Kh. Pannell et al., (1,1'-FERROCENEDIYL)FERROCENYL(METHYL)SILANE, ITS THERMALLY RING-OPENED POLYMER, AND OLIGOMER MODELS, Organometallics, 13(9), 1994, pp. 3644-3650
The synthesis and spectroscopic and structural characterization of a f
errocenyl-substituted silyl-[1]-ferrocenophane, (1,1'-ferrocenediyl)fe
rrocenyl(methyl)silane, 1, is reported. 1 crystallizes in space group
P2(1)/c, with a = 20.344(8) Angstrom, b = 7.336(3) Angstrom, c 11.567(
7) Angstrom, and beta 90.51(4)degrees. The dihedral angles between the
two ferrocenophane cyclopentadienyl rings are 21.3 degrees, and the r
ing centroid-Fe-ring centroid angle is 164.3 degrees. Cyclic voltammet
ric analysis illustrates that both of the Fe centers, ferrocenyl and f
errocenophane, exhibit reversible redox behavior. This reversibility d
istinguishes the complex from other [1]-ferrocenophanes which exhibit
irreversible oxidation under similar conditions. Thermal treatment of
1 results in facile polymerization to high molecular weight amorphous
poly(ferrocenyleneferrocenyl(methyl)silane), 2. The molecular weight o
f the polymer was considerably increased by performing the polymerizat
ion in solution as opposed to the melt, M(w) = 210 000 vs 45 000. The
electrochemical properties of the polymer indicate that neighboring Fe
centers of the ferrocenylenesilane chain and pendant ferrocenyl group
s interact, and four independent redox processes are observed. As a mo
del for the ferrocenylenedialkylsilane polymers the synthesis and X-ra
y structure of 1,1'-bis(ferrocenyldimethylsilyl)ferrocene, 3, is also
reported. 3 crystallizes in space group P2(1)/c, with a 10.084(2) Angs
trom, b = 14.958(2) Angstrom, c 11.175(2) Angstrom, and beta = 114.98(
1)degrees. The ferrocenyl and ferrocenylene units are perpendicular to
each other, and each of the Fe units exhibits an individual redox pro
cess upon cyclic voltammetric investigation. Molecular mechanics calcu
lations reveal a range of structures with local energy minima for such
oligomers, one of which is equivalent to the single-crystal X-ray str
ucture obtained for 3. The Fe-Fe distances in these conformers differ
significantly, 6.1-6.9 Angstrom, suggesting that high molecular weight
polymers also possess a range of possible conformations and inter-Fe
Coulombic interactions.