Carbon-carbon bond formation and cleavage in the dimerization of a nickelacycle

Addition of 1,12-dilithiotriphenylenediyl to L2NiCl2 (L = PEt3) gives the nickelacycle L2Ni(1,12-triphenylenediyl), which decomposes to a dimer (L2NiC36H20) 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.