PHOTOCATALYTIC TRANSFER HYDROGENATION OF SCHIFF-BASES WITH PROPAN-2-OL BY SUSPENDED SEMICONDUCTOR PARTICLES LOADED WITH PLATINUM DEPOSITS

Photoirradiation at >300 nm of platinized titanium(IV) oxide (TiO2-Pt) or cadmium(II) sulfide loaded with platinum(IV) oxide suspended in pr opan-2-ol has been shown to lead to transfer hydrogenation of Schiff b ases [N-benzylidenebenzylamine (BdBA) and N-benzylideneaniline] to the corresponding secondary amines [dibenzylamine (DBA) and N-benzylanili ne, respectively]. Dehydrogenation of propan-2-ol also occurred as a s ide reaction. The transfer hydrogenation required both the photoirradi ation and suspended semiconductor particles, indicating that photoexci ted electrons and positive holes induces the reaction. Platinization o f the semiconductor particles was also necessary and TiO2-Pt prepared by impregnation followed by H-2 reduction showed the highest yield of DBA from BdBA. The most efficient catalyst was prepared by reduction a t an H-2 flow rate of 35 cm(3) min(-1) and had small Pt deposits dispe rsed uniformly on each TiO2 particle. Addition of molecular sieve 3A t o the reaction mixture improved the selectivity to DBA from BdBA by ab sorbing contaminant water and thereby inhibiting the hydrolysis of BdB A and subsequent formation of N-benzylpropyl-2-amine.