Synthesis of Vinylene-Co,N-Linked Multi(porphyrin)s by the Addition of Free-Base Porphyrins to a C2H2 Complex of Cobalt(III) Porphyrin and Their Oxidative Rearrangement to Vinylene-N,N‘-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 CoIII porphyrin intermediate afforded good yields of vinylene-Co,N‘-linked bis(porphyrin)s, (Por)CoIII−CHCH−(N-Por)H2. 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-N,N‘-linked bis(meso-tetraarylporphyrin) with (OEP)CoIII(H2O)2ClO4 (OEP:  octaethylporphyrin dianion) and acetylene. The tetrakis(porphyrin) proved to be a 1:1 mixture of Ci- and C2-symmetric regioisomers. These organometallic CoIII complexes underwent facile oxidative migration of the Co-bound vinyl group to a porphyrin pyrrole nitrogen when treated with FeIII salts or HClO4 to provide moderate to good yields of CoII vinylene-N,N‘-linked multi(porphyrin) complexes. (Vinylene-N,N‘)bis(porphyrin) free bases with combinations of different porphyrins have been obtained by this procedure. The homobinuclear (2CoII, 2CuII, and 2ZnII) and heterobinuclear (CoIICuII and CoIIZnII) complexes have been prepared and characterized spectroscopically. The single-crystal X-ray analysis of (CHCH-N,N‘)[(OEP)CoIICl][(TPP)ZnIICl] (TPP:  meso-tetraphenylporphyrin dianion) showed a face-to-face structure with an average inter-ring separation of 4.39 Å (triclinic P1̄; Z = 2; a = 14.806(4), b = 18.703(10), c = 13.796(3) Å, α = 97.69(3), β = 99.57(2), γ = 96.74(3)°).