Description:
<jats:title>Abstract</jats:title><jats:p>(±)‐[1‐hydro‐8H‐HDP]cobalt(I) <jats:bold>1</jats:bold><jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#note1" /><jats:fn><jats:p>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<jats:italic>H</jats:italic>,23<jats:italic>H</jats:italic>‐10,20‐diaza‐porphinato]cobalt(I); full name of <jats:bold>2a</jats:bold>: 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<jats:italic>H</jats:italic>,21<jats:italic>H</jats:italic>‐10,20‐diazaporphinato]cobalt(III).</jats:p></jats:fn>
<jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#note2" /><jats:fn><jats:p>For the nomenclature of [HDP]‐complexes see addendum in [2].</jats:p></jats:fn>
is obtained by chemical or electrochemical four‐electron reduction of (±)‐dibromo‐ or (±)‐dicano[1‐hydroxy‐8H‐HDP]cobalt(III) <jats:bold>2a</jats:bold> or <jats:bold>2b</jats:bold><jats:sup>4</jats:sup>, respectively. The crystal nad molecular structure of <jats:bold>1</jats:bold> was determined by combination of X‐ray analysis and MS, <jats:sup>1</jats:sup>H‐, and <jats:sup>13</jats:sup>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 <jats:bold>2</jats:bold> in its different metal oxidation states were determined. The pathway of the overall four‐electron reduction of <jats:bold>2a</jats:bold> to <jats:bold>1</jats:bold> 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.</jats:p>