Phase transfer generation of acyltetracarbonyliron anions: their role in the phase transfer carbonylation of reactive halides to give carboxylic acids and symmetrical and unsymmetrical ketones

Acyltetracarbonyliron anions RCOFe(CO)4–(3) are readily synthesised under mild phase transfer (PT) conditions from pentacarbonyliron and reactive organic halides; the in situ generated anions (3)(R = ArCH2) are the true catalysts in the PT carbonylation of benzyl halides to give ketones or carboxylic acids.