The Influence of Steric Congestion on the Catalytic Performance of TiIV Active Centers in the Epoxidation of Alkenes

✍ Scribed by Marek C. Klunduk; Thomas Maschmeyer; John Meurig Thomas; Brian F. G. Johnson

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 146 KB
• Volume: 5
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/(sici)1521-3765(19990503)5:5<1481::aid-chem1481>3.0.co;2-8

✦ Synopsis

Elucidation of the catalytic performance of Ti IV centers in titanium-silica epoxidation catalysts has been probed by studying a range of soluble titanium-based silsesquioxane analogues. Several related and new Ti IV complexes in which the Ti IV is coordinated to only one or two siloxides of the silsesquioxane backbone have enabled us to modify, in a controlled fashion, the degree of steric congestion around the active site. It has been shown that the performance of these model catalysts is strongly influenced by the precise nature of the coordination environment about the Ti IV active site, both in terms of steric crowding and in the likely occurrence of dative bonding.