Sodium tetracarbonylferrate halide carbonylation

The direct oxidation of alkyl halides to carbonyl compounds by DMSO occurs in good yield under mild conditions in the presence of silver ion, which assists formation of the alkoxysulphonium intermediate silver perchlorate is the salt of choice, other salts competing nucleophilically with DMSO for the substrate. Oxidation of primary halides stops cleanly at the aldehyde stage, except when an excess of silver salt is present. As has been already described, sodium tetracarbonylferrate converts alkyl bromides into the homologous aldehydes this conversion is most successful with primary halides, n-decanal being obtained in 77% yield from n-nonyl bromide. 

The iron chemistry which is related to these reversible carbonylations is most usefully revealed by an ionic compound, sodium tetracarbonylferrate. The highly carbonylated Fe(-2) anion can effect the conversion of alkyl halides and tosylates into aldehydes, ketones, and carboxylic acid derivatives. The reactions begin by oxidative addition of the halide to the very nucleophilic iron atom, followed by carbonyl insertion. This particular reagent illustrates several of the crucial reactions... 

Applications of carbonylaie reactions in organic synthesis are numerous. Particularly noteworthy are schemes involving tetracarbonylferrate( - ID (referred to as Collman s reagent), which can be isolated as a. sodium salt, NanFe(CO)4-1.5 dioxane, and is commercially available. The highly nucleophilic [Fe(CO)4p reacts readily with alkyl halides to yield alkyl iron carbonylates ... 

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