Direct synthesis of ruthenium catalyst precursors from ammonium (oxide) chloride salts via hydrothermal reaction

Synthetic pathways to (NH4)2RuCl6 and [RuCl2(COD)]x from mixed ammonium ruthenium (oxide) chlorides (ARC) have been developed that bypass the current, energy intensive route through Ru metal and RuCl3·nH2O. Hydrothermal treatment of ARC with concentrated HX (X = Cl, Br) produces (NH4)2RuX6 in up to 94% yield. Further reaction of (NH4)2RuCl6 with 1,5-cyclooctadiene in ethanol with 1 equivalent FeCl2 affords [RuCl2(COD)]x in up to 89% yield for an overall yield of 84%.