Water-soluble (η 6-arene)ruthenium(II)-phosphine complexes and their catalytic activity in the hydrogenation of bicarbonate in aqueous solution

Abstract

The reactions of [(η 6-C 6H 6)RuCl 2] 2 and [(η 6- p-cymene)RuCl 2] 2 with hydrogen in the presence of the water-soluble phosphines tppts ( meta-trisulfonated triphenylphosphine) and pta (1,3,5-triaza-7-phosphaadamantane) afforded as the main species [(η 6-C 6H 6)RuH(tppts) 2] +, [(η 6-C 6H 6)RuH(pta) 2] +, [(η 6- p-cymene)RuH(tppts) 2] + and [(η 6- p-cymene)RuH(pta) 2] +. This latter complex was also formed in the reaction of [(η 6- p-cymene)RuCl 2(pta)] and hydrogen with a redistribution of pta. In addition, prolonged hydrogenation at elevated temperatures and in the presence of excess of pta led to the formation of the arene-free [RuH(pta) 4Cl], [RuH(pta) 4(H 2O)] +, [RuH 2(pta) 4] and [RuH(pta) 5] + complexes. Ru-hydrides, such as [(η 6-arene)RuH(L) 2] +, catalyzed the hydrogenation of bicarbonate to formate in aqueous solutions at p(H 2)=100 bar, T=50–70 °C.