Synthesis of ferrocene-based redox-active polymers via palladium-catalysed coupling reactions

1,1'-Difunctionalised ferrocenes Fe(C(5)H(4)Z)(2) [Z = 4-BrC6H4 (1) 4-BrC6H4CH2C(O)- (4a), 4-BrC6H4CH=CH- (6a)] undergo cross-coupling reactions with the dizinc reagent (ClZnC6H4)(2)COCH2CHC(Me)O (2) to give a series of conjugated and non-conjugated aromatic poly(ferrocenes) with ferrocenediyl moieties as part of the polymer backbone. Similar products are obtained by Heck-arylation of 1,1'-divinylferrocene with diiodoarenes I-R-I (R = 1,4-C6H4, 1,1'-C6H4-C6H4, 2,5-C4H2S, 1,1'-C6H4OC6H4). The coupling products form orange to deep red solids, which are poorly soluble and oligomeric in most cases. Cyclic voltammetry measurements in dichloromethane solution give redox potentials close to the parent ferrocenes, with apparently very little interaction between the widely spaced iron centres.