Surface study of organopalladium molecules on S‐terminated GaAs

Abstract

Organopalladium species ({Pd}) immobilized on an Sterminated GaAs substrate (S/GaAs) effectively catalyzes C-C bond formation in the Mizoroki-Heck reaction with cycle durability. However, the immobilizing mechanism of {Pd} is unknown. In this study, we deposited Pd(OCOCH 3 ) 2 on S/GaAs in two different methods, namely dry-physical vapor-deposition and wetchemical deposition, and compared the catalytic activities in the Mizoroki-Heck reaction.Also, S-termination and {Pd}-immobilization on GaAs grains were performed by the wet-chemical method to monitor the change in the surface chemical structure during the preparation process with diffuse reflectance Fourier transform infrared spectroscopy (FT-IR). FT-IR measurements implied that the immobilization of catalytic active {Pd} was related to the OH groups on the S-terminated surface. {Pd}-S/GaAs prepared dryphysically showed poor catalytic activity, because {Pd} was not immobilized under absence of OH groups.

Hydroxylated surface of GaAs as a scaffold for a heterogeneous Pd catalyst

“…On the other hand, the broad absorption disappeared after heating with Pd(OAc) 2 in MeCN for 1 h (A-1), which implies that Pd(OAc) 2 reacted with the hydroxy groups on the GaAs surface. 28 Moreover, two new absorptions appeared at 1560 and 1450 cm À1 with prolonged heating time (A-24), which are presumably due to acetate ions (AcO À ). 29,30 These intriguing results prompted us to monitor surface changes with respect to the heating time by DRIR measurement (Fig.…”