Water-soluble (η6-arene)ruthenium(II)-phosphine complexes and their catalytic activity in the hydrogenation of bicarbonate in aqueous solution

The reactions of [(η6-C6H6)RuCl2]2 and [(η6-p-cymene)RuCl2]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 [(η6-C6H6)RuH(tppts)2]+, [(η6-C6H6)RuH(pta)2]+, [(η6-p-cymene)RuH(tppts)2]+ and [(η6-p-cymene)RuH(pta)2]+. This latter complex was also formed in the reaction of [(η6-p-cymene)RuCl2(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(H2O)]+, [RuH2(pta)4] and [RuH(pta)5]+ complexes. Ru-hydrides, such as [(η6-arene)RuH(L)2]+, catalyzed the hydrogenation of bicarbonate to formate in aqueous solutions at p(H2)=100 bar, T=50–70 °C.