Photochemical reactions of digermanyl-substituted naphthalenes: The germyl migration to the aromatic ring

Photochemical reactions of digermanyl-substituted naphthalenes have been investigated by chemical studies using trapping agents, laser flash photolysis, and ab initio MO calculations. Irradiation of 1-(pentamethyldigermanyl)naphthalene (1) afforded mainly an isomer, 1-(dimethylgermyl)-8-(trimethylgermyl)naphthalene (4), via photochemical formation of a pair of trimethylgermyl radical and 1- naphthyldimethylgermyl radical, and then recombination at the 8-position of the latter followed by an intramolecular 1,4-hydrogen shift. At the same time a small amount of 1-(trimethylgermyl)naphthalene (5) was formed through the dimethylgermylene extrusion from 1. From photolysis of 2-(pentamethyldigermany)naphthalene a high molecular weight polymer was obtained. The excited states of digermanyl-substituted naphthalenes responsible for the photodecomposition are also discussed.