Synthesis of Monophasic Hybrid Organic−Inorganic Solids Containing [η6-(Organosilyl)arene]chromium Tricarbonyl Moieties

Abstract

Silica gel containing benzenechromium tricarbonyl units have been obtained from molecular organosilicon precursors. The hydrolytic sol−gel polymerization of [η6-C6H5Si(OMe)3]Cr(CO)3 (1), [η6-1,4-C6H4RR‘]Cr(CO)3 [R = R‘ = Si(OMe)3 (2), R = R‘ = CH2Si(OMe)3 (3), R = R‘ = CH2CH2Si(OMe)3 (4)], {η6-1,3,5-C6H3[Si(OMe)3]3}Cr(CO)3 (5), under nucleophilic catalysis by fluoride ion (NH4F), have led quantitatively to new monophasic hybrid organic−inorganic silica gels. The derived xerogels X were characterized by FT IR, 13C and 29Si solid state CP MAS NMR spectroscopies. The silicon−carbon bond and the tricarbonylchromium ligand were retained within the gel. The major environment of the Si atoms corresponded to a T2:CSi(OR)(OSi)2 substructure for X2−X4, a T3:CSi(OSi)3 one for X1 and a Ts:CSi(OR)2(OSi) in the case of X5. In most cases, these were amorphous materials that exhibited low specific surface areas (∼10 m2 g-1). Upon heating the xerogels X1, X2, and X4 at 400 °C under an argon flow, weight losses corresponding to complete carbon monoxide elimination were obtained, leading to chromium in a low oxidation state within the solid.