the diene π-electrons within the heterocyclic ring system.     

The mechanism of formation of π-allyl complexes: The reaction of PdCl2−4 with isoprene in methanol

A kinetic study of the reaction between PdCl^2?₄ and isoprene is described. The results are interpreted in terms of the formation of two π-complexes between palladium(II) and isoprene, one having only one double bond coordinated to the metal, the other being a chelated diene compound. Nucleophilic attack of solvent methanol on these intermediate complexes gives the methoxy π-allyl complex.     

Crystal and Molecular Structures of (η4-Cyclohexa-1,3-Diene) (2-Tert-Butyl-1,1,4,4-Tetrafluoro-1,4-Disilabutene) Metal Carbonyls. M?Fe,W

Molecular structures of the two title compounds were investigated to reveal the relationship between the structure of the reaction intermediates and the reaction pathways in the transition metal-mediated cycloaddition reaction between tetrafluorodisilacyclobutene and conjugated dienes. The structures were determined by X-ray diffraction. Both cyrstals are orthorhombic. Compound I. C₁₄H₁₈O₂Si₂F₄Fe. is of space group P2₁2₁2₁ with Z=4; a=6.862(7) Å. b=10.9560(10) Å. c=23.597(25) Å. and Dc=1.562 gcm^?1. Compound II, C₁₅H₁₈O₃Si₂F₄W, is of space group Pbca with Z=8; a=16.999(8) Å, b=15.948(6), c=14.045(7) Å, and Dc=1.962 gcm^?1. Both structures were solved by heavy-atom methods and refined by full-matrix least-squares using anisotropic temperature factors for all non-hydrogen atoms to R values of 0.092 for 1544 observed reflections and 0.078 for 2751 observed reflections, respectively, for compound I and compound II. The butadiene segment of the cyclohexadiene ligand is essentially planar in compound I while it is twisted with a torsional angle of 22° (2) in compound II. The five-membered disilametallacycle ring is planar in compound II while ii is in an envelope comformation in compound I. The coordination geometry of the iron atom may be considered as a distorted tetragonal-pyramidal with the diene unit occupying the apical site, That of tungsten is a distorted seven-coordinated pentagonal-bipyramidal with the two axial carbonyl groups displaced toward the disilabutene ligand. The disilabutene of compound I lies almost parallel and cis to the plane of the butadiene segment while that of compound II orients almost perpendicular to the diene group. The differences in the structural features of the two complexes explain clearly their product patterns and the reactions are apparently stereo-controlled.     

Hexabromocyclopentadiene V. The Diels-Alder reaction of hexabromocyclopentadiene

The reactivity of hexabromocyclopentadiene (1) as a diene in the Diels-Alder reaction has been determined with a number of dienophiles. The results of the present study show that 1 behaves as an electron-poor diene in that cyclopentadiene is a more reactive dienophile than maleic anhydride. Qualitatively, 1 has been found to be a less reactive diene than hexachlorocyclopentadiene. Several new Diels-Alder adducts of 5,5-dibromo-1,2,3,4-tetrachlorocyclopentadiene are also reported.     

On the synthesis of pure (meth) acrylate esters and their corresponding homopolymers

We have observed that homopolymers of certain (meth)acrylate esters, prepared by the Schotten–Baumann method of (meth)acryloyl chloride and desired alcohol, in the presence of triethylamine or pyridine, formed gels. The mechanism of gelation was investigated and found to be due to a diene impurity, (meth)acrylic anhydride, which cannot be easily separated from many (meth)acrylate esters. For preparation of pure (meth)acrylate esters, the S_N2 displacement reaction of (meth)acrylate anion with the desired chloro compound is recommended. The yields of the two reactions are comparable, and even t-butoxycarbonylmethyl methacrylate is produced in 73% yield by the recommended method.     

Crystal and molecular structure of the mixed-ligand complex ZnPhen((i-C3H7O)2PS2)2

Bis(diisopropyldithiophosphato)zinc(II) Zni-PrO)₂PS_{2 2} (I) possesses high volatility, which is useful for gas-chromatographic determination of zinc [1]. In the solid state the compound has a dimeric structure [2]. As shown for dimeric zinc(II) dialkyldithiocarbamates and tetrameric zinc(II) alkylxanthates, reactions of these chelates with nitrogen heterocycles [1,10-phenanthroline (Phen) or 2,2′-bipyridyl (2,2′-Bipy)] form volatile mixed-ligand compounds having a monomeric structure [3, 4]. It is interesting to synthesize and study the mixed-ligand compounds of chelate I with nitrogen-containing heterocycles. Synthesis of a mixed-ligand complex of this chelate with Phen was reported in [5, 6] but no structure determination was performed for the compound. We synthesized the compound ZnPhen[(i-PrO)₂PS₂]₂ (II) using a slightly modified procedure [5], grew single crystals, and investigated its molecular and crystal structure. Translated from Zhumal Struktumoi Khimii, Vol. 41, No. 1, pp. 191-195, January-February, 2000.     

The crystal and molecular structure of 1,1,2,4,4,5-hexaphenyl-1,4-diphosphoniacyclohexadiene-2,5 dibromide

The crystal and molecular structure of 1,1,2,4,4,5-hexaphenyl-1,4-diphosphoniacyclohexadiene-2,5 dibromide has been determined by a single crystal, x-ray diffraction study using diffractometer data. The compound crystallizes in the space group P2₁/_c with unit cell constants a = 8.813(1), b = 36.736(4), c = 12.478(1) Å, and β = 120.91°(1). The structure was solved by the heavy atom method and refined by block-diagonal least-squares to a final R = 0.04 for the 2761 statistically significant reflections. The structure determination shows that the central phosphonium ring is a diene and not a delocalized structure as anticipated. The ring is in the boat conformation with the axial phenyl rings aligned essentially parallel to each other and 3.55 Å apart.     

The crystal structure of bis(triphenylphosphine)-(η-cyclohexa-1,3-diene)rhenium trihydride

Bis(triphenylphosphine)(η-cyclohexa-1,3-diene)rhenium trihydride, (Ph₃P)₂(η-C₆H₈)ReH₃ (I) crystallises in the space group C2/c with cell dimensions a 22.76(2), b 10.14(1) c 29.813(6) Å, β 97.69(8)°. The final refinement of 126 variables using 1580 non-zero reflections resulted in a final R value of 0.064. In spite of uncertainties in some of the atomic positions, the structure of I is compatible with a trihydrido diene compound with a distorted pentagonal bipyramidal configuration, rather than with a dihydrido cyclohexenyl compound having an “agostic” CH ? Re interaction. The factors which govern the structure of the complexes (Ph₃P)₂(η-1,3-diene)ReH₃ are discussed.     

Synthetic Approach Towards Hexaprismane. A Novel Entry to Homosecohexaprismane Skeleton by Cage Enlargement

A series of caged 1,4-diols, 26, 29a/29b, 31 , were synthesized from the Diels-Alder cycloadduct 21 of 1,2,3,4-tetrachloro-5,5-dimethoxycyclopentadiene and 1,4-benzoquinone. Reduction of enedione 21 with aqueous TiCl₃, followed by base-catalyzed enolization in the presence of acetic anhydride, gave diene 23b , which reacted with maleic anhydride and 1,4-benzoquinone to produce the corresponding [4+2] cycloadducts 24b and 27 , respectively. The adduct 24b was converted to birdcaged 1,4-diol 26 by photocyclization followed by decarboxylative olefination of resulted caged anhydride 25b . The adduct 27 was photocyclized to cage compound 28 , which was aromatized to dihydroquinone 29a by acid-catalyzed enolization, or benzo-annulated compound 31 by reduction and dehydration. The birdcaged 1,4-diols 26 and 31 underwent fragmentation induced by (diacetoxyiodo)benzene to give enediones 38/39 and 41/42 , respectively. Photocyclization of 38 and 39 produced the corresponding caged compounds 43 and 44 , respectively, possessing homosecohexaprismane skeletons. The corresponding monohydrate 43a of 43 was structurally characterized by single-crystal X-ray diffraction.     

Two polycyclic compounds derived from a Diels–Alder reaction

In both 9,10‐di­methoxy‐11‐oxatri­cyclo­[6.2.1.0^2,7]­undeca‐4,9‐diene‐3,6‐diol, C₁₂H₁₆O₅, (I), and 5,6‐di­methoxy‐3,7‐dioxa­tetra­cyclo­[6.4.0.0^2,6.0^4,12]­dodec‐9‐en‐11‐ol, C₁₂H₁₆O₅, (II), the hetero‐oxygen‐containing five‐membered rings have an envelope conformation. The six‐membered rings are in a boat conformation in compound (I), and in (II), one is in a half‐boat and the other is in a slightly distorted boat conformation. The mol­ecules in both compounds interact through classical hydrogen bonds and C—H?O contacts.     

A study of the reaction of bicyclo[5.1.0]octa-2,5-diene with sulphur dioxide

Thermally-induced reaction between bicyclo[5.1.0]octa-2,5-diene (I) and sulphur dioxide under dry conditions is toluene-d₈ as solvent leads to the unexpected formation of the hitherto unknown diene sulphone 7-thiabicyclo[4.2.1]nona-2,4-diene 7,7-dioxide (II).     

X-ray photoelectron spectra and structure of cobalt compounds with N-heterocyclic ligands

The electronic structure of cobalt complexes with bi-, tri-, and tetradentate ligands and the mutual influence of ligands in them have been studied by X-ray photoelectron spectroscopy. The Co2p, N1s, and O1s photoelectron spectra have been studied. Unlike low-spin Co(III) complexes, the high-spin Co(II) compound exhibits a strong satellite line in the Co2p spectrum. For the high-spin Co(II) compound having unpaired 3d electrons, the Co2p _1/2-Co2p _3/2 spin-orbit splitting is larger than that in the low-spin Co(III) complexes. All cobalt complexes under consideration contain strongly bound dioxygen, which can be considered an inherent structural unit.     

Theoretical insights into the reaction between vinylidenesilanediyl and double bond compounds (formaldehyde and methyleneimine): the formation of heterocyclic silylene and spiro-Si-heterocyclic compounds

Abstract

The reaction mechanism between vinylidenesilanediyl and doubly bonded compounds (formaldehyde and methyleneimine) has been systematically investigated employing the second-order Møller-Plesset perturbation theory (MP2) method in order to better understand the reactivity of vinylidenesilanediyl. Geometry optimizations and vibrational analyses have been performed for the stationary points on the potential energy surfaces of the system. Calculations show that the four-membered heterocyclic silylene intermediate and Si-heterocyclic conjugated diene compound could be produced through addition and rearrangement processes between vinylidenesilanediyl and double bond compound. The silylene intermediate can react with second formaldehyde (or methyleneimine) to form a spiro-Si-heterocyclic product. The present study is helpful to understand further characterization of the C₂H₂Si molecular system and to offer an alternative approach to the formation of heterocyclic silylene and spiro-Si-heterocyclic compounds.     

3,17‐Dioxoandrosta‐4,6‐dien‐11‐yl acetate

The synthesis and crystal structure analysis via X‐ray diffraction of the title compound, C₂₀H₂₄O₄, (I), are described. The title compound is an androstadione bearing a diene in the A and B rings [Krause & Thorand (1999). Inorg. Chim. Acta, 296 , 1–11]. The diene conjugates with the carbonyl group. Intermolecular H?O contacts (2.53 and 2.64 Å; C—H?O angles 161 and 158°) indicate hydrogen bonds.     

Solvation controlling reaction paths and gel-formation in imide derivatives

1,8-Naphthalic anhydride condenses with 4-nitro-1,2-diaminobenzene in acetic acid to give 11-nitrobenzo[d,e]benzo[2,1-a]isoquinoline-1,3-dione (1), whereas the same reaction carried out in DMF gives 2-(2-amino-4-nitrophenyl)-benzo[d,e]isoquinoline-1,3-dione (2). The condensation reaction of 1,8-naphthalic anhydride with 1-amino 3,5-benzene dicarboxylic acid leads to corresponding imide, which forms a gel in a mixed solvent such as water in DMSO. A similar compound 5-(1,3-dioxo-1,3-dihydroisoindol-2-yl)-isophthalic acid derived from phthalic anhydride forms gel in a mixed solvent of DMSO and water, whereas a crystalline solvate of DMSO with 2 could be obtained upon crystallization from DMSO. The crystal structure of this solvate is determined and its structure is compared with 2-(1,3-dioxo-1,3-dihydro-isoindol-2-yl)-benzoic acid. The latter does not form a gel in the mixed solvent and adopts an intermolecular hydrogen bonded structure.