Incorporation of chromium carbenes in a silica matrix by sol-gel processing: Application to aminolysis of alkoxycarbene complexes

Chromium carbene complexes have been immobilized in a silica matrix by sol - gel processing based on the polycondensation of (trialkoxy)silylethylphos phane ligands and tetraalkoxysilanes. The microstructure of the material ob tained depends on the gelation conditions. In situ gelation of alkoxy- or a minocarbene complexes with tetramethoxysilane (TMOS) affords mesoporous mat erials with a homogeneous distribution of the metal complex. The metal carb ene moiety is accessible for small substrates as demonstrated for the amino lysis of the incorporated methoxy(phenyl)carbene complex which slows down w ith increasing bulk of the amine.