Cyclopentadienyliron moieties polymers

Cationic cyclopentadienyl iron fragments have been generated by photolysis of [(C5H5)Fe(C6H6)] [PF6] and shown to form transient cationic triple-decker sandwich complexes with [(t-Bu3C3P2)Fe(r-Bu2P3)]. Similar photolytic removal of cyclopentadienyliron moieties has been utilized as a key step in the synthesis of ether and thioether building blocks for polymer synthesis. ... 

Aromatic and aliphatic spaces have been incorporated into organoiron polymers to determine their affect on the thermal stability and glass transition temperature of the polymers.256 The thermal stability of these polymers increased after the loss of the metallic moieties. The metallated polymer shows two decomposition steps at 245°C, corresponding to decomposition of the cyclopentadienyliron moieties and a second weight loss beginning at 511°C, corresponding to... 

At low concentrations (0.025 M) the photolysis of these polymers resulted in the decoloration due to the degradation of the azo dye.260 After the cationic cyclopentadienyliron moieties are cleaved from the polymer, they form complexes with the azo chromophore, which then leads to photodegradation of the azo chromophore. 

Cationic polyferrocenes containing pendent cyclopentadienyliron moieties as well as azo dyes in their backbone, 210, have been prepared.261 These polymers displayed excellent solubility in polar organic solvents and exhibited max around 419 nm. Electrochemical studies showed that these polymers underwent two redox couples corresponding to the two different iron centers. The oxidation of the ferrocene occurred at Ey2 = 0.89 V and the reduction of the cationic cyclopentadienyliron complex occurred atEV2 = —1.42 V. Photolytic cleavage of the cationic cyclopentadienyliron moieties produced the neutral polyferrocene analogs. 

Recently, Abd-El-Aziz and colleagues reported different hyperbranched poly(arylethers) (4,5) and poly(arylthioethers) (6) containing cyclopentadienyliron moieties, which were successfully furnished by nucleophilic substitution of A + Bj type monomers (Scheme 2.3) [54], The polymers were thoroughly characterized by standard spectroscopic analysis techniques, they exhibited generally low viscosities, and the organometallic complexes were stable up to 230 °C, as evaluated by thermal gravimetric analysis (TGA). 

TGA analysis showed that polymers 25 were thermally stable with the first weight loss starting between 225 and 241 °C as a result of the decomplexation of the cyclopentadienyliron moieties as well as partial decomposition of the polymer side chains. The second weight-loss beginning between 400 and 450 °C was attributed to the degradation of the polymer backbone. DSC analysis showed that the organoiron... 

The synthesis of a water-soluhle metallodendrimer containing six cationic cyclopentadienyliron moieties was also reported (249). This dendrimer was examined as a redox catalyst for the cathodic reduction of nitrates and nitrites to ammonia. Star-shaped polyaromatic ether complexes of cyclopentadienyliron were recently reported hy Ahd-El-Aziz and co-workers (250). These complexes contained up to 15 cationic cyclopentadienyliron moieties pendent to aromatic rings in the star branches (111). Electrochemical analysis of these star polymers showed that the iron centers underwent reversible reduction processes. 

The synthesis of polymers containing cyclopentadienyliron moieties within and pendent to their backbones (38) was reported by Abd-El-Aziz and coworkers. The cationic cyclopentadienyliron moieties were pendent to the polymer backbones, while the neutral ferrocene units were incorporated into the polymer backbones. The cationic iron centers underwent reversible reduction processes, while the neutral iron centers underwent reversible oxidation processes. The cationic cyclopentadienyliron moieties were cleaved from the polymer backbones by photolysis however, the ferrocene units in the polymer backbones were not degraded. 

Star polymers and dendrimers have been synthesized by Astruc using cyclopentadienyliron-mediated peralkylation, benzylation, and allylation reactions of cationic tri-, tetra-, and /iexa-methylbenzene cyclopentadienyliron com-plexes. " " These star and dendritic polymers contained cationic cyclopentadienyliron moieties at the core and/or the periphery. The cathodic reduction of nitrates and nitrites to ammonia has been achieved using a water-soluble dendrimer containing six cationic cyclopentadienyliron moieties as a redox catalyst. " The octametallic star (41) was prepared by deprotonation of permethylated iron complexes. ... 

IV POLYMERS CONTAINING NEUTRAL AND CATIONIC CYCLOPENTADIENYLIRON MOIETIES... 

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... 

Monomers 49 and 50 were subsequently reacted with 2d, 7, and lOd in the presence of potassium carbonate in DMF, resulting in the formation of polymers 51a-f as shown in Scheme 14. These polymers are unique in that they bear neutral ferrocenyl units in their backbones and cationic cyclopentadienyliron moieties pendent to their backbones. These polymers were isolated as orange solids in yields ranging from 86 to 91%. These organoiron polymers demonstrated good solubility in polar organic solvents such as DMF and DMSO. 

The thermal properties of the carboxylic acid-frmctionalized polymers were compared with the azo-frmctionalized polymers in order to examine the effects of the azobenzene sidechains. In addition, a comparison of the thermal properties of the metallated and demetallated azo-frmctionalized polymers could provide information on the influence of the cyclopentadienyliron moieties on these materials. Thermal analysis of these polymers was performed using thermogravimetric analysis and differential scanning calorimetry. 

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 and coworkers have reported the synthesis of highly branched polymers coordinated to cyclopentadienyliron and pentamethylcyclopentadienyl-ruthe-niiun cations." The catalytic and sensing ability of star polymers and dendrimers has also been reviewed. Multifunctional core molecules suitable for the synthesis of star and dendritic materials were synthesized by peralkylation or aUylation of methyl-substituted arene complexes of cyclopentadienyliron." The benzylic protons on these complexed arenes are acidic, which permits their facile alkylation. These branched polymers contained cationic cyclopentadienyliron moieties at the core and/or the periphery. The synthesis of a water-soluble metallodendrimers... 

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