η1-silolyl-FeCp(CO)2 complexes. Is there a way to sila-ferrocene?

Abstract

The reaction of 1-chlorosilols (12, 13) and K[Fe(CO)2Cp] in THF yielded two new η1-silolyl-FeCp(CO)2 complexes (15, 16) in good yield. These complexes are the first covalent Fe–Si bonded silolyl complexes reported in the literature, which were structurally proven by single crystal X-ray diffraction and multinuclear NMR spectroscopy. By temperature dependent NMR spectroscopy a rotational barrier of 14.4 kcal/mol was revealed, in agreement with the calculated 14.9 kcal/mol barrier of the phenyl rotation. The attempted transformation of these complexes to the corresponding silaferrocene by CO elimination failed. DFT calculations revealed that the rather high stability of the Si–Fe comparing to the C–Fe bond might be responsible for the stability of the complexes.