ANCHORING RHODIUM(I) ON BENZOYLTHIOUREA-FUNCTIONALIZED SILICA XEROGELS - PRODUCTION OF RECYCLABLE HYDROFORMYLATION CATALYSTS AND THE CRYSTAL-STRUCTURE OF THE MODEL-COMPOUND [RH(COD)(HBZTU)CL]

Two benzoylthiourea-functionalized silica xerogels, 4.5SiO(2).SiO3/2(C H2)(3)NHC(S)NHC(O)Ph (XGbztu) and SiO3/2 (CH2)(3)NHC(S)NHC(O)Ph (XGbzt u) have been prepared from (EtO)(3)Si(CH2)(3)NHC(S)NHC(O)Ph by the so l-gel process. They are able to bind rhodium(I) species giving the com posite materials Rh/XGbztu and Rh/XGbztu, which are very active insol uble and recoverable catalysts for the hydroformylation of styrene. Th e anchored species undergo major changes during the catalytic cycles, particularly in the Rh/XGbztu system, whose iso/normal selectivity rat io gradually increased in the first five runs. Furthermore, CH3(CH2)(2 )NHC(S)NHC(O)Ph (HBztu) has been studied as a model of the surface bin ding function. The structure of [Rh(cod)(Hbztu)Cl](1), which represent s a suitable molecular model for the anchored complexes, has been dete rmined by X-ray diffraction.