Iron carbonyl hydride

Covalent. Formed by most of the non-metals and transition metals. This class includes such diverse compounds as methane, CH4 and iron carbonyl hydride, H2Fe(CO)4. In many compounds the hydrogen atoms act as bridges. Where there are more than one hydride sites there is often hydrogen exchange between the sites. Hydrogens may be inside metal clusters. 

If this iron carbonyl hydride is formed by a -elimination from the intermediate (CO)4Fe(COOH)-, a carbonyl must be lost in a prior step since this hydroxycarbonyl is coordinatively saturated. An alternative mechanism would be reductive decarboxylation followed by protonation of the very basic Fe(CO) intermediate. 

In an earlier related study, Evans and Newell (112) demonstrated the anionic iron carbonyl hydrides [HFe3(CO),][PNP] and [HFe(CO)4][PNP] to be catalytically active for this reaction, generating yields no greater than 5.8 1 moles of formate per mole of catalyst precursor. The low yields were attributed to catalyst degradation caused by oxidation by carbon dioxide as evidenced by the detection of carbonates in the system. 

Iron carbonyl hydrides, preparation and properties, 6, 7 Iron cations, acyclic (rj5-pentadienyl) Fe, 6, 153-154 Iron clusters... 

After our discovery of the metal carbonyl hydrides, other authors (32) pointed out their acidic character in aqueous solution. Potentiometric titrations by Reppe and later by us, showed that in water HCo(CO)4 possesses an acidity (pWa l) comparable to that of nitric acid. The first ionization stage for H2Fe(CO)4 corresponds approximately to that of acetic acid (33), whereas the pentacarbonyl hydrides HM(CO)5 (M = Mn or Re) (VII, 11, 26) are hardly acidic at all. The redox potentials of the cobalt and iron carbonyl hydrides were also measured (33). 

The mercury compounds HgFe(CO)4 and Fe(CO)4(HgX)2 (X = C1, Br, I), which were the first representatives of non-ionic metal derivatives of iron carbonyl hydrides, were discovered by Hock and Stuhlmann (V, 36). During investigations into the preparation of cobalt carbonyls from cobalt halides under CO pressure, in the presence of another metal as a halogen acceptor, we discovered the mixed metal carbonyls M[Co(CO)4]2 (M = Zn, Cd, Hg, Sn) and M[Co(CO)4]3 (M = In, Tl) (44), e.g.,... 

Figure 2.13 Synthesis of iron carbonyl hydride complexes...

Carbon monoxide reduces aromatic nitro compounds when iron pentacarbonyl is used as catalyst." A direct homogeneous catalytic reduction of nitro derivatives with water under moderate carbon monoxide pressure also occurs when rhodium carbonyl derivatives in aqueous organic bases are used as catalysts (equation 21). Presumably hydridorhodium carbonyl species are the active agents whose preferred formation in aqueous organic base may be analogous to that of iron carbonyl hydrides. 

The mechanism for homogeneous hydrogenation of methyl linoleate by Fe(CO)s based on kinetic evidences and radioactive tracers involves monoene- and diene-Fe(CO)4 and diene-Fe(CO)3 complexes as important intermediates. Contrary to our previous postulate (7) the free conjugated diene is only a minor intermediate. Confirmatory evidence is needed for the occurrence of oleate- and linoleate-Fe(CO)4 complexes during hydrogenation and isomerization with Fe(CO)r>. Also, the species of iron carbonyl hydrides formed during hydrogenation should be elucidated. 

The Fe3(CO)i2-catalyzed isomerization of 3-ethyl-l-pentene-3di gives 3-ethyl-2-pentene in which the deuterim label is randomly scrambled among the three methyl groups without loss of deuterium . The recovered 1-olefin also shows rapid random scrambling. These experiments demonstrate the intermediacy of w-allyl iron carbonyl hydrides and indicate Aat multiple addition-eliminations proceed before decomplexation of the catalyst occurs as... 

A. SODIUM SALT OF IRON CARBONYL HYDRIDE Sodium Tetracarbonylferrate(-II))... 

An ether-soluble iron carbonyl hydride Fe4(CO)i3H3 was isolated from the reaction of pyridine-iron carbonyl with acids [W. Hieber and R. Werner, Chem. Ber. 90, 286 (1957)]. 

This and the next compound are complex salts of polynuclear iron carbonyl hydrides. 

Like the Pb—N bond (see Section IV,B) the Pb—O bond is also easily affected by exchange reactions. Hydrogenation to Pb—H with B2H6 (11) was already mentioned in Section III,A,l,b. Proton-donating substances, including iron carbonyl hydrides (104), react at once (42, 44). 

Reaction of the iron carbonyl-hydride anion [HFe(CO)3(PMc3)] with diselenides leads to formation of iron carbonyl selenolate complexes and elimination of RSeH (Scheme 79). " The rw,r7r,/ra j-configuration of the final product was established by single crystal X-ray diffraction. 

Cr(C6H6)2 dibenzenechromium The handling of carbonyl derivatives in the examples will be noted names/such as di-iron ennea-carbonyl (with its irregular final -yl ending) and iron carbonyl hydride or iron tetracarbonyl dihydride can well be spared. 

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