Mechanism of the oxidation and reduction of metal ions by hydrogen atoms

RECENT demonstrations^1-3 that metal hydrides such as CuH ⁺, AgH⁺ and AgH are formed as intermediates in the reduction of metal ions by molecular hydrogen in aqueous solution suggest that similar species may be involved in the oxidation and reduction of metal ions by hydrogen atoms, for example, in the well-known reactions : and These and related reactions between hydrogen atoms and metal ions have now been observed in aqueous solutions in which hydrogen atoms were generated in a variety of ways^4-6 or introduced from the gas phase^7,8; but their mechanisms are still uncertain and the subject of considerable controversy.