Photolytic demetalation

The photolytic demetallation of polymers 3a-h was achieved in solutions of acetonitrile, or acetonitrile/DMF, resulting in the isolation of polymers 4a-h. The photolytic reactions were conducted for 4h, and after that time, there was no evidence of the cyclopentadienyliron moieties in the NMR spectra of the organic polymers... 

The organoiron polymers 48a and 48b were subjected to photolytic demetallation to produce the corresponding organic polymers with norbomene groups in their sidechains as shown in Scheme 20. GPC analysis showed fliat these organic polymers had molecular weights of—10,000. 

Polymethacrylates and polystyrenes with cationic cyclopentadienyliron moieties coordinated to their sidechains were prepared by radical polymerization of their corresponding organoiron monomers as shown in Scheme 19. Electrochemical analysis showed that the cyclopentadienyliron coordinated monomers (74) and polymers (75) underwent reversible reduction processes. Photolytic demetallation of die cyclopentadienyliron-coordinated polymethacrylates resrrlted in the corresponding organic analogs with M =48,000-68,000. 

Astruc has also reported the use of arene complexes of iron and ruthenium in the design of star-shaped complexes. The cyclopentadienyliron moiety in 93 (Scheme 25) was utilized to activate the complexed arene toward bromobenzyla-tion to produce 95. Following photolytic demetallation, 96 was reacted with 97 to yield the /jexa-metallic complex 98. These complexed arenes were then subjected to nucleophilic aromatic substitution reactions with 99 allowing for the isolation of 100. 

Polymers 57a-c, 58a-c, and 59a-c were demetallated using photolytic techniques to give polymers 60a-c, 61a-c, and 62a-c in moderate yields (Scheme 19). 

Following isolation of the methacrylate complex 11, this monomer was polymerized in the presence of AIBN as shown in Scheme 4 to produce polymer 12. Polymethacrylate 12 displayed good solubility in acetonitrile, DMF and DMSO. Polymethacrylate 12 was subsequently demetallated using photolytic techniques to yield the organic polymer 13. 

The reaction can be carried out under photolytical conditions applying pentacarbonyliron. More frequently, however, nonacarbonyldiiron is employed that does not require irradiation. The reaction is typically carried out in tetrahydrofuran at room temperature. The allyliron complex obtained is part of a ferralactone ring system that after demetalation is transformed to give P or 6-lactones (Scheme 4-82). The formation of ferralactone complexes is a multistep process. This can be concluded from its stereochemical outcome. The relative configuration of the oxirane ring of Cl-monosubstituted vinyloxiranes is not preserved in the course of the reaction, but a mixture of four possible diastereoisomers can be obtained exo,cis exo,trans endo,cis endojrans Scheme 4-83). In most cases, cis-products are formed with respect to the position of the allyl moiety. 

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