The chemistry of electrogenerated transition metals species - the insertion of olefins into a nickelcarbon bond

Healy, K. P.; Pletcher, Derek

doi:10.1016/s0022-328x(00)80916-x

Cited by 66 publications

(31 citation statements)

References 3 publications

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“…In this case the reaction is catalytic,[3Y. IS21 The electrochemical allylation of carbonyl compounds by electroreductive regeneration of a diallyltin reagent from ally1 bromide and an Sno compound leads in methanol or methanollwater to formation of homoallylic alcohols in yields of 70-90Y0. '~~~~ Using a cathodically generated and regenerated bis(bipyridine)rhodium(l) complex as two-electron transfer agent it was possible for the first time to achieve the nonenzymatically coupled selective regeneration of NADH from NAD@.…”

Section: Indirect Electrochemical Reductions With Transition Metal Comentioning

confidence: 99%

Indirect Electroorganic Syntheses—A Modern Chapter of Organic Electrochemistry [New Synthetic Methods (59)]

Steckhan

1986

Angew. Chem. Int. Ed. Engl.

267

162

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The electrochemical formation and regeneration of redox agents for organic syntheses (indirect electrolysis) widens the potential of electrochemistry, as higher or totally different selectivities can often be obtained while at the same time the energy input can be lowered significantly. Higher current densities can also be obtained by preventing otherwise often encountered electrode inhibition. New types of redox catalysts can be formed in-situ and can be regenerated after reaction with the substrates. This principle is of increasing importance also for the application of already known redox agents with regard to environmental protection, since large amounts of a product can be generated in a closed circuit using only relatively small amounts of the redox reagent. Consequently the operation of such a process can be greatly simplified, and the release of ecologically objectionable spent reagents into the environment can be prevented. The broad spectrum of redox catalysts currently in use includes, inter alia, metal salts in very low or high oxidation states, halogens in various oxidation states, and, in particular, a wide variety of transition-metal complexes. A great deal of progress has recently been made in the application of organic electron transfer agents, since compounds have been found that are sufficiently stable in both the reduced as well as the oxidized state.

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Section: Indirect Electrochemical Reductions With Transition Metal Comentioning

confidence: 99%

Indirect Electroorganic Syntheses—A Modern Chapter of Organic Electrochemistry [New Synthetic Methods (59)]

Steckhan

1986

Angew. Chem. Int. Ed. Engl.

267

162

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“…A number of investigations have dealt with the use of electrogenerated nickel(I) complexes as catalysts for the reduction of alkyl halides [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. In the late 1970s, Pletcher and co-workers [1][2][3][4][5] proposed a short-lived alkylnickel(III) species as an intermediate in the catalytic reduction of bromoalkanes by nickel(I) macrocyclic complexes in organic solvents, particularly acetonitrile.…”

Section: Introductionmentioning

confidence: 99%

Stoichiometric reduction of primary alkyl monohalides with electrogenerated nickel(I) salen: Formation of aldehydes

Vanalabhpatana

Peters

Karty

2005

Journal of Electroanalytical Chemistry

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“…In the first of these papers, 1 Gosden, Healy, and Pletcher stated "… decomposition of this reduced organonickel species must lead to a complex which is electroinactive, and although the exact nature of this species was not ascertained it is probably an octahedral nickel(II) complex." In a subsequent publication, 2 Healy and Pletcher reported "[An alternate pathway] again results in the formation of a nickel(II) complex but it is not the original square planar complex but an electroinactive species." These suggestions that nickel(II) salen undergoes change during the catalytic reduction of an alkyl halide, together with our own findings, prompted a project 16 conducted in our laboratory that involved the analyses of post-electrolysis solutions with the aid of high-performance liquid chromatography (HPLC).…”

Section: Death Of the Catalystmentioning

confidence: 99%

“…In their pioneering papers, Pletcher and co-workers [1][2][3][4][5] In the early 2000s, our laboratory endeavored to employ in situ electrochemical-electron paramagnetic resonance (EC-EPR) studies of the nickel(I) salen-catalyzed reduction of some n-alkyl bromides and iodides to search for the possible intermediacy of organonickel(III) intermediates, such as [RNi(III)X salen] -depicted in the preceding three reactions. Despite the fact that this species should be paramagnetic, no evidence for its existence in these systems was obtained by means of EC-EPR.…”

Section: Are Nickel(iii) Intermediates Involved?mentioning

confidence: 99%

Catalytic Reduction of Organic Halides by Electrogenerated Nickel(I) Salen

2016

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Catalytic reduction of halogenated organic compounds by electrogenerated nickel(I) complexes first appeared in the literature as a series of publications [1][2][3][4][5] from the laboratory of Derek Pletcher. In this early work, a family of nickel(II) procatalysts (or catalyst precursors) was employed, which included the compound [[2,2′-[1,2-ethanediylbis-(nitrilomethylidyne)]bis [phenolato]]-N,N′,O,O′]nickel(II), hereafter called nickel(II) salen (1). At a variety of cathodes (mercury, glassy carbon, platinum, and gold) and in numerous non-aqueous solventelectrolyte media [for example, dimethylformamide containing tetran-butylammonium tetrafluoroborate (DMF-TBABF 4 ) or acetonitrile containing tetramethylammonium perchlorate (CH 3 CN-TMAP)], chocolate-brown nickel(II) salen (1) undergoes a reversible, metalcentered, one-electron reduction to green nickel(I) salen (2). On the basis of density functional theory, it was established later 6 that reduction of nickel(II) salen can also produce a ligand-reduced form (3) of the parent complex in which a single electron is added to the carbon atom of one imino (C=N) bond of the ligand:Furthermore, the energy of 3 was calculated to be approximately only 2-3 kcal mol -1 higher than that of 2, meaning that both reduced states of 1 are accessible electrochemically-which becomes vitally important in later discussion.Shown in Fig. 1 is a cyclic voltammogram, recorded at 100 mV s -1 on a glassy carbon electrode in dimethylformamide containing tetramethylammonium tetrafluoroborate (TMABF 4 ) as the supporting electrolyte, which reveals the reversible one-electron reduction of nickel(II) salen. For the experimental conditions employed, the cathodic and anodic peak potentials (E pc and E pa ) are -0.95 and -0.84 V, respectively, and the cathodic and anodic peak currrents (I pc and I pa ) are identical. What is not seen in Fig. 1 (and what must be avoided) is that, at more negative potentials, another prominent cathodic peak is observed, due to the fact that the salen ligand itself can undergo further and irreversible degradation-which destroys the desired catalytic ability of 2. Our First Use of Electrogenerated Nickel(I) SalenOur first published effort to employ nickel(I) salen (2), electrogenerated at a reticulated vitreous carbon cathode in dimethylformamide-tetraethylammonium perchlorate (DMF-TEAP), was as a catalyst for the reductive intramolecular cyclizations of two acetylenic halides-namely, 6-bromo-1-phenyl-1-hexyne (4) and 6-iodo-1-phenyl-1-hexyne (5) Our goals were: (a) to overcome problems associated with direct reduction of these two compounds at mercury pool or reticulated vitreous carbon electrodes; and (b) to maximize the yield of the desired product (benzylidenecyclopentane, 6). Earlier, when these two acetylenic halides were reduced directly at a mercury pool cathode, 8 more than seven different products were obtained, and 6 was obtained in a yield below 25%. Then, in a subsequent investigation of the direct reduction of 6-iodo-1-phenyl-1-hexyne at a reticulated...

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The chemistry of electrogenerated transition metals species - the insertion of olefins into a nickelcarbon bond

Cited by 66 publications

References 3 publications

Indirect Electroorganic Syntheses—A Modern Chapter of Organic Electrochemistry [New Synthetic Methods (59)]

Indirect Electroorganic Syntheses—A Modern Chapter of Organic Electrochemistry [New Synthetic Methods (59)]

Stoichiometric reduction of primary alkyl monohalides with electrogenerated nickel(I) salen: Formation of aldehydes

Catalytic Reduction of Organic Halides by Electrogenerated Nickel(I) Salen

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