Article pubs.acs.org/Organometallics
Ethylene Polymerization at High Temperatures Catalyzed by DoubleDecker-Type Dinuclear Iron and Cobalt Complexes: Dimer Effect on Stability of the Catalyst and Polydispersity of the Product Daisuke Takeuchi,* Shigenaga Takano, Yuji Takeuchi, and Kohtaro Osakada Chemical Resources Laboratory R1-04, Tokyo Institute of Technology, 4259 Nagatsuta, Yokohama 226-8503, Japan S Supporting Information *
ABSTRACT: Dinuclear Fe and Co complexes with a double-decker structure were synthesized by using macrocyclic ligands having two bis(imino)pyridine groups. X-ray crystallography of the dinuclear Co complex revealed that the two bis(imino)pyridine Co moieties stack in an antiparallel manner with a distance of 7.74 Å. A dinuclear Fe complex catalyzes ethylene polymerization at 80−120 °C (5 atm ethylene) to produce polymers with a relatively narrow molecular weight distribution (Mw/Mn = 1.75−2.77); its highest activity is 975 g (mmol Fe)−1 h−1 atm−1 at 100 °C. Ethylene polymerization at room temperature under 1 atm ethylene catalyzed by the dinuclear Co and Fe complexes produces polymers with much higher molecular weight (Mn up to 15.5-fold increase) than the corresponding mononuclear complexes.
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INTRODUCTION Late-transition-metal catalysts for ethylene and olefin polymerization have attracted current attention because of their unique catalytic behavior.1 Fe complexes with bis(imino)pyridine ligands are one type of central catalysts that afford high molecular weight polyethylene.2,3 The high initial activity of the catalyst, however, rapidly falls within a short time even at room temperature, and the resulting polymer often has a wide molecular weight distribution (Mw/Mn > 5) probably owing to the presence of multiple active sites including a short-lived one.2,4 Recently, several research groups have investigated these issues. Sun designed Fe catalysts with modified ligands and observed their catalytic activity up to 254 g (mmol Fe)−1 h−1 atm−1 at 100 °C (30 atm).5 Gao and Wu reported that Fe catalysts with bulky N-aryl groups on a bis(imino)pyridine ligand show less serious decay of their activity at 70 °C than a catalyst with a bis(isopropyl)phenyl group at the imine nitrogen.6 Di- and triiron catalysts with linear structures exhibit constant catalytic activity at 60−90 °C, and a triiron catalyst having a cyclic structure keeps its catalytic activity for a longer time than the mononuclear one at 0 °C.7,8 The interaction among metal centers and a growing polymer chain within a molecule may enhance the stability of the catalyst used. Recently, we have found that dinuclear Ni, Pd, and Fe catalysts with macrocyclic supporting ligands show unique catalytic behaviors owing to the effective interaction of polymers and metal centers.9 In this paper, we present the successful ethylene polymerization at 80−120 °C using a diiron catalyst containing a bifunctional macrocyclic ligand.10 The ethylene polymerization at room temperature catalyzed by a dicobalt catalyst as well as the diiron catalyst produces a polymer with much higher © XXXX American Chemical Society
molecular weight than the corresponding mononuclear complexes.
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RESULTS AND DISCUSSION Synthesis of Double-Decker-Type Dinuclear Complexes. The reaction of 2,6-diacetylpyridine with ethylenebis(aniline) in the presence of p-toluenesulfonic acid afforded a cyclic dimer of the bis(imino)pyridine compounds (1−3). The cyclic compound 1 reacts with CoCl2 to produce dinuclear complex Co2Cl4(1) (eq 1). Figure 1 shows the 1H NMR
spectrum of Co2Cl4(1), and the signals observed in the range −30 to 120 ppm suggest paramagnetic character of the complex. A similar reaction of 1 with FeCl2 in THF also yields dinuclear complex Fe2Cl4(1) in 54% yield. The HRMS-ESI spectrum of the complex contained a peak with m/z = 1007.2494, which corresponds to a monocation formed by the elimination of Cl−, [Fe2Cl3(1)]+. The 1H NMR spectrum of the complex in C2D2Cl4 at room temperature Received: June 13, 2014
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dx.doi.org/10.1021/om500629a | Organometallics XXXX, XXX, XXX−XXX
Organometallics
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FeCl2(4), whose ligand has 2,4,6-trimethylphenyl groups at imine nitrogens, as the catalyst.
Figure 1. 1H NMR spectrum of Co2Cl4(1) in CD2Cl2 at rt.
The reaction catalyzed by FeCl2(4) proceeds more rapidly than that catalyzed by Fe2Cl4(1) in the initial stage, but ceases after 7 min, indicating rapid deactivation of the catalyst. An increase in TON for the polymerization catalyzed by the dinuclear complex continues even after 30 min. Thus, the dinuclear iron complex shows a higher thermal stability and a longer catalyst lifetime than the mononuclear complex. Table 1 summarizes the results of ethylene polymerization catalyzed by the di- and mononuclear Fe complexes. Fe2Cl4(1)/MMAO catalyzes ethylene polymerization at temperatures from rt to 120 °C in 5 atm of ethylene (runs 1−6). With increasing polymerization temperature, the catalytic activity of the dinuclear complex increases to up to 975 g (mmol Fe)−1 h−1 atm−1 at 100 °C (Figure 4a). The GPC trace of the polyethylene produced at rt to 60 °C is bimodal and/or extremely broad, and the polymer obtained above 80 °C has a narrower molecular weight distribution (Mw/Mn = 1.8−2.8). The produced polyethylene is linear, as confirmed by differential scanning calorimetry (DSC) (Tm = 124.5−134.4 °C). The catalytic activity of Fe2Cl4(1) is increased with an increase in temperature up to 100 °C in the ethylene polymerization (10 atm) (runs 7−11) (Figure 4b). In contrast to Fe2Cl4(1), the catalytic activity of the mononuclear complex FeCl2(4) decreased above 60 °C (5 atm ethylene, runs 12−16) or 80 °C (10 atm ethylene, runs 17−21) in the ethylene polymerization. In the polymerization for 15 min at 100 °C, Fe2Cl4(1) shows a higher activity than FeCl2(4) (runs 5, 11, 16, and 21). The molecular weight distribution of the polymer obtained by FeCl2(4) at higher temperature is narrower than that obtained at lower temperature. In the ethylene polymerization under 1 atm of ethylene at rt to 60 °C, Fe2Cl4(1) shows higher catalytic activity at higher temperature (runs 22−24), whereas the catalytic activity of FeCl2(4) decreases above 40 °C (runs 25−27). The molecular weight of the polyethylene obtained using Fe2Cl4(1) at rt and 1 atm of ethylene (Mn = 38 300, run 22) is much higher than that obtained using FeCl2(4) under the same conditions (Mn = 5570, run 25). The dinuclear Fe complex with a bulky isopropyl substituent, Fe2Cl4(2), shows higher catalytic activity than Fe2Cl4(1) in the ethylene polymerization at rt under 1 atm of ethylene. Although the activity of Fe2Cl4(2) is lower than the mononuclear analogue FeCl2(5) (runs 28 and 34), the polyethylene obtained by Fe2Cl4(2)/MMAO has a much higher molecular weight (Mn = 62 700, run 28) than that obtained by FeCl2(5)/MMAO (Mn = 8930, run 34). The ethylene polymerization catalyzed by Fe2Cl4(2) (5 atm) shows higher catalytic activity at 100 °C than 80 °C (runs 31−33). The catalytic activity of FeCl2(5) at 100 °C is lower than 80 °C (runs 37, 38). The mononuclear Fe complex without a substituent on one of the ortho positions of the N-aryl group tends to give volatile α-olefins.11 The dinuclear Fe complex Fe2Cl4(3) affords low molecular weight polymer after removal of the volatile fraction (Mn = 820, run 39).
showed broadened signals in the range −30 to 90 ppm due to paramagnetic Fe(II) centers, and the peak number was consistent with the formation of the dinuclear complex. The dinuclear complexes Co2Cl4(2), Fe2Cl4(2), Co2Cl4(3), and Fe2Cl4(3) are synthesized from tetra(imino)bis(pyridine) ligands (2, 3) and CoCl2 or FeCl2. X-ray crystallography of Co2Cl4(1) revealed the dinuclear structure of the complex (Figure 2). The two bis(imino)pyridine Co moieties stacked in
Figure 2. Structure of Co2Cl4(1) determined by X-ray crystallography. Hydrogen atoms are omitted for clarity.
an antiparallel manner at a distance of 7.74 Å. The cobalt centers adopted a square-pyramidal coordination and deviated from the bis(imino)pyridine plane by 0.43 Å. Ethylene Polymerization by Double-Decker-Type Dinuclear Fe Complexes. The dinuclear Fe complex Fe2Cl4(1) catalyzes ethylene polymerization at 100 °C in the presence of a modified methylaluminoxane (MMAO) cocatalyst. Figure 3 shows a plot of the change in the turnover number (TON) of ethylene polymerization (5 atm) at 100 °C catalyzed by Fe2Cl4(1)/MMAO. It is compared with the results obtained by using the corresponding mononuclear complex
Figure 3. Plots of change of TON in ethylene polymerization (5 atm) catalyzed by Fe2Cl4(1)/MMAO (red squares) and FeCl2(4)/MMAO (blue circles) at 100 °C. B
dx.doi.org/10.1021/om500629a | Organometallics XXXX, XXX, XXX−XXX
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Table 1. Polymerization of Ethylene Catalyzed by Dinuclear and Mononuclear Fe Complexesa run
complex
ethylene/atm
temp/°C
yield/g
activity/g (mmol Fe)−1 h−1 atm−1
Mnb
Mw/Mnb
Tm/°C
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39
Fe2Cl4(1) Fe2Cl4(1) Fe2Cl4(1) Fe2Cl4(1) Fe2Cl4(1) Fe2Cl4(1) Fe2Cl4(1) Fe2Cl4(1) Fe2Cl4(1) Fe2Cl4(1) Fe2Cl4(1) FeCl2(4) FeCl2(4) FeCl2(4) FeCl2(4) FeCl2(4) FeCl2(4) FeCl2(4) FeCl2(4) FeCl2(4) FeCl2(4) Fe2Cl4(1) Fe2Cl4(1) Fe2Cl4(1) FeCl2(4) FeCl2(4) FeCl2(4) Fe2Cl4(2) Fe2Cl4(2) Fe2Cl4(2) Fe2Cl4(2) Fe2Cl4(2) Fe2Cl4(2) FeCl2(5) FeCl2(5) FeCl2(5) FeCl2(5) FeCl2(5) Fe2Cl4(3)
5 5 5 5 5 5 10 10 10 10 10 5 5 5 5 5 10 10 10 10 10 1 1 1 1 1 1 1 1 1 5 5 5 1 1 1 5 5 1
rt 40 60 80 100 120 rt 40 60 80 100 rt 40 60 80 100 rt 40 60 80 100 rt 40 60 rt 40 60 rt 40 60 80 100 120 rt 40 60 80 100 rt
1.113 1.052 1.619 3.932 4.874 2.131 1.691 1.045 1.590 6.321 7.276 1.004 1.941 6.645 5.101 3.588 1.454 3.149 6.366 7.682 4.759 0.338 0.529 0.579 1.695 1.956 1.230 0.684 0.643 0.717 1.693 1.880 1.127 1.468 1.208 1.266 3.127 1.764 1.435
223 210 324 787 975 426 169 105 159 632 728 201 388 1330 1020 718 145 315 637 768 476 338 529 579 1700 1960 1230 684 643 717 339 376 225 1470 1210 1270 625 353 1440
8810 3410 2520 2230 2200 1390 8640 4280 3290 2720 2380 3260 3090 4350 3090 2200 4040 5300 4120 3070 2380 38300 14800 9530 5570 4860 7260 62 700 19 600 15 300 3780 3410 2440 8930 6480 10 260 2910 2160 820
56 67 48 2.2 2.8 1.8 71 67 46 2.9 7.8 8.3 5.3 4.6 3.5 2.1 8.1 9.2 4.7 2.5 2.7 18 29 23 6.4 10 4.9 16 15 14 12 5.8 5.4 12 9.9 8.3 7.4 4.1 1.6
134.4 128.7 126.1 124.5 131.5 130.0
132.8
131.6
Reaction conditions: [Fe] = 4 μmol, cocatalyst = MMAO, [Al]/[Fe] = 1000, solvent = toluene (50 mL), reaction time = 15 min. bDetermined by GPC based on polyethylene standard using o-dichlorobenzene as eluent at 140 °C. a
Mononuclear Fe catalysts often produce polyethylene with a broad molecular weight distribution. This suggests the existence of multiple catalyst centers with different activities, lifetimes, and chain transfer frequencies. The dinuclear Fe catalyst in this study also yielded a polymer with unregulated molecular weight at room temperature to 60 °C (runs 1−3). The polymerization using a dinuclear catalyst at high temperatures, however, afforded a polymer with a narrow molecular weight distribution, suggesting the presence of catalyst sites with uniform activity under the conditions used.12,13 Ni(II) and Pd(II) catalysts for ethylene polymerization, having a square-planar metal center, also have drawbacks in terms of the thermal stability of their active sites. The introduction of sterically bulky groups to ligands serves to
Figure 4. Catalytic activity of Fe2Cl4(1) (red squares) and FeCl2(4) (blue circles) in ethylene polymerization ((a) 5 atm, (b) 10 atm) at various temperatures.
C
dx.doi.org/10.1021/om500629a | Organometallics XXXX, XXX, XXX−XXX
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Table 2. Polymerization of Ethylene Catalyzed by Dinuclear and Mononuclear Co Complexesa run
complex
ethylene/atm
temp/°C
yield/g
activity/g (mmol Co)−1 h−1 atm−1
Mnb
Mw/Mnb
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22c 23 24c
Co2Cl4(1) Co2Cl4(1) Co2Cl4(1) Co2Cl4(1) Co2Cl4(1) CoCl2(4) CoCl2(4) CoCl2(4) CoCl2(4) CoCl2(4) Co2Cl4(2) Co2Cl4(2) Co2Cl4(2) Co2Cl4(2) Co2Cl4(2) CoCl2(5) CoCl2(5) CoCl2(5) CoCl2(5) CoCl2(5) Co2Cl4(3) Co2Cl4(3) CoCl2(6) CoCl2(6)
1 1 1 5 5 1 1 1 5 5 1 1 1 5 5 1 1 1 5 5 1 1 1 1
rt 40 60 80 100 rt 40 60 80 100 rt 40 60 80 100 rt 40 60 80 100 rt rt rt rt
0.293 0.321 0.316 0.604 0.274 0.445 0.368 0.150 1.726 0.801 0.139 0.100 0.132 0.191 0.079 1.100 0.810 0.619 1.726 0.801 0.430 0.825 trace trace
293 321 316 121 54.8 445 368 150 345 160 139 100 132 38.1 16.0 1100 810 619 345 160 430 825
27 600 7770 11 400 5580 3830 1780 1600 1500 1200 1200 9760 6590 8150 6660 6890 3300 2750 2680 2100 2000 14 500 100 500
43 39 9.6 28 18 2.0 1.8 2.1 1.5 1.5 25 21 13 14 12 2.1 2.1 2.0 1.9 1.8 11 2.1
Tm/°C
133.2
Reaction conditions: [Co] = 4 μmol, cocatalyst = MMAO, [Al]/[Co] = 1000, solvent = toluene (50 mL), reaction time =15 min. bDetermined by GPC based on polyethylene standard using o-dichlorobenzene as eluent at 140 °C. cMAO was used as the cocatalyst.
a
enhance such stability. Moreover, diimine Ni and Pd catalysts with bulky aryl substituents14 or a cyclophane structure15 have improved thermal stability. Diimine Ni catalysts with diphenylmethyl substituents promote highly stable ethylene polymerization at 80−100 °C.16 Previous experimental5,6 and theoretical studies17 of Fe catalysis revealed that complexes with bulky bis(imino)pyridine ligands efficiently promote ethylene polymerization at high temperatures. Fe centers of the dinuclear catalyst used in this study are less sterically crowded. However, the two Fe centers are at close positions within a macrocyclic framework. The interaction between a metal center and a growing polymer chain may stabilize the Fe−C bond to inhibit undesired deactivation of the active center.10,13,18 Ethylene Polymerization by Double-Decker-Type Dinuclear Co Complexes. Table 2 shows a summary of the results of ethylene polymerization catalyzed by di- and mononuclear Co complexes. The dinuclear cobalt complex Co2Cl4(1) catalyzes ethylene polymerization, yielding a polymer with a higher molecular weight (Mn = 27 600, run 1) than the product of the corresponding mononuclearcomplex-catalyzed ethylene polymerization (Mn = 1780, run 6). The much broader molecular weight distribution of the polymer obtained by Co2Cl4(1) compared to CoCl2(4) is partly due to the low solubility of Co2Cl4(1) in toluene. Co2Cl4(1) shows similar catalytic activity for ethylene polymerization (1 atm) at rt to 60 °C (runs 1−3), whereas the catalytic activity of CoCl2(4) decreases above rt in ethylene polymerization at 1 atm of ethylene (runs 6−8). Both Co2Cl4(1) and CoCl2(4) show decreased catalytic activity at 100 °C compared to that at 80 °C at 5 atm of ethylene (runs 4, 5, 9, and 10).
The dinuclear cobalt complex with a bulky isopropyl substituent, Co2Cl4(2), also catalyzes ethylene polymerization and affords the polymer with a higher molecular weight than CoCl2(5) at rt and 1 atm ethylene (runs 11 and 16). The catalytic activity is similar in the temperature range rt to 60 °C (runs 11−13), whereas that of CoCl2(5) decreases above rt (runs 16−18). Catalytic activities of both Co2Cl4(2) and CoCl2(5) decrease at 100 °C compared to that at 80 °C in 5 atm of ethylene (runs 14, 15, 19, and 20). Co2Cl4(3), which does not have a substituent at an ortho position of the N-aryl group, shows activity as high as 430 (MMAO cocatalyst) and 825 (MAO cocatalyst) g (mmol Co)−1 h−1 atm−1 (runs 21 and 22). The high molecular weight of the obtained polyethylene (Mn = 14 500, 100 500) is remarkable because of infrequent chain transfer processes even in the presence of a large space on one side of the coordinating plane.11b The corresponding mononuclear analogue with a 2ethylphenyl group at the coordinating nitrogens, CoCl2(6), does not catalyze the polymerization. Thus, the molecular weight of the polymers produced by the dinuclear complexes is higher than those by mononuclear complexes. It is noted that the complex Co2Cl4(3), with monosubstituted N-aryl groups, produces high-mass polymer, D
dx.doi.org/10.1021/om500629a | Organometallics XXXX, XXX, XXX−XXX
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17 h under an argon atmosphere in a stainless steel reactor. The reaction mixture was cooled to room temperature and diluted with CH2Cl2 (120 mL), washed with water (75 mL), and dried over anhydrous MgSO4. The solvent was removed in vacuo, and the crude product was purified by silica gel chromatography (eluting with hexane/ethyl acetate (10:1)) to give 2,4-dimethyl-6-vinylphenylcarbamic acid tert-butyl ester as a white solid (1.87 g, 8.03 mmol, 85%). 1H NMR (500 MHz, CDCl3, rt): δ 7.21 (s, 1H, Ar-H), 6.97 (s, 1H, Ar-H), 6.88 (m, 1H, CHCH2), 5.87 (br s, 1H, N-H), 5.67 (d, 1H, J = 17.5, CHCH2), 5.28 (d, 1H, J = 11.0, 1.5, CHCH2), 2.30 (s, 3H, ArMe), 2.23 (s, 3H, Ar-Me), 1.51 (s, 9H, CMe3). 13C{1H} NMR (125 MHz, CDCl3, rt): δ 153.87 (OC), 136.62, 136.00, 135.27, 133.115, 130.88, 130.20, 124.10, 115.55, 79.90 (OCMe3), 28.30 (OCMe3), 21.03 (Ar-Me), 18.20 (Ar-Me). FAB mass spectrum: m/z = 249 [M + H+]. IR (KBr): 3351, 3236, 3098, 3007, 2981, 2923, 1685, 1481, 1445, 1410, 1390, 1363, 1300, 1254, 1229, 1167, 1047, 1023, 991, 901, 852, 777, 720, 669 cm−1. Anal. Calcd for C15H21NO2(H2O)0.1: C, 71.85; H, 8.52; N, 5.59. Found: C, 72.09; H, 8.59; N, 5.60. (E)-2,2′-Bis(tert-butoxycarbamate)-3,3′,5,5′-tetramethylstilbene. A solution of 2-bromo-4,6-dimethylphenylcarbamic acid tert-butyl ester (553 mg, 1.84 mmol), 2,4-dimethyl-6-vinylphenylcarbamic acid tert-butyl ester (537 mg, 2.30 mmol), Pd(OAc)2 (20.7 mg, 0.092 mmol), and tris(o-tolyl)phosphine (112 mg, 0.369 mmol) in NEt3 (14 mL) was heated under argon in a glass reactor at 90 °C for 54 h. The cooled reaction mixture was diluted with CH2Cl2 (80 mL) and H2O (30 mL). The CH2Cl2 layer was separated, washed with water (30 mL), and dried over anhydrous MgSO4. The volatile fractions were removed in vacuo, and the crude product was purified by silica gel chromatography (eluting with hexane/ethyl acetate (8:2)) to give (E)2,2′-bis(tert-butoxycarbamate)-3,3′,5,5′-tetramethylstilbene as a white solid (706 mg, 1.52 mmol, 82%). 1H NMR (500 MHz, CDCl3, rt): δ 7.31 (s, 2H, Ar-Hm), 7.17 (s, 2H, CC-H), 6.97 (s, 2H, Ar-Hm), 5.86 (br s, 2H, N-H), 2.32 (s, 6H, Ar-Me), 2.26 (s, 6H, Ar-Me), 1.50 (s, 18H, CMe3). 13C{1H} NMR (125 MHz, CDCl3, rt): δ 154.58 (O C), 136.63, 135.98, 135.41, 135.29, 130.69, 126.43, 124.30, 80.04 (OCMe3), 28.35 (OCMe3), 21.02 (Ar-Me), 18.23 (Ar-Me). FAB mass spectrum: m/z = 467 [M + H+]. IR (KBr): 3337, 2970, 2921, 2739, 2677, 2491, 1697, 1508, 1446, 1390, 1364, 1274, 1247, 1166, 1061, 1046, 1024, 982, 850, 628 cm−1. Anal. Calcd for C28H38N2O4(H2O)0.2: C, 71.04; H, 8.18; N, 5.92. Found: C, 70.71; H, 8.26; N, 5.89. N,N′-Bis(tert-butoxycarbonyl)-4,4′,6,6′-tetramethyl-2,2′-ethylenedianiline. A suspension of (E)-2,2′-di(tert-butoxycarbamate)3,3′,5,5′-tetramethylstilbene (854 mg, 1.83 mmol) and Pd/C (91.4 mg) in THF (20 mL) was stirred under a hydrogen atmosphere (1 atm) at 50 °C for 66 h, then cooled to room temperature. After removal of the catalyst by filtration, the volatile fractions was removed in vacuo, and the crude product was purified by silica gel chromatography (eluting with hexane/ethyl acetate (7:3)) to give N,N′-bis(tert-butoxycarbonyl)-4,4′,6,6′-tetramethyl-2,2′-ethylenedianiline as a white solid (742 mg, 1.59 mmol, 87%). 1H NMR (500 MHz, CDCl3, rt): δ 6.91 (s, 2H, Ar-H), 6.89 (s, 2H, Ar-H), 5.36 (br s, 2H, N-H), 2.77 (s, 4H, CH2), 2.27 (s, 6H, Ar-Me), 2.17 (s, 6H, Ar-Me), 1.49 (s, 18H, CMe3). 13C{1H} NMR (125 MHz, CDCl3, rt): δ 154.22 (OC), 139.01 (Ar-C), 136.99 (Ar-C), 136.48 (Ar-C), 131.42 (ArC), 129.55 (Ar-Cm), 128.38 (Ar-Cm), 79.72 (OCMe3), 33.75 (ArCH2), 28.51 (t-Bu), 21.06 (Ar-Me), 18.37 (Ar-Me). FAB mass spectrum: m/z = 470 [M + H+]. IR (KBr): 3326, 2997, 2965, 2917, 2879, 1696, 1508, 1461, 1444, 1389, 1365, 1268, 1247, 1172, 1058, 1027, 907, 777, 723, 641 cm−1. Anal. Calcd for C28H40N2O4: C, 71.76; H, 8.60; N, 5.98, O, 13.66. Found: C, 71.74; H, 8.90; N, 5.96, O, 13.46. 1,2-Bis(2-amino-3,5-dimethylphenyl)ethylene. A solution of N,N′bis(tert-butoxycarbonyl)-4,4′,6,6′-tetramethyl-2,2′-ethylenedianiline (618 mg, 1.33 mmol) in CH2Cl2 (20 mL) was treated with trifluoroacetic acid (2 mL, 26.5 mmol) and stirred at room temperature under argon for 1 h. The solution was washed with an aqueous solution of NaHCO3 (40 mL) and extracted with CH2Cl2 (50 mL × 2). The organic phase was separated and dried over anhydrous MgSO4. The volatile fractions were removed in vacuo, and the crude product was purified by silica gel chromatography (eluting with
although the mononuclear analogues with similar N-aryl groups do not afford polymers. The chain transfer reaction is effectively prohibited in the dinuclear complex, via the interaction between the metal center and the growing polymer chain.10 In summary, the new double-decker-type dinuclear Fe complex with the macrocyclic bis(imino)pyridine ligands shows a high thermal stability and a longer catalyst lifetime than the corresponding mononuclear Fe complex. Thus, it is suitable as a catalyst of ethylene polymerization at high temperatures (80−120 °C), which may be favorable for highly exothermic reactions without temperature control in a large scale. The dinuclear Co complexes with macrocyclic bis(imino)pyridine ligands afford polyethylene with much higher molecular weight than that obtained by the mononuclear Co complexes. The cooperative interaction between the growing polymer and the second metal center is suggested to retard the undesirable deactivation of the catalyst and/or chain transfer.
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EXPERIMENTAL SECTION
General Procedures. All manipulations of the reactions were carried out under nitrogen or argon using standard Schlenk techniques. Toluene was purified by using a solvent purification system (Glass Contour). MAO and MMAO were purchased from TOSOH-FINECHEM and stored under nitrogen or argon. Other chemicals were used as received from commercial suppliers. 1H and 13 C NMR spectra were recorded on a Bruker AVANCE-400 spectrometer (400 MHz) or JEOL JNM-500 spectrometer (500 MHz). The peaks were referenced to residual undeuterated solvents as follows: CDCl3, δ 7.26 for 1H and 77.0 for 13C; CD2Cl2, δ 5.30 for 1H; C2D2Cl4, δ 5.91 for 1H and 74.2 for 13C. FABMS spectra were measured with a JEOL JMS-700. High-resolution electrospray ionization mass spectrometry (HR-ESI-MS) was recorded on a Bruker micrOTOF II. Elemental analysis was carried out using a LECO CHNS-932 or Yanaco MT-5 CHN autorecorder at the Center for Advanced Materials Analysis, Technical Department, Tokyo Institute of Technology. IR spectra were measured with a Shimadzu FTIR8100A. To prepare KBr pellets, about 1−2 mg of sample was taken, ground together with about 100 mg of KBr. X-ray crystallography was performed on a Rigaku Saturn CCD area detector equipped with monochromated Mo Kα radiation (λ = 0.710 73 Å) at −160 °C. Gel permeation chromatography (GPC) was performed at 140 °C on a Waters 150C system equipped with a Foxboro Miran 1A IR detector, using ortho-dichlorobenzene as eluent with Shodex AD806M/S columns. DSC was recorded on a Seiko DSC6200R instrument. Synthesis of Ligands and Complexes. 2-Bromo-4,6-dimethylphenylcarbamic Acid tert-Butyl Ester. 2-Bromo-4,6-dimethylaniline (4.97 g, 24.9 mmol) and di-tert-butyldicarbonate (13.6 g, 62.1 mmol) were dissolved in toluene (35 mL) and heated at 90 °C under an argon atmosphere for 33 h. The solvent was evaporated to give a red oil. Flash chromatography on silica, eluting with hexane/ethyl acetate (20:1), gave 2-bromo-4,6-dimethylphenylcarbamic acid tert-butyl ester as a white solid (5.10 g, 17.0 mmol, 68%). 1H NMR (500 MHz, CDCl3, rt): δ 7.24 (s, 1H, Ar-Hm), 6.96 (s, 1H, Ar-Hm), 6.08 (br s, 1H, N-H), 2.28 (s, 3H, Ar-Me), 2.26 (s, 3H, Ar-Me), 1.50 (s, 9H, CMe3). 13 C{1H} NMR (125 MHz, CDCl3, rt): δ 153.42 (OC), 137.86, 137.82, 131.61, 130.53, 130.43, 122.44, 80.18 (OCMe3), 28.20 (OCMe3), 20.54 (Ar-Me), 18.87 (Ar-Me). FAB mass spectrum: m/z = 301 [M+ + H+]. IR (KBr): 3367, 3231, 3197, 3127, 2977, 2930, 1711, 1563, 1493, 1472, 1453, 1364, 1287, 1254, 1239, 1165, 1128, 1046, 1019, 908, 852, 834, 775, 721, 643, 539, 445 cm−1. Anal. Calcd for C13H18BrNO2: C, 51.75; H, 5.83; Br, 26.33, N, 4.69, O, 10.58. Found: C, 52.01; H, 6.04; Br, 26.62, N, 4.67, O, 10.66. 2,4-Dimethyl-6-vinylphenylcarbamic Acid tert-Butyl Ester. A solution of KBF3(CHCH2) (2.69 g, 20.1 mmol), PdCl2 (71.1 mg, 0.40 mmol), PPh3 (316 mg, 1.20 mmol), Cs2CO3 (19.6 g, 60.2 mmol), and (2-bromo-4,6-dimethylphenyl)carbamic acid tert-butyl ester (3.01 g, 10.0 mmol) in THF/water (9:1) (60 mL) was heated at 80 °C for E
dx.doi.org/10.1021/om500629a | Organometallics XXXX, XXX, XXX−XXX
Organometallics
Article
1470, 1389, 1365, 1245, 1168, 1051, 1026, 981, 798, 776, 726, 603, 583 cm−1. Anal. Calcd for C30H42N2O4: C, 72.84; H, 8.56; N, 5.66. Found: C, 72.44; H, 8.34; N, 5.59. N,N′-Bis(tert-butoxycarbonyl)-6,6′-diisopropyl-2,2′-ethylenedianiline. A suspension of (E)-2,2′-bis(tert-butoxycarbamate)-3,3′-diisopropylstilbene (115 mg, 0.234 mmol) and Pd/C (10.0 mg) in THF (3 mL) was stirred under a hydrogen atmosphere (1 atm) at room temperature for 39 h. After removal of the catalyst by filtration, the volatile fractions were removed in vacuo, and the crude product was crystallized from CH2Cl2/hexane to give N,N′-bis(tert-butoxycarbonyl)-6,6′-diisopropyl-2,2′-ethylenedianiline as a white solid (734 mg, 0.148 mmol, 64%). 1H NMR (500 MHz, CDCl3, rt): δ 7.29−7.15 (m, 4H, Ar-H), 7.01 (d, 2H, J = 5.5, Ar-H), 5.60 (s, 2H, N-H), 3.11 (br s, 2H, CHMe2), 2.62 (s, 4H, CH2), 1.51 and 1.35 (s, 18H, CMe3), 1.18 (d, 12H, J = 6.5, CHMe2). 13C{1H} NMR (75 MHz, CDCl3, rt): δ 154.42 (OC), 146.93 (NH-C), 139.79 (Ar-C), 132.33 (Ar-C), 127.79 (Ar-C), 127.55 (Ar-C), 123.88 (Ar-C), 79.79 (OCMe3), 33.55 (Ar-CH2), 28.47 (CHMe2), 28.32 (CMe3), 23.44 (CHMe2). FAB mass spectrum: m/z = 498 [M + H+]. IR (KBr): 3384, 3342, 3320, 2977, 2930, 2868, 1703, 1593, 1510, 1472, 1456, 1390, 1365, 1248, 1167, 1053, 1025, 942, 911, 837, 802, 776, 726, 626 cm−1. Anal. Calcd for C30H44N2O4(H2O)0.67: C, 70.68; H, 9.03; N, 5.48. Found: C, 70.83; H, 8.98; N, 5.51. 1,2-Bis(2-amino-3-isopropylphenyl)ethylene. A solution of N,N′bis(tert-butoxycarbonyl)-6,6′-diisopropyl-2,2′-ethylenedianiline (296 mg, 0.596 mmol) in CH2Cl2 (8 mL) was treated with trifluoroacetic acid (0.9 mL, 11.9 mmol) and stirred at room temperature under argon for 2 h. The solution was washed with an aqueous solution of NaHCO3 (16 mL). The organic phase was extracted by CH2Cl2 (25 mL × 2) and dried over anhydrous MgSO4. The volatile fractions were removed in vacuo, and the crude product was purified by silica gel chromatography (eluting with hexane/ethyl acetate (7:3)) to give 1,2bis(2-amino-3-isopropylphenyl)ethylene as a white solid (0.140 g, 0.473 mmol, 79%). 1H NMR (500 MHz, CDCl3, rt): δ 7.07 (d, 2H, J = 7.5 Hz, Ar-Hm), 7.00 (d, 2H, J = 7.0 Hz, Ar-Hm), 6.78 (t, 2H, J = 7.0 Hz, Ar-Hp), 3.68 (br s, 4H, N-H2), 2.90 (septet, 2H, J = 7.0 Hz, CHMe2), 2.84 (s, 4H, Ar-CH2), 1.26 (d, 12H, J = 6.5 Hz, CHMe2). 13 C{1H} NMR (125 MHz, CDCl3, rt): δ 141.25 (NH2-C), 132.61 (ArC), 126.76 (Ar-C), 126.22 (Ar-C), 123.39 (Ar-C), 118.61 (Ar-C), 31.43 (Ar-CH2), 27.819 (CHMe2), 22.37 (CHMe2). FAB mass spectrum: m/z = 298 [M + H+]. IR (KBr): 3409, 3339, 3073, 3014, 2966, 2954, 2896, 2870, 2837, 1628, 1479, 1453, 1439, 811, 757, 741, 684, 667, 561, 546 cm−1. Anal. Calcd for C20H28N2: C, 80.98; H, 9.82; N, 9.36. Found: C, 81.03; H, 9.52; N, 9.45. Macrocyclic Bis(bis(imino)pyridine) Ligand (1). A suspension of bis(2-amino-3,5-dimethylphenyl)ethylene (142 mg, 0.541 mmol), 2,6diacetylpyridine (88.2 mg, 0.541 mmol), and p-toluenesulfonic acid monohydrate (5.1 mg) in n-BuOH (2.5 mL) was refluxed under argon in a glass reactor for 10 h. The reaction mixture was cooled, and the resulting solid was washed with MeOH to give 1 as a yellow solid (203 mg, 0.257 mmol, 95%). 1H NMR (500 MHz, CDCl3, rt): δ 8.12 (d, 4H, J = 8.0, Py-Hm), 7.72 (t, 2H, J = 8.0, Py-Hp), 7.01 (s, 4H, Ar-Hm), 6.92 (s, 4H, Ar-Hm), 3.22 (m, 4H, Ar-HCH), 2.42 (m, 4H, Ar-HCH), 2.34 (s, 12H, NCMe), 2.16 (s, 12H, CMe), 1.90 (s, 12H, CMe). 13 C{1H} NMR (125 MHz, CDCl3, rt): δ 166.96 (NC), 155.01 (PyC0), 146.04 (Ar-C), 136.53, 132.68, 130.50, 129.29, 128.78, 125.45, 121.47, 33.79 (Ar-CH2), 20.90 (NC-Me), 18.13 (Ar-Mep), 16.41 (Ar-Meo). FAB mass spectrum: m/z = 791 [M+ + H+]. IR (KBr): 2997, 2933, 2920, 1648, 1634, 1568, 1454, 1362, 1215, 1121, 856, 819, 793. Anal. Calcd for C54H58N6: C, 81.99; H, 7.39; N, 10.62. Found: C, 81.96; H, 7.67; N, 10.56. Macrocyclic Bis(bis(imino)pyridine) Ligand (2). A suspension of 1,2-bis(2-amino-3-isopropylphenyl)ethylene (102 mg, 0.342 mmol), 2,6-diacetylpyridine (55.9 mg, 0.342 mmol), and p-toluenesulfonic acid monohydrate (5.0 mg) in xylene (6 mL) was refluxed under argon for 17 h. The cooled reaction mixture was concentrated by evaporation and recrystallized from Et2O to give 2 as pale yellow crystals (57.9 mg, 0.068 mmol, 40%). 1H NMR (500 MHz, CDCl3, rt): δ 8.18 (d, 4H, J = 7.5, Py-Hm), 7.77 (t, 2H, J = 8.0, Py-Hp), 7.20 (d, 4H, J = 7.5, ArHm), 7.14 (d, 4H, J = 7.5, Ar-Hm), 7.06 (t, 4H, J = 8.0, Ar-Hp), 3.22
hexane/ethyl acetate (7:3)) to give 1,2-bis(2-amino-3,5dimethylphenyl)ethylene as a white solid (326 mg, 1.23 mmol, 93%). 1H NMR (500 MHz, CDCl3, rt): δ 6.85 (s, 2H, Ar-Hm), 6.82 (s, 2H, Ar-Hm), 3.56 ((br s, 4H, N-H2), 2.77 (s, 4H, Ar-CH2), 2.25 (s, 6H, Ar-Me), 2.18 (s, 6H, Ar-Me). 13C{1H} NMR (125 MHz, CDCl3, rt): δ 139.95 (NH2-C), 129.33 (Ar-Cm), 127.78 (Ar-Cm), 127.60 (Ar-C), 126.17 (Ar-C), 122.70 (Ar-C), 31.60 (Ar-CH2), 20.59 (Ar-Me), 17.89 (Ar-Me). FAB mass spectrum: m/z = 270 [M + H+]. IR (KBr): 3416, 3350, 3008, 2964, 2920, 2858, 2735, 2722, 1626, 1604, 1486, 1371, 1306, 1252, 1238, 1162, 1117, 1039, 1030, 1011, 857, 690 cm−1. Anal. Calcd for C18H24N2: C, 80.55; H, 9.01; N, 10.44. Found: C, 80.43; H, 8.76; N, 10.45. 2-Bromo-6-isopropylphenylcarbamic Acid tert-Butyl Ester. 2Bromo-6-isopropylaniline (7.14 g, 33.4 mmol) and di-tert-butyldicarbonate (18.2 g, 83.4 mmol) were dissolved in toluene (45 mL) and heated at 90 °C under an argon atmosphere for 95 h. The solvent was removed by evaporation. Flash chromatography of the resulting red oil on silica, eluting with hexane/ethyl acetate (20:1), gave 2-bromo-6isopropylphenylcarbamic acid tert-butyl ester as a white solid (4.32 g, 13.7 mmol, 41%). 1H NMR (400 MHz, CDCl3, rt): δ 7.45 (dd, 1H, J = 8.0, 1.6, Ar-H0), 7.25 (d, 1H, J = 8.0, Ar-H0), 7.12 (t, 1H, J = 7.6, ArHp), 5.97 (br s, 1H, N-H), 3.26 (br s, 1H, CHMe2), 1.50 (s, 9H, CMe3), 1.21 (d, 6H, J = 6.8, CHMe2). 13C{1H} NMR (100 MHz, CDCl3, rt): δ 154.11 (OC), 149.32 (NH-C), 133.05, 130.05, 128.80, 125.29, 124.33, 80.41 (OCMe3), 29.33 (CHMe2), 28.25 (CMe3), 23.16 (CHMe2). FAB mass spectrum: m/z = 315 [M + H+]. IR (KBr): 3312, 2961, 2925, 2867, 2852, 1698, 1569, 1506, 1469, 1457, 1436, 1389, 1365, 1277, 1250, 1172, 1056, 1024, 894, 839, 788, 778, 716, 603 cm−1. Anal. Calcd for C14H19BrNO2(H2O)0.25: C, 59.92; H, 6.19; N, 4.41. Found: C, 53.08; H, 6.24; N, 4.42. 2-Isopropyl-6-vinylphenylcarbamic Acid tert-Butyl Ester. A solution of KBF3(CHCH2) (1.75 g, 13.1 mmol), PdCl2 (57.9 mg, 0.327 mmol), PPh3 (257 mg, 0.980 mmol), Cs2CO3 (12.8 g, 39.2 mmol), and 2-bromo-6-isopropylphenylcarbamic acid tert-butyl ester (2.05 g, 6.53 mmol) in THF/water (9:1) (40 mL) was heated at 80 °C for 38 h under an argon atmosphere in a stainless steel reactor. The reaction mixture was cooled to room temperature and diluted with CH2Cl2 (100 mL). The organic phase was washed with water (52 mL) and dried over anhydrous MgSO4. The solvent was removed in vacuo, and the crude product was purified by silica gel chromatography (eluting with hexane/ethyl acetate (9:1)) to give 2-isopropyl-6vinylphenylcarbamic acid tert-butyl ester as a white solid (1.52 g, 5.80 mmol, 89%). 1H NMR (500 MHz, CDCl3, rt): δ 7.33 (dd, 1H, J = 5.0, 2.5, Ar-H), 7.25 (m, 2H, Ar-H), 6.91 (m, 1H, CHCH2), 5.91 (br s, 1H, N-H), 5.69 (dd, 1H, J = 20.0, 1.0, CHCH2), 5.30 (dd, 1H, J = 10.0, 1.5, CHCH2), 3.20 (br s, 1H, CHMe2), 1.51 and 1.36 (s, 9H, CMe3), 1.22 (d, 6H, J = 10.0, CHMe2). 13C{1H} NMR (125 MHz, CDCl3, rt): δ 154.22 (OC), 146.51 (NH-C), 136.30, 133.42, 127.63, 125.33, 123.52, 115.68, 79.96 (OCMe3), 28.27 (CHMe2, CMe3), 23.38 (CHMe2). FAB mass spectrum: m/z = 263 [M + H+]. IR (KBr): 3268, 3081, 2966, 2925, 2853, 1683, 1584, 1509, 1466, 1391, 1281, 1251, 1173, 1053, 1027, 994, 908, 808, 730. Anal. Calcd for C16H22NO2: C, 73.53; H, 8.87; N, 5.36. Found: C, 73.13; H, 8.89; N, 5.24. (E)-2,2′-Bis(tert-butoxycarbamate)-3,3′-diisopropylstilbene. A solution of 2-bromo-6-isopropylphenylcarbamic acid tert-butyl ester (233 mg, 0.741 mmol), 2-isopropyl-6-vinylphenylcarbamic acid tertbutyl ester (242 mg, 0.926 mmol), Pd(OAc)2 (8.30 mg, 37.1 μmol), and tris(o-tolyl)phosphine (45.1 mg, 0.148 mmol) in NEt3 (7 mL) was heated under argon in a glass reactor at 90 °C for 19 h. The volatile fractions were removed in vacuo, and the crude product was purified by silica gel chromatography (eluting with hexane/ethyl acetate (7:3)) to give (E)-2,2′-bis(tert-butoxycarbamate)-3,3′-diisopropylstilbene as a white solid (332 mg, 0.671 mmol, 91%). 1H NMR (500 MHz, CDCl3, rt): δ 7.52 (br s, 2H, Ar-H), 7.29−7.23 (m, 6H, Ar-H and CC-H), 5.95 and 5.75 (s, 2H, N-H), 3.21 (br s, 2H, CHMe2), 1.52 and 1.34 (s, 18H, CMe3), 1.23 (d, 12H, J = 6.5, CHMe2). 13C{1H} NMR (75 MHz, CDCl3, rt): δ 154.22 (OC), 146.61 (NH-C), 136.27, 131.69, 127.71, 126.93, 125.24, 123.61, 79.98 (OCMe3), 28.39 (CHMe2), 28.28 (CMe3), 23.39 (CHMe2). FAB mass spectrum: m/z = 496 [M + H+]. IR (KBr): 3357, 3071, 3037, 2969, 2932, 2871, 1703, 1588, 1508, F
dx.doi.org/10.1021/om500629a | Organometallics XXXX, XXX, XXX−XXX
Organometallics
Article
1213, 1102, 1048, 1027, 1010, 814, 775, 568, 465 cm−1. HRMS-ESI (m/z): [M]+ calcd for C58H66Cl3Co2N6 1069.3074, found 1069.3073. Dinuclear Fe Complex (Fe2Cl4(3)). A suspension of 3 (50.0 mg, 0.073 mmol) and iron(II) chloride anhydrate (18.6 mg, 0.147 mmol) in THF (5.0 mL) was stirred at room temperature under argon in a glass reactor for 24 h. The solid product was collected by filtration and washed with THF to give Fe2Cl4(3) as a black solid (42.9 mg, 0.046 mmol, 63%). FAB mass spectrum, m/z = 897 [M+ − Cl], 734 [M+ − FeCl3]. IR (KBr): 3083, 3011, 2948, 2922, 2865, 1662, 1646, 1625, 1591, 1472, 1444, 1371, 1294, 1262, 1215, 1077, 1033, 859, 772, 741, 687 cm−1. Anal. Calcd for C46H42Cl4Fe2N6(CH2Cl2)2: C, 52.30; H, 4.21; N, 7.62. Found: C, 52.47; H, 4.20; N, 7.99. Dinuclear Co Complex (Co2Cl4(3)). A suspension of 3 (50.0 mg, 0.073 mmol) and cobalt(II) chloride anhydrate (19.1 mg, 0.147 mmol) in THF (5.0 mL) was stirred at room temperature under argon in a glass reactor for 24 h. The solid product was collected by filtration and washed with CHCl3 and then by MeOH to give Co2Cl4(3) as a green powder (63.7 mg, 0.068 mmol, 84%). 1H NMR (300 MHz, D2O, rt): δ 97.72 (4H, s, Py-Hm), 39.65 (2H, s, Py-Hp), 17.49 (4H, s, Ar-H), 13.87 (12H, s, NCMe), 12.88 (4H, s, Ar-H), −4.10 (4H, s, Ar-H), −5.98 (2H, s), −26.50 (4H, s), −35.50 (2H, s). FAB mass spectrum, m/z = 901 [M+ − Cl], 737 [M+ − CoCl3]. IR (KBr): 3069, 3019, 2968, 2948, 2925, 2857, 1633, 1586, 1486, 1446, 1373, 1318, 1264, 1227, 1199, 1162, 1116, 1096, 1045, 1028, 817, 790, 752, 495, 478 cm−1. Polymerization of Ethylene. Polymerization of Ethylene (1 atm). To a two-necked Schlenk flask containing a toluene suspension (18 mL) of Fe2Cl4(1) (2.10 mg, 0.002 mmol) was added an MMAO solution in toluene (6.5 wt % Al, 2 mL, 4.00 mmol) under argon, and the solution was stirred for 1 min. Ethylene was introduced with a flow rate of 60 L/h, and the solution stirred for 15 min. The reaction mixture was poured into a large amount of acidified methyl alcohol (100 mL containing 25 mL of conc HCl). The formed solid was collected and dried in vacuo at room temperature to give polyethylene as a white solid. Polymerization of Ethylene (5 and 10 atm). To a 100 mL autoclave containing a toluene suspension (48 mL) of Fe2Cl4(1) (2.10 mg, 0.002 mmol) was charged ethylene (5 atm). The reaction mixture was stirred at the temperatures rt to 120 °C for 2 min (800 rpm), and an MMAO solution in toluene (6.5 wt % Al, 2 mL, 4.00 mmol) was added. After the reaction, the mixture was poured into a large amount of acidified MeOH (100 mL containing 25 mL of conc HCl). The formed solid was collected and dried in vacuo at room temperature to give the polyethylene as a white solid. The TON of the catalyst was determined from the polymer yield and the amount of Fe catalyst.
(m, 4H, Ar-HCH), 2.63 (m, 4H, CHMe2), 2.44 (m, 4H, Ar-HCH), 2.15 (s, 12H, NCMe), 1.13 (d, 12H, J = 7.0, CHMe2), 1.09 (d, 12H, J = 7.0, CHMe2). 13C{1H} NMR (125 MHz, CDCl3, rt): δ 166.40 (NC), 154.90 (Py-C0), 147.41 (Ar-C), 136.51, 136.28, 130.13, 127.63, 123.69, 123.52, 121.46, 33.56 (Ar-CH2), 27.89 (NC-Me), 23.27 (CHMe2), 23.05 (CHMe2), 16.54 (CHMe2). FAB mass spectrum: m/z = 848 [M + H+]. IR (KBr): 3061, 3016, 2960, 2929, 2868, 1700, 1645, 1588, 1569, 1456, 1364, 1235, 1198, 1121, 1104, 822, 769, 741. Anal. Calcd for C58H66N6: C, 82.23; H, 7.85; N, 9.92. Found: C, 82.21; H, 7.61; N, 9.80. Macrocyclic Bis(bis(imino)pyridine) Ligand (3). A suspension of 1,2-bis(2-aminophenyl)ethylene (1.30 g, 6.13 mmol), 2,6-diacetylpyridine (1.00 g, 6.13 mmol), and acetic acid (3 drops) in EtOH (2.5 mL) was refluxed under argon for 36 h. The cooled reaction mixture was cooled, and the resulting solid was collected by filtration and washed with Et2O, hexane, and warm 1,2-dichloroethane to give 2 as a yellow solid (1.08 g, 1.59 mmol, 52%). 1H NMR (500 MHz, C2D2Cl4, 80 °C): δ 8.00 (d, 4H, J = 7.5, Py-Hm), 7.58 (t, 2H, J = 7.5, Py-Hp), 7.36 (d, 4H, J = 7.5, Ar-H), 7.15 (t, 4H, J = 7.5, Ar-H), 7.07 (t, 4H, J = 7.5, Ar-H), 6.53 (d, 4H, J = 7.5, Ar-H), 2.87 (s, 8H, Ar-CH2), 2.26 (s, 12H, NCMe). 13C{1H} NMR (125 MHz, C2D2Cl4, 80 °C): δ 166.32 (NC), 155.45 (Py-C0), 149.51 (Ar-C), 136.47, 132.58, 130.54, 126.94, 124.44, 121.69, 119.19, 33.94 (Ar-CH2), 16.43 (NC-Me). FAB mass spectrum: m/z = 679 [M+ + H+]. IR (KBr): 3061, 3016, 2960, 2929, 2868, 1700, 1645, 1588, 1569, 1456, 1364, 1235, 1198, 1121, 1104, 822, 769, 741 cm−1. Anal. Calcd for C46H42N6: C, 81.42; H, 5.92; N, 12.44. Found: C, 81.38; H, 6.24; N, 12.38. Dinuclear Fe Complex (Fe2Cl4(1)). A suspension of 1 (25.4 mg, 0.032 mmol) and iron(II) chloride anhydrate (8.1 mg, 0.64 mmol) in THF (5.0 mL) was stirred at room temperature under argon in a glass reactor for 24 h. The solid product was collected by filtration and washed with THF to give Fe2Cl4(1) as a blue powder (18.0 mg, 0.017 mmol, 54%). 1H NMR (500 MHz, C2D2Cl4, rt): δ 84.7 (s, 4H, PyHm), 67.6 (s, 2H, Py-Hp), 21.4 (s, 12H, p- or o-CH3), 11.59 (s, 8H, C6H2 or CH2CH2), 2.06, 1.19, 0.79 (m, 20H, p- or o-CH3 and C6H2 or CH2CH2), −23.9 (s, 12H, NCMe). IR (KBr): 3066, 3003, 2944, 2908, 2857, 2734, 1614, 1583, 1472, 1441, 1369, 1266, 1219, 1151, 1096, 1021, 978, 906, 851, 816, 744, 649, 566, 534 cm−1. HRMS-ESI (m/z): [M]+ calcd for C54H58Cl3Fe2N6 1007.2494, found 1007.2486. Dinuclear Co Complex (Co2Cl4(1)). A suspension of 1 (50.0 mg, 0.063 mmol) and cobalt(II) chloride anhydrate (16.4 mg, 0.126 mmol) in THF (7.5 mL) was stirred at room temperature under argon in a glass reactor for 11 h. The residual solid product was collected by filtration and washed with CHCl3 and then by MeOH to give Co2Cl4(1) as an ocher powder (54.1 mg, 0.052 mmol, 81%). 1H NMR (500 MHz, CD2Cl2, rt): δ 118.5 (s, 4H, Py-Hm), 52.5 (s, 2H, Py-Hp), 16.7 (s, 12H, p-CH3), 8.08 (s, 12H, NCMe), 5.39 (s, 8H, Ar-H), −2.54 (s, 4H, Ar-HCH), −25.7 (s, 12H, o-CH3), −28.04 (s, 4H, ArHCH). IR (KBr): 3070, 3010, 2950, 2914, 1650, 1620, 1585, 1474, 1445, 1376, 1323, 1266, 1224, 1189, 1151, 1096, 1027, 848, 822, 748, 709, 652, 569, 463 cm−1. HRMS-ESI (m/z): [M]+ calcd for C54H58Cl3Co2N6 1013.2436, found 1013.2447. Anal. Calcd for C54H58Cl4Co2N6(CH2Cl2)0.5: C, 59.88; H, 5.44; N, 7.69. Found: C, 59.75; H, 5.67; N, 7.66. Dinuclear Fe Complex (Fe2Cl4(2)). A suspension of 2 (14.4 mg, 0.017 mmol) and iron(II) chloride anhydrate (4.3 mg, 0.034 mmol) in THF (3.0 mL) was stirred at room temperature under argon in a glass reactor for 24 h. The solid product was collected by filtration and washed with THF to give Fe2Cl4(2) as a blue powder (6.3 mg, 0.006 mmol, 34%). IR (KBr): 3064, 2962, 2924, 2865, 1694, 1615, 1584, 1468, 1443, 1372, 1264, 1208, 1189, 1101, 1045, 922, 806, 769, 738, 714, 687, 555, 460 cm−1. HRMS-ESI (m/z): [M]+ calcd for C58H66Cl3Fe2N6 1063.3114, found 1063.3112. Dinuclear Co Complex (Co2Cl4(2)). A suspension of 2 (40.8 mg, 0.048 mmol) and cobalt(II) chloride anhydrate (12.5 mg, 0.096 mmol) in THF (7.0 mL) was stirred at room temperature under argon in a glass reactor for 13 h. The solid product was collected by filtration and washed with CHCl3 and then by MeOH to give Co2Cl4(2) as an ocher powder (33.7 mg, 0.030 mmol, 63%). IR (KBr): 3065, 3023, 2963, 2925, 2868, 1620, 1584, 1471, 1444, 1373, 1339, 1319, 1265,
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ASSOCIATED CONTENT
* Supporting Information S
Analytical data for the ligands and complexes and GPC profiles of the produced polymer. This material is available free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported by a Grant-in-Aid for Young Scientist (22685012) for Scientific Research from the Ministry of Education, Science, Sports and Culture, Japan.
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REFERENCES
(1) Recent reviews: (a) Gao, R.; Sun, W.-H.; Redshaw, C. Catal. Sci. Technol. 2013, 3, 1172−1179. (b) Luk, Y.-Y. G.; Foucher, D. A.; Gossage, R. A. C. R. Chim. 2013, 16, 573−579. (c) Fujisawa, K.;
G
dx.doi.org/10.1021/om500629a | Organometallics XXXX, XXX, XXX−XXX
Organometallics
Article
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dx.doi.org/10.1021/om500629a | Organometallics XXXX, XXX, XXX−XXX
