Cobaltocenium-Containing\nPolysiloxanes: Catalytic\nSynthesis, Structure, and Properties

Two\ndifferent catalytic approaches to synthesize non-cross-linked\nand cross-linked cobaltocenium-containing polysiloxanes (Cc-polysiloxanes)\nwere proposed and represent copper-catalyzed azide–alkyne cycloaddition\n(CuAAC) and platinum-catalyzed hydrosilylation reactions. CuAAC of\nethynylcobaltocenium hexafluorophosphate with azide-substituted oligo/polysiloxanes\nleads to obtain Cc-oligo/polysiloxanes with the highest Cc-substituted\nunit content up to 91 mol % compared to the hydrosilylation reaction\nwith polymethylhydrosiloxane (53 mol %). The structure of the obtained\nCc-oligo/polysiloxanes was confirmed by <sup>1</sup>H, <sup>13</sup>C{<sup>1</sup>H}, <sup>29</sup>Si{<sup>1</sup>H} NMR, and UV–vis\nspectroscopies. The non-cross-linked Cc-oligo/polysiloxanes are predominantly\nsoluble in polar solvents (acetone, CH<sub>3</sub>OH, CH<sub>3</sub>CN, and H<sub>2</sub>O) due to hydrophilic cobaltocenium cationic\nmoieties attached to the polysiloxane chain, making them different\nfrom typical polydimethylsiloxane and ferrocenyl-containing polysiloxanes.\nAll the obtained Cc-oligo/polysiloxanes exhibit redox properties.\nCyclic voltammograms of the Cc-oligo/polysiloxanes contain two pairs\nof redox peaks corresponding to Co<sup>II</sup>/Co<sup>III</sup> (<i>E</i><sub>1/2</sub> ≈ –1.4 V) and Co<sup>I</sup>/Co<sup>II</sup> (<i>E</i><sub>1/2</sub> ≈ –2.3\nV). The cross-linked Cc-polysiloxanes are thermally stable to <i>approx.</i> 230 °C both in the air and argon.