Reversible Binding of Acetylene to Cationic Cobalt(III) Octaethylporphyrin

Acetylene is reversibly inserted into a Co–N bond of bis(aquo)octaethylporphyrinatocobalt(III) perchlorate, (OEP)CoIII(H2O)2ClO4 (1), in CH2Cl2 solution, generating a d6 high spin (S = 2) complex. Addition of 2,6-lutidine to a mixture of 1 and acetylene gave a σ-vinylcobalt(III) complex, (OEP)CoIII–CH=CH–L+ClO4 [L = 2,6-lutidine], whereas pyridine replaced the acetylene ligand to afford (OEP)CoIII(PY)2ClO4. These results suggest the intermediacy of a CoIII acetylene π-complex.

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