Stereodivergent Syntheses of (Z)- and (E)-Alkenylsilanes via Hydrosilylation of Terminal Alkynes Catalyzed by Rhodium(I) Iodide Complexes and Application to Silicon-Containing Polymer Syntheses

摘要

RhI(PPh_3)_3 or [RhI(cod)]_2 (cod=1,5-cyclooctadiene) as a catalyst delivers both (Z)- and (E)-alkenylsilanes in the stereodivergent hydrosilylation of terminal alkynes with heteroatom-substituted organosilane reagents.Treatment of the rhodium catalyst and the silane reagent followed by addition of terminal alkyne at room temperature leads to (Z)-silanes,while addition of the silane and the alkyne to the rhodium catalyst in one portion and heating at 60degC affords (E)-silanes highly selectively.The obtained (E)- and (Z)-alkenylsilanes bearing heteroatom substituents on the silicon atom are subjected to the palladium-catalyzed cross-coupling reaction with aryl halides to form a carbon-carbon bond with retention of stereochemistry.The stereodivergent hydrosilylations are applied to the polyaddition with bifunctional alkynes (1,3- and 1,4-diethynylbenzene) and silanes (1,3- or l,4-bis(dimethyl-silyl)benzene),giving silicon-containing polymers,poly(aryleneethenylenesilylene)s,in highly stereocontrolled manners.A fluorine-containing silicon reagent bearing a 3,3,3-trifluoropropyl group is also subjected to the polymerization,in which [RhI(cod)]_2 is found to be an efficient catalyst.Measurement of UV-vis absorption/emission spectra and several thermal analyses of the polymers are also conducted.