Reactions of metal carbonyl derivatives. Part III. The mechanism of halogenation of tetracarbonylbis-π-cyclopentadienyldi-iron and its derivatives
- 1 January 1970
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc. A
- p. 2341-2346
- https://doi.org/10.1039/j19700002341
Abstract
A study of the halogenation of [{Fe(π-RC5H4)(CO)2}2](R = H or Me) has revealed that under the appropriate experimental conditions, products other than [Fe(π-RC5H4)(CO)2X]viz.[{Fe(π-RC5H4)(CO)2}2X]X and [Fe(π-RC5H4)(CO)3]X (X = Cl, Br, or I), are also formed. it is further shown that the derivative [{Fe(π-RC5H4)(CO)2}2X]X containing a bridging halogen group is an intermediate in the formation of [Fe(π-RC5H4)(CO)2X] and that the yield of [Fe(π-RC5H4)(CO)3]X increases along the series I < Br < Cl. The experimental results are interpreted in terms of a mechanism involving electrophilic attack of the halogen on [{Fe(π-RC5H4)(CO)2}2] followed by (I) asymmetric cleavage of the bridging carbonyl groups of the parent dimer to yield [Fe(π-RC5H4)(CO)3]X and/or (II) symmetric cleavage of these carbonyl groups to afford [{Fe(π-RC5H4)(CO)2}2X]X. Subsequent nucleophilic attack of halide ions on this latter derivative produces the neutral compound [Fe(π-RC5H4)(CO)2X]. The proposed mechanism is compared with that well established for the electrophilic addition of halogens to olefins.Keywords
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