Reversible Stannylenoid Formation from the Corresponding Stannylene and Cesium Fluoride.

A fluorostannylenoid (Cs [R SnF] (9), R =(TMS) CCH CH C(TMS) ) was prepared by reacting a stable dialkylstannylene (R Sn (8), R =(TMS) CCH CH C(TMS) ) with cesium fluoride at room temperature in THF. While 9 is stable in THF and DME, removal of the solvent leads to the regeneration of stannylene 8. No reaction occurred when 8 was treated with CsF in a hydrocarbon solvent. Addition of dibenzo-21-crown-7 ether to the THF solution of stannylenoid 9 followed by usual workup affords the corresponding crystalline stannylenoid crown ether complex, the X-ray structural analysis of which revealed a fluorine-bridged contact ion-pair structure. The reaction of 9 with excess phenylacetylene gives the corresponding di(phenylethynyl)stannane.