SURFACE ORGANOMETALLIC CHEMISTRY ON ZEOLITES - CONTROL OF THE PORE OPENING OF MORDENITE BY GRAFTING OF THERMALLY STABLE -GEBU(3) FRAGMENTS

GeBu(4) reacts at 250 degrees C with the external silanols of two different mordenites (Si/Al= 11 or 40) to give the surface organometallic complex -Si-O-GeBu(3) 1 which has been characterized by C-13 CP-MAS NMR; 1 is able to discriminate sterically different alkanes such as n-hexane, 2-methyl-pentane, 2,3-dimethyl butane, 2,2,4-trimethyl pentane. Such discrimination is parallel to that already observed for -Si-O-SnBu(3) grafted on the same mordenites. Interestingly and in contrast to the behaviour of the grafted tin complex, 1 even after treatment at 400 degrees C is still able to separate n-hexane from isooctane, a property ascribed to a steric molecular control of the Ge(Bu)(3) fragment which has an exceptional thermal stability.