Surface Organometallic Chemistry of Main Group Elements: Selective Synthesis of Silica Supported [#ident toSi-OB (C_6F_5)_3]~-[HNEt_2Ph]~+

摘要

The reaction of the Lewis acid B(C_6F_5)_3 with silanol groups of silica surfaces, dehydroxylated at different temperatures (300, 500, 700, and 800deg C), has been investigated in presence of the BrOnsted based NEt_2Ph. The structure of the resulting modified silica supports [#ident toSI-OB(C_6F_5)_3~-[NHEt_2Ph]~+ (1) has been carefully identified by IR and multinuclear solid-state NMR spectroscopies, isotopic ~2H and ~(18)C labeling, elemental analysis, molecular modeling, and comparison with synthesized molecular models. Highly dehydroxylated silcia surfaces were required to transform selectively each silanol group into unique [ident toSi-OB(C_6F_5)_3]~-[HNEt_2Ph]~+ fragments. For lower dehydroxylation temperatures, two sorts of surface sites were coexisting on silica; the free silanol groups [ident toSiOH] and ionic species 1.