Photochemical hydrogen production from ascorbic acid catalysed by tris(2, 2′-bipyridyl)ruthenium(II) and hydridotris(triethylphosphine)palladium(II)

Abstract

Hydrogen is produced catalytically, over a limited period of time, on photolysis of aqueous solutions containing [PdH(PEt₃)₃]⁺, [Ru(bipy)₃]²⁺(bipy = 2,2′-bipyridyl), and ascorbic acid. Kinetic studies suggest a rate-determining electron transfer from photochemically produced [Ru(bipy)₃]⁺ to [PdH(PEt₃)³]⁺ to give a palladium(I) radical from which hydrogen is rapidly produced. Termination of the hydrogen-producing reaction is shown to occur because [PdH(PEt₃)₃]˙ is oxidised by product dehydroascorbic acid in a competing reaction to H₂ production, and because of substantial bleaching of the [Ru(bipy)₃]²⁺.