THE PALLADIUM-CATALYZED CROSS-COUPLING POLYMERIZATION OF DIETHYNYLMETHYL (N-OCTYL)SILANE WITH DIHALOARENES

Polymers of structure [ C=CSi(MeOct(n))C=C-Z ]n(Z = 1,4-benzene, 4,4'-biphenyl, 9,10-anthracene, 2,7-fluorent, 2,5 and 2,6-pyridine, 6,6'-bipyridine, 2,5-thiophene, 2,6-p-dimethylamino-nitrobenzene 2,6-p-nitroaniline, 2,7-fluoren-9-one, p-tetrafluorobenzene, 2,6-p-nitrophenol or 2,6-p-cyanophenol) were prepared by reaction of diethynylmethyl(n-octyl)silane with the appropriate heter(aromatic) dibromide or diiodide in the presence of (PPh3)2PdCl2 and CuI. The polymer where Z = 6,6'-bipyridine reacted with copper(II) trifluoromethanesulphonate to give a copper(II)-containing polymer, reduction of which with hydrazine afforded the Cu(I)-containing polymer. The effect of change in reaction conditions on the cross-coupling polymerization was investigated. High molecular weights are favoured by use of: (a) the diiodo- rather than the dibromoarene, (b) an equimolar mixture of the reactants or excess diethynylsilane, and in most cases (c) toluene cosolvent. The molecular weight passes through a maximum as the total catalyst concentration is increased, or as the individual Cu and Pd catalyst concentrations are separately raised. The presence of tetraethylammonium chloride or high concentrations of triphenylphosphine reduces the molecular weight.