Synthesis of Vinylene-<i>Co,N</i>-Linked Multi(porphyrin)s by the Addition of Free-Base Porphyrins to a C<sub>2</sub>H<sub>2</sub> Complex of Cobalt(III) Porphyrin and Their Oxidative Rearrangement to Vinylene-<i>N,N</i>‘-Linked Multi(porphyrin)s

The nucleophilic addition reaction of a pyrrole nitrogen of free-base porphyrins to a π-complexed acetylene ligand in a cationic Co<sup>III</sup> porphyrin intermediate afforded good yields of vinylene-<i>Co,N</i>‘-linked bis(porphyrin)s, (Por)Co<sup>III</sup>−CHCH−(<i>N-</i>Por)H<sub>2</sub>. N-substituted porphyrin free bases are N-vinylated regioselectively at the pyrrole adjacent to the original N-substituted pyrrole in this reaction. Tris- and tetrakis(porphyrin)s have been prepared by reacting a vinylene-<i>N,N</i>‘-linked bis(<i>meso</i>-tetraarylporphyrin) with (OEP)Co<sup>III</sup>(H<sub>2</sub>O)<sub>2</sub>ClO<sub>4</sub> (OEP:  octaethylporphyrin dianion) and acetylene. The tetrakis(porphyrin) proved to be a 1:1 mixture of <i>C</i><i><sub>i</sub></i>- and <i>C</i><sub>2</sub>-symmetric regioisomers. These organometallic Co<sup>III</sup> complexes underwent facile oxidative migration of the Co-bound vinyl group to a porphyrin pyrrole nitrogen when treated with Fe<sup>III</sup> salts or HClO<sub>4</sub> to provide moderate to good yields of Co<sup>II</sup> vinylene-<i>N,N</i>‘-linked multi(porphyrin) complexes. (Vinylene-<i>N,N</i>‘)bis(porphyrin) free bases with combinations of different porphyrins have been obtained by this procedure. The homobinuclear (2Co<sup>II</sup>, 2Cu<sup>II</sup>, and 2Zn<sup>II</sup>) and heterobinuclear (Co<sup>II</sup>Cu<sup>II</sup> and Co<sup>II</sup>Zn<sup>II</sup>) complexes have been prepared and characterized spectroscopically. The single-crystal X-ray analysis of (CHCH-<i>N,N</i>‘)[(OEP)Co<sup>II</sup>Cl][(TPP)Zn<sup>II</sup>Cl] (TPP:  <i>meso</i>-tetraphenylporphyrin dianion) showed a face-to-face structure with an average inter-ring separation of 4.39 Å (triclinic <i>P</i>1̄; <i>Z</i> = 2; <i>a</i> = 14.806(4), <i>b</i> = 18.703(10), <i>c</i> = 13.796(3) Å, α = 97.69(3), β = 99.57(2), γ = 96.74(3)°).