Reactivity of Long Chain α,ω-Dibromoalkanes at Palladized Solid Cathodes: Homocoupling vs Oligomerization

Abstract

Copper-palladium ͑Cu-Pd͒ and silver-palladium ͑Ag-Pd͒ systems are used as cathode materials for reducing long chain ␣,-dibromoalkanes ͓Br-͑CH 2 ͒ n -Br͔ with n Ͼ 3. Such interfaces globally permit the cleavage of the two C-Br bonds in a single two-electron process. A spectacular potential shift ͑⌬E͒ is obtained in comparison with glassy carbon electrodes at which the total reduction corresponds to a four-electron process. Such potential shifts are typically of the order of 1 V. In particular, cathodic reactions are easily achieved at Ag-Pd interfaces. Under these conditions, supporting evidences are given for the formation ͑according to simultaneous or sequenced processes͒ of a transient ␣,-biradical with different lengths of the alkyl chain ͑6 Ͻ n Ͻ 12͒. Macroelectrolysis data show that palladized interface reactions give rise to heterogeneous couplings and, markedly, the formation of homodimers. Reductions of ␣,-dibromoalkanes in the presence of copper-palladium, palladium, and silverpalladium fine powders efficiently induce the deposit of Cu, Pd, and Ag nanoparticles at chemically inactive electrified surfaces ͑glassy carbon and graphite͒.

Novel Method for Grafting Alkyl Chains onto Glassy Carbon. Application to the Easy Immobilization of Ferrocene Used as Redox Probe

“…On the other hand, the doubly branched ferrocene Fc(C 6 –I) 2 (image B) leads to the appearance of grooves in quite thick layers that could be due to an intermolecular Wurtz-type polymerization process that takes place along with some localized graftings that permits the polymeric form to resist against intensive ultrasonic rinsing. Such anionic polymerization is well-known for α,ω-dihaloalkanes at strongly reducing potentials . We verified that the extent of ferrocene grafting is about 10 times greater for image B than for image A.…”

“…Such anionic Langmuir ARTICLE polymerization is well-known for α,ω-dihaloalkanes at strongly reducing potentials. 29 We verified that the extent of ferrocene grafting is about 10 times greater for image B than for image A. Finally, EDX analyses revealed that these polymeric deposits have a high iron content.…”

Electrochemical conversion of glassy carbon into a poly-nucleophilic reactive material. Applications for carbon chemical functionalization. A mini-review

“…The immobilization of CO 2 [17], which can be realized on most types of carbons (including graphite and graphene), enables a facile synthesis of poly-carboxylated GC eventually covered with graphene [22]; strongly hydrophilic, such interfaces can be readily transformed into redox materials by simple reactions of the carboxylate group. Also, the use of non-Kolbe oxidation of the polycarboxylate (at + 1.3 V) easily allows [12] the efficient conversion of GC into a poly-electrophilic material with a wide range of interesting reactions that could be regarded as a new chapter in the field of surface electrophilic displacement reactions.…”

Electrochemical Immobilization of a Benzylic Film through the Reduction of Benzyl Halide Derivatives: Deposition onto Highly Ordered Pyrolytic Graphite

“…When required for the investigation of the reduction of benzyl bromide under catalytic conditions, glassy carbon electrodes (GC, surface area of 0.8 mm 2 ) were palladized or silvered. They were obtained following the procedure described in ref . Briefly, prior to metallization, all GC electrodes were carefully polished with silicon carbide paper (Struers) or with Norton polishing paper (types 02 and 03).…”