Reusable and environmentally friendly ionic trinuclear iron complex catalyst for atom transfer radical polymerization

Niibayashi, Shota; Hayakawa, Hitoshi; Jin, Ren‐Hua; Nagashima, Hideo

doi:10.1039/b617722k

Cited by 73 publications

(59 citation statements)

References 31 publications

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“…[12] The catalyst is easily removable from the polymer by simple washing with methanol, and furthermore, the recovered catalyst is reusable. However, the reaction rate is relatively low and polymerization of MMA and BA with 1 gave a polymer with a relatively broad molecular weight distribution.…”

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New Iron(II) Complexes for Atom‐Transfer Radical Polymerization: The Ligand Design for Triazacyclononane Results in High Reactivity and Catalyst Performance

et al. 2009

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Mononuclear cordinatively unsaturated iron(II) complexes having a triazacyclononane ligand were developed as highly efficient and environmentally friendly catalysts for the atom-transfer radical polymerization (ATRP). These iron catalysts showed high performance in the well-controlled ATRP of styrene, methacrylates, and acrylates. The high reactivity of these catalysts led to well-controlled polymerization and block copolymerization even with lower catalyst concentrations.Keywords: atom transfer radical polymerization; environmentally friendly catalyst; iron; ligand design; polymerization Transition metal-catalyzed atom-transfer radical polymerization (ATRP) is a representative example of controlled radical polymerization (CRP), which is an important methodology to construct well-defined polymers on both laboratory and industrial scales. [1,2] In ideal cases, good catalysts for ATRP realize: 1) access to polymers with the desired molecular weight and narrow molecular weight distribution, 2) high reaction rate and durability to achieve complete monomer conversion in the construction of block co-polymers, 3) versatile applicability to several monomers, and 4) minimum residual heavy metal catalysts in the product. While the first three points are general requirements for CRP, the fourth point is a special problem for transition metal-catalyzed reactions. It is known that residual metals make the properties of the formed polymers worse and can be potentially harmful. Facile removal of the catalyst from the polymer has thus been investigated using biphasic systems, solid-supported catalysts, and solubility control of catalysts. [3][4][5][6][7][8] Recent results by Matyjaszewski and coworkers showed that reduction of the catalyst concentration to be a solution for this problem as well. [9]

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New Iron(II) Complexes for Atom‐Transfer Radical Polymerization: The Ligand Design for Triazacyclononane Results in High Reactivity and Catalyst Performance

et al. 2009

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“…[55][56][57][58][59][60]75,76 In particular, Nagashima and co-workers recently reported recyclable iron catalysts with nitrogen-based ligands for living radical polymerizations. 77,78 However, almost all of the ironbased systems consist of lower oxidation state iron(II) or iron(I) species in the presence of the appropriate ligands coupled with halide initiators. Although the iron(III) species is more stable than iron(II), it is known as a radical inhibitor and is thus inactive for the activation of the carbon-halogen bond because of its higher oxidation state.…”

Section: Metal-catalyzed Living Radical Polymerization M Kamigaitomentioning

confidence: 99%

Recent developments in metal-catalyzed living radical polymerization

Kamigaito

2010

Polym J

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This review presents a short overview of recent developments in metal-catalyzed living radical polymerization, mainly focusing on our recent research studies related to the subject. Metal-catalyzed living radical polymerization or atom transfer radical polymerization, which was originally developed via evolution of the metal-catalyzed Kharasch or atom transfer radical addition to chain-growth polymerization via reversible activation, has now been widely developed in many aspects. The effective metal catalysts include various transition metals, such as ruthenium, copper, iron and nickel, and highly active and versatile catalytic systems have been developed by designing ligands, applying lower oxidation metal species and using additives to widen the scope of controllable monomers and to minimize the amount of metal catalysts and the residual metals in the products. The development of the initiating systems has enabled the synthesis of a wide variety of novel, well-defined polymers, including end-functionalized, block, graft and star polymers, but also more complicated polymers possessing multiple controlled structures. Furthermore, metal-catalyzed living radical polymerization has been judiciously combined with stereospecific radical polymerization based on the use of polar solvents or Lewis acid additives, resulting in the dual control of the molecular weight and the tacticity of the resulting polymers and enabling the preparation of stereoblock and stereogradient polymers. Keywords: block polymer; living radical polymerization; precision polymer synthesis; transition metal catalyst; star polymer; stereospecific polymerization INTRODUCTIONSince the discovery of metal-catalyzed living radical polymerization or atom transfer radical polymerization (ATRP), there have been many developments in this research area, including active and versatile metal catalytic systems; the scope of controllable monomers; well-defined polymers with various controlled architectures; hybridization of the controlled polymers with inorganic, metal and biomolecular compounds; and attempts or real applications to a variety of industrial materials. 1-17 Besides these metal catalytic systems, there have also been substantial developments in various living radical polymerizations, such as nitroxide-mediated polymerizations, reversible addition fragmentation chain-transfer polymerizations and others, and in all of these, there are characteristic features of the mechanisms and components. [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] The metal-catalyzed living radical polymerization was originally discovered via evolution of the metal-catalyzed Kharasch or atom transfer radical addition reaction 35 to the chain-growth polymerization of vinyl monomers (Figure 1). 1 The initiating system generally consists of a transition metal complex in a lower oxidation state and an organic halide, in which the carbon-halogen bond of the halogen compound is activated by the metal catalyst to generate the carbon radical species upon a one-e...

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“…Belonging to the group-8 family as with ruthenium, divalent iron (Fe II ) also potentially catalyzes living radical polymerization, and since the first successful example with FeCl 2 (PPh 3 ) 2 , 9 a fairly wide variety of iron catalysts have been developed with the use of different ligands, including bipyridine, 10 cyclopentadiene (Cp), 11 pentamethylcyclopentadiene, 12 isophthalic acid, 13 imidazolidene, 14 diimine, 15 diiminopyridine, 16 salicylaldiminato, 17 pyridylphosphine, 18 triazacyclononane, 19 alkyl phosphine, 20 bis(oxazoline), 21 phosphine-nitrogen chelates 22 and phosphazene. 23 The increasingly extensive development primarily stems from the additional advantages of iron complexes: environmentally benign, safe (or less toxic), biocompatible and abundant.…”

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Carbonyl-phosphine hetero-ligated half-metallocene iron(II) catalysts for living radical polymerization: concomitant activity and stability

Ishio

Terashima

Ouchi

et al. 2010

Polym J

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Two neutral ligands, carbonyl (CO) and phosphine, were cooperatively incorporated into half-metallocene iron(II) complexes (CpFeBr(CO)(PR 3 ); Cp¼C 5 H 5 ; PR 3 ¼PPh 3 , P(OPh) 3 , PMePh 2 , PMe 2 Ph, P(n-Bu) 3 ) for more active and versatile systems in transition metal-catalyzed living radical polymerization. For methyl methacrylate (MMA) with a bromide initiator [Me 2 C(CO 2 Me)CH 2 C(Me)-(CO 2 Me)Br; Me¼CH 3 ] [H-(MMA) 2 -Br], these hetero-ligated catalysts are superior, in terms of catalytic activity and molecular weight control, to similar homo-ligated half-metallocenes carrying two identical ligands such as CpFeBr(CO) 2 and CpFeBr(PR 3 ) 2 . Among the CpFeBr(CO)(PR 3 ) complexes examined, CpFeBr(CO)(PMePh 2 ) showed the highest activity and the best controllability (490% conversion within 24 h; M w /M n ¼1.29), and the 'living' character of the polymerizations therewith was proved by sequential monomer addition experiments. In spite of the high activity, the Fe(II) complex is stable and robust enough to be handled under air, rendering it suitable for practical use. The concomitant high activity and high stability were attributed to the in situ generation of a real active catalyst with a 16-electron configuration by the irreversible release of the CO group from CpFeBr(CO)(PR 3 ) on the activation of a terminal C-Br bond, as confirmed by the Keywords: carbonyl ligand; half-metallocene; iron catalyst; living radical polymerization; metal catalysis; methacrylate; phosphine ligand INTRODUCTION A key component of transition metal-catalyzed chemical reactions is obviously a metal complex catalyst, which determines and controls critical parameters including rate, efficiency, selectivity, versatility and so on, 1 and it is particularly true for metal-mediated living radical polymerization (Scheme 1), which we have been pursuing for over a decade (for recent reviews on transition metal catalyzed living radical polymerization, see Kamigaito et al., 2,3 Ouchi et al. 4 and Matyjaszewski and Xja 5 ). In general, a metal complex consists of a transition metal center and ligands, and the two components are connected through coordination and sometimes through metal-carbon bonds formed from a vacant d-orbital of the former and s-, p-or n-electrons of the latter. The ligands thereby affect the electronic as well as steric environments of complexes and, in turn, their catalytic performance.Living radical polymerizations are now powerful tools to synthesize controlled polymeric architectures, because, unlike the ionic counterparts, they are simple and easy to execute, robust and reproducible under varying conditions, and, above all, versatile and applicable to a wide range of monomers including functional derivatives that are often required in biochemistry, materials science and other disciplines

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Reusable and environmentally friendly ionic trinuclear iron complex catalyst for atom transfer radical polymerization

Cited by 73 publications

References 31 publications

New Iron(II) Complexes for Atom‐Transfer Radical Polymerization: The Ligand Design for Triazacyclononane Results in High Reactivity and Catalyst Performance

New Iron(II) Complexes for Atom‐Transfer Radical Polymerization: The Ligand Design for Triazacyclononane Results in High Reactivity and Catalyst Performance

Recent developments in metal-catalyzed living radical polymerization

Carbonyl-phosphine hetero-ligated half-metallocene iron(II) catalysts for living radical polymerization: concomitant activity and stability

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