Formation of Phenylene Oligomers Using Platinum−Phosphine Complexes

The reaction of biphenylene with a series of platinum bis-phosphine precursors [PtL 2 ] leads to a variety of C−H and C−C bond activation reactions. With L = triethylphosphine, cleavage of the carbon−carbon bond of biphenylene has been shown to catalytically form tetraphenylene. With L 2 = Bu t 2 PCH 2 PBu t 2, the simple C−C cleavage of biphenylene is observed. With L = PPh 2 Bu t, ortho metalation of the phosphine occurs to give a C−H activation product. Mechanistic details of these reactions are discussed. With L = triphenylphosphine, however, biphenylene is not cleaved by the [L 2 Pt] fragment, but the independently prepared C−C insertion adduct does react with biphenylene to give five different products, including triphenylene, tetraphenylene, phenyltriphenylene, and hexaphenylene isomers.