GAS-PHASE ALKYLATION OF PHENYLTRIMETHYLGERMANES

The reaction of Me3GeC6H5 and Me3GeC6H4Me with Me2CH+, Me3C+, and Me2C l+ has been studied in the gas phase at pressures spanning from 1 Torr (chemical ionization mass spectrometry) to 1 atm (radiolytic techniqu e). The reactions conform to the general model of electrophilic aromat ic substitution reactions, proceeding via sigma-complex intermediates, which show a tendency to isomerize to arenium ions bearing a proton o n the germylated carbon. Such 1,2-H shift processes occur in the time scale of 10(-8) s. The fate of the germylated arenium ions is controll ed by competing deprotonation and degermylation reactions showing a be havior similar to their silicon analogues. The Me3X (X = Si, Ge) group s are seen to show a comparable electronic effect with regard to elect rophilic attack at the unsubstituted ring positions of an attached phe nyl group. (C) 1997 Elsevier Science B.V.