CHR‐Insertion (RH, CH3) into Cyclohexyl‐Substituted Silsesquioxanes: Reactivity and Decomposition Studies. Issue 46 (1st September 2014)

• Record Type: Journal Article
• Authors: Ward, Antony J.; Lesic, Rebecca A.; Fisher, Keith; Proschogo, Nicholas; Fábos, Viktória; Masters, Anthony F.; Maschmeyer, Thomas
• Is Part Of: Chemistry. Volume 20:Issue 46(2014)
• Page Start: 15169
• Page End: 15177
• Publication Date: 2014-09-01
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201403709
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Amorphous silica plays an important role in heterogeneous catalysis as a support and is frequently presumed to be "inert". The structure of the supported catalyst is key to understanding the stability and reactivity of catalytic systems. To provide vital insights into the surface reactivity of silica, Polyhedral oligomeric silsesquioxanes (POSSs) can act as realistic homogeneous molecular models for silica surfaces. Here, we report novel reactivities associated with the silica surface, derived from our insights obtained by means of such model systems with potentially significant implications in catalysis when employing silica‐supported catalysts. In this work, the gas‐phase reactivities of two cyclohexyl‐substituted POSSs, namely the completely condensed triganol prism [Si<sub>6</sub>cy<sub>6</sub>O<sub>9</sub>] (<italic>a</italic>6<italic>b</italic>0), and the incompletely‐condensed partial cube [Si<sub>7</sub>cy<sub>7</sub>O<sub>9</sub>(OH)<sub>3</sub>] (<italic>a</italic>7<italic>b</italic>3), with cy=<italic>c</italic>‐C<sub>6</sub>H<sub>11</sub>, were studied by using atmospheric pressure chemical ionisation (APCI) and collision‐induced decomposition (CID) spectroscopies. Silsesquioxane <italic>a6b0</italic>, containing three‐membered rings, was found to be much more reactive, undergoing novel CH<sub>2</sub>‐insertion on reaction with gas phase molecules—a reaction not observed for <italic>a7b3</italic>, containing only four‐membered rings. Both silsesquioxanes displayed the ability to trap ammonia formed in situ within the mass spectrometer from N<sub>2</sub> in the instrument. This work also demonstrates the applicability of APCI and the role of CID in elucidating reactive POSS structures, highlighting novel gas‐phase reactivities of POSS.</p> </abstract>