Iron, carbonyl compounds diiron nonacarbonyl

Various substituted silacyclopentadienes react with iron or cobalt carbonyl compounds to give stable i 4-silacyclopentadiene complexes. Thus, with iron pentacarbonyl, reaction occurs at 150°-200° in an autoclave, with Fe2(CO)9 at 40°-60°, and with Fe3(CO)12 at 80° (20, 21, 49, 132) the same complex can be obtained from a dibromosilacyclopen-tene and diiron nonacarbonyl, under mild conditions (19) ... 

First, cis- and trans-2-phenylmethylenecyclopropanes-3-d were shown to give trimethyl-enemethane complexes with the deuterium at a location consistent only with disrotatory ring-opening (Figure 41). Second, reaction of 2,2-diphenylmethylenecyclopropane with a variety of iron carbonyl reagents allowed isolation of the methylenecyclopropane iron tetracarbonyl complex. This compound could be shown to give the trimethylenemethane complex on reaction with trimethylamine-N-oxide or diiron nonacarbonyl, both of which... 

Another synthetically useful carbon bond-forming reaction involves reaction of diiron nonacarbonyl with halo-carbonyl compounds. Noyori found that a,a -dibromoketones (498) react with diiron nonacarbonyl [Fe2(CO)9] to give an iron stabilized alkoxy zwitterion (499). The intermediate Jt-allyl iron species reacts with alkenes in a stepwise manner (initially producing 500) to give cyclic ketones such as 501, 23 and the product is equivalent to the product of a [3-t2]-cycloaddition with an alkene (sec. 11.11). This cyclization method is now known as Noyori annulation. This reaction is related to the Nazarov cyclization previously discussed in Section 12.3.C. Enamines can react with 498, but the initially formed enamino ketone product eliminates the amino group to form cyclopentanone derivatives. Intermediates such as 499 may actually exist as cations hound to a metal rather than as the alkoxide-iron structures shown.323b-d noted that Zn/B(OEt)3 is... 

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