Reaction Of Cis Research Articles

Ion-molecule reactions ofcis- andtrans-cyclopropane derivatives with methane, acetone and vinyl acetate under chemical ionization conditions

Ion–molecule reactions of four isomeric cyclopropane derivatives were investigated under chemical ionization(CI) conditions, using methane, acetone and vinyl acetate as reagent gases. The methane positive-ion CI mass spectra of each of two isomer pairs 1,2 and 3,4 are identical, and so are the collision-induced dissociation (CID) spectra of the protonated molecules of each of the two isomer pairs. The protonation reactions for the isomer pairs 1,2 and 3,4 occurred on the sites of the carboxyl groups and the R groups, respectively. Differences between isomers 1 and 2 are observed in their acetone (A) positive-ion CI mass spectra and in the CID spectra of their adduct ions ([M+H+A]+). The adduct ions of compounds 2, 3 and 4 with protonated acetone and with protonated acetone dimer are observed in their CI mass spectra. However, only the adduct ions of compound 1 with protonated acetone appear in its CI mass spectrum. The protonated dimers of each of the four compounds are found in their vinyl acetate positive-ion CI mass spectra, and the CID spectra of these dimers for isomers 1 and 2 can also reflect their stereostructural difference. © 1998 John Wiley & Sons, Ltd.

Synthesis, structure and properties of new dithiolene complexes containing a 1,3,5-trithiepin ring

Mono-tetrabutylammonium salts of nickel, copper, and gold 1,3,5-trithiepin-6,7-dithiolato (ttdt) complexes1a–c have been prepared and the structures of 1b and 1c determined by X-ray crystallography. Cyclic voltammograms of these complexes showed oxidation peaks in the range 0.23–0.46 V (vs. SCE). Partially oxidised salts of these complexes were obtained either as amorphous or polycrystalline solids. The electrical conduction properties are reported. The crystal structure of (TTF)[Au(ttdt)2 ] obtained from the reaction of 1c and TTF3(BF4)2 was determined by X-ray crystallography.

Dichlorogermylene‐Alkyldichlorophosphane Reactions Revisited: Characterisation of Bis(trichlorogermyl)phosphanes, Trichlorogermyldiphosphanes, and Ge‐P Heterocycles

AbstractThe reactions of alkyldichlorophosphanes 1 (RPCl2; R = tert‐butyl: 1a, R = isopropyl; 1b, R = 1‐adamantyl: 1c) with the germanium dichloride dioxane complex were followed by 31P NMR. Depending on the organic substituents and the reaction conditions, mixtures of trichlorogermylphosphanes RP(GeCl3)2 4a‐c, RPHGeCl3 5a‐c, diphosphanes R(H)PP(H)GeCl3 6a‐c, R(Cl)PP(H)GeCl3 7a, b cyclophosphanes, and Ge‐P heterocycles such as triphosphadigermolanes (RP)3(GeCl2)2 8a, b and tetraphosphagermolane (RP)4)GeCl2 10b are formed. As a further unexpected byproduct of the reaction of 1a with GeCl2–dioxane, a small amount of tri‐tert‐butyl(trichlorogermyl)cyclotetraphosphane 9a was isolated. From the reaction of 1c with two equivalents of GeCl2–dioxane, separation from byproducts 5c and 6c by crystallisation furnished colourless crystals of 4c (R = 1‐adamantyl) as the first pure organylbis(trichlorogermyl)phosphane. Surprisingly, the reaction of isoprophylphosphane with germanium tetrachloride, intended to prepare 5a, led to crystalline isopropylphosphonium trichlorogermanate(II) 11. The structures of molecular 4c and 9a and ionic 11 were determined by X‐ray crystallography.

Dissolving Metal Reductions of Fullerenes

Treatment of fullerenes with reducing metals and a proton source leads to the formation of hydrogenated fullerenes (C60Hn and C70Hn). The reaction of C60 with a variety of metals was investigated, using metals that span a broad range of reducing power, from tin (E° = −0.14 V) to magnesium (E° = −2.36 V). We report useful synthetic routes to a number of reduced fullerenes, including C60H2, C60H4, and C60H6, and we have determined that, despite the huge number of isomers that are possible, a small number are actually formed in these cases. For example, only two isomers of C60H6 are obtained in the Zn(Cu) reduction of C60, in a 6:1 ratio. Three isomers of C70H10 are produced, in ratios that are dependent on reaction time.

A quantum chemical study of the isomers of bis(methano)fullerene, C60(CH2)2

Building on past success using quantum chemical predictions of relative isomer stabilities in guiding the synthesis of the hydrofullerenes C60H2C60H4 and C70H2, semiempirical and ab initio methods are used to examine the eight isomers of bis(methano)fullerene, C60(CH2)2. The calculated lowest energy structure has two-CH2- units bridging adjacent junctions between six-membered rings. Structural and energetic comparisons are made between the C60(CH2)2 isomers and the analogous forms of C60 H4. From a thermodynamic point of view, it is predicted that reactions of C60 that product C60(CH2)2 (and C60(CR2)2) will yield mixtures of isomers, and not a few discrete products as found for the hydrofullerenes.

A quantum chemical study of the isomers of bis(methano)fullerene, C60 (CH2)2

Building on past success using quantum chemical predictions of relative isomer stabilities in guiding the synthesis of the hydrofullerenes C60H2C60H4 and C70H2, semiempirical and ab initio methods are used to examine the eight isomers of bis(methano)fullerene, C60(CH2)2. The calculated lowest energy structure has two-CH2- units bridging adjacent junctions between six-membered rings. Structural and energetic comparisons are made between the C60(CH2)2 isomers and the analogous forms of C60 H4. From a thermodynamic point of view, it is predicted that reactions of C60 that product C60(CH2)2 (and C60(CR2)2) will yield mixtures of isomers, and not a few discrete products as found for the hydrofullerenes.

Reaction of C60 with Oxygen Initiated by Radicals from Azo(Bisisobutyronitrile)

In an o-dichlorobenzene solution exposed to an atmosphere of air or pure oxygen, C60 reacts with radicals generated by thermal decomposition of azo(bisisobutyronitrile) and with oxygen to form mixtures of highly substituted and oxygenated monomelic, dimeric, and trimeric derivatives. LSIMS, LDMS, and SIMS (Liquid Secondary Ion, Laser Desorption, and Secondary Ion Mass Spectrometry) of these mixtures give clusters of peaks for C2n from C40 to greater than C200. Elemental analyses show large H, N, and 0 contents that increase with the amount of AIBN and the partial pressure of oxygen during the reaction. 1H and 13C NMR spectra consist of broad bands assigned to complex mixtures of substituted fullerenes containing many 2-cyano-2-propyl groups derived from AIBN. Diffuse reflectance infrared spectra show hydroxyl and carbonyl functional groups. Thermal gravimetric analysis (TGA) of the mixture prepared under oxygen retained 40% of the initial weight at 640 °C, while <19 % of the initial weight remained from the mixture prepared under argon.

Dimerization reaction of C60

Dimerization reaction of C60

Methanofullerene Molecular Scaffolding: Towards C60‐substituted poly(triacetylenes) and expanded radialenes, preparation of a C60–C70 hybrid derivative, and a novel macrocyclization reaction

AbstractThe synthesis of (E)‐hex‐3‐ene‐l, 5‐diynes and 3‐methylidenepenta‐1, 4‐diynes with pendant methano[60]‐fullerene moieties as precursors to C60‐substituted poly(triacetylenes) (PTAs, Fig. 1) and expanded radialenes (Fig. 2) is described. The Bingel reaction of diethyl (E)‐2, 3‐dialkynylbut‐2‐ene‐1, 4‐diyl bis(2‐bromopropane‐dioates) 5 and 6 with two C60 molecules (Scheme 2) afforded the monomeric, silyl‐protected PTA precursors 9 and 10 which, however, could not be effectively desilylated (Scheme 4). Also formed during the synthesis of 9 and 10, as well as during the reaction of C60 with thedesilylated analogue 16 (Scheme 5), were the macrocyclic products 11, 12, and 17, respectively, resulting from double Bingel addition to one C‐sphere. Rigorous analysis revealed that this novel macrocyclization reaction proceeds with complete regio‐ and diastereoselectivity. The second approach to a suitable PTA monomer attempted N, N′‐dicyclohexylcarbodiimide(DCC)‐mediated esterification of (E)‐2, 3‐diethynylbut‐2‐ene‐l, 4‐diol (18, Scheme 6) with mono‐esterified methanofullerene‐dicarboxylic acid 23; however, this synthesis yielded only the corresponding decarboxylated methanofullerene‐carboxylic ester 27 (Scheme 7). To prevent decarboxylation, a spacer was inserted between the reacting carboxylic‐acid moiety and the methane C‐atom in carboxymethyl ethyl 1, 2‐methano[60]fullerene‐61, 61‐dicarboxylate (28, Scheme 8), and DCC‐mediated esterification with diol 18 afforded PTA monomer 32 in good yield. The formation of a suitable monomeric precursor 38 to C60‐substituted expanded radialenes was achieved in 5 steps starting from dihydroxyacetone (Schemes 9 and 10), with the final step consisting of the DCC‐mediated esterification of 28 with 2‐[1‐ethynyl(prop‐2‐ynylidene)]propane‐1, 3‐diol (33). The first mixed C60‐C70 fullerene derivative 49, consisting of two methano[60]fullerenes attached to a methano[70]fullerene, was also prepared and fully characterized (Scheme 13). The Cs‐symmetrical hybrid compound was obtained by DCC‐mediated esterification of bis[2‐(2‐hydroxy‐ethoxy)ethyl] 1, 2‐methano[70]fullerene‐71, 71‐dicarboxylate (46) with an excess of the C60‐carboxylic acid 28. The presence of two different fullerenes in the same molecule was reflected by its UV/VIS spectrum, which displayed the characteristic absorption bands of both the C70 and C60 mono‐adducts, but at the same time indicated no electronic interaction between the different fullerene moieties. Cyclic voltammetry showed two reversible reduction steps for 49, and comparison with the corresponding C70 and C60 mono‐adducts 46 and 30 indicated that the three fullerenes in the composite fullerene compound behave as independent redox centers.

Gas-Phase Ion-Molecule Reactions of C60 and Theoretical Studies of [C60C2H3O]+ Adduct Cations

Gas-phase ion-molecule reactions of buckminsterfullerene (C-60) with the acetyl cation CH3-C-+=O (m/z 43) and formylmethyl cation (CH2)-C-+-CH=O (m/z 43, or oxiranyl cation), generated from the self-chemical ionization of acetone and vinyl acetate, respectively, were studied in the ion source of a mass spectrometer. Adduct cations [C60C2H3O](+) (m/z 763) and protonated C-60, [C60H](+) (m/z 721), were observed as the major products. AM1 semiempirical molecular orbital calculations on the possible structures, stabilities and charge locations of the isomers of the adducts [C60C2H3O](+) were carried out at the restricted Hartree-Fock level. The results indicated that the sigma-addition product [C-60-COCH3](+) is the most stable adduct for the reaction of C-60 with CH3-C-+=O rather than that resulting from the [2+2] cycloaddition. The [2+3] cycloadduct and the sigma-adduct [C60CH2CHO](+) might be the most possible coexisting products for the reactions of C-60 with (CH2)-C-+-CH=O or oxiranyl cation. Other [C60C2H3O](+) isomers are also discussed. (C) 1997 by John Wiley & Sons, Ltd.

Eindimensionale Kupfer(II)-Koordinationspolymere: Kristall-Engineering durch variable Verknüpfungsmuster [1] / One Dimensional Copper(II) Coordination Polymers: Crystal Engineering through Variable Types of Linkage [1

Reaction of a methanolic copper(II) acetate solution with tetrazolyl enol derivatives 2a or 2b leads to the formation of the corresponding lD-coordination polymer 1 ∞[CuL2] 3a and pseudo 1D-coordination polymer [CuL2]2 3b, respectively. On the contrary, reaction of 2c with methanolic copper(II) acetate solution yields OH-bridged 1D-coordination polymer 1 ∞[CuL2(MeOH)2 3c. Single-crystal X-ray diffraction of the supramolecular species 3 established unequivocally the structures of the stairlike coordination compounds. Reaction of a methanolic copper(II) acetate solution with amidotetrazole derivative 6 leads to the formation of the lD-coordination polymer 1 ∞ [CuL2] 7. The structure of 7 has been established by X-ray structure analysis

Synthesis, characterisation, reactivity and stereochemical studies of heterobimetallic complexes containing an orthometallated cyclopentadienylphosphine bridge

The heterobimetallic diastereoisomer complexes [X(η 5 -C 5 H 5 )Mo{(η 5 -C 5 H 4 )PPh(o-C 6 H 4 )}M(CO) 5 ] (X = Cl 1 and 1′ or I 2 and 2′; M = Cr a, Mo b or W c) containing an orthometallated cyclopentadienylphosphine bridge have been prepared and characterised. They were obtained by reaction of Li[M(CO) 5 (PPh 2 )] and the corresponding metallocene dichloride in tetrahydrofuran. The crystal structures of 1a and 2c showed that the η 5 -C 5 H 4 PPh[M(CO) 5 ]C 6 H 4 fragment chelates the Mo. Similarly, methylated complexes 3 were prepared when [Mo(η 5 -C 5 H 4 Me) 2 Cl 2 ] was used as metallocene dichloride; the 1,3 regioselectivity of these reactions has been assigned on the basis of 1 H and 31 P NMR data. Compound 1c reacted with LiAlH 4 to give a dihydride molybdenocene complex [H(η 5 -C 5 H 5 )Mo(η 5 -C 5 H 4 PPh 2 )HW(CO) 4 ]. Alkylated diastereoisomers [R(η 5 -C 5 H 5 )Mo{(η 5 -C 5 H 4 )PPh(o-C 6 H 4 )}M(CO) 5 ] (R = Me or Et) were obtained by reaction of 1c with a Grignard reagent; cleavage of the Mo–Me bond with hydrochloric acid has been found to occur with retention of configuration.

Structural diversity of tetranuclear tungsten sulfide clusters: syntheses and crystal structures of clusters containing raft-type W4(μ3-S)2(μ-S)4 and tetrahedral W4(μ-S)6 cores

Reaction of cis-[W(N 2 ) 2 (PMe 2 Ph) 4 ] 1 with 2 equivalents of (Me 3 Si) 2 S in the presence of an excess of MeOH gave a tetranuclear tungsten sulfide cluster [W 4 (µ 3 -S) 2 (µ-S) 4 (SH) 2 (PMe 2 Ph) 6 ] 2. Substitution of chloride anions for the terminal SH ligands in 2 took place on reaction with 1 equivalent of SnCl 2 , giving the isostructural W 4 cluster [W 4 (µ 3 -S) 2 (µ-S) 4 Cl 2 (PMe 2 Ph) 6 ] 3. Both 2 and 3 with ten skeletal electrons consist of an almost equilateral raft-type W 4 framework with five metal–metal bonds. On treatment with 2.4–3 equivalents of AgOSO 2 CF 3 , compound 3 underwent two-electron oxidation to give [W 4 (µ 3 -S) 2 (µ-S) 4 Cl 2 (PMe 2 Ph) 6 ][OSO 2 CF 3 ] 2 4, which has a distorted raft-type W 4 core owing to the presence of only eight skeletal electrons. On the other hand, reduction of 3 with an excess of Na/Hg resulted in formation of the twelve-skeletal-electron cluster [W 4 (µ-S) 6 (PMe 2 Ph) 4 ] 5 containing a tetrahedral W 4 core with six W–W bonds. The detailed structures of 2–5 were determined by single-crystal X-ray diffraction.

Dependence of hydrolytic cleavage of histidine-containing peptides by palladium(II) aqua complexes on the co-ordination modes of the peptides

S. U. Milinković, T. N. Parac, M. I. Djuran and N. M. Kostić, J. Chem. Soc., Dalton Trans., 1997, 2771 DOI: 10.1039/A701491K

The Dark Reaction of C60 and of C70 with Molecular Oxygen at Atmospheric Pressure and Temperatures between 300 K and 800 K

The solid fullerenes C60 and C70 react in deliberate and adventitious situations with molecular oxygen in a wide range of temperatures. Using thin films and polycrystalline bulk samples with well-defined structures and chemical histories we investigated the complex process from molecular intercalation over atomic adduct formation to deep oxidation and polymerisation which together describe the oxidation reaction. A combination of photoemission (UPS, XPS) photoabsorption (XAS), FT-IR, temperature-programmed and isothermal gravimetric measurements and DSC allowed to identify the existence and gradual interconversion of the three types of solid products besides the gas phase products CO and CO2. Both fullerenes react along the same reaction path. The difference of the molecular structures results in different activation barriers in the initial step of intercalation and in the final step of cage-opening. The overall reactivity of both fiiHerenes is quite similar at temperatures above the gasification onset of 570 K. The formation of the various adduct compounds was found to exert a detectable influence upon the overall molecular shape of the fiiHerenes and a small effect on the electronic structure was observed. The only moderate differences in electronic and geometric structures of pristine and initially oxidised fullerenes precludes a pronounced molecule-by-molecule reaction control and allows the topochemistry of the intercalation to control the shape of the reaction interface. This control is less effective for C70 than for the C60 fullerene.

Kinetic and thermodynamic studies of carbon monoxide insertion in alkylosmium(II) complexes and comparison with iron(II) and ruthenium(II) isoelectronic complexes

The equilibrium constants of the reaction of cis,trans-[Os(CO) 2 (PMe 3 ) 2 (Me)I] 1c with carbon monoxide to give cis,trans-[Os(CO) 2 (PMe 3 ) 2 (COMe)I] 2c have been measured and compared with the values obtained for the isoelectronic complexes of iron and ruthenium. The kinetics of the above reaction as well as of the analogous insertion reaction with C 6 H 11 NC, which affords trans-[Os(CO)(PMe 3 ) 2 (C 6 H 11 NC)(COMe)I] 3, has been investigated. The results are interpretable by the methyl migration mechanism. The crystal structure of the new complex 3 has been determined. Furthermore, the isomer trans,trans-[Os(CO) 2 (PMe 3 ) 2 (Me)I] 1t has been synthesized by the photochemical isomerization of 1c in the solid state. The spectroscopic properties of the cis,trans (c) and trans,trans (t) isomers for the triad Fe, Ru and Os are compared.

Full-potential linear muffin-tin orbital calculation of atomic forces and optimization of atomic structure of fullerence epoxide derivatives C60O and C60O2

Atomic force calculations and the optimization of atomic structure in the ground state have been made in the cluster version of the full-potential linear muffin-tin orbital method. Relaxation along atomic forces in the ground state enabled us to estimate the main parameters of the atomic structure and total energy in the ground state of fullerene epoxide derivatives C60O and C60O2, obtained recently in the reaction of C60 with ozone in toluene. We found the C60O isomer, with the oxygen atom bridging the 6.6 carbon bond, to be more stable than that with the oxygen atom bridging the 6,5 bond. The most polar isomer of C60O2 with the oxygen atoms placed at the same 6,6 ring, is found to have the lowest energy compared with other bridgings of oxygen atoms, in agreement with experimental data.

4‐Cyano‐2‐oxo‐1,2,4‐oxadiazolo[2,3‐a]quinoxaline 5‐N‐oxides. New synthetic method and reaction with alcohols. Potential cytotoxic activity

AbstractSeveral quinoxaline 1,4‐di‐N‐oxides have been shown to be efficient and selective cytotoxins for hypoxic cells. We present now a series of 4‐cyano‐2‐oxo‐1,2,4‐oxadiazolo[2,3‐a]quinoxaline 5‐N‐oxides 2a‐2k. They were prepared starting from 3‐amino‐2‐quinoxalinecarbonitrile 1,4‐di‐N‐oxides 1a‐1k and 2‐chloroethyl isocyanate in dry dioxane at 100–110°. A reaction mechanism is proposed. The treatment of 1a with phenyl isocyanate afforded 2a. Reaction of 2c with silica gel yielded 1c. Compounds 2a‐2g were heated in the presence of ethanol and 2‐propanol giving the corresponding carbamates 3a‐3g and 4a‐4g. Compound 2d was already obtained by heating a mixture of 1d and ethyl chloroformiate. Compound 2b was prepared when the carbamate 3b was heated at 150°. Quinoxalines were tested as cytotoxic agents both in oxic and hypoxic cells. The most interesting compounds were 3g and 4g.

Highly Selective Synthesis of Methyl 1-Phenyl-1-(9-hydro-)fullerenylacetate

Abstract Isomerically pure methyl 1-phenyl-1-(9-hydro-)fullerenylacetat is synthesized in 75% yield by the reaction of C60 with the carbanions of methyl phenylacetate in C6H6/THF mixed solvent under a purified N2 atmosphere at 20°C.

Reaction of C60 with α-Diazoketones: Methano- and Dihydrofuranofullerenes

The reaction of C60 2 with α-diazoketones 1 leads to 6,6-bridged, closed 1,2-methano[60]fullerenes 4a - e and - after their rearrangement on the C60 surface - to 2’-substituted 6,6-bridged, closed 1,2-dihydro-(4’,5’-dihydrodurano)-[60]fullerenes 5a, d, e.