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A Reduction Catalyst Powered by Its Own 10‐Electron Battery: Synthesis and properties of a pentaviologen‐linked corrinatocobalt complex
Author(s) -
Steiger Beat,
Walder Lorenz
Publication year - 1992
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19920750107
Subject(s) - chemistry , viologen , corrin , intramolecular force , catalysis , redox , electron transfer , iodide , bromide , reductive elimination , alkylation , electron donor , molecule , cyclohexene , derivative (finance) , medicinal chemistry , photochemistry , stereochemistry , inorganic chemistry , organic chemistry , cobalt , financial economics , economics
The synthesis and properties of the molecular reduction device 7b (Co II –V 5 ++ ) consisting of a reduction catalyst (a derivative of vitamin B 12 , Co II ) and a covalently linked 10‐electron reservoir (five viologen units, V ++ ) is described. The five viologen subunits were introduced at C(2) and C(3) of the side chains c and g and b, e and f , respectively, of an appropriate derivative of heptamethyl cob(III)yrinate by N ‐alkylation of 1‐methyl‐4,4′‐bipyridinium iodide (see Scheme ). The pentaviologen‐linked corrinatocobalt(II) complex 7b behaves as a molecular electron trap with respect to the Co III /Co II redox couple. The phenomenon is related to the structural and thermodynamic relation of the corrin and viologen subunits in 7b , i.e. the relative redoc energies and the spherical inner‐outer arrangement of the types of redox systems. When completely reduced to Co I –V 5 0 , 7b exhibits multiple reductive elimination of trans ‐1,2‐dibromocyclohexane to cyclohexene under concomitant oxidation to Co II –V 5 ++ . Rate measurements indicate that the reduction occurs via Co I which is regenerated by intramolecular electron transfer from the periphery of the molecule, i.e. by V 0 and V ++ .