Hieber reaction

The low-valent ferrate [Fe(CO)3(NO)] 76 or Hieber anion was discovered some 50 years ago by Hieber and Beutner [43, 44] in order to extend the Hieber base reaction [45,46], in which iron pentacarbonyl 78 reacts with alkaline bases to form the [Fe(CO)4] anion [47, 48]. Compared to its homoleptic analogue, the Hieber anion is more stable because the electron-withdrawing character of the nitrosyl ligand stabilizes the negative charge at the iron atom. 

With Roustan et al. using the sodium salt of the Hieber anion 76-Na, the procedure was improved by Xu and Zhou in 1987 when they introduced the corresponding shelf-stable tetrabutylammonium salt 76-[Bu4N] which is available from Fe(CO)5 78, NaN02 and Bu4NBr (Scheme 17) [61,62]. As well as discovered by Roustan they obtained the substitution products with an ipso-preference (Scheme 16) albeit in a significantly lower yield. In order to maintain the catalytic activity of the product, the reactions were performed under CO-gas atmosphere. 

After these encouraging results, it is surprising that no further investigations have been performed on this reaction, which might be attributed to problems regarding catalyst stability, reproducibility, or the use of a problematic CO gas atmosphere. The comeback of the Hieber anion dates back to 2006 when our group... 

Apart from this mechanistic hypothesis, another scenario, with a ferrate complex as intermediate, may be possible. In 1928, Hieber discovered that Fe(CO)5 78 underwent a disproportionation in the presence of ethylenediamine 122 [97-101]. Depending on the reaction temperature, different ferrate complexes were formed that incorporated a [Fe(en)3] cation (en = ethylenediamine) and mono-, di- or trinuclear ferrate anions (Scheme 32) [102-107]. As the reaction discussed above is also performed with amines at high temperatures, these ferrates may well be involved in the catalytic cycle of the carbonylation discussed above. 

Another catalytic application emanating from the Hieber base reaction was developed by Reppe and Vetter [108]. They showed that 1-propanol 126 could be generated by treatment of ethylene 125 with catalytic amounts of Fe(CO)5 78 under CO-pressure and basic reaction conditions (Scheme 33). Thereby, trimethylamine and V-alkylated amino acid derivatives mrned out to be optimal bases for this reaction. Like ethylene 125, propylene could be transferred mainly to 1-butanol diolefins like butadiene only reacted to monoalcohols. By employing these reaction conditions to olefins in the presence of ammonia, primary or secondary amines, mono-, di-, and trialkylamines were obtained whose alkyl chains were elongated with one carbon atom, compared to the olefins. 

The reaction of Ni(PhHritc)2 with Na2S2 does not lead to a Ni(IV) product as postulated by Hieber and Briick 109). A sulfur-rich dithiocarbimate of formula... 

The synthesis of [Fe4(CO)i3]2- (structure in Fig. 10) has been extensively studied by Hieber and co-workers. The reaction of a variety of ligands1 1 with Fe(CO)s results in redox condensation reactions and formation of the dark red dianion [Fe4(CO)I3]2... 

Nickel tetracarbonyl may be prepared in the laboratory by the Hieber process, a disproportion reaction of several nickel compounds of organic thio acids, such as nickel(II) phenyldithiocarbamate, (CeHs— NH—C(=S)—S)2Ni, with carbon monoxide under controlled conditions. In such disproportionation reactions, the divalent nickel ion converts to a tetravalent nickel complex (Hieber. H. 1952. Z.anorg.Chem., 269, pp. 28). The overall reaction is ... 

Hieber et al.s originally isolated Ir(CO)3Cl l0 from the products of the reaction of finely divided IrCl3 H20 with CO (1 atm) at 150°C, but they formulated the compound as Ir(CO)3Cl. The preparation given below is due to Fischer and Brenner,6 who also assigned the integral stoichiometry. The method for prepar-... 

The classic Hieber-base reaction 16 is that of a hydroxide with metal carbonyls, which proceeds by nucleophilic attack of the hydroxide at a carbon atom of a carbonyl ligand to give a carboxy group or consequently carbon dioxide and a metal hydride.17 Metal carbonyls are catalysts for the water-gas shift reaction.18 Pentacarbonyl(tetrafluoroborato)rhenium reacts with alkali hydroxide in a similar way however, due to the coordinatively unsaturated nature of the [Re(CO)5]+ group polynuclear compounds are formed.15... 

Hieber and Heusinger (3) reported an interesting reaction in which a liquid ammonia solution of ruthenium carbonyl iodide decomposed above — 30 °C to produce free and coordinated formamide ... 

Compounds containing four iron atoms were first described by Hieber (63) from the reaction between [NH4]2[SnCl6] and [Fe(CO)3(NO)], which... 

Finally, we note a number of higher nuclearity iron-containing clusters. Hieber (74) reported a complex formulated as [Sn2Fe5(CO)2o], 62, although no structural details were presented. Hieber also described a complex formulated as [PbFe3(CO)12], but later work by Whitmire (71) indicates that this compound is probably the tetrairon species, 56. Mackay and Nicholson (75) have described the synthesis and structures of three polynuclear species [Fe2(CO)7 //-E(Fe2(CO)8) 2] (63, E = Ge 64, E = Sn) and [Fe3(CO)10- //-Ge(Fe2(CO)8) 2], 65, from reactions involving germanium or tin... 

Anionic clusters are good nucleophiles (see Section III,A) and are often easy to make. On the other hand, the electrophilic nature of most monometallic complexes is obvious from ligand substitutions. The combination of these properties makes a strategy for cluster expansion. This strategy was used for the first time by Hieber (130) in making Fe4(CO)fc from Fe3(CO),7 and Fe(CO)s. It is probably active in many syntheses of large metal carbonyl clusters because the Re, Os, Rh, Ir, Ni, and Pt clusters involved are almost always anionic. However, simple stoichiometries can rarely be written for such reactions (122). This route makes mixed metal clusters accessible, e.g.,... 

A further novel method for demetallation provides even higher yields. Hieber-type reaction of the tricarbonyl(ri4-cydopentadienone)iron complex with sodium hydroxide to the corresponding hydride complex followed by ligand exchange with iodo-pentane affords an intermediate iodoiron complex, which is readily demetallated in the presence of air and daylight at room temperature (Scheme 1.4) [9]. Combining steps a-c in a one-pot procedure without isolation of the intermediate hydride complex gave yields of up to 98%. 

Although this catalytic reaction appeared to be of synthetic interest, it has since then neither been applied in synthesis nor further developed. This might be attributed in part to problems with reproducibility and catalyst stability under the reaction conditions, although the Hieber complex was used in a stoichiometric manner for the preparation of a variety of 7i-allyl-Fe complexes. These latter compounds served as starting materials for a plethora of subsequent reactions [34]. The results obtained by Nakanishi and coworkers on the stability and reactivity of n-allyl-Fe-nitrosyl complexes proved such intermediates to be reactive towards a variety of nucleophiles however, the Fe complexes formed upon nucleophilic substitution were catalytically inactive. Hence, in order to maintain the catalytic activity, the formation of intermediate 7i-allyl-Fe complexes had to be circumvented. About 3 years ago we started our research in this field and envisioned the use of a monodentate ligand to be a suitable way to stabilize the proposed catalytically active G-allyl complex. The replacement of one CO by a non-volatile basic ligand was thought to prevent the formation of the catalytically inactive 7t-allyl-Fe complex (Scheme 7.21). 

Once the trifluoromethyl-containing organometallic compounds have been formed, ligand-exchange reactions usually proceed readily. The first example was reported by Hieber, who observed that NO reacted cleanly with CF3Co(CO)3P(0)3 to afford CF3Co(NO)2P(Ot/>)3 quantitatively (22). 

The first stable cobalt carbonyl cation to be prepared was traw-bis(tri-phenylphosphine)cobalt tricarbonyl cation (219), obtained by disproportionation of cobalt carbonyl and carbonylation of Co(PPh3)2I2. Hieber and Freyer examined the reaction of triphenylphosphine with cobalt carbonyl (129, 130). The product from the reaction with triphenylarsine and triphenylstibine is a salt at low temperatures, but, on warming, a redox reaction occurs, producing a substituted cobalt carbonyl (129). Thus the reaction scheme is... 

In 1943, Hieber and Lagally reported that the reaction of anhydrous rhodium trichloride with carbon monoxide at 80°C, under pressure, and in the presence of silver and copper as halogen acceptors, gave a black crystalline product which, on the basis of elemental analysis, was formulated as Rh4(CO)n 75). The exact nature of this compound was established 20 years later by Dahl using three-dimensional X-ray analysis which led to its reformulation as Rh6(CO)i6 53). This discovery can be regarded as the birthday of the chemistry of high nuclearity clusters. 

The relevance of redox condensation, which by contrast generally requires very mild conditions, began to emerge slowly after 1965 (15, 110) when Hieber and Shubert reported the first example of such a reaction (78) ... 

Recent work (Wender, Sternberg, and Orchin, 36) suggests a revision of the view (Hieber, Muhlbauer, and Ehmann, 37) that the reaction between dicobalt octacarbonyl and compounds like methanol, ethanol pyridine, and o-phenanthroline involves only the displacement of one or more carbon monoxide groups of the carbonyl by the base according to Equation (1), using pyridine as an example. 

A more favorable synthesis of salts of the iron, cobalt and nickel carbonyl anions, which were initially prepared by disproportionation reactions of Fe(CO)5, Co2(CO)8, and Ni(CO)4 with pyridine and other amines, was found by treatment of the neutral carbonyls with alkali in aqueous or alcoholic solutions. Careful studies by Hieber revealed that Fe(CO)5 as well as Fe3(CO)12 reacted with exactly four equivalents of hydroxide ions to give the corresponding dianionic iron carbonylates (Scheme 4.4). These dianions are relatively strong bases and readily accept a proton from a water molecule to give the monoanionic hydrido carbonylates [I IFe(CO)4] and [HFe3(CO)n], respectively [36]. The related carbonylates of cobalt and manganese, [Co(CO)4] and [Mn(CO)5], were obtained by a similar way as [Fe(CO)4]2 [25]. With regard to the mechanism of Hieber s Basenreaktion , the most plausible explanation is based on an initial nucleophilic attack by the hydroxide ion at the carbon atom of a CO... 

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