The reaction of the isolated (η5-pentadienyl)tricarbonyliron cation 2 with trimethylphosphite gives not only the (η4-butadienyl)tricarbonyliron phosphates 1 and 6 but also the σ-π allyl derivative 7; the unusual regioselectivity of this nucleophilic addition is attributed to the presence of the ester group in 2. A new and efficient synthesis of 1 has been devised based upon the in situ trapping of a transient (η5-pentadienyl) complexed cation by P(OMe)3. The reactions of 1 with two aldehydes have been studied. Low temperature bond-shift isomerizations of the initially-produced trienes complexed by Fe(CO)3 are observed in several cases.
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We thank Professor Donaldson for sharing his results with us prior to publication and for fruitful discussions. L-S. thanks Roussel-Uclaf for a fellowship. Partial financial support from CNRS is also gratefully acknowledged.