Mj. Calhorda et al., FERROCENYLSILATRANES - A SYNTHETIC, STRUCTURAL AND THEORETICAL INVESTIGATION, Journal of organometallic chemistry, 543(1-2), 1997, pp. 93-102
Ferrocene derivatives containing the silatranyl moiety were prepared a
nd studied by NMR spectroscopy and cyclic voltammetry. Compared with t
he corresponding triethoxysilanyl derivatives, the silatranes are much
more easily oxidized (Delta E-1/2(ox) up to 0.26V). In order to under
stand this result, theoretical calculations (extended Huckel (EH) and
density functional theory (DFT)) were performed. The geometries of the
four complexes were optimized using DFT calculations. The change in t
he energy of the HOMO when exchanging Si(OMe)(3) for silatranyl as wel
l as the transition state energy using the half-electron approach foll
ow the oxidation potentials. This result can be rationalized from the
Si-N anti-bonding character of the HOMO in the silatrane derivatives w
hich leads to an increase in energy. Such a bond is absent in the othe
r species. The prototype of this class of compounds, silatranylferroce
ne, was characterized by crystal structure analysis. The Si-N distance
is 2.181(2)Angstrom and thus lies in the range expected for an aromat
ic substituent at silicon. The agreement between calculated and observ
ed structure is quite good except for the Si-N distance, where a compa
ratively large deviation was found which reflects the difference betwe
en gas and solid state. A direct interaction between iron and silicon
can be excluded for both structural and theoretical reasons. (C) 1997
Elsevier Science S.A.