Metal-mediated oxidative polymerization

The Ullmann reaction (79) and the metal mediated oxidative polymerization (20) were used for the synthesis. These methods are replaced by metal catalyzed reactions nowadays. Schluter and Wegner (27) used in 1989 the coupling of boronic acids described by Susuki (22) to synthesize soluble polyphenylenes. The Pd catalyzed reaction tolerates a large number of functional groups. The diaryl coupling of Kumada can be used as well to synthesize polyphenylenes (29,J0). 

PEDOT PSS can be synthesized by (1) oxidative, (2) electrochemical, or (3) transition metal-mediated coupling polymerizations in the presence of a monomeric or polymeric counterion. The synthesis of PEDOT PSS by oxidative polymerization... 

This chapter illustrates that electron-rich transition metal-diene complexes can couple with carbon electrophiles and, thereby, provide unusual methods for carbon-carbon bond formation. These procedures are of interest from a synthetic viewpoint since normally uncomplexed dienes or polyenes are not reactive toward weak carbon electrophiles or, with strong electrophiles, undesirable reactions such as polymerization occur. Furthermore, the metal-mediated route often results in desirable regio- and/or stereo-selectivity. Important to the utility of these methods is the ability to free the organic ligand from the metal. In most instances efficient oxidative procedures have been developed for such cleavage reactions. 

PPys synthesized by both oxidative routes are also subject to coupling defects, which drastically reduce sought after properties. To circumvent this problem, transition metal-mediated polymerizations have been explored. Once again, the synthetic inflexibility of the pyrrole moiety has proven to be a formidable obstacle in obtaining such materials. The Stille coupling scheme [12], shown in Scheme 60, has been used to prepare a BOC-substitued PPy 63 with the protecting group subsequently removed by thermolytic treatment to yield unsubstitut-... 

A molecular conversion system based on a four-electron transfer to 02 was accomplished in the 02-oxidative polymerization of diphenyl disulfide (Figure 14) [116]. This is the first example of a multielectron mediator that is applied to molecular conversion systems. The multielectron transfer process from the reduced vanadium(III) complex (VOV+) to 02 not only revealed the 02 oxidation mechanism but also provided additional insight into the unique chemistry of vanadium with possible relevance to metal mono-oxygenases. 

The -conjugated polyselenophene named PEDOS (182) the analog of poly-3,4-ethylenedioxythiophene (PEDOT) [281], one of the most successful conductive polymers, was obtained from 3,4-ethylenedioxyselenophene (89) using different polymerization techniques. These were oxidative chemical polymerization, solid-state polymerization, transition metal-mediated polymerization, and electrochemical polymerization (Scheme 46) [293, 294], The derivatives of PEDOS having the... 

Yang, I.V. Thorp, H.H. Kinetics of metal-mediated one-electron oxidation of guanine in polymeric DNA and in oligonucleotides containing trinucleotide repeat sequences. Inorg. Chem. 2000, 39, 4969-4976. 

In addition to the design of the solubility properties, the reactivity of organome-tallic species toward CO2 [13] (and many other potential supercritical reaction media) must be considered as important criteria for the choice of the catalyst. For example, the bisallyl ruthenium complex shown in Table 1 cannot be utilized as a precursor for ring-opening metathesis polymerization (ROMP) in SCCO2, because the insertion of CO2 into the Ru-allyl bond prevents the initiation mechanism [14]. Metal-mediated oxygen transfer to form CO and phosphine oxide was found to lead to deactivation of the [Ni(cod)2]/PMe3 (cod = 1,5-m-cycloocta-diene) catalyst system [15]. On the other hand, the reactivity of CO2 with metal... 

A radical initiator based on the oxidation adduct of an alkyl-9-BBN (47) has been utilized to produce poly(methylmethacrylate) (48) (Fig. 31) from methylmethacrylate monomer by a living anionic polymerization route that does not require the mediation of a metal catalyst. The relatively broad molecular weight distribution (PDI = (MJM ) 2.5) compared with those in living anionic polymerization cases was attributed to the slow initiation of the polymerization.69 A similar radical polymerization route aided by 47 was utilized in the synthesis of functionalized syndiotactic polystyrene (PS) polymers by the copolymerization of styrene.70 The borane groups in the functionalized syndiotactic polystyrenes were transformed into free-radical initiators for the in situ free-radical graft polymerization to prepare s-PS-g-PMMA graft copolymers. 

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