Carbon−Carbon Bond Formation and Cleavage in the Dimerization of a Nickelacycle

Addition of 1,12-dilithiotriphenylenediyl to L 2 NiCl 2 (L = PEt 3 ) gives the nickelacycle L 2 Ni(1,12-triphenylenediyl), which decomposes to a dimer (L 2 Ni 2 C 36 H 20 ) containing two coupled triphenylene moieties with a new C−C bond. Thermolysis of the dimer completes the coupling, yielding a chiral tetraphenylene, while alkyne addition leads to cleavage of the newly formed C−C bond of the dimer and cycloaddition of the alkyne to the triphenylene fragment.