A stable dialkylstannylene [2,2,5,5-tetrakis(trimethylsilyl)stannacyclopentane-1,1-diyl] was synthesized by the reduction of the corresponding dichlorostannane with KC 8 in THF at low temperature. The stannylene showed reversible complexation with tetrahydrofuran (THF) with ΔH=-7.0 kcal mol - 1 and ΔS=-48 cal mol - 1 K - 1 , suggesting that the complexation is energetically favored but disfavored by the steric hindrance. No such complexation with THF was observed for the corresponding germylene and silylene.