Benzene Complexes Research Articles

Acid-catalysed cyclisations of cyclo-octenylidene derivatives to produce bicyclo[3.3.1]nonanes

Heating ethyl (cyclo-oct-4-enylidene)acetate (8) with boron trifluoride–ether complex in benzene gives a mixture of ethyl 1-phenylbicyclo[3.3.1]nonane-9-carboxylate (11) and the corresponding acid (12). Reduction of (11) with lithium aluminium hydride followed by dehydration yields 9-methylene-1-phenylbicyclo[3.3.1]nonane (14) whose structure was confirmed by an independent synthesis.

Some unusual iridium-(I), -(II), and -(III) complexes formed from 2-methoxyphenyl- or 2-hydroxyphenyl-di-t-butylphosphine

O-Metallated yellow iridium(I) complexes, [[graphic omitted])}{PBut2(C6H4OX–2)}](I; X = H or Me), are described. 1H–, 31P–, And 1H–{31P}-INDOR studies show a complex behaviour with temperature, probably due in part to the complexity of the spin systems and to the presence of rotational isomers. A benzene solution of (I; X = H) in air gives, after an induction period, the blood-red paramagnetic iridium(II) complex trans-[[graphic omitted])}2]. The latter reacts with hydrogen to give the dark purple iridium(III) hydride [[graphic omitted])}2], (IV), also prepared from hydrated iridium(III) chloride and (2-hydroxyphenyl)di-t-butylphosphine in isopropyl alcohol. Complex (IV) in benzene slowly reacts with air to give the IrII complex or rapidly with carbon monoxide to give colourless [[graphic omitted])}2]. A benzene solution of trans-[[graphic omitted])}2] in air slowly (24 h) gives the purple five-co-ordinate C-metallated IrIII complex [[graphic omitted])}]; this readily takes up carbon monoxide in the sixth co-ordination position to give a colourless adduct. Various other reactions to give unidentified products are described. 1H and 31P n.m.r. and i.r. data are given.

The activation of saturated hydrocarbons by transition-metal complexes in solution. Part IV. Oxidation of benzene and of alkanes by hexachloroplatinate(IV)

Benzene is oxidised to chiorobenzene by H2PtCl6 in aqueous trifluoroacetic acid at 120 °C. The initial formation of a water-soluble complex of platinum(IV) and benzene is accelerated by an increase in the H2PtCl6 concentration and by addition of K2[PtCl4], and is reduced by the addition of chloride ion. Subsequent reactions give chlorobenzene; some of it complexes with platinum. An analogous study has been made of the oxidation of alkanes, particularly hexane, using the same system. Evidence for the formation of chlorohexanes from hexane and of platinum complexes with hydrocarbon ligands has been obtained. 2- and 3-chlorohexanes are further oxidised and, from determinations of the amount of PtIV reduced during the reaction, it appears likely that polychlorinated carboxylic acids are formed. The mechanisms of aromatic and alkane oxidation in this system are initially very similar. The reaction of cyclohexane with H2PtCl6 is more complex. In addition to chlorination, dehydrogenation occurs to give benzene and chlorobenzene.

The thermolysis of some μ-Alkyne-bis(tricarbonylcobalt) complexes

Thermolysis of the μ-alkyne-bis(tricarbonylcobalt) complexes Co2(CO)6(C6F5C2C6F5), Co2(CO)6. (C6H5C2C6F5), Co2(C6H2C2H) , and [ Co2( CO)6]2(C6H5C2C2C6H5) has given a wide range of products. The substituents on the alkyne affect the nature of the products formed in these reactions, and small changes in the thermolysis conditions have a significant effect on the yields of particular products. Major products formed in the thermal degradation of Co2(CO)6(C6F5C2C6F5) are the free alkyne C6F5C≡CC6F5 and the cyclopentadienone C4(C6F5)4CO. The degradation of CO2(CO)6- (C6H5C2C6F5) gives two isomers of the cyclopentadienone C4(C6H5)2(C6F5)2CO and one isomer of the benzene C6(C6H5)3(C6F5)3. Organometallic complexes of probable formula Co2(CO)6 (C6H5C2C6F5)3 and Co(C6H5C2C6F4)[C4(C6H5)2(C6F5)2CO] are also formed in this decomposition reaction. Thermolysis of the terminal alkyne complex Co2(CO)6(C6H5C2H) gives 1,2,4-triphenyl- benzene and several complexes of general formula Co3(CO)9CY. One of these is the new complex Co3(CO)6C3H2C6H5 which has been separated into two isomers. Degradation of the diyne complex [Co2(CO)6]2(C6H5C2C6H5) has given the monoalkyne complex Co2(CO)6(C6H5C2C6H5) which degrades further to form tetraphenylcyclopentadienone and hexaphenylbenzene. When this degradation is conducted in the presence of some diphenylacetylene, an additional arene of formula C6(C6H5)5(C2C6H5) can be isolated.

Calculation of complexes with charge transfer and their spectra by the pariser-parr-pople method considering configurational interaction

1. Theπ-π complexes of benzene and pyridine with chloranil and tetracyanoethylene were calculated. 2. The calculated absorption spectra of the benzene complexes are in good agreement with the experimental data. 3. The model of theπ-π complex cannot explain the mechanism of the reaction of ion radical formation in the interaction of pyridine with chloranil and tetracyanoethylene.

ChemInform Abstract: THE PROTON MAGNETIC RESONANCE IN THE DPPH‐BENZENE COMPLEX

Chemischer InformationsdienstVolume 5, Issue 19 Physical Organic Chemistry ChemInform Abstract: THE PROTON MAGNETIC RESONANCE IN THE DPPH-BENZENE COMPLEX TOSHIO YOSHIOKA, TOSHIO YOSHIOKASearch for more papers by this authorHIROAKI OHYA-NISHIGUCHI, HIROAKI OHYA-NISHIGUCHISearch for more papers by this authorYASUO DEGUCHI, YASUO DEGUCHISearch for more papers by this author TOSHIO YOSHIOKA, TOSHIO YOSHIOKASearch for more papers by this authorHIROAKI OHYA-NISHIGUCHI, HIROAKI OHYA-NISHIGUCHISearch for more papers by this authorYASUO DEGUCHI, YASUO DEGUCHISearch for more papers by this author First published: May 14, 1974 https://doi.org/10.1002/chin.197419084AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume5, Issue19May 14, 1974 RelatedInformation

Chemical shift nonequivalence of sulfinates: Structural, solvent and temperature effects

AbstractThe structural, solvent and temperature effects on the PMR spectra of several alkyl alkanesulfinates and arenesulfinates are discussed. A low order intrinsic nonequivalence was observed in substituents alpha to the sulfinate sulfur atom, the nonequivalence being significantly less than in sulfoxides, and solvent and temperature dependent. Nonequivalence of diastereotopic substituents on the ester oxygen exceeded nonequivalence in similar sulfoxides and is largely insensitive to temperatures from 25° to 120°C. Benzene complexes with sulfinates greatly enhancing the proton nonequivalence of alpha substituents apparently by causing a further shielding of the already more shielded nonequivalent protons.

The Proton Magnetic Resonance in the DPPH–Benzene Complex

Abstract The proton magnetic resonance in single crystals of the DPPH–benzene complex has been measured around three Cartesian axes. All the spectra are highly complex, but some lines are clearly identified around all axes. The principal values of their anisotropic hyperfine tensors have been evaluated, in addition to the isotropic hyperfine coupling constants. In the crystalline state, the unpaired electron-spin distributions of one phenyl group is almost twice as large as that of the other phenyl group, as is to be expected from the crystal structure. Besides, the unpaired electron-spin delocalization is larger in the crystalline state than that in solution, particularly on the picryl group and on one phenyl group.

Catalysis by reversed micelles in non-polar solvents: aquation and electron-transfer reactions of chromium(III) and cobalt(III) complexes in benzene

Rate constants for aquation of the ion [Cr(C2O4)3]3– by octylammonium tetradecanoate-solubilized water in benzene and for aquations of [Cr(C2O4)3]3–, [CO(C2O4)3]3–, and cis-[Co(en)2(N3)2]+(en = ethylenediamine) by dodecylammonium propionate-solubilized water in benzene are factors of up to 5 × 106, 1 × 106, ca. 1 500, and 11, respectively, greater than those for the same reactions in water. At constant surfactant concentration there is a linear dependence of the aquation rate on the concentration of solubilized water, while at constant water concentration increasing surfactant concentration results in an exponential rate decrease. These results are discussed in terms of favourable substrate orientation in polar cavities of alkylammonium carboxylate aggregates, formed from these surfactants in benzene, where hydrogen bonding facilitates proton transfer and enhanced water activity accelerates synchronous M–O bond-breaking and nucleophilic attack by water. An implication of these results is that, in the hydrophilic environment of the reversed micelle, aquations of CoIII and CrIII complexes follow rate-determining bimolecular mechanisms subsequent to formation of ‘one-ended dissociated’ species. No micellar effects have been observed for the electron-transfer process in the aquation of the ion [Co(C2O4)2(H2O)2]–. Rate enhancement by surfactant-solubilized water in non-aqueous solutions and the utility of these systems in elucidating the mechanistic roles of water are discussed.

Transition metal complexes of substituted alkynes. XI. The reactions of But-2-yne and Hexafluorobut-2-yne with Dicarbonyl(η-cyclopentadieny)-cobalt and -rhodium

The thermally initiated reaction of hexafluorobut-2-yne and (q-C5H5)C~(C0)2 gives the 1-4-q- hexakis(trifiuoromethy1)benzene complex (7-C5H5)Co [(CF3C2CF3)3] in addition to the known cyclopentadienone complex (q-C5H5)Co [(CF3C2CF3)2CO]. The related reaction of but-2-yne with (q-CjH j)Co(CO)2 gives several compounds in addition to the cyclopentadienone complex (q-C jHj)C~- [(MeC2Me)2CO] which has been isolated previously from this reaction. Thus, the duroquinone complex (q-C5H5)Co [(MeC2Me)2(C0)2], the maleoyl complex (q-C5H5)Co(MeC2Me)(C0)3, and free duroquinone have been obtained. The yields of the various products are influenced by the reaction conditions. The metallocyclopentadiene complex (q-C jH j)2Rh2(CF3C2CF3)2, which is formed in the reaction between (q-C,H,)Rh(CO), and hexafluorobut-2-yne, exhibits fluxional behaviour in solution at c. 130". Two complexes are formed in the reaction at 100-120' between (q-C5Hj)Rh- (CO)2 and but-2-yne. These are the cyclopentadienone complex (q-C5H5)Rh [(MeC2Me)2CO] and the duroquinone complex (7-CjH5)Rh [(MeC2Me)2(C0)2]. Comparison of the various reactions indicates that: (i) a cyclopentadienone complex (q-CgH5)M- [(MeC2Me)2CO] is generally formed as major product and a duroquinone complex (q-C5Hj)M- [(MeC2Me)2(C0)2] is generally formed as a minor product in reactions between (q-C5H5)M(C0)2, M = Co and Rh, and but-2-yne; and (ii) a tetrahaptobenzene complex (q-C5H5)M [(CF3C2CF3)3] is formed as major product when M = Rh and as a minor product when M = Co in reactions between (q-C5H5)M(CO)2 and hexafluorobut-2-yne.

Hydrogen adduct radical formation in γ-irradiated α-, β-, and γ-cycloamylose–benzene complexes

α-, β-, and γ-Cycloamyloses are suitable ‘host’ matrices for stabilising hydrogen adduct radicals formed by hydrogen atom addition to the benzene ‘guest’ during γ-irradiation and compare favourably with the extensively used adamantane matrix for the observation of extremely well resolved e.s.r. spectra.

Preparation and X-ray molecular structure of an unusal copper(I) polynuclear species: tetrakis(copper trifluoroacetate)dibenzene

The preparation, some of the reactions with olefins, and the crystal and molecular structure of a unique polynuclear CuI–benzene complex are reported: Cu4(F3CCO2)4·2C6H6.

Incorporation of doubly excited configurations in calculating the benzene-cyanoethylene complex

A calculation by Pople's method with configuration interaction is presented for the weakπ complex of benzene with tetracyanoethylene incorporating doubly excited configurations; the bond strength is found as 1.8 kcal/mole, as well as the contributions from the charge-transfer and dispersion forces. The energies of the first four transitions are calculated, the lowest of which are of charge-transfer type.

The benzene—oxygen complex in the vapour phase

The absorption spectrum of the benzene—oxygen contact complex from 2350 to 2120 Å has been derived from the difference in the absorption spectra of benzene vapour (70 torr) in the presence and absence of oxygen (760 torr). The complex has an absorption maximum at 2190 Å (5.65 eV), corresponding to a formation energy of 0.42 eV from 1B 1U benzene and 3Σ − g oxygen, and of 2.90 eV from the benzene cation and oxygen anion. The excited complex has an electric dipole length of 5.0 Å. The data are compared with those for benzene complexes with other electron acceptors.

Geltungsbereich und Mechamismus der durch Silberionen katalysierten Propargylester‐Allenylester‐Umlagerung nach Saucy und Marbet

AbstractThe mechanism of the catalysis of the reversible (propargyl ester)/(allenyl ester) rearrangement (10 ⇄ 11) by silver(I) ions was investigated, using optically active and diastereoisomeric esters as well as 14C‐ and 18O‐labelling. magnified imageIn order to work with crystalline materials, mainly p‐nitrobenzoates (10, 11: R4 = pO2NC6H4) were used. In some cases the rearrangement 10 ⇄ 11 was studied using acetates (R4 = CH3). The alkyl substituents R1, R2, R3, were widely varied (cf. Tables 1, 2). The solvents in which the rearrangements were performed were in most cases dry chlorobenzene and 96% aqueous dioxane. Silver tetrafluoroborate, the benzene complex of the latter, and silver trifluoroacetate (in chlorobenzene) as well as silver nitrate (in aqueous dioxane) served as catalysts. The amounts of the silver catalysts used varied between 0,5 and 10 mol‐%; reaction temperatures applied were in the range 35–95°, The results obtained are as follows: The rate‐determining step of the (propargyl ester)/(allenyl ester) rearrangement (10 ⇄ 11) occurs in a silver(I) complex with the substrates (10, 11), which is formed in a pre‐equilibrium. This follows from kinetic experiments (cf. Fig. 6, 7, 8, 10) and the fact that the rate of rearrangement (of 10a) is strongly decreased when cyclohexene is added (cf. Fig. 9). In solvents which are known to form complexes with silver(I) ions the rate of rearrangement (of 10a)is much slower than in solvents with similar dielectric constants but with small capacity for complex formation with silver(I) ions (cf. Table 4). Taking into account what is known about silver(I)‐alkene and ‐alkyne complexes (cf. [18]), it is obvious that the (propargyl ester)/(allenyl ester) rearrangement occurs in a π‐complex of the silver(I) ion with the triple bond in the propargyl ester or one of the two C,C double bonds in the allenyl ester, respectively. The shift of the carboxyl moiety in the reversible rearrangement 10 ⇄ 11 occurs intramolecularly. p‐Nitrobenzoic acid‐[carboxyl‐14C] is not incorporated during the rearrangement, neither in the reactant 10 nor in the product 11 and vice versa. A crossing experiment gave no mixed products (cf. Scheme 2, p. 882). An internal ion pair can be excluded for the rearrangement 10 ⇄ 11 because the 18O‐carbonyl label in the reactant is found exclusively in the alkoxy part of the product (cf. Scheme 3, p. 886, and Table 9). Thus, the rearrangement 10 ⇄ 11 occurs with inversion of the carboxyl moiety. The rearrangement of optically active propargyl esters (10g, 10i) leads to completely racemic allenyl esters (11g, 11i). However, rearrangement of erythro‐ and threo‐10j‐[carbonyl‐18O] (Scheme 3) shows that the stereospecifically formed allenyl esters erythro‐ and threo‐11j‐[18O]‐epimerize rapidly in the presence of silver(I) ions. This epimerization is twice and forty times, respectively, as fast as the rearrangement of the corresponding propargyl esters (cf. Fig. 1–5). During epimerization or racemization the 18O‐label is not randomized (cf. also Scheme 4, p. 898). The equilibrium of the rearrangement 10 ⇄ 11 depends on the bulkiness of the substituents R1, R2, R3 and of the carboxyl moiety (cf. Table 2). Taking into account these facts (points 1–5), the reversible (propargyl ester)/(allenyl ester) rearrangement promoted by silver(I) ions can be described as a [3s, 3s]‐sigmatropic reaction occurring in a silver(I)‐π‐complex with the C,C triple bond in 10 and a C,C double bond in 11. It is suggested that complex formation in 10 and 11 occurs with the π‐bond which is not involved in the quasicyclic (containing six orbitals and six electrons) transition state of the rearrangement (Fig. 11). Thus, the rearrangement is of a type which has recently been called a charge‐induced sigmatropic reaction (cf. [26]). Therefore, in our case, the catalysis by silver(I) ions is of a different type from that of transformations of strained cyclic molecules promoted by silver(I) ions (cf. [14] [16] [27]–[31]).Side reactions. Whereas the rearrangement of propargyl esters 10 in presence of silver tetra‐ fluoroborate in chlorobenzene or silver nitrate in aqueous dioxane leads to the corresponding allenyl esters 11, the rearrangement of 10 with silver trifluoroacetate, especially in the presence of trifluoroacetic acid, results in the formation of the dienol esters 12 and 13, which clearly are derived from 11 (see Scheme 1, p. 881). As shown by the rearrangement of 11 in the presence of p‐nitrobenzoic acid‐[carboxyl‐14C], 12 and 13 arise in part from a not isolated di‐p‐nitrobenzoate (cf. Scheme 6, p. 905), since radioactivity is found in 12 and 13.

Aromatic complexes of copper(I) trifluoromethanesulphonate

The benzene complex of copper(I) trifluoro-methanesulphonate undergoes ready ligand exchange in paraffinic slurries with alkyl benzenes, whereby a unique ordering of stabilities of the complexes is manifested; a preliminary X-ray structural determination of the benzene complex is presented.

Charge-transfer complexes. Part XII. Viscosity dependence of the intensity of contact charge-transfer absorption bands

As the viscosity of the solvent is increased by addition of ethylene glycol to ethanol, the intensity of the contact charge-transfer absorption bands of the oxygen complexes of benzene and NN-dimethylaniline diminishes, tending towards zero in highly viscous media. This contrasts with the behaviour of the π-molecular complex, chloranil–hexamethylbenzene, which has the intensity of its charge-transfer band essentially independent of viscosity. These results are in accord with the model for contact complexes in which the light absorption to the charge-transfer state occurs during random collisions between the components.

Ionic dissociation of the s—tetracyanobenzene—benzene complex from the excited Franck—Condon state

From measurements of the fluorescence decay process as well as the rise process of the laser—induced photocurrent, it is concluded that the ionic dissociation of the s—tetracyanobenzene—benzene—1,2—dichloroethane system occurs in the excited Franck—Condon state.

Interlamellar Metal Complexes in Layer Silicates III Silver(I)—Arene Complexes in Smectites

AbstractThe complexation of benzene and several methyl substituted benzenes with exchangeable silver(I) on the interlamellar surfaces of Ag(I)-montmorillonite has been studied using spectroscopic methods. There are no physically adsorbed molecules interacting with the internal silicate surfaces and the only chemisorbed species present are those which are coordinated through π electrons to the exchangeable Ag(I) ions. In each case the coordinated species are similar to the previously studied Cu(II)-montmorillonite Type I complexes where aromaticity is retained. Complete replacement of coordinated and other interlamellar water molecules was accomplished with relative ease. Stoichiometric determinations indicate a 2:1 benzene: Ag(I) complex. Similarities between the Cu(II) and Ag(I) complexes are discussed in relation to electronic configurations.

Trace Analysis of Metals by ESR. I. Microdetermination of Copper by Means of Solvent Extraction of Copper(II) Diethyldithiocarbamate

Abstract A new method was developed for the direct determination of copper using ESR. Cupric diethyldithiocarbamate complex dissolved in benzene shows a unique ESR spectrum. The bivalent complex in benzene gave a very strong ESR signal with intensity sensitive to 0.005 ppm of Cu(II)-ion. Thus the ESR signal can be utilized for the trace analysis of Cu(II)-ion. The ESR signal intensity was linear in the ranges 1.0–0.1 γ/ml and 0.1–0.01 γ/ml of Cu(II)-ion. Mg2+, Fe2+, Ba2+, Mn2+, Zn2+, Co2+, Pb2+, Ni2+, I−, Br−, and NO3− did not interfere with the determination, while Hg2+ and CN− did. Comparing this method with photometric determination, we see that a very low content of Cu(II)-ion can be determined with a very small amount of sample.