Iron, carbonyl compounds reaction with base

Hydroxy-substituted iron-acyl complexes 1, which are derived from aldol reactions of iron-acyl enolates with carbonyl compounds, are readily converted to the corresponding /i-methoxy or /1-acetoxy complexes 2 on deprotonation and reaction of the resulting alkoxide with iodomethane or acetic anhydride (Tabic 1). Further exposure of these materials to base promotes elimination of methoxide or acetate to provide the a,/ -unsaturated complexes (E)-3 and (Z)-3 (Table 2). 

The solvent process involves treating phthalonitrile with any one of a number of copper salts in the presence of a solvent at 120 to 220°C [10]. Copper(I)chloride is most important. The list of suitable solvents is headed by those with a boiling point above 180°C, such as trichlorobenzene, nitrobenzene, naphthalene, and kerosene. A metallic catalyst such as molybdenum oxide or ammonium molybdate may be added to enhance the yield, to shorten the reaction time, and to reduce the necessary temperature. Other suitable catalysts are carbonyl compounds of molybdenum, titanium, or iron. The process may be accelerated by adding ammonia, urea, or tertiary organic bases such as pyridine or quinoline. As a result of improved temperature maintenance and better reaction control, the solvent method affords yields of 95% and more, even on a commercial scale. There is a certain disadvantage to the fact that the solvent reaction requires considerably more time than dry methods. 

Complex compounds [455] and multinuclear iron carbonyls [456] can take part as acceptors (A) in the examined reactions with use of metal-carbonyl bases. In this respect, a series of recently reported reactions (3.209) [455] and (3.210) [456] are representative ... 

In contrast to the chalcogen-bridged complexes, no similar oxygen-bridged compounds of iron, cobalt, or nickel exist. However, we obtained such oxo or i-ol-carbonyl complexes of chromium and its homologs, as well as of rhenium. The compounds are the products of the reactions of the respective metal carbonyls with bases (VII). 

The simpler iron carbonyls, Fe(CO)5 and Fe2(CO)9, can also deoxygenate nitrobenzenes to anilines in an aqueous base-organic solvent system. With these carbonyls, however, a phase-transfer catalyst is not only unnecessary, its presence results in reduced product yields Furthermore, the nitro compound must be present to induce attack of hydroxide ion on Fe(CO)s t0 give HFe(CO)4 [and possibly HFe2(CO)8 ] (77). Such a phenomenon was also noted by Pettit and co-workers (23) in their excellent work on the use of water gas shift reaction conditions for the Fe(CO)5-cat-alyzed deoxygenation of nitrobenzenes. 

Carbonyl compounds can be reduced efficiently in hydrosilylation reactions with an inorganic solid acid or base catalyst present [108, 109]. Iron montmorillonite catalyses hydrosilylation reactions most effectively (e.g. equation 4.21) [108], while sodium montmorillonite is completely inactive. 

The highly reactive allyl-iron hydride [HFe(CO)3(T 3-CH2CHCH2)], first proposed over 30 years ago as a key intermediate in the [Fe(CO)s]-catalysed isomerisation of alkenes, has been characterised by NMR spectroscopy for the first time53. A procedure has been reported for the synthesis of tetrahydrofuran esters based on a formal [3 + 2] cycloaddition reaction of [CpFefii -C3H5)(CXD)2] with unactivated carbonyl compounds. 

The reactions of cyclopropenium ions with nucleophiles have led to several interesting observations. In the carbohydrate area, diphenylcyclopropenium perchlorate has been employed in an improved oligosaccharide synthesis based on the glycosylation of sugar diphenylcyclopropenyl ethers. With certain cyclopenta-dienyl-co-ordinated metal carbonyls (Mo, W), tri-t-butylcyclopropenium tetrafluoro-borate affords products derived from electrophilic attack of the cyclopropenium ion on the co-ordinated cyclopentadienyl anion, while for the analogous co-ordinated iron species attack at a carbonyl ligand occurs. With the cyclopentadienyl or indenyl anion, cyclopropenium ion (225) yields the tripolar mesomeric compounds (227), and... 

Recent work by Ford et al. demonstrates that a variety of metal carbonyl clusters are active catalysts for the water-gas shift under the same reaction conditions used with the ruthenium cluster (104a). In particular, the mixed metal compound H2FeRu3(CO)13 forms a catalyst system much more active than would be expected from the activities of the iron or ruthenium systems alone. The source of the synergetic behavior of the iron/ruthenium mixtures is under investigation. The ruthenium and ruthenium/iron systems are also active when piperidine is used as the base, and in solutions made acidic with H2S04 as well. Whether there are strong mechanistic similarities between the acidic and basic systems remains to be determined. 

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