Silicon-iron bonds, cleavage

However, an alternative mechanism has been suggested to us by Prof. H. Saku-rai. It involves the homolytic cleavage of the iron-silicon bond Scheme 3). 

The iron-silicon bond in these complexes appeared to be very stable. Nucleophilic cleavage was observed only with water and with lithium aluminum hydride (Scheme 52). Although not specific, nucleophilic cleavage occurs with predominant retention of configuration at silicon. 

The iron-silicon bond is more easily cleaved by electrophilic reagents. Results obtained in the chlorine or bromine cleavage reaction are given in equation [68]. 

TAN 04] Tanabe M., Manners 1., photolytic living anionic ring-opening polymerization (ROP) of silicon-bridged [Ijferrocenophanes via an iron-cyclopentadienyl bond cleavage mechanism . Journal of American Chemical Society,vo. 126, pp. 11434-11435,2004. 

Iron-carbon bond cleavage in the reaction of MeaC-CHD-CHD-Fe-(A -C6H5)(CO)a with bromine also takes place predominantly with inversion of configuration at the carbon." Thus it would seem more likely that the correct interpretation of the stereochemistry of a-bromopropionate addition to iridium(i) is that this reaction involves inversion at the carbon atom, but at the time of writing none of the evidence available gives unequivocal support to this hypothesis. Reaction of silanes with trans-[IrCl(CO)(PPh3)a] seems to involve retention of configuration at silicon. ... 

The mechanism for the unusually rapid acid cleavage of the Si—Si bond in disilanylferrocenes is not yet clearly understood. A mechanism was originally proposed involving an a-ferrocenylsiliconium ion intermediate (or transition state), possibly stabilized by overlap of filled 3 d orbitals of iron with the electron-deficient p orbital of silicon (117). However, the observations described above and the current concepts of electrophilic substitution... 

Predominant retention or inversion at silicon was observed depending on the ligands attached to iron and on the nature of the reagent. By contrast the cleavage of Si-Co bonds (eq. [80]) was shown always,to involve retention of configuration at silicon (239). 

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