Catalytic Synthesis of Poly(arylmethylgermanes) by Demethanative Coupling: A Mild Route to σ-Conjugated Polymers

A variety of poly(arylmethylgermanes) have been synthesized from aryldimethylgermanes in high yield via mild catalytic demethanative coupling using tetrakis(trimethylphosphine)dimethylruthenium as a convenient catalyst precursor. Polymerizations of germanes Me 2 GeArH (Ar = phenyl, p -tolyl, p -fluoro, p -trifluorotolyl, p -anisyl, and m -xylyl) proceed in neat monomer at room temperature. Catalyst removal can be effected by treatment of the reaction mixture with air, which gives polymer yields between 70% and 100%. Alternatively, separation of the catalyst by precipitation of the polymers from THF solution with methanol gives lower yields, but of somewhat higher molecular weight material. The new polygermanes are characterized by 1 H NMR and by gel permeation chromatography (GPC) using both polystyrene standards and light scattering methods. Molecular weights calculated by polystyrene analysis fall in the ranges of M w = 3 × 10 3 to 7 × 10 3 and M n = 2 × 10 3 to 6 × 10 3 . Values obtained from light scattering are approximately 60% and 82% higher, respectively, resulting in M w measured by SEC/LS in the range 5 × 10 3 to 1 × 10 4, with M w / M n ∼ 1.3. The absorption spectra of the polygermanes exhibit λ max in the range 326−338 nm. Comparison of the properties of poly(phenylmethylgermane) prepared by catalytic demethanative coupling and Wurtz coupling of MePhGeCl 2 with sodium revealed no significant differences.