C–H Activation of Cycloalkenes by Dimetallynes (M = Ge, Sn) under Ambient Conditions

Treatment of the dimetallynes Ar′EEAr′ [E = Ge, Sn; Ar′ = C6H3-2,6-(C6H3-2,6-iPr2)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 π-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.