No abstract

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.

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The permeability of microporous amorphous carbon preforms with varying pore size and pore distributions has been experimentally examined. The porous structures have been characterized by mercury porosimetry and by quantitative metallography of pressure-infiltration-cast metal matrix composites based on the carbon preforms. The permeability shows a linear correlation with the fraction porosity and the square of the pore diameter.