Redox Chemistry of Nickelocene-Based Monomers and Polymers

• Published in: Organometallics 2021-06, Vol.40 (12), p.1945-1955
• Main Authors: Musgrave, Rebecca A, Russell, Andrew D, Gamm, Paul R, Hailes, Rebekah L. N, Lam, Kevin, Sparkes, Hazel A, Green, Jennifer C, Geiger, William E, Manners, Ian
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/acs.organomet.1c00247

The oxidation of [n]­nickelocenophanes [Ni­(η5-C5H4)2(CH2)3] (3), [Ni­(η5-C5H4)2(SiMe2)2] (10), [Ni­(η5-C5H4)2(SiMe2)2O] (11), [Ni­(η5-C5H4)2(CH2)4] (12), and poly­(nickelocenylpropylene) [Ni­(η5-C5H4)2(CH2)3] n (4) to both the monocationic and dicationic species was investigated in dichloromethane by cyclic voltammetry (CV) and square-wave voltammetry. The presence of acetonitrile on the oxidation potentials of 3 in dichloromethane was also investigated by CV. The [n]nickelocenophanes 3 and 10–12 exhibited two single-electron Nernstian redox processes, and the monocations [3] + , [10] + , [11] + , and [12] + were isolable as [B­(C6F5)4]− salts after chemical oxidation, and were structurally characterized. Ni–Cpcent distances in all four monomers decreased upon oxidation, with a structural distortion manifested in the ring-tilt angle, α, among other angles. CV studies of the reversible first oxidation process to the polyelectrolyte {[Ni­(η5-C5H4)2(CH2)3]+} n ([4] n+ ) were used to estimate the molecular weight of the polymeric material (M w = 5300 g mol–1) by comparing its diffusion coefficient with that of a monomeric analogue, and the second electrochemical oxidation of polymer 4 was found to be only partially chemically reversible.