Iron complexes alkyl cleavage

The reductive dehalogenation of haloalkanes has also been achieved in high yield using polymer supported hydridoiron tetracarbonyl anion (Table 11.15). In reactions where the structure of the alkyl group is such that anionic cleavage is not favoured, carbonylation of the intermediate alkyl(hydrido)iron complex produces an aldehyde (see Chapter 8) [3]. 

Iron complexes containing bidentate alkyl and aryl phosphorus ligands cleave a variety of C-H bonds under mild conditions, Hydrido acetylide complexes were prepared by oxidative addition of primary acetylenes in the Fe(DPPE)2 and the Fe(DMPE)2 systems [DPPE = bis(diphenylphos-phino)ethane, DMPE = bis(dimethylphosphino)ethane]. The Fe(DMPE)2 system also cleaves C-H bonds of activated methyl groups, aromatic compounds, and certain other sp hybridized molecules. The C-H cleavage reactions are reversible, resulting in equilibrium mixtures of isomeric products in many cases. Studies of substituted benzenes show that while product stability is favored by electron withdrawing substituents, steric effects play a predominant role in the determination of product distribution. 

In an elegant synthetic application of iron-diene complexes, Knox30 has reported acylation of a series of 1-alkyl-substituted diene complexes which after cleavage, reduction and esterification give a series of moth pheromones (Scheme 11). 

S. Y. Han et al. (2000). New insights into the mechanisms of 0-0 bond cleavage of hydrogen peroxide and tert-alkyl hydroperoxides by iron(III) porphyrin complexes. J. Am. Chem. Soc. 122, 8677-8684. 

Cleavage of the Zr—C c-bond of [(rj-CBH5)aZr(Cl)(CHDCHDBu )] (1) with bromine and iodine proceeds with retention of configuration at carbon, in contrast to M—C bond cleavage in alkyl-iron and -cobalt complexes in which inversion at carbon is the norm (see Scheme 1). This difference is attributed to the fact that with... 

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