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Synthesis, Structure, and Redox Chemistry of a Vitamin‐B 12s ‐Related Macrocyclic Complex of Cobalt(I)
Author(s) -
Walder Lorenz,
Rytz Gerhard,
Vögeli Ulrich,
Scheffold Rolf,
Engel Peter
Publication year - 1984
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.19840670718
Subject(s) - chemistry , cobalt , intramolecular force , protonation , metal , coordination sphere , redox , crystallography , electron transfer , coordination complex , crystal structure , electrochemistry , stereochemistry , inorganic chemistry , photochemistry , ion , organic chemistry , electrode
(±)‐[1‐hydro‐8H‐HDP]cobalt(I) 1 Full name of 1: [2,2,3,3,7,7,8,8,12,12,13,13,17,17,18,18,‐hexadecamethyl‐2,3,7,8,12,13,17,18,‐octahydro‐1 H ,23 H ‐10,20‐diaza‐porphinato]cobalt(I); full name of 2a : dibromo[2,2,3,3,7,7,8,8,12,12,13,13,17,17,18,18‐hexadecamethyl‐2,3,7,8,12,13,17,18‐octahydro‐1 H ,21 H ‐10,20‐diazaporphinato]cobalt(III).For the nomenclature of [HDP]‐complexes see addendum in [2]. is obtained by chemical or electrochemical four‐electron reduction of (±)‐dibromo‐ or (±)‐dicano[1‐hydroxy‐8H‐HDP]cobalt(III) 2a or 2b 4 , respectively. The crystal nad molecular structure of 1 was determined by combination of X‐ray analysis and MS, 1 H‐, and 13 C‐NMR spectroscopy. Square‐planar coordinated Co(I) lies closely to the best plane through the four N‐atoms which form the first coordination sphere. Thermodynamic data for the coordination of axial bases with the cation of [1‐hydroxy‐8H‐HDP]cobalt 2 in its different metal oxidation states were determined. The pathway of the overall four‐electron reduction of 2a to 1 was elucidated: it involves a two‐electron reduction of the central metal, a two‐electron reduction of the macrocycle accompanied by elimination of the OH‐group and final protonation at C(1). Evidence for an intramolecular electron transfer between the central metal and the macrocycle is presented.