| Abstract
| - Disilazane reagents of type HN(SiRR2)2 carrying organic substituents R1,2 = H, Me, Ph, n-Bu, n-Oct, Vin(Vin = vinyl) of varying longitudinal and lateral extension are reacted with high quality MCM-41 samplesof different pore sizes, i.e., effective pore diameters of 2.8 and 3.8 nm according to the BJH pore size analysisof the desorption branch. The reaction of the standard silylating reagent hexamethyldisilazane, HN(SiMe3)2,is shown to be controlled by the amount of added silylamine and the contact time, resulting in effective poresize engineering. Calculations from elemental analysis revealed that the degree of silylation (silylationefficiency) and hence the surface hydroxyl consumption depend on the steric bulk/shape of the groups R.The surface coverage varies from 0.74 to 1.85 silyl groups/nm2. The sterically least demanding tetramethyldisilazane, HN(SiHMe2)2, is the most efficient silylating reagent, while silyl groups with bulky phenylsubstituents produce the lowest surface coverage featuring considerable interaction with nonsilylated silanolgroups. The formation of various covalently linked siloxy functionalities [OSiR1R22] is reflected in the changeof the pore volume and mean pore diameter as evidenced by nitrogen physisorption measurements at 77.4 K.A monofunctional surface reaction and the structural integrity of the immobilized (functionalized) silyl groupsis quantitatively revealed by means of FT IR and 1H/13C MAS NMR spectroscopy. Heterobisilylated organic/inorganic hybrid materials are synthesized both via consecutive and competitive silylation utilizing mixturesof silylamines. The latter silylation procedure provides important mechanistic and kinetic details of this peculiarsurface silylation reaction emphasizing the preformation of a four-centered “O···H···N···Si” transposition asthe rate-determining step. Fully silylated materials carrying reactive vinyl moieties were functionalized byhydroboration with BH3(THF) and 9-BBN.
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