Substituted Iron Dicarbonyl Cations

Submitted by E. O. FISCHER and E. MOSER Cheeked by P. M. TREICHELf and J. P. STENSONt 

In recent years more and more emphasis has been laid on the chemistry of cyclopentadienyl metal carbonyls. In this field the reactions of cyclopentadienyl metal carbonyl halides with electron donors deserve special attention. Many of these reactions yield cations by replacement of halogen. In the following report, general procedures will be described by which substituted cyclopentadienyliron dicarbonyl cations of the type [C5H5Fe(CO)2L]+ can be prepared. 

Most cyclopentadienyl metal carbonyl compounds are to some extent sensitive to air. The compounds described herein can be exposed to air for a short time however, it is recommended that they should be handled in an inert-gas atmosphere in order to obtain pure samples. Even if there is no decomposi- 

DICARBONYL TETRAPHENYLBORATE—THE REACTION OF CYCLOPENTADIENYLIRON DICARBONYL HALIDES WITH DONOR MOLECULES 

A 210-mg. (1-namole) sample of CsH6Fe(CO)2Cl is placed in a small Schlenk tube (see Fig. 1, page 10) of about 100-ml. volume. 

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Alkenes in (alkene)dicarbonyl(T -cyclopentadienyl)iron(l+) cations react with carbon nucleophiles to form new C —C bonds (M. Rosenblum, 1974 A.J. Pearson, 1987). Tricarbon-yi(ri -cycIohexadienyI)iron(l-h) cations, prepared from the T] -l,3-cyclohexadiene complexes by hydride abstraction with tritylium cations, react similarly to give 5-substituted 1,3-cyclo-hexadienes, and neutral tricarbonyl(n -l,3-cyciohexadiene)iron complexes can be coupled with olefins by hydrogen transfer at > 140°C. These reactions proceed regio- and stereospecifically in the successive cyanide addition and spirocyclization at an optically pure N-allyl-N-phenyl-1,3-cyclohexadiene-l-carboxamide iron complex (A.J. Pearson, 1989). 

Cationic ri -allyl(tetracarbonyl)iron complexes are powerful electrophiles that react with nucleophiles primarily to T -alkene(tetracarbonyl)iron complexes. Those species are rather labile and decompose during workup to afford substituted alkenes. This methodology has been described for the first time by Pearson using organocadmium nucleophiles. Similarly, Ti -allyl(dicarbonyl)(nitrosyl)iron complexes, despite the lacking positive charge, also smoothly react with various nucleophiles. As... 

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