Redox-Active Macrocyclic and Linear Oligo-Carbosiloxanes Prepared via Hydrosilylation from 1,3-Divinyl-1,3-Dimethyl-1,3-Diferrocenyldisiloxane

• Published in: Macromolecules Vol. 45; no. 2; pp. 781 - 793
• Main Authors: Bruña, Sonia, González-Vadillo, Ana Ma, Nieto, Daniel, Pastor, César J, Cuadrado, Isabel
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 24.01.2012
• Subjects: Applied sciences; Exact sciences and technology; Inorganic and organomineral polymers; Physicochemistry of polymers; Preparation; Linear copolymer; Ferrocene derivative copolymer; Organometallic copolymer; Cyclic copolymer; Hydrosilylation; Experimental study; Oligomer; Lattice parameters; Redox polymer; Polyaddition; Electrochemical properties; Preparation; Methylene copolymer; Siloxane copolymer; Crystalline structure
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma202521n

A series of novel, precisely defined, redox-active macrocyclic and linear co-oligocarbosiloxanes containing pendant ferrocenyl moieties attached to the carbosiloxane backbones, have been synthesized via hydrosilylation reactions of the bifunctional 1,3-divinyl-1,3-dimethyl-1,3-diferrocenyldisiloxane [(CH2CH)(Fc)MeSi]2O (6) (Fc = (η5-C5H4)Fe(η5-C5H5)). Specifically, 6 was reacted with 1,1,3,3-tetramethyldisiloxane, in the presence of Karstedt’s catalyst, to afford both the cyclic species 7, 8 and 9 n (n = 3–6) and several linear co-oligomeric carbosiloxanes 10 and 11 n (n = 2–5), containing a backbone in which the −Me2Si–O–SiMe2– moiety and the ferrocenyldisiloxane unit −MeFcSi–O–SiFcMe– are alternately linked by −(CH2)2– bridges. Ferrocenyl cyclocarbosiloxanes 7 and 8, as well as linear 10, were isolated by column chromatography. The crude reaction mixtures, as well as pure macrocycles and oligocarbosiloxanes have been thoroughly characterized by elemental analysis, multinuclear (1H, 13C, 29Si) NMR spectroscopy, FT-IR and MALDI–TOF mass spectrometry, to establish their chemical structures and chain-end functionalities. The molecular structure of 7, in solid state, has been determined by single-crystal X-ray analysis. Cyclocarbosiloxane 7 shows a bent arrangement of the ferrocenyl-substituted disiloxane linkage (Si–O–Si angle of 144.05(16)°). The electrochemical behavior of 7–11 n has been examined by cyclic (CV) and square wave (SWV) voltammetries, in dichloromethane solution using [PF6]− and [B(C6F5)4]−, as supporting electrolyte anions of different coordinating ability. Macrocycles 7 and 8 and oligomer 10 show two well-resolved oxidation waves, which suggests significant interaction between neighboring ferrocenyl redox centers linked by the Si–O–Si bridge. The linear oligomer 11 n , containing the higher number of pendant ferrocenyl moieties, undergoes oxidative precipitation yielding electroactive films on platinum electrode surfaces.