New Rhodium Complexes Containing a Hydrogen-Metal Bond

New and unexpectedly stable compounds of rhodium with hydrogen directly co-ordinated to the metal have been prepared. They are soluble in water, and their cold aqueous solutions readily take up ethylene and acetylene with the formation of ethyl and vinyl derivatives in which the organic radical is co-ordinated directly to the metal. These hydrido-compounds have a potential usefulness as catalysts for the hydrogenation of unsaturated organic acids.