An Efficient One-Pot Access to Poly(arylene ethynylene) Homopolymers. Use of the Bu3Sn- Moiety as a Recyclable Carrier to Introduce the Ethynyl Unit into the Chain

The palladium-catalyzed Stille coupling of an aromatic diiodide with half an equivalent of tributyl(ethynyl)tin results in a complex mixture containing the diethynylaromatic compound, the iodo(ethynyl)aromatic compound, unreacted diiodide and the tributyltin iodide side product. Addition of LDA to this mixture, while leaving the iodoaromatic moieties unaffected, causes deprotonation of the ethynyl functionalities which immediately recombine with tributyltin iodide to form a mixture of bis(tributylethynyltin)aromatic, iodo(tributylethynyltin)aromatic and unchanged diiodide. Being the palladium catalyst still active, it is sufficient to warm up this mixture to obtain the coupling of the tributylethynyltin and iodo moieties resulting in the formation of a poly(arylene ethynylene) polymer. Isolation of the polymer is easily and rapidly achieved by precipitation, while distillation of the mother liquor allows recovery of the tributyltin iodide side product. The latter can be utilized for the preparation of new tributyl(ethynyl)tin, thus allowing a convenient turnover of the tributyltin moiety.