Treatment of the dimetallynes Ar'EEAr' [E = Ge, Sn; Ar' = C6H3-2,6-(C6H3-2,6-iPr(2))(2)] with a cyclic olefin-cyclopentadiene (CpH), cyclopentene, 1,4-cyclohexadiene (CHD), or cyclohexene-showed that, with the exception of cyclohexene, they react readily, affording C-H activation at room temperature. Reaction of the digermyne and distannyne with CpH gave the cyclopentadienyl anion, which is bound in a pi-fashion to a mononuclear group 14 element center, along with evolution of hydrogen gas. Unusually, the digermyne also reacted with cyclopentene to give the same dehydroaromatization product, formed from triple C H activation/dehydrogenation. It also was found to react with CHD to give a mixture of (Ar'GeH)2, benzene, and a new 7-germanorbornadiene species bound to a cyclohex-2-enyl fragment.