Electrochemical generation and reactions of a macrocyclic nickel (1) complex of 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclote tradecane
Electrochemical generation and reactions of a macrocyclic nickel (1) complex of 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclote tradecane
Square planar nickel complexes of the type MIILn+ have been prepared, where L are the macrocyclic tetradentate ligands, 5,7,7,12,14,14-, hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene, (trans[14]diene)i 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, (tet a) and 11,13-dimcthyl-1,4,7,10-tetraazacyclotrideca-10,12-diene, (A[13]T), The electrochemical reduction of these complexes to the corresponding nickel (I) complexes at a platinum cathode in acetonitrile has been studied using cyclic voltammetry and controlled potential coulometry. he complexes Ni(tet a)2+ and Ni(trans [14)diene) 4+ undergo an electrochemically reversible one electron reduction and solutions of these nickel (I) complexes are stable in the absence of air. The reactions of the nickel(I) complex, Ni(tet a)+, with alkyl halides, including a series of octyl bromides, has been investigated using cyclic voltammetry, coulometry and preparative electrolyses. It has been shown that the Ni(tet a)+ reacts rapidly with alkyl bromides and for the secondary and tertiary octyl bromides, the reaction forms products derived from alkyl radicals and regenerates the electroactive Ni(tet a)2+ forming a catalytic cycle. The reaction with the primary octyl bromide is not catalytic and gives rise to products derived from a carbanion intermediate. In most cases, the electrolysis of alkyl halides in the presence of a small quantity of Ni(tet a)2+ leads to their complete reduction. It is proposed that the chemical reaction involves an organo-nickel species and that the overall behaviour of the systems is determined by the stability of the nickel-carbon bond. When an activated olefin is present, an insertion reaction occurs between the organo-nickel species and the olefin. The new nickel-carbon bond is cleaved by further reduction and the overall reduction of Ni(tet a)2+ in the presence of RSr and C82 = COX leads to high yields of RCH2CR2X.
University of Southampton
1979
Healy, Keith Philip
(1979)
Electrochemical generation and reactions of a macrocyclic nickel (1) complex of 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclote tradecane.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Square planar nickel complexes of the type MIILn+ have been prepared, where L are the macrocyclic tetradentate ligands, 5,7,7,12,14,14-, hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene, (trans[14]diene)i 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, (tet a) and 11,13-dimcthyl-1,4,7,10-tetraazacyclotrideca-10,12-diene, (A[13]T), The electrochemical reduction of these complexes to the corresponding nickel (I) complexes at a platinum cathode in acetonitrile has been studied using cyclic voltammetry and controlled potential coulometry. he complexes Ni(tet a)2+ and Ni(trans [14)diene) 4+ undergo an electrochemically reversible one electron reduction and solutions of these nickel (I) complexes are stable in the absence of air. The reactions of the nickel(I) complex, Ni(tet a)+, with alkyl halides, including a series of octyl bromides, has been investigated using cyclic voltammetry, coulometry and preparative electrolyses. It has been shown that the Ni(tet a)+ reacts rapidly with alkyl bromides and for the secondary and tertiary octyl bromides, the reaction forms products derived from alkyl radicals and regenerates the electroactive Ni(tet a)2+ forming a catalytic cycle. The reaction with the primary octyl bromide is not catalytic and gives rise to products derived from a carbanion intermediate. In most cases, the electrolysis of alkyl halides in the presence of a small quantity of Ni(tet a)2+ leads to their complete reduction. It is proposed that the chemical reaction involves an organo-nickel species and that the overall behaviour of the systems is determined by the stability of the nickel-carbon bond. When an activated olefin is present, an insertion reaction occurs between the organo-nickel species and the olefin. The new nickel-carbon bond is cleaved by further reduction and the overall reduction of Ni(tet a)2+ in the presence of RSr and C82 = COX leads to high yields of RCH2CR2X.
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Published date: 1979
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Local EPrints ID: 462406
URI: http://eprints.soton.ac.uk/id/eprint/462406
PURE UUID: 82457305-adac-4cce-9a0d-4b71052f3074
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Date deposited: 04 Jul 2022 19:07
Last modified: 04 Jul 2022 19:07
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Author:
Keith Philip Healy
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