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 [η 6 -C 6 H 5 Si(OMe) 3 ]Cr(CO) 3 ( 1 ), [η 6 -1,4-C 6 H 4 RR‘]Cr(CO) 3 [R = R‘ = Si(OMe) 3 ( 2 ), R = R‘ = CH 2 Si(OMe) 3 ( 3 ), R = R‘ = CH 2 CH 2 Si(OMe) 3 ( 4 )], {η 6 -1,3,5-C 6 H 3 [Si(OMe) 3 ] 3 }Cr(CO) 3 ( 5 ), under nucleophilic catalysis by fluoride ion (NH 4 F), have led quantitatively to new monophasic hybrid organic−inorganic silica gels. The derived xerogels X were characterized by FT IR, 13 C and 29 Si 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 T 2:CSi(OR)(OSi) 2 substructure for X2−X4, a T 3: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 m 2 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.