The reactions of [(eta(6)-C6H6)RuCl2](2) and [(eta(6)-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 [(eta(6)- C6H6)RuH(tppts)(2)](+), [(eta(6)-C6H6)RuH(pta)(2)](+), [(eta(6)-p-cymene)RuH(tppts)(2)](+) and [(eta(6)-p-cymene)RuH(pta)(2)](+). This latter complex was also formed in the reaction of [(eta(6)-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)(4)CI], [RuH(pta)(4)(H2O)](+), [RuH2(pta)(4)] and [RuH(pta)(5)](+) complexes. Ru-hydrides, such as [(eta6-arene)RuH(L)(2)](+), catalyzed the hydrogenation of bicarbonate to formate in aqueous solutions at p(H-2) = 100 bar, T = 50-70 degreesC. (C) 2004 Elsevier B.V. All rights reserved.