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Bi- and Triferrocene Complexes Containing Silylenevinylenephenylene Bridges. Model Compounds for Poly{ferrocene(phenylene)bis(silylenevinylene)}s

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journal contribution
posted on 28.03.2005, 00:00 by Rajsapan Jain, Hojae Choi, Roger A. Lalancette, John B. Sheridan
A series of conjugated ferrocene-based organosilicon complexes with one, two, or three ferrocene units have been prepared via hydrosilylation of alkynes with ferrocenylsilanes using Karstedt's catalyst (platinum-divinyltetramethyldisiloxane) and Rh(PPh3)3I. Reaction of 1,1‘-bis(dimethylsilyl)ferrocene (1) with 2 equiv of RC⋮CR1 (R = H, R1 = Ph, SiMe3, Fc {Fc = (η-C5H5)Fe(η-C5H4)}; R = SiMe3, R1 = Ph, Fc) gave Fe[(η5-C5H4)(Me)2SiC(R)CHR1]2 complexes (type 1) with varying regiochemical distributions. Addition of 2 equiv of dimethylsilylferrocene (2) to dialkynes R−C⋮C−X−C⋮C−R [R = H, X = C6H4 (1,4- and 1,3-), SiMe2; R = Me, X = Fc‘ {Fc‘ = (η-C5H4)Fe(η-C5H4)}; R = SiMe3, X = C6H4 (1,4- and 1,3-); R = Ph, X = nothing] resulted in Fc(Me)2Si(R)CC(H)−X−(H)CC(R)Si(Me)2Fc complexes (type 2), again with varying regiochemical distributions. The platinum-promoted hydrosilylations resulted in β-(E) and α-regioisomers, whereas the rhodium-catalyzed reactions gave primarily β-(Z) species with minor amounts of the β-(E) isomer. X-ray crystallographic studies of the predominant adducts obtained from 1 and Me3SiC⋮CPh as well as 2 and Me3Si−C⋮C−C6H4−C⋮C−SiMe3 (1,4-) using Karstedt's catalyst are described. Cyclic voltammetry shows single redox waves for most systems indicative of no interaction between the Fe−Fe centers. One complex, Fc(Me)2Si(CCH2)−Fc‘−Si(CCH2)(Me)2Fc, shows two reversible waves for the two different types of ferrocene center.