Cyclic organometallic iron complexes

The chemistry of iron vinylidene complexes is dominated by the electrophilicity of the carbon atom adjacent to the iron organometallic unit. While addition of water leads to an acyl complex (i.e., the reverse of the dehydration shown in equation 10), addition of an alcohol leads to a vinyl ether complex. Similarly, other iron vinyl complexes can be prepared by the addition of thiolate, hydride, or an organocuprate (Scheme 33). " The nucleophilic addition of imines gave enaminoiron intermediates that could be further elaborated into cyclic aminocarbenes. This methodology has been used to provide access to /3-lactams and ultimately penicillin analogs, and good diastereoselectivities were observed (6 1-15 1) (Scheme 34). 04 Iso, vinylidene complexes are intermediates in cyclizations of alkynyl irons with substituted ketenes, acid chlorides, and related electrophiles an example is shown (equation 11). These cyclizations led to the formation of a series of isolable and characterizable cyclic vinyl iron complexes. 

Scheme 9.7 shows the oxidations of two organometallic iron complexes 21 [10, 18] and 22 [10, 18b, 19] having two Fe(II) alkynyl moieties connected via meta-and /) r -phenylene rings, respectively. Cyclic voltammetry reveals the stronger communication conveyed by the y r -complex 22, reflected in a larger separation between the first and second oxidation potentials = 0.26 V) than in the... 

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