Benzene, 1 - complexes

The copper complex 1s available from Strem Chemicals, Inc., under the name cuprous triflate (benzene complex). The checkers recommend handling the material In a dry box because of Its high moisture and air sensitivity. 

Ethylene, bromo-(8) Ethene, bromo- (9) (593-50-2) Bicyclo[3.2.0]heptan-2-ol, 3,3-dimethyl- (9) (71221-67-5) Bis(copper(I) trif1uoromethanesulfonate)benzene complex Copper,... 

Mercaptobenzothiazole [149-30-4] M 167.2, m 182°, pK 7.5 (50% aq AcOH). Crystd repeatedly from 95% EtOH, or purified by incomplete pptn by dilute H2SO4 from a basic soln, followed by several crystns from acetone/H20 or benzene. Complexes with Ag, Au, Bi, Cd, Hg, Ir, Pt, and Tl. 

Cupric trifluoromethylsulfonate (copper II triflate) [34946-82-2] M 361.7, pK <-3.0 (for triflic acid). Dissolve in MeCN, add dry Et20 until cloudy and cool at -20° in a freezer. The light blue ppte is collected and dried in a vacuum oven at 130°/20mm for 8h. It has Xmax 737nm (e 22.4M cm ) in AcOH. [J Am Chem Soc 95 330 1973], It has also been dried in a vessel at O.lTorr by heating with a Fischer burner [J Org Chem 43 3422 1978], It has been dried at 110-120°/5mm for Ih before use and forms a benzene complex which should be handled in a dry box because it is air sensitive [Chem Pharm Bull Jpn 28 262 I980-, J Am Chem Soc 95 330 1973]. 

A selected strain o1 Streptomyces halstedii was cultivated in an aqueous nutrient medium under aerobic conditions and the resulting broth containing carbomycin antibiotics was filtered. The solutions was extracted twice at pH 6.5 with one-quarter volume of methyl isobutyl ketone. The combined extracts were concentrated to one-tenth volume under vacuum, and the antibiotics were extracted into water adjusted to a pH of about 2 with sulfuric acid. After adjusting the separated aqueous solution to pH 6.5, the antibiotic was extracted into benzene and the solution was concentrated to a small volume. Addition of hexane resulted in the separation of a solid product containing the benzene complexes of carbomycin A and carbomycin B, present in the fermentation broth. 

The benzene complexes have silver bound rf to two benzene rings in the perchlorate but only to one in the tetrachloro aluminate (Figure 4.31), while in the COT complex, each silver is bound to two double bonds in one molecule. 

The parent bis-benzene complex is hydrolytically sensitive [20] and must be used in its crude form. All the reactions with carbanions give ET products. First, the purple 19e mono-cation [Fe(C6Me6)2] + [25-28] is formed immediately at —90 °C. Then the black 20e complex Fe(C6Me6)2 is observed [25-29], However, recently, Zaworotko et al. have succeeded in making a C-C bond using AlEt3 as the carbanion source [30]. 

The reaction was extended to PhCH2X (X = Cl or Br) which gives the hexa(phenyl-ethyl)benzene complex. The new free aromatic ligand is easily disengaged by photolysis in acetonitrile [76a] Eq. (20). This line of research is now offering us the perspective of making new discotic liquid crystals using suitably substituted... 

The x-ray crystal structures of the hexaethyl- and hexabutenylbenzene complexes show noteworthy conformational effects [78] (Fig. 6). The hexaethylbenzene complex has four distal chains [76] contrary to all the previous conformations of C6Et6 and (M)C6Et6 of C3 symmetry. This conformation also depends on the counter-anion as the three conformations with four, five, and six distal ET groups have close energies and can be observed by low-temperature 1H NMR. The hexabutenyl benzene complex has five distal chains [77]. 

It forms a complex with dioxane contg 2 moles of TNMe to one of dioxane, mp 44—4.5°, bp at 8mm, 61—2° (Ref 19a, p 33). It reacts with aromatic dlazonium salts to give compds of the type ArN NC(N02)3. The compds are relatively unstable and their expl props have not been examined (Ref 12). It reacts with N-hydroxymethyl compds to form adducts of the type RNHCH2C(N02)3. The same compds are formed from TNMe, formaldehyde, and the amine or from trinitroethanol and the amine (Ref 31). It forms complexes with N-contg heterocyclics whose expl props have not been examined (Ref 42). It forms complexes with benzene and methylbenzenes. The formation constants for these complexes vary from 8.46 for the benzene complex to 279.4 for the hexa methylbenzene complex (Ref 49)... 

Part C of the present procedure illustrates a mild method for effecting the elimination of thiophenol from thioacetals and thioketals under essentially neutral conditions. The reaction of simple thioacetals and thioketals with bis[copper(I) trifluoro-methanesulfonate] benzene complex in benzene-tetrahydrofuran at room temperature affords vinyl sulfides in high yield (Table I). The reaction presumably occurs by coordination of the thiophilic copper(I) reagent with sulfur, heterolysis to a phenylthio-stabilized... 

The procedure described above provides a sufficient quantity of bis[copper(I) trifluoromethanesulfonate] benzene complex for several reactions at the scale used in Part C. If bis[copper(I) trifluoromethanesulfonate] benzene complex for a single reaction is desired, the same procedure can be followed at the appropriate scale without the use of the glove bag. In this case, the decolorized solution is not filtered but instead is cooled, and the product is allowed to crystallize in the reaction vessel. The supernatant benzene is decanted, and the crystals are washed in the flask with fresh benzene. The bis[copper(I) trifluoromethanesulfonate] benzene complex is then used without drying hj the same flask. 

Given the zwitterionic natnre of single carbenes, the possibility exists for coordinating solvents such as ethers or aromatic compounds to associate weakly with the empty p-orbital of the carbene. Several experimental stndies have revealed dramatic effects of dioxane or aromatic solvents on prodnct distribntions of carbene reactions. Computational evidence has also been reported for carbene-benzene complexes. Indeed, picosecond optical grating calorimetry stndies have indicated that singlet methylene and benzene form a weak complex with a dissociation energy of 8.7kcal/mol. ... 

Fig. 6 Proposed structures for iodine-benzene complex a resting, b axial, c oblique (turned 30° around center of mass), d above carbon, e above bond, f resting on bond, g displaced resting, and h T-shaped [79]...

The X-ray structure of the dibromine complex with toluene (measured at 123 K) is more complicated, and shows multiple crystallographically independent donor/acceptor moieties [68]. Most important, however, is the fact that in all cases the acceptor shows an over-the-rim location that is similar to that in the benzene complex. In both systems, the acceptor is shifted by 1.4 A from the main symmetry axis, the shortest Br C distances of 3.1 A being significantly less than the sum of the van der Waals radii of 3.55 A [20]. Furthermore, the calculated hapticity in the benzene/Br2 complex (x] = 1.52) is midway between the over-atom (rj = 1.0) and over-bond (rj = 2.0) coordination. In the toluene complex, the latter varies from rj = 1.70 to 1.86 (in four non-equivalent coordination modes) and thus lies closer to the over-bond coordination model. Moreover, the over-bond bromine is remarkably shifted toward the ortho- and para-carbons that correspond to the positions of highest electron density (and lead to the transition states for electrophilic aromatic bromination [12]). Such an experimental location of bromine is in good agreement with the results of high level theoretical... 

An intriguing annulation has been observed upon treatment of a Zr(II)-borata-benzene complex with an alkyne (Scheme 23).38 This reaction is believed to proceed through generation of the normal metallacyclopentadiene intermediate, followed by migration of the Zr—C bond to the electrophilic boron, and then formation of the C—C bond. Both the starting Zr(II) complex and the annulation product have been crystallographically characterized. 

Silver perchlorate forms solid complexes with aniline, pyridine, toluene, benzene and many other aromatic hydrocarbons [1], A sample of the benzene complex exploded violently on crushing in a mortar. The ethanol complex also exploded similarly, and unspecified perchlorates dissolved in organic solvents were observed to explode [2], Solutions of the perchlorate in benzene are said to be dangerously explosive [3], but this may be in error for the solid benzene complex. The energy released on decomposition of the benzene complex has been calculated as 3.4 kJ/g, some 75% of that for TNT [4],... 

The simplest aromatic-aromatic system, the benzene-benzene complex, has been studied by Jorgensen and Severance41" using intermolecular potential functions in a Lennard-... 

As a 3-step mechanism, the electron-transfer paradigm provides a pair of discrete intermediates [D, A] and D+, A for the prior organization and the activation, respectively, of the donor and the acceptor. The quantitative evaluation of these intermediates would allow the overall second-order reaction (k2) to be determined. Although the presence of [D, A] does not necessarily imply its transformation to D+, A-, a large number and variety of donor/ acceptor couples showing transient charge-transfer absorptions associated with [D, A] have now been identified. In each case, the product can be predicted from the expected behavior of the individual ion radicals D+ and A-. Consider for example, the labile 1 1 benzene complex with bromine that has been isolated at low temperatures and characterized crystallographically (Chart 9).256... 

It is noteworthy that the starting tf -benzene complex was prepared by cyclo-trimerization of acetylene by IrCl(C2H4)(triphos) [16]. All of the attempts to react the fragment [Ir(triphos)]+ with benzene were unsuccessful, which reflects the difficulty met by a transition-metal fragment to overcome the energy barrier to /4-benzene coordination. 

One of the earliest reports of enantioselective transfer hydrogenation was by Alper et al., who used chiral Schiff bases and a dichlororuthenium(II)benzene complex employing the IPA system [5]. In another report, Lemaire et al. utilized... 

Crystal structures of stable arene complexes are also known, for example the benzene complex of (lR,2R)-trans-l,2-bis((diphenylphosphino)-methyl)cyclobu-tane-Rh1 [46], [Rh((R,R)-Et-DuPHOS)(benzene)]BF4 (Fig. 44.7), and [Rh((S,S)-Me-DuPHOS)(toluene)]BF4 [47]. 

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