D. Cauzzi et al., SULFUR LIGAND-STABILIZED PALLADIUM AGGREGATES PRODUCED ON THE SURFACEOF BENZOYLTHIOUREA-FUNCTIONALIZED SILICA XEROGELS, Journal of materials chemistry, 5(9), 1995, pp. 1375-1381
Two benzoylthiourea-functionalized silica xerogels, 4.5SiO(2) . SiO3/(
2)(CH2)(3)NHC(S)NHC(O)Ph (XGbztu) and SiO3/2(CH2)(3)NHC(S)NH-C(O)Ph (X
Gbztu), prepared by the set-gel process, are able to bind palladium b
y reaction with Pd(OAc)(2), giving the hybrid materials Pd/XGbztu and
Pd/XGbztu. The ligand CH3(CH2)(2)NHC(S)NHC(O)Ph (Hbztu), a model of t
he surface-binding function, on reaction with Pd(OAc)(2), afforded the
mononuclear complex [Pd(bztu)(2)] and a sulfur-containing metal collo
id. Diffuse reflectance FTIR (DRIFT) experiments have shown that Pd/XG
bztu is able to fix CO at room temperature, giving a three nu(CO) fre
quency pattern, which changes with increasing temperature. Pd/XGbztu a
nd Pd/XGbztu are effective catalysts in the hydrogenation of phenylac
etylene to give styrene or ethylbenzene, depending on the reaction tim
e. Nanoscale palladium aggregates have been evidenced by transmission
electron microscopy (TEM) investigations on the materials after the hy
drogenation processes; energy-dispersive Xray (EDX) analysis has revea
led a significant presence of sulfur in the vicinity of the particles.
X-Ray photoelectron spectroscopy (XPS) data have shown that Pd2+ and
Pd-o are simultaneously present in Pd/XGbztu recovered after the catal
ytic cycle.