| Abstract
| - Differently sized disilazanes HN(SiHMe2)2 and HN(SiMe2Ph)2 are efficient reagents to examine the accessibility of the porous structure of cagelike silicas SBA-1 and SBA-2. SBA-2 shows a size-selective behavior toward bulky silylamines, affording organic−inorganic hybrid materials with organic groups exclusively attached to the external surface of the silica particles.
- Dehydrated, structurally ordered silica materials SBA-1 and SBA-2 were reacted with two differentlysized silylamines, tetramethyldisilazane (HN(SiHMe2)2) and tetramethyldiphenyldisilazane (HN(SiMe2Ph)2),at ambient temperature. The intraporous silylation is controlled by the different sizes of the pore entrances/cage windows of these “mesoporous” silica materials. According to nitrogen physisorption, Fouriertransform infrared spectroscopy, and carbon elemental analysis, the vast majority of the channels andpore openings, interconnecting the supercages of SBA-2 (P63/mmc), display a diameter larger than thesize of a HN(SiHMe2)2 molecule (silylation efficiency, SE, 1.98−2.28 mmol SiHMe2/1 g); however, thisis smaller than that of a HN(SiMe2Ph)2 molecule (SE, 0.40−0.63 mmol SiMe2Ph/1 g). The inner surfaceof SBA-1 (space group Pm3n) is fully accessible to both disilazane reagents giving SE values of 4.03mmol SiHMe2/1 g and 2.91 mmol SiMe2Ph/1 g. The lower SE value for material SiMe2Ph@SBA-1reflects the increased steric bulk of the silylating reagent which hampers the silylation of neighboredsilanol functional groups.
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