ROMP Synthesis and Redox Properties of Polycationic

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ROMP Synthesis and Redox Properties of Polycationic Metallopolymers Containing the Electron-Reservoir Complex [Fe(η5‑C5H5)(η6‑C6Me6)][PF6] Haibin Gu,†,‡ Roberto Ciganda,‡,§ Ricardo Hernandez,§ Patricia Castel,‡ Pengxiang Zhao,∥ Jaime Ruiz,‡ and Didier Astruc*,‡ †

Key Laboratory of Leather Chemistry and Engineering of Ministry of Education, Sichuan University, Chengdu 610065, P. R. China ISM, UMR CNRS No 5255, Univ. Bordeaux, 33405 Talence, Cedex, France § Facultad de Quimica de San Sebastian, Universidad del Pais Vasco, Apdo 1072, 20080 San Sebastian, Spain ∥ Science and Technology on Surface Physics and Chemistry Laboratory, PO Box 718-35, Mianyang 621907, Sichuan P. R. China ‡

S Supporting Information *

ABSTRACT: Electron-reservoir metallopolymers in which these nanomaterials are robust in at least two oxidation states are being actively investigated in view of applications as stable electron-transfer reagents. Here living ring-opening metathesis polymerization (ROMP) and diblock copolymerization of norbornene derivatives are conducted in which the cationic organoiron complex [FeCp(η6-C6Me6)][PF6] (Cp = η5-C5H4R) is covalently attached to the norbornene motif with a short trimethylene amido linker or a longer linker containing also the triethylene glycol (TEG) unit. Solubility constraints involved with the shorter linker require that the ROMP reaction be conducted in dimethylformamide (DMF), whereas the solubilizing longer linker conveniently allows carrying out the ROMP reaction in dichloromethane (DCM). Cyclic voltammetry (CV) of all these metallopolymers shows the full reversibility of the FeII → FeI reduction wave at −1.35 V vs decamethylferrocene, [FeCp*2], and the numbers of monomer units found using the Bard−Anson method by CV are close to the monomer/catalyst ratio used in the ROMP reaction.

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INTRODUCTION

in these compounds is essentially the permethylation of the arene ligand such as in hexamethylbenzene complexes. Thus, the complexes [Fe(η5-C5R4R′)(η6-C6Me6)] (R = R′ = H or Me, R = H, R′ = alkyl, CO2H, CO2-alkyl, C(O)N-alkyl, CO2−) could be isolated in Fe(II) and Fe(I) forms, and for R = R′ = Me also in Fe(III) form, and present a variety of stoichiometric and catalytic electron-transfer processes.5 However, only a few dendritic molecules containing the complex [FeCp(η6C6Me6)][PF6] connected to the branch termini have so far been reported, due to the difficulty related to the weak solubility resulting from the simultaneous presence in this complex of the positive charge and large bulk of the arene ligand.6 We therefore envisaged to introduce this complex on the side branches of polymers given the fast and living polymerization provided by the third-generation Grubbs ruthenium ring-opening metathesis polymerization (ROMP) catalyst.7 The use of this very useful ROMP catalyst 4 for poly(alkyl)metallocene synthesis has been initiated in 2012,8 and these seminal studies have been followed by reports of

Metallopolymers have recently been increasingly investigated using various new synthetic methods owing to their materials properties and uses provided by the presence therein of metal groups.1 Redox-robust polymers are of particular interest because of the possibility to synthesize them as stable materials in two or several oxidation states, allowing to tune their physical and chemical properties upon redox switch. Among them, ferrocene polymers constitute one of the most important metallopolymer family that has been developed using the extensive possibilities of ferrocene chemistry with properties such as electrochrome involving the redox activity of the iron(II/III) redox center.2 Abd-El-Aziz’s group3 has also elegantly developed an extensive family of metallomacromolecules containing the cationic 18-electron sandwich complexes [Fe(η5-C5H5)(η6-arene)]+ in the main chain or in the side chain, which are isolobal4 to ferrocene. These polymers are built starting from such cationic precursor chloroarene or pdichlorobenzene complexes by facile nucleophilic substitution of the chloro group by O, N, or S nucleophiles. These materials show the fully reversible Fe(II) → Fe(I) reduction wave by cyclic voltammetry, but the Fe(I) complexes are not stable for longer time scales.3 The condition for stability of the Fe(I) state © XXXX American Chemical Society

Received: July 18, 2015 Revised: August 8, 2015

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DOI: 10.1021/acs.macromol.5b01603 Macromolecules XXXX, XXX, XXX−XXX

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Macromolecules Scheme 1. Synthesis of Cationic [FeCp(η6-C6Me6)]-Containing Polymer 5 by ROMP in DMF

other polymetallocene derivatives using this catalyst.2b,3,9 ROMP syntheses of polymers containing cationic complexes [FeCp(η6-arene)][PF6] in which the arene ligand is paradisubstituted were first reported by the Abd-El-Aziz group using RuCl3·hydrate and Grubbs’ first-generation metathesis catalyst, [RuCl2(PCy3)2(CHPh)].10 Our goal is ultimately to synthesize living cationic electron-reservoir polymers that can be reduced to stable Fe(I) complexes. In this article the strategy involves the synthesis of the norbornene derivatives with a tether of variable length functionalized with the cationic complex [Fe(η5-C5H4COCl)(η6-C6Me6)][PF6], 2, followed by ROMP polymerization of the functional monomers with the catalyst 4. Finally, the solubilities and electrochemical studies of the metallopolymers will be examined as crucial aspects toward further use.

however, after the DCM solution of monomer 3 was added to the catalyst solution at rt, which was caused by the poor solubility of the polymer 5 in DCM. Subsequently, the polar solvent dimethylformamide (DMF), in which both the monomer 3 and the polymer 5 are soluble, was used for the preparation of 5. A kinetic study was carried out to monitor the ROMP of monomer 3. At different reaction intervals, such as 0.5, 1, and 2 h, an aliquot (0.05 mL) of the reaction mixture was quenched with 0.05 mL of ethyl vinyl ether (EVE). The monomer conversion was determined by the in situ 1H NMR analysis of the reaction mixture in acetone-d6. When the signal of olefinic protons for monomer 3 at 6.30 ppm disappeared, the conversion was deemed to be 100%. After a few hours conversion was not complete, and quantitative monomer conversion required overnight stirring, the slow reaction rate being seemingly caused by the arene ligand bulk combined with the positive charge. Figure S7 shows the 1H NMR spectrum of the polymer 5. The characteristic double peaks arising from the olefinic protons of polynorbornene appeared at 5.62 and 5.52 ppm, while the single peak at 6.30 ppm corresponding to the olefinic protons of monomer 3 disappeared, showing completion of polymerization. The peak at 7.72 ppm is assigned to the amido proton, and the peaks at 5.08 and 4.92 ppm correspond to the substituted Cp protons, while the methyl protons of η6-C6Me6 are found at 2.48 ppm. Furthermore, after ROMP the other sharp signals of the cisnorbornene backbone in monomer 8 changed into broad signals. All these data confirm the successful ROMP of 3 and the structure of polymer 5. The UV−vis spectrum of the polymer 5 (Figure S11) shows a similar absorption to that of monomer 3, which is also consistent with the integrity of the [FeCp[(η6-C6Me6)][PF6] unit. The 13C NMR (Figure S9) and IR (Figure S10) also provided clear evidence for the formation and structure of 5. In this study, two molar feed ratios of monomer to catalyst (25:1 and 50:1) were used to prepare the polymers 5 with different sizes, i.e., 525 and 550. The polymers 5 were obtained as yellow-brown powders after precipitation from diethyl ether. Unlike the monomer 3, they are not soluble in common organic solvents including DCM, chloroform, tetrahydrofuran (THF), and methanol; they are partly soluble in acetone and acetonitrile and easily soluble in the more polar solvents DMF and dimethyl sulfoxide (DMSO). Figure S12 shows the MALDI-TOF mass spectrum of the polycationic polymer 525. The highest molecular peak that could be observed was that of 1288.1 Da corresponding to a polymer fraction containing two monomer units without a phosphorus atom. As shown in Figure S12B, the enlarged region of the spectrum from 2419 to 3691 Da, there are several peaks for polymer fragments that are separated by 660 ± 1 Da corresponding to the MW of monomer 3, which can indicate

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RESULTS AND DISCUSSION Synthesis and ROMP of Monomer 3. As shown in Scheme 1, the new monomer 3 containing the mixed-sandwich group [Fe(η5-C5H4-)](η6-C6Me6)][PF6] was prepared by the amidation reaction between N-(2-aminoethyl)-cis-5-norbornene-exo-2,3-dicarboximide (1) and the chlorocarbonyl complex [Fe(η5-C5H4COCl)(η6-C6Me6)][PF6] (2)5 in the presence of triethylamine. Figure S1 shows the 1H NMR spectrum of monomer 3. The peak at 7.77 ppm corresponds to the amido proton, while the peak at 6.30 ppm originates from the olefinic protons. For the mixed-sandwich complex unit, the chemical shifts of the cyclopentadienyl (Cp) protons are found at 5.10 and 4.94 ppm, respectively, and the characteristic methyl protons of η6C6Me6 are located at 2.51 ppm. The methylene protons next to the imide and amido groups are observed at 3.57−3.71 ppm. All the other peaks were clearly assigned. In the 13C NMR spectrum of 3 (Figure S2), the peak at 164.18 ppm is assigned to the carbon of the amido group, while the peaks at 100.35 and 17.00 ppm correspond to the carbons of the η6-C6Me6 ligand. The substituted Cp carbons are located at 85.02, 81.17, and 77.23 ppm. All the other peaks of the 13C NMR are well assigned and match well with the structure of the monomer 3. The high-resolution mass spectrum (Figure S3) shows the molecular peak at 515.1984 Da, in good agreement with the theoretical value of 515.1991 Da. Furthermore, the IR (Figure S4) and UV−vis. (Figure S5) spectra are also consistent with the structure of 3 including the mixed-sandwich complex [FeCp(η6-C6Me6)][PF6]. ROMP was used to synthesize the homopolymer 5 containing the cationic side-chain mixed-sandwich complex [FeCp(η6-C6Me6)][PF6] from monomer 3 at room temperature (rt) using the ROMP catalyst 4. We first attempted to carry out the polymerization in dry dichloromethane (DCM). Precipitation was found to quickly occur (less than 2 min), B

DOI: 10.1021/acs.macromol.5b01603 Macromolecules XXXX, XXX, XXX−XXX

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Scheme 2. Synthesis in DCM of the Monomer 7 and Polymer 8 Containing the Cationic Complex [FeCp(η6-C6Me6)][PF6]

Therefore, the tetraethylene glycol (TEG) group was introduced in order to connect the cis-norbornene backbone and the mixed-sandwich complex as shown in Scheme 2 and to provide a more flexible side arm. This new monomer 7 was prepared by the amidation reaction between N-[11′-amine3′,6′,9′-trioxahendecyl]-cis-5-norbornene-exo-2,3-dicarboximide (6) and the chlorocarbonyl complex (2) in the presence of triethylamine (Scheme 2). Figure S14 shows the 1H NMR spectrum of 7 in CDCl3. The peak at 7.32 ppm corresponds to the amido proton, while the peak at 6.27 ppm originates from the olefinic protons. For the mixed-sandwich complex unit, the chemical shifts of the substituted Cp protons are found at 5.02 and 4.60 ppm, and the characteristic methyl protons of η6-C6Me6 are located at 2.41 ppm. The TEG methylene protons between the imide and amido groups are observed at 3.55−3.66 ppm, and all the other peaks were assigned. In 13C NMR (Figure S16), the peak at 163.27 ppm is assigned to the amido group carbon, and the peaks at 99.30 and 16.79 ppm correspond to the carbon atoms of the η6-C6Me6 unit. The signals of the substituted Cp carbons are located at 83.95, 80.11, and 76.27 ppm. The peaks corresponding to the TEG methylene carbons appear at 70.45− 66.90 ppm, and all the other peaks are assigned and match well with the structure of 7. In the high-resolution mass spectrum (Figure S17), the molecular peak at 647.3 Da showed a good agreement with the theoretical value of 647.5 Da, and the IR (Figure S18) is in agreement with the presence of the complex [FeCp(η6-C6Me6)][PF6]. Unlike that of the monomer 3, the ROMP of monomer 7 was carried out successfully in dry DCM at rt using the catalyst 4. There is no precipitation during the whole period of polymerization, and precipitation was observed only after the addition of the quenching agent, EVE. A kinetic study was carried out to monitor the ROMP of monomer 7. At different reaction intervals, 5, 10, 20, 30, 45, and 60 min, an aliquot (0.05 mL) of the reaction mixture was removed and quenched with 0.05 mL of EVE. The in situ 1H NMR analysis in acetone-d6 was conducted, and the monomer conversions were calculated by monitoring the change of the relative intensities of the signals the olefinic protons between monomer 7 (6.31 ppm) and the polymers 8 (5.80 and 5.56 ppm). When the peak at 6.31 ppm disappeared, the monomer conversion was deemed to be 100%. It is found that 100% monomer conversion was achieved in 10 min, indicating that the ROMP rate of monomer 7 in DCM is faster than that of monomer 3 in DMF. This higher conversion rate of ROMP of monomer 7 than that of 3 is taken into account by both the longer connection tether in 7 compared to 3 that releases the steric constraints involved in the ROMP reaction and the much higher solubility of 7 than that of 3 in DCM.

the formation of polymer 5. These peaks are weak, however, presumably because of the poor solubility and cationic nature of polymer 525. Characterization of the MW distribution of polymer 5 by SEC is very difficult or hazardous in such polycationic complexes.11 The polymerization degree of polymers 5 was then determined using Bard−Anson’s electrochemical method12 which is a good method in the case of redox-active metallopolymers and has been used appropriately for macromolecules containing ferrocenyl or cobalticenium groups.8b,13,14 The electrochemical properties15 of monomer 3 and polymers 5 have been investigated by cyclic voltammetry (CV) using decamethylferrocene as the internal reference16 (Figures S6 and S13). Dry DMF was used as the solvent, and the E1/2 data (measured vs [FeCp*2]) are gathered in Table S1. The CV curves of polymers 5 are very similar to that of monomer 3. A single reversible CV wave was observed, corresponding to the cathodic reduction FeII → FeI for all the [FeCp[(η6-C6Me6)] units of the metallomacromolcules.6 The FeII/I reduction potential is −1.35 V vs [FeCp*2]. In the cyclic voltammogram (CV) measurement, the total number of electrons transferred in the oxidation wave for the polymer (np) should be the same as that of monomer units in the polymer, as only one electron from FeII to FeI is transferred from each monomer unit to the anode. Thus, this electron number np can be estimated using Bard−Anson’s empirical equation which was previously derived for conventional polarography:14 np =

0.275 idp/Cp ⎛ M p ⎞ ⎟ ⎜ idm /Cm ⎝ M m ⎠

(1)

The id, M, and C are the CV wave intensity of the diffusion current, molecular weight, and concentration of the monomer (m) and polymer (p), respectively. The intensities in the CVs of the polymers and monomer are compared, and consequently the electron numbers np are determined. As shown in Table S2, the estimated values of electron numbers (np3) and polymerization degrees (np1) obtained from 1H NMR data show an excellent consistency. For instance, for the polymer 550, the polymerization degree (np3) from the above formula is 47 ± 3, which is close to the theoretical value of 50 (np1) from the conversion ratio. In conclusion, the electrochemical measurements verified the controlled characteristics for the ROMP of the monomer 3 containing the fragment [FeCp[(η6-C6Me6)][PF6]. Synthesis and ROMP of Monomer 7. It was desirable to improve the solubility of the monomer containing the complex [FeCp(η6-C6Me6)][PF6] and the polymers synthesized by ROMP in DCM. Indeed, DCM is a typical and excellent solvent for this reaction using the ruthenium catalyst 4. C

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is 21 ± 2, which is much lower than the theoretical value 50 from the monomer conversion, indicating that the NMR endgroup analysis is not reliable for such large polymers. Similarly, the polymerization degrees of polymers 8 were determined also by Bard−Anson’s electrochemical method. The electrochemical properties14 of the monomer 7 and those of the corresponding polymers 8 were investigated by CV using [FeCp*2]15 as the internal reference (Figures S19 and S25). Dry DMF was used as a solvent, and the E1/2 data (measured vs [FeCp*2]) are gathered in Table S3. Like the situation of monomer 3 and its polymers 5, monomer 7 and polymers 8 showed similar CV curves in which only a single reversible CV wave was observed corresponding to the cathodic reduction FeII → FeI for all the [FeCp(η6-C6Me6)][PF6] units.5,15 The FeII/I reduction potential is −1.35 V vs [FeCp*2]. As shown in Table 1, whether the polymer is small or large, the estimated values of electron numbers (np3) and polymerization degrees (np1) obtained from 1H NMR data show a good consistency. For instance, for the polymer 850, the polymerization degree (np3) from the above formula is 46 ± 4, which is close to the theoretical value of 50 (np1) from the conversion rate. In conclusion, this result demonstrates the controlled polymerization of the monomer 7. Synthesis of the Copolymer 11. The known monomer (9)9b was used to synthesize the diblock copolymers 11 containing [FeCp(η6-C6Me6)][PF6] units. The copolymers 11 were synthesized by chain extension of the polymer intermediate 10 resulting from the living ROMP of monomer 9 followed by in situ ROMP of the second monomer 7. This process is a one-pot two-step sequential ROMP (Scheme 3). The preparation of the first block was accomplished with 100% monomer conversion in 8 min, whose controlled characteristic has been shown by SEC results and end-group analysis.9b Then, monomer 7 in DCM was added, and the polymerization was allowed to continue another 10 min before it was quenched by EVE. There was no precipitation during the whole period of the polymerization reaction and even after the EVE was added. The in situ 1H NMR analysis in CDCl3 was conducted to monitor the ROMP process of monomer 7. Its conversion was deemed to be 100% when the signal of the olefinic protons at 6.27 ppm for monomer 7 disappeared. Actually, the polymerization of the second block was completed in 10 min with 100% monomer conversion. In the 1H NMR spectrum of the copolymer 11 (Figure S26), the peak at 7.59 ppm is assigned to the amido proton, and the peaks at 5.01 and 4.66 ppm correspond to the substituted Cp protons, while the methyl protons of η6-C6Me6 are found at 2.40 ppm. The appearance of the above new peaks indicates the successful preparation of the diblock copolymer 11, and its formation is confirmed by the 13C NMR (Figures S27) and IR spectra (Figures S28). Similarly, two polymers 11 with different sizes were prepared using the molar feed ratios of monomers 9 and 7 to catalyst 4 of 20:10:1 and 100:50:1. The copolymers 11 were obtained as brown solids after precipitation from diethyl ether. Because of the introduction of the organic block, 11 showed a better solubility than the homopolymers 8. The copolymers 11 are soluble not only in acetone and acetonitrile but also in DCM, chloroform, and THF, whether the copolymers are large or small. DMF and DMSO are also good solvents for 11. The MWs of copolymer 11 were also characterized by MALDI-TOF MS, end-group analysis, and Bard−Anson’s electrochemical method. The MALDI-TOF mass spectrum of

In the 1H NMR spectrum of the polymer 8 (Figure S20), the characteristic double peaks arising from the olefinic protons of polynorbornene appear at 5.80 and 5.56 ppm, respectively, while the single peak at 6.31 ppm corresponding to the olefinic protons of monomer 7 disappears. The peak at 7.73 ppm is assigned to the amido proton, and the peaks at 5.15 and 4.92 ppm correspond to the substituted Cp protons, while the methyl protons of η6-C6Me6 are found at 2.51 ppm. The structure 8 is confirmed by the 13C NMR (Figure S22) and IR (Figure S23) spectra. In this study, two molar feed ratios of monomer to catalyst (15:1 and 50:1) were used to prepare polymers 8 with different sizes, i.e., 815 and 850. The polymers 8 were obtained as brown solids after precipitation from diethyl ether. There is a little difference in solubility between the large and small polymers. Like the polymers 5, the larger polymer 850 is not soluble in common organic solvents including DCM, chloroform, THF, and methanol, but it presents good solubility in acetone, acetonitrile, DMF, and DMSO. The smaller polymer 815 shows a better solubility than 850, and it is soluble even in DCM and chloroform, which is attributed to the presence of the TEG fragment in the linker. In this study, several methods were used including MALDITOF MS, end-group analysis and Bard−Anson’s electrochemical method12 to characterize the MWs and polymerization degrees of the polymers 8. The MALDI-TOF mass spectrum of the polymer 815 (Figure S24) showed well-defined individual peaks for polymer fragments that are separated by 792 ± 1 Da, which exactly corresponds to the mass of one monomer unit 7. The intensities of these peaks progressively decrease and vanish toward high molecular masses. The largest molecular peak that was observed was that of 3128.2 Da corresponding to a polymer fraction of C6H6(C35H47N2O6FePF6)3(C35H47N2O6Fe)C2H2 (calculated MW: 3129 Da), which contains four monomer units. It is very difficult to observe the peak corresponding to the molecular weight of a polymer fraction with up to 15 monomer units. Meanwhile, the MWs of the polymers 8 were obtained through the 1H NMR end-group analysis in acetone-d6 (Figures S20 and S21) that was conducted by comparing the five protons of the end-group phenyl (7.39−7.23 ppm) with the amido proton (7.73 ppm), olefinic protons (5.80 and 5.56 ppm), substituted Cp protons (5.15 and 4.92 ppm), TEG methylene protons (3.68−3.51 ppm), and methyl protons of η6-C6Me6 (2.51 ppm). As shown in Table 1, for the small polymer 815, in which the feed molar ratio of monomer 7 to catalyst 4 is 15:1, the calculated polymerization degree (np2) is 10 ± 1, which is compared to the theoretical value 15. For the larger polymer 850, however, the result from end-group analysis Table 1. Polymerization Degree Data for Polymers 8 [M7]:[C]a convb (%) np1c np2d np3e

15:1 >99 15 10 ± 1 16 ± 2

50:1 >99 50 21 ± 2 46 ± 4

a

[M7]:[C]: feed molar ratio of monomer 7 and catalyst 4. bMonomer conversion determined by 1H NMR. cDegree of polymerization obtained from 1H NMR data using the conversion of monomer 7. d Degree of polymerization determined via end-group analysis by 1H NMR spectroscopy in acetone-d6. eDegree of polymerization determined using the Bard−Anson electrochemical method. D

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Macromolecules Scheme 3. Synthesis of [FeCp(η6-C6Me6)]-Containing Diblock Copolymer 11 by ROMP in DCM

cathodic reduction FeII → FeI for all the [FeCp(η6-C6Me6)] units appeared at −1.34 V vs [FeCp*2] for both copolymers 1120/10 and 11100/50. As shown in Table 2, the estimated values of electron numbers (np3) also exhibit an excellent consistency with the polymerization degrees (np1) obtained from 1H NMR data, whether the copolymer is large or small. For instance, for the large copolymer 11100/50, the polymerization degree (np3) from the above formula is 48 ± 3, which is very close to the theoretical value of 50 (np1) from the conversion ratio. So, these results further demonstrate the controlled living polymerization of monomer 7 containing the complex [FeCp(η6-C6Me6)][PF6].

the small copolymer 1120/10, in which the molar feed ratio of monomers 9 and 7 to 4 is 20:10:1, showed well-defined individual peaks for polymer fragments that are separated by 309 ± 1 Da, which exactly corresponds to the MW of one monomer 9 unit (Figure S27). Peaks with the interval corresponding to the MW of monomer 7 were not observed, however, probably because the weak signals from the cationic block containing the group [FeCp(η6-C6Me6)] were submerged by the strong signals resulting from the first organic block. The polymerization degrees of the first block, polymers 10, were previously shown to be the same as the theoretical values from 1H NMR conversion by the end-group analysis in CD3CN and SEC data.9b So, using the 1H NMR spectrum of copolymer 11 in CDCl3, the polymerization degrees of the second block containing the fragment [FeCp(η6-C6Me6)][PF6] were calculated by comparing the integration of the methylene protons (3.35 ppm) with those of the amido protons (7.59 ppm), substituted Cp protons (5.01 and 4.66 ppm), and methyl protons (2.40 ppm) of η6-C6Me6. As shown in Table 2, the

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CONCLUSION The first polymers containing the covalently attached electronreservoir complex [FeCp(η6-C6Me6)][PF6] have been synthesized by living ROMP of norbornene derivatives. The use of Grubb’s ruthenium benzylidene catalyst of third generation provides very fast polymerization and the living character of the polymerization allowing the synthesis of diblock polymer for a better control of the solubility and other properties. The variation of the linker length between the norbornene unit and the very bulky cationic organoiron group is decisive to optimize these properties. Although the molecular weight of the large polymers of this family is not accessible using the end-group analysis and SEC methods, the Bard−Anson cyclic voltammetry method provides a good confirmation of molecular weights that are close to the theoretical values defined by the monomer/ catalyst ratio in the ROMP reaction. Redox-robust and soluble organometallic polymers are thus accessible with potential applications such as stoichiometric and catalytic electrontransfer reagents, polyelectrolytes, and battery components.

Table 2. Polymerization Degree of the Second Block in Copolymers 11 [M9]:[M7]:[C]a convb (%) np1c np2d np3e

20:10:1 >99 10 10 ± 0.2 10 ± 1

100:50:1 >99 50 50 ± 1 48 ± 3

a

[M9]:[M7]:[C]: feed molar ratio of monomers 9 and 7 to catalyst 4. Monomer conversion determined by 1H NMR. cDegree of polymerization obtained from 1H NMR data using the conversion of monomer 7. dDegree of polymerization determined via end-group analysis by 1H NMR spectroscopy in CDCl3. eDegree of polymerization determined using the Bard−Anson electrochemical method. b

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ASSOCIATED CONTENT

* Supporting Information

polymerization degrees from end-group analysis (np2) show excellent consistency with the theoretical value (np1) obtained using the 1H NMR conversion, whether the copolymer is large or small. These results show the controlled polymerization of monomer 7. Similarly, the polymerization degrees of the second block containing [FeCp(η6-C6Me6)][PF6] in copolymers 11 were determined by Bard−Anson’s electrochemical method. The electrochemical properties of the copolymers 11 have been investigated by CV. Therefore, the solvent was dry DMF with [FeCp*2] as the internal reference (Figure S30), and the E1/2 data measured vs [FeCp*2] are listed in Table S5. The copolymers 11 show similar CV curves to the polymers 5 and 8, as expected. A single reversible wave corresponding to the

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The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.macromol.5b01603. Spectra, CVs, syntheses, and full characterizations of monomers and polymers (PDF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected] (D.A.). Notes

The authors declare no competing financial interest. E

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(11) Mayer, U. F. J.; Gilroy, J. B.; O’Hare, D.; Manners, I. J. Am. Chem. Soc. 2009, 131, 10382−10383. (12) Flanagan, J. B.; Margel, S.; Bard, A. J.; Anson, F. C. J. Am. Chem. Soc. 1978, 100, 4248−4253. (13) (a) Ornelas, C.; Ruiz, J.; Belin, C.; Astruc, D. J. Am. Chem. Soc. 2009, 131, 590−601. (b) Diallo, A. K.; Daran, J.-C.; Varret, F.; Ruiz, J.; Astruc, D. Angew. Chem., Int. Ed. 2009, 48, 3141−3145. (c) Diallo, A. K.; Ruiz, J.; Astruc, D. J. Am. Chem. Soc. 2011, 133, 629−641. (d) Wang, Y.; Rapakousiou, A.; Astruc, D. Macromolecules 2014, 47, 3767−3774. (14) Bard, A. J.; Faulkner, L. R. Electrochemical Methods: Fundamentals and Applications, 2nd ed.; Wiley: New York, 2001. (15) Geiger, W. E. Organometallics 2007, 26, 5738−5765. (16) Ruiz, J.; Daniel, M.-C.; Astruc, D. Can. J. Chem. 2006, 84, 288− 299.

ACKNOWLEDGMENTS Financial support from the National Science Foundation of China (21106088), the PhD program Foundation of the Ministry of Education of China (20110181120079), the Centre National de la Recherche Scientifique (CNRS), the Universities of Bordeaux, Chengdu, and San Sebastian and the laboratory of Mianyang is gratefully acknowledged.

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DOI: 10.1021/acs.macromol.5b01603 Macromolecules XXXX, XXX, XXX−XXX