Singly and doubly β-to-β platinum-bridged porphyrin dimers and their reductive eliminations

2-Borylated porphyrins reacted with Pt(cod)Cl₂ to give β-to-β platinum-bridged porphyrin dimers, which were converted to β-to-β directly linked porphyrin dimers through triphenylphosphine-mediated reductive elimination. Similar reactions of 2,18-diborylated Ni(ii)-porphyrin and Zn(ii)-porphyrin gave the corresponding doubly β-to-β platinum-bridged porphyrin dimers. Treatment of the doubly β-to-β platinum-bridged Ni(ii)-porphyrin dimer with triphenylphosphine caused a single reductive elimination to produce a Ni(ii)-porphyrin dimer possessing a β-to-β platinum bridge and a β-to-β direct C-C bond.