Pentenediyl iron complexes

Iron carbonyl complexes containing 77 -alkyl-77 -allyl coordinated hydrocarbon ligands are obtained in several ways. Nucleophilic addition to cationic iron complexes containing 77 -pentadienyl ligands yields (pentenediyl)iron complexes. Oxidatively-induced reductive elimination of these complexes can be utilized as a means to generate 1,2,3-trisubstituted cyclopropanes.The reaction of cationic cycloheptadienyl complexes (Scheme 22) with appropriate nucleophiles also yields the alkyl-allyliron carbonyl complexes. Fe(CO)s also reacts with a- or /3-pincnc in refluxing dioxane (Scheme 22) to produce an alkyl-allyliron complex. Recently, 1,2- and 1,4-disubstituted [(pentadienyl)Fe(CO)3] cations were shown to react with carbon nucleophiles, such as sodium dimethylmalonate, to yield 77 77 -allyl complexes as products. 

Reaction of ferralactone complexes with amines provides ferralactam complexes. Aromatic amines require the addition of a Lewis acid, whereas alkyl amines react spontaneously. In the course of the reaction, the iron complex moiety moves from one end of the allyl system to the other with concomitant inversion of the configuration at Cl and C4. Reaction of a tricarbonyl(vinylketene)iron complex with electron-deficient alkenes gives (pentenediyl)iron complexes that can be oxidized to tetrasubstituted cyclopropanes. ... 

Scheme 4—97. Oxidative demetalation of (pentenediyl)iron complexes.

Another class of Tj -allyliron complexes is represented by (pentenediyl)iron complexes. These compounds result from nucleophilic addition to the 2-position of... 

T -dienyliron cations (Scheme 4-97) (c/ Section 2.5.2.b). Oxidatively induced reductive elimination of (pentenediyl)iron complexes gives vinylcyclopropanesJ 2-226] Depending on the substitution pattern and the conditions applied in some cases the reaction proceeds with retention of the configuration, whereas sometimes inversion of the configuration at the vinylcyclopropyl carbon is observed in combination with an inversion of the configuration at the double bond. The latter has been proven by monodeuteration of the terminal vinylic carbon atom. ... 

To a solution of the (pentenediyl)iron complex (0.12 g, 0.29 mmol) in DMF (15 mL) at room temperature solid CAN (1.75 g, 3.19 mmol) is added in one portion. The reaction mixture is stirred for 3 h, poured into water (20 mL), and extracted with dichloromethane (3 X 25 mL). The combined extracts are dried (magnesium sulfate) and the solvent is evaporated under reduced pressure. The residue is purified by chromatography (Si02, hexane-ethyl acetate [3 1]) to give the cyclopropane product as a translucent oil 44 mg (56%). 

Scheme 4-98. Synthesis of divinylcyclopropanes from vinyl(pentenediyl)iron complexes.

---