The effects of tin on the hydrogenation of alpha-diketones over platinum nanoclusters

The effect of tin on the hydrogenation of alpha -diketones over polymer-sta bilized platinum nanoclusters (PVP-Pt) or the corresponding Al2O3 supported platinum nanoclusters (Pt/Al2O3) was investigated. It was shown that Sn2has a rate-promoting effect either on the enantioselective hydrogenation of alpha -diketones modified with cinchonidine or on the racemic hydrogenatio n of them. The average rate increases by a factor of more than 2 for the ra cemic hydrogenation of 3,4-hexanedione over polymer-stabilized platinum nan oclusters in ethanol solution with a Sn2+ concentration of 1.6 x 10(-4) mol /l. The enantioselectivity could also be enhanced by the addition of Sn2+ i n the, enantioselective hydrogenation of these compounds. It is believed th at the electrophilic nature of Sn2+ is responsible for the rate promotion. (C) 2001 Elsevier Science B.V. All rights reserved.