Arene-transition metal polymers complexes

Transition metal n-complexes can be used in photolabile linkers. The ir-complex 40 was formed from the chromium arene complex 39 and polymer-supported tri-phenylphosphine (38) [60] (Scheme 17.20). The complex 40 tolerated LiAlH4 reduction and acetylation, but released the product 41 in 70% yield when oxidized with air under the influence of UV irradiation. 

Two different classes of organoiron polymers are the focus of this voliune ferrocene-based macromolecules and polymers containing cationic arene cyclopen-tadienyliron complexes incorporated into their structures. Ferrocene-based polymers are the best-examined class of organo-transition-metal polymer. Since they were first examined in the 1950s, this class of organoiron polymer has been synthesized by almost all imaginable polymerization techniques. 

Apart from the metal atom aggregation reactions described below, bis(arene)metal complexes of the early transition metals are resistant to ligand displacement The rings on the corresponding bis(naphthalene)metal species (41) are by, contrast, labile. Polymer-supported analogs of these naphthalene compounds with vanadium and chromium are known (42), but Ti atoms attack the polymer at the silicon ether linkage. These and other hybrid polymers can be further modified once the metal atom is incorporated. Thus a-methyl naphthalene is displaced from the hybrid organometallic polymer shown in Scheme 7 (43). 

A modern series of new plastics are based on transition metals (e.g. Fe, Ti, Cr, Zn, V) to form polymers and possess unusual properties such as variable oxidation states, and ligand exchange on the metal atom. They have reduced UV absorption and visible radiation and exhibit electrical conductivity. Examples include cyclopentadienyl and arene metal n polymeric complexes that act as electron rich aromatic system and are very reactive to a range of monomers to form polymers. 

Various oxidations with [bis(acyloxy)iodo]arenes are also effectively catalyzed by transition metal salts and complexes [726]. (Diacetoxyiodo)benzene is occasionally used instead of iodosylbenzene as the terminal oxidant in biomimetic oxygenations catalyzed by metalloporphyrins and other transition metal complexes [727-729]. Primary and secondary alcohols can be selectively oxidized to the corresponding carbonyl compounds by PhI(OAc)2 in the presence of transition metal catalysts, such as RuCls [730-732], Ru(Pybox)(Pydic) complex [733], polymer-micelle incarcerated ruthenium catalysts [734], chiral-Mn(salen)-complexes [735,736], Mn(TPP)CN/Im catalytic system [737] and (salen)Cr(III) complexes [738]. The epox-idation of alkenes, such as stilbenes, indene and 1-methylcyclohexene, using (diacetoxyiodo)benzene in the presence of chiral binaphthyl ruthenium(III) catalysts (5 mol%) has also been reported however, the enantioselectivity of this reaction was low (4% ee) [739]. 

POLYMERS CONTAINING ARENES COORDINATED TO TRANSITION METAL COMPLEXES... 

There has been a great deal of interest in the design of dendrimers using arene complexes of transition metals (246-252). Astruc has developed an efficient route to core molecules suitable for the synthesis of star and dendritic materials via peralkylation or allylation of methyl-substituted arene complexes of cyclopen-tadienyliron. The resulting branched polymers contained cationic cyclopentadi-enyliron moieties at the core and/or the periphery. Complexes containing aryl ethers coordinated to six CpFe+ moieties (110) were synthesized via SNAr reactions (248). 

A review on the industrial applications of homogeneous catalysts is particularly welcome. The proceedings of recent symposia and a general text have been published in addition to reviews on metal cluster catalysts, activation of saturated hydrocarbons by metal complexes in solution, catalysis by arene Group-VIB tricarbonyls, titanocene-catalysed reactions ofalkenes, transition-metal hydrides in catalysis, the mechanisms of the catalytic cyclization of aliphatic, hydrocarbons, asymmetric hydrosilylation and asymmetric synthesis. A n.m.r. study of the conformations of chelated Diop and a MO study of organo-metallic migration reactions are also of interest. Polymer supported catalysts have been reviewed and the relationship between cross-linking of the polymer and catalytic activity has been discussed. ... 

There have been many studies on this important class of arene iron compound, in part, because they can be used in organic synthesis, polymer synthesis, and for the preparation of a range of new organoiron derivatives that are both mononuclear and polynuclear. Kiindig has written a review on the synthesis of transition metal 77 -arene complexes, which includes a section on [Ee(arene)Gp] cations. 

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