名称:
Substituent effects in multiply trimethylsilyl-substituted ferrocenes. Molecular structure of 1,1′,2,2′,4,4′-hexakis(trimethylsilyl)ferrocenium tetrafluoroborate
摘要:
Cyclic voltammograms, electronic and Mossbauer spectra were recorded for a series of sterically hindered ferrocenes bearing trimethylsilyl and tert-butyl groups Fe[eta-5-C5H3(EMe3)2-1,3]2, Fe[eta-5-C5H2(EMe3)-4-(SiMe3)2-1,2]2 (E = C, Si), and Fe[eta-5-C5H2(SiMe3)3-1,2,4](eta-5-C5R5) (R = H, CH3). The redox potential of Fe[eta-5-C5H2(SiMe3)3-1,2,4]2 is more negative than is expected for the trimethylsilyl group's electron-withdrawing property, which is confirmed by the value of the lowest wavenumber electronic absorption and of the quadrupole splitting. Oxidation of Fe[eta-5-C5H2(SiMe3)3-1,2,4]2 with AgBF4 gives [Fe{eta-5-C5H2(SiMe3)3-1,2,4}2]BF4. A single crystal X-ray structural analysis shows that the cation adopts a conformation with a pair of trimethylsilyl groups eclipsed. The compound crystallizes in the monoclinic space group P2(1)/n, with a = 10.597(1), b = 20.739(4), c = 18.450(3) angstrom, beta = 105.49(1)-degrees and V = 3907 angstrom 3.