When a Side Reaction Is a Benefit: A Catalyst-Free Route to Obtain High-Molecular Cobaltocenium-Functionalized Polysiloxanes by Hydroamination

Cobaltocenium-containing (co)polysiloxanes (Cc-PDMSs) with terminal and side groups were synthesized by the reaction of catalyst-free hydroamination between ethynylcobaltocenium hexafluorophosphate and polysiloxanes comprising amino moieties as terminal and side groups. The conversion of NH₂ groups in the polymers reaches 85%. The obtained (co)polysiloxanes "gelate" due to an increase in their molecular weight by approx. 30 times, when stored at room temperature over one week. "Gelated" Cc-PDMSs remain soluble in most polar solvents. The structure of Cc-PDMSs and the mechanism of "gelation" were established by ¹H, ¹³C{¹H}, ²⁹Si{¹H}, ¹⁹F{¹H}, ³¹P{¹H} nuclear magnetic resonance, infrared, ultraviolet-visible, and X-ray photoelectron spectroscopies. As determined by cyclic voltammetry, Cc-PDMSs possess redox properties (Co^II/Co^III transitions at <i>E</i>_1/2 = -1.8 and -1.3 V before and after "gelation", respectively). This synthetic approach allows to increase the molecular weights of the synthesized polysiloxanes functionalized with cobaltocenium groups easily, leading to their higher film-forming ability, which is desirable for some electronic applications. Cc-PDMSs can be utilized as redox-active polymer films in modified electrodes, electrochromic devices, redox-active coatings, and components for batteries.