Simple Iron Carbonyl Hydrides

The slow step in the iron carbonyl-catalyzed water gas shift reaction (Equation (3)) is the proton transfer from water to the iron hydride anion (Equation (7)). Ab initio calculations have been made on this process. It was found that in solution, the proton transfer was still endothermic (as in the gas phase) however, there was a reduction in the reaction energy of about SOkcalmoF.  

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All the simple carbonyl hydrides (Table IY) may be readily prepared by acidification of alkali metal salts derived from the simple carbonyls. Only the carbonyl hydrides of Mn, Re, Co, and Fe are well characterized. They form highly toxic volatile liquids and are unstable thermally and with respect to oxidation. Pentacarbonylmanganese hydride is stable to light and air for several hours at room temperature (173), while the very unstable cobalt and iron complexes decompose spontaneously at — 20°C (167, 251). It may be noted that solutions of these carbonyl hydrides in inert solvents undergo spontaneous decomposition much more slowly than the pure substances. 

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