Synthesis of Sodium Complexes Supported with NNO-Tridentate

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Synthesis of Sodium Complexes Supported with NNO-Tridentate Schiff Base Ligands and Their Applications in the Ring-Opening Polymerization of L‑Lactide Hsiu-Wei Ou,† Kai-Hsuan Lo,† Wei-Ting Du,† Wei-Yi Lu,† Wan-Jung Chuang,‡ Bor-Hunn Huang,† Hsuan-Ying Chen,*,‡ and Chu-Chieh Lin*,† †

Department of Chemistry, National Chung Hsing University, Taichung 402, Taiwan, Republic of China Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 80708, Taiwan, Republic of China

‡

S Supporting Information *

ABSTRACT: A series of sodium complexes bearing NNOtridentate Schiff base ligands with an N-pendant arm were synthesized and used as catalysts for the ring-opening polymerization of L-lactide (L-LA). Electronic effects of ancillary ligands coordinated by sodium complexes substantially influence the catalysis, and ligands with electron-donating groups increase the catalytic activity of the sodium complexes for catalyzing L-LA polymerization. In particular, a sodium complex bearing a 4methoxy group has the highest activity with conversion up to 95% within 30 s at 0 °C and a low polydispersity index of 1.13, whereas the 4-bromo group showed the poorest performance with regard to the catalytic rate of L-LA polymerization in the presence of benzyl alcohol (BnOH). 1H NMR pulsed-gradient spin−echo diffusion experiments and single-crystal X-ray analyses showed that sodium complexes [LHNa(THF)]2 and [L4‑ClNa(THF)]2 were dinuclear species in both solution and the solid state. The kinetic results indicated a first-order dependence on each of [[L4‑ClNa]2], [L-LA], and [BnOH].

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INTRODUCTION Petrochemical plastics are currently widely used because they are light and easy to use and thus are suitable for use as wrappers and containers. However, they cause severe environmental pollution when discarded arbitrarily. Developing environmentally friendly materials to replace petrochemical plastics has therefore been a research area of interest for decades. Polylactide (PLA) is a synthetic biodegradable polymer derived from renewable resources. Ring-opening polymerization (ROP) is a viable route of producing such polymers in a controlled manner under mild conditions. Many metal complexes (such as lithium,1 aluminum,2 magnesium,3 calcium,4 zinc,5 tin,6 copper,7 iron,8 indium,9 lead,10 group 3,11 group 4,12 and lanthanide13) have been used as catalysts for ROP of lactides (LAs). However, the presence of metallic residues is a critical problem when polymers are used as biomaterials for tissue repair and regeneration. Therefore, noncytotoxic sodium complexes have been used as catalysts for ROP of L-lactide (L-LA).14 Ligands are crucial in catalyst design because they improve the polymerization activity of metal catalysts and avoid transesterification. Schiff base ligands are the most common because of their diversity and ease of preparation. A variety of metal complexes supported by Schiff base ligands including bidentate,15 tridentate,16 and tetradentate2a,f,17 have been © XXXX American Chemical Society

widely used in ROP. However, examples of sodium complexes bearing Schiff base ligands are relatively rare.18 Sodium complexes14,18 typically show high activity for ROP, with transesterification as a side reaction, thus producing a polymer with an unexpected molecular weight and a broad polydispersity index (PDI). Such transesterification can be minimized by using a ligand with pendant arms to coordinate with the active metal center, which provides a steric barrier, thus preventing undesired side reactions.18c However, the catalytic activity of sodium complexes is reduced in the presence of the pendant arms. An ideal catalyst design is the one in which the pendant arm avoids transesterification and the associated sodium catalyst has a high catalytic activity. Ligands with longer pendant arms than those in our earlier research18c can influence the structure and catalytic activity of the sodium complexes for L-LA polymerization. In this paper, we report the synthesis of a series of NNO-tridentate Schiff base ligands with a pendant amino group and the associated sodium complexes and discuss the catalytic activity of the sodium complexes for L-LA polymerization. Received: September 3, 2015

A

DOI: 10.1021/acs.inorgchem.5b02043 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry Scheme 1. Synthesis of NNO-Tridentate Schiff Base Ligand Precursors LXH

Scheme 2. Synthesis of Sodium Complexes

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RESULTS AND DISCUSSION Synthesis and Characterization of Sodium Complexes. Ligand precursors LXH were prepared by the reaction of N-(2-aminobenzyl)-N-cyclohexyl-N-methylamine with the related 2-hydroxybenzaldehyde derivatives under refluxing toluene. Further reaction of LXH with a stoichiometric quantity of sodium bis(trimethylsilyl)amide under −95 °C in tetrahydrofuran (THF) produced sodium complexes [LXNa(THF)]2 in moderate yield (Schemes 1 and 2). The coordinated THF can be removed completely under vacuum, yielding [LXNa]2. These complexes have been characterized using 1H and 13C NMR spectroscopic studies as well as elemental analysis. Single crystals of [LHNa(THF)]2 and [L4‑ClNa(THF)]2 suitable for X-ray structural determination were grown from a saturated THF solution. Solid-state structures of [LHNa(THF)]2 and [L4‑ClNa(THF)]2 indicate that both are fivecoordinated dimeric complexes. The Na centers are bonded to two •2-bridged phenoxy groups, a methylcyclohexylamino group, an imine group, and THF, as shown in Figures 1 and 2. [LHNa(THF)]2 exhibited a distorted trigonal-bipyramidal geometry (τ = 0.494) with an average compressed axial O(1)− Na−N(1) bond angle of 163.57(5)°, and the equatorial bond angles of O(2)−Na−O(1A), O(1A)−Na−N(2), and O(2)− Na−N(2) were 133.89(5)°,118.97(5)°, and 101.72(5)°, respectively. Moreover, the distances between the Na atom and O(2), O(1), O(1A), N(2), and N(1) were 2.439(1), 2.318(1), 2.273(1), 2.606(2), and 2.386(2) Å, respectively.

Figure 1. Molecular structure of [LHNa(THF)]2 as 20% ellipsoids. All H atoms were omitted for clarity.

The X-ray structure of [L4‑ClNa(THF)]2 demonstrated that the Na center is a distorted trigonal bipyramid (τ = 0.530) with an average compressed axial O(1A)−Na−N(1) bond angle of 163.10(6)°, and the equatorial bond angles of O(2)−Na− O(1), O(1)−Na−N(2), and O(2)−Na−N(2) were 131.31(6)°, 121.32(5)°, and 101.51(5)°, respectively. Moreover, the distances between the Na atom and O(2), O(1A), O(1), N(1), and N(2) were 2.423(2), 2.315(2), 2.280(2), B


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Inorganic Chemistry

optimal conditions for L-LA polymerization were [LHNa]2 catalyst in the presence of BnOH and toluene at 0 °C. Other solvents, such as THF and CH2Cl2, reduced the polymerization rate probably because the coordinating solvents competed with L-LA to coordinate with the metal center. Furthermore, the electronic effect of the Schiff base on the sodium complexes affecting the ROP of L-LA in the presence of BnOH as an initiator was examined, as shown in Table 2. Their activities in different solvents were also demonstrated.

Experimental results indicated that the catalytic activity of sodium complexes dramatically varied with the electronic effect of the substituents on the ligands (Table 2, entry 6) with the reactivity of sodium complexes in the order [L4‑OMeNa]2 > [L5‑NEt2Na]2 > [L5‑OMeNa]2 > [LHNa]2 > [L4‑ClNa]2 ≥ [L4‑BrNa]2. The presence of electron-donating groups on the ligand increases the catalytic activity of sodium complexes in LLA polymerization. This phenomenon is attributable to the higher electronegative effect of the substituent on the ligand, causing the stronger interaction between sodium and BnOH and therefore decreasing the reaction rate. It is also worth noting that the activity of [L4‑OMeNa]2 is higher than that of [L5‑OMeNa]2. According to the Hammett equation,20 the methoxy (OMe) group in [L5‑OMeNa]2 is electron-donating toward the immine (CN) bond but electron-withdrawing toward the phenolate (PhO−) group. Conversely, the OMe group in [L4‑OMeNa]2 is electron-withdrawing toward the immine (CN) bond but electron-donating toward phenolate (PhO−). Thus, the electronic influence at the para positions of PhO− is more important than that in the meta position. Among these six complexes, the best choice for ROP is probably [L5‑NEt2Na]2 because it not only exhibits high catalytic activity with conversion up to 89% in 30 s but also yields polymers with the expected molecular weight and narrow PDI (1.06). Polymerization of L-LA using [LHNa]2 (2.5 mM) as a catalyst was systematically investigated in the presence of CH2Cl2

Figure 2. Molecular structure of [L4‑ClNa(THF)]2 as 20% ellipsoids. All H atoms were omitted for clarity.

2.381(2), and 2.600(2) Å, respectively. According to the literature,18,19 sodium complexes bearing Schiff base ligands exist in two forms, cubic (tetramer) and quadrilateral (dimer) (Figure 3). Both sodium complexes presented in this paper are dimers of the quadrilateral form. The bond length between the O atom of THF and the Na atom in the quadrilateral form is longer than those in the cubic form. In addition, the environment around the Na atom in the cubic form was more crowded than that in the quadrilateral form. These differences might influence the catalytic activity of sodium complexes for L-LA polymerization. Polymerization of L-LA. Table 1 lists the conditions of optimization of L-LA polymerization using [LHNa]2 as a catalyst and benzyl alcohol (BnOH) as an initiator. Entries 1−3 of Table 1 clarify that the polymerization rate in the absence of BnOH was obviously slower than that in the presence of BnOH, implying that initiation by BnOH was more effective than initiation by the ligand. Because of the low solubility of LLA in toluene at 0 °C, the L-LA concentration ([L-LA]) was reduced to half the original concentration (entry 4, Table 1). The catalytic results, that is, a narrow PDI (1.09) and similar values of Mn(cal), Mn(NMR), and Mn(GPC), revealed that the

Figure 3. Bond-length discussion between the quadrilateral (left) and cubic18c (right) forms. C


Article

Inorganic Chemistry Table 1. Polymerizations of L-LA Catalyzed by [LHNa]2 entry d

1 2d 3d 4e 5f 6g

T (°C)

[L-LA]0:[cat.]:[BnOH]

t (min)

conv (%)a

Mn(cal)a

30 30 30 0 30 30

200:1:0 200:1:0 200:1:2 100:1:2 200:1:2 200:1:2

1 5 0.5 0.5 1 0.5

24 92 95 65 85 73

3500 13200 13800 4800 12400 10600

Mn(NMR)b

Mn(GPC)c

PDIc

10200 4700 10000 7100

22400 72500 10500 5000 5900 5900

1.06 1.32 1.27 1.09 1.37 1.26

Obtained from 1H NMR analysis. bCalculated from the molecular weight of L-LA × [L-LA]0/[BnOH]0 × conversion yield + Mw(BnOH). Obtained from GPC analysis and calibrated using the polystyrene standard. Values in parentheses are the values obtained from GPC × 0.58. d Reaction conditions: toluene (25 mL), [LHNa]2 (0.025 mmol), and [L-LA]0 = 0.2 M. eReaction conditions: toluene (25 mL), [LHNa]2 (0.025 mmol), and [L-LA]0 = 0.1 M. fReaction conditions: THF (10 mL), [LHNa]2 (0.025 mmol), and [L-LA]0 = 0.5 M. gReaction conditions: CH2Cl2 (25 mL), [LHNa]2 (0.025 mmol), and [L-LA]0 = 0.5 M. a c

Table 2. Polymerizations of L-LA Catalyzed by Sodium Complexes in the Presence of BnOH as an Initiatora entry 1 2 3 4 5 6

catalyst H

[L Na]2 [L5‑NEt2Na]2 [L5‑OMeNa]2 [L4‑OMeNa]2 [L4‑ClNa]2 [L4‑BrNa]2

conv (%)b

Mn(cal)c

Mn(NMR)b

Mn(GPC)d

PDId

65 89 82 95 26 24

4800 6500 6000 7000 2000 1800

4700 6700 4700 5900 1500 1400

5000 6800 4300 6600 2700 2900

1.09 1.06 1.19 1.13 1.20 1.17

Reaction conditions: 30 s, 0 °C, toluene (25 mL), catalyst (0.025 mmol), [L-LA]0 = 0.1 M, and [L-LA]0:[cat.]:[BnOH] = 100:1:2. bObtained from H NMR analysis. cCalculated from the molecular weight of L-LA × [L-LA]0/[BnOH]0 × conversion yield + Mw(BnOH). dObtained from GPC analysis and calibrated using the polystyrene standard. Values in parentheses are the values obtained from GPC × 0.58. a

1

Table 3. Polymerizations of L-LA Using the Complex [LHNa]2 with BnOH as an Initiator at 0 °C in CH2Cl2a entry

[L-LA]0:[cat.]:[BnOH]

time (min)

conv (%)b

Mn(cal)c

Mn(NMR)b

Mn(GPC)d

PDId

1 2 3 4 5

50:1:2 100:1:2 200:1:2 300:1:2 400:1:2

2 3 4 5 6

99 93 96 96 92

3700 6800 13900 20900 26600

2800 4700 10200 22700 29100

2400 5000 13400 18700 22800

1.20 1.16 1.13 1.17 1.12

a Reaction conditions: 0 °C, CH2Cl2 (10 mL), and catalyst (0.025 mmol). bObtained from 1H NMR analysis. cCalculated from the molecular weight of L-LA × [L-LA]0 × conversion yield + Mw(BnOH). dObtained from GPC analysis and calibrated using the polystyrene standard. The values obtained from GPC × 0.58.

(Table 3). Experimental results reveals that conversion higher than 92% can be achieved within 2−6 min at 0 °C in CH2Cl2 with a [LA]0/[BnOH] ratio ranging from 25 to 200 (Table 3), and the reaction is highly controllable, as confirmed by the linear relationship between Mn(GPC) and [M]0/[[BnOH]0 (Figure 4) with narrow PDIs. The 1H NMR spectrum of PLA (entry 1) confirmed one benzyl group and hydroxyl chain ends with an integral ratio of 5:1, suggesting that initiation occurred through BnOH insertion into L-LA (Figure 5). Polymers with different chain ends can be prepared using various initiators, such as 2-(dimethylamino)ethanol (DMAE), mPEG-350, 2,2′-disulfanediyldiethanol (HOSSOH), and 2-[(2hydroxyethyl)disulfanyl]ethyl-2-bromo-2-methylpropanoate (BrSSOH). According to Table 4, all of the conversions were up to 91% within 30 s ([L-LA]0:[[L5‑NEt2Na]2]:[initiator] = 50:1:2, [L-LA] = 2.5 mM, entries 1−3), except when BrSSOH was used as the initiator (conv = 73%). When [L-LA] was increased to 10 mM, the conversions were up to 90% within 1− 1.5 min, except when BrSSOH was used as the initiator (conv = 96% after 5 min). The molecular weight of the polymers increased as the [L-LA]0/[initiator] ratio increased with the narrow PDIs. 1H NMR spectra of the PLAs with various initiators (entries 1−4 in Table 4) are presented in Figures S1− S4.

Figure 4. Linear plot of Mn(GPC) versus [LA]0/[BnOH], with the PDI indicated by closed circles (GPC; Table 3, entries 1−5). 1 H NMR Pulsed-Gradient Spin−Echo (PGSE) Diffusion Study of [LHNa]2 and [L4‑ClNa]2. PGSE NMR is useful for investigating the nuclearity of organometallic species in a solution.21 The diffusion coefficient (D) of the molecule can be experimentally measured, and the solution hydrodynamic radius can be calculated using the Stokes−Einstein equation

D


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Inorganic Chemistry

Figure 5. 1H NMR spectrum of PLLA (entry 1 of Table 3) with BnOH as an initiator.

Table 4. Polymerizations of L-LA Catalyzed by Using [L5‑NEt2Na]2 as a Catalyst with Various Initiators entry

initiator

time (min)

conv (%)a

Mn(cal)a

Mn(NMR)b

Mn(GPC)c

PDIc

1d 2d 3d 4d 5e 6e 7e 8e

DMAE mPEG-350 HOSSOH BrSSOH DMAE mPEG-350 HOSSOH BrSSOH

0.5 0.5 0.5 0.5 1 1 1.5 5

92 96 91 73 90 96 90 96

3400 3800 3400 2900 13100 14200 13100 14140

4000 2700 7500 14700 15400 11300 39900 85400

3000 1800 8200 6400 16500 9900 40700 36200

1.21 1.08 1.12 1.25 1.14 1.16 1.12 1.28

Obtained from 1H NMR analysis. bCalculated from the molecular weight of L-LA × [L-LA]0/[initiator]0 × conversion yield + Mw(initiator). Obtained from GPC analysis and calibrated using the polystyrene standard. Values in parentheses are the values obtained from GPC × 0.58. d Reaction conditions: [L-LA]0:[cat.]:[initiator] = 50:1:2, catalyst (0.025 mmol), CH2Cl2 (10 mL), and 0 °C. eReaction conditions: [L-LA]0:[cat.]: [initiator] = 200:1:2, catalyst (0.025 mmol), CH2Cl2 (10 mL), and 0 °C. a c

Figure 6. Diffusion constants (D) of [LHNa]2, [L4‑ClNa]2, and [L4‑ClNa]2 + 2BnOH. The average diffusion constants were 5.86, 5.53, and 6.38 Å2 s−1, respectively.

(eq 1), where D is the diffusion constant, kB is the Boltzmann constant, η is the dynamic viscosity, and r is the solution hydrodynamic radius. Although crystal structural studies indicate that both [LHNa]2 and [L4‑ClNa]2 are dimeric in the solid state with a quadrilateral form, the activities of sodium complexes are determined by the structure of the complexes in solution. Therefore, the PGSE diffusion experiment was conducted at 298 K in toluene-d8. The diffusion constants of [LHNa]2 and [L4‑ClNa]2 were measured and are shown in

Figure 6, and the average diffusion constants were estimated as 5.86 and 5.53 Å2 s−1, respectively. The experimental hydrodynamic radii (r) of [LHNa]2 and [L4‑ClNa]2 in solution were 6.74 and 7.14 Å, respectively, which is as expected, that is, that the complex with larger complex size ([L4‑ClNa]2) will result in a lower diffusion rate (Table 5). According to the polymerization data (entries 2 and 3 in Table 1), BnOH considerably promoted the rate of ROP. It is interesting to understand whether the complexes dissociate into E


Article

Inorganic Chemistry −d[L‐LA]/dt = 132.57[L‐LA]1 [[L4‐ClNa]2 ]0.837

Table 5. Comparison PGSE

complex [LHNa]2 [L4‑ClNa]2 [L4‑ClNa]2 + 2BnOH a

[BnOH]1.062

X-ray crystallography

average diffusion constant D (Å2 s−1)

average solvodynamic radius r (Å)

volume (Å3)

radius (Å)

structure

5.86 5.53 6.38

6.74 7.14 6.19

1152 1180 a

6.50 6.55 a

dimer dimer a

(5) 4‑Cl

To investigate the Gibbs energy Ea of the ROP, [L Na]2 was used as a catalyst, and the reactions were carried out at [LLA]0/[[L4‑ClNa]2]/[BnOH] = 400:1:2 ([LA] = 0.5 M in 10 mL of CH2Cl2 at −20, 0, and +30 °C). Furthermore, ln([LA]0/ [LA]t) was plotted against time (Figure 7), and different slopes

Not available.

mononuclear or remain dinuclear in the presence of BnOH. Therefore, the PGSE experiment of [L4‑ClNa]2/BnOH (1:2) was performed as shown in Figure 6. The observed average diffusion constant was 6.38 Å2s−1, and the hydrodynamic radii (r) of 6.19 Å indicated that the conformation of the dinuclear sodium complex remained unchanged in the presence of BnOH, similar to the manner in which THF coordinated to the Na atom observed in [LHNa(THF)]2. In addition, 1H NMR spectroscopic studies indicate that there was a interaction between [L4‑ClNa]2 and BnOH because all of the proton peaks of methine in the imine group, methyl and methylene groups of the pendant amino group, and methylene groups of BnOH shifted slightly after the addition of BnOH in [LHNa]2. kBT 2 −1 D= Å s 6πηr

Figure 7. First-order kinetic plots for LA polymerizations versus time in CH2Cl2 (10 mL) at −20, 0, and +30 °C.

(1)

represented different kobs values at different temperatures (0.00405, 0.00093, and 0.00007 at +30, 0, and −20 °C, respectively). kp can be described in eq 6, where the kp values at +30, 0, and −20 °C were 1296, 298, and 21, respectively. The Arrhenius equation (eq 7) was used to plot ln kp against 1/T (K) (Figure 8); a straight line of slope −6227 and intercept

Kinetic Studies of Polymerization of L-LA. Kinetic studies of polymerization of L-LA catalyzed by [L4‑ClNa]2 in the presence of BnOH were performed to establish the reaction order with respect to [L-LA], [catalysts], and [BnOH]. The experiments were performed at [L-LA]0/[[L4‑ClNa]2]/[BnOH] ratios of 400:0.5:4, 400:1:4, 400:1.5:4, and 400:2:4 ([L-LA] = 0.5 M in 10 mL of CH2Cl2 at 0 °C). The preliminary results indicated that the reaction rate has a first-order dependence on [L-LA] in all four ratios (Figure S5) according to eq 2, where kobs = kprop[[L4‑ClNa]2]x[BnOH]y and kprop is the propagation rate constant. To determine the order of [L4‑ClNa]2 (x), different [[L4‑ClNa]2] (0.625, 1.25, 1.875, and 2.5 mM) with the same [L-LA] (0.5 M) and [BnOH] (5 mM) were used. In addition, [BnOH] is regarded as a constant and is incorporated into k1 (k1 = kprop[BnOH]y; Figure S5). The variable kobs is described in eq 3. The order of [[L4‑ClNa]2] was 0.837 by plotting ln kobs against ln [[L4‑ClNa]2] (Figure S6), and thus the reaction followed first-order kinetics with respect to [L4‑ClNa]2, and k1 = 0.447. The variable kobs is described in eq 4, where [[L4‑ClNa]2] is regarded as a constant and is incorporated into k2. Furthermore, various concentrations of [BnOH] (2.5, 5, 7.5, and 10 mM) with the same [L-LA] (0.5 M) and [[L4‑ClNa]2] (1.25 mM) (Figures S7 and S8) were used, and the order of [BnOH] was calculated as 1.062. Thus, the reaction followed first-order kinetics with respect to [BnOH], and k2 = 0.524. Next, kprop was calculed to be 132.57 by averaging k1/ [BnOH]1.062 and k2/[[L4‑ClNa]2]0.837. Therefore, L-LA polymerization by using [[L4‑ClNa]2] and [BnOH] followed an overall kinetic law of eq 5. −d[L‐LA]/dt = kobs[L‐LA]

(2)

kobs = k1[[L4‐ClNa]2 ]x

(3)

kobs = k 2[BnOH]

y

Figure 8. Linear plot of ln kp versus 1/T (K) for the polymerization of L-LA with [L-LA] = 0.5 M in CH2Cl2 (10 mL) at −20, 0, and +30 °C.

+27.95 was obtained. Therefore, the Gibbs energy Ea was estimated as 51.8 kJ mol−1 [6227 × 8.3145 J K−1 mol−1 (ideal gas constant)], and the frequency factor A was 1.37 × 1012 L mol−1 s−1. According to the literature,22 the Gibbs energy of tin(II) 2-ethylhexanoic acid for ROP of L-LA is 70.9 kJ mol−1. The catalytic activity of the sodium complex in this study is higher than that of tin(II) 2-ethylhexanoic acid. k p = kobs/[[L4 ‐ ClNa]2 ][BnOH]

(4) F

(6) DOI: 10.1021/acs.inorgchem.5b02043 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

Figure 9. Proposed mechanism for ROP of L-LA catalyzed by a sodium complex.

of [L4‑ClNa]2 was 51.8 kJ mol−1. Such sodium complexes bearing NNO-tridentate Schiff base ligands are the most effective sodium catalysts for ROP of L-LA.14,18

k = A e−Ea / RT or ln k = ln A + ( −Ea /RT ) = ( −Ea /R )(1/T ) + ln A

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(7)

Proposed Mechanism. PGSE NMR studies revealed that sodium complexes remain dinuclear in the solution, and kinetic results indicate that the polymerization followed first-order kinetics with respect to [L-LA], [[L4‑ClNa]2] and [BnOH]. It is believed that BnOH is probably activated by the hydrogen bond between BnOH and the phenoxy O atom and a weak interaction with the Na center similar to that found in the [Mg(•-MEMPEP)(THF)]2 system.23 A feasible mechanism is proposed, as shown in Figure 9. The intermediate A is formed by an extra hydrogen bond to the phenoxy O atom of [L4‑ClNa]2. Subsequent coordination of L-LA with the same Na atom enables the insertion of BnOH into L-LA in intermediate B. Deprotonation of BnOH and attack of the carbonyl group of − L-LA by BnO give the acetal intermediate C. After dissociation of the BnO group from the crowded Na center, intermediate D is formed. Proton transfer to the O atom of the nearby C−O segment in the L-LA ring weakens the C−O bond in intermediate E and finally causes ring opening in L-LA. After ring opening, intermediate F forms, with the newly formed ROH binding through the hydrogen bond. Subsequent coordination of L-LA through a similar cycle results in the formation of PLA.

EXPERIMENTAL SECTION

General Procedures. Standard Schlenk techniques and a N2-filled glovebox were used throughout the isolation and handling of all of the compounds. Solvents, L-LA, and deuterated solvents were purified prior to use. N-(2-Aminobenzyl)-N-cyclohexyl-N-methylamine was purchased from Sigma-Aldrich. Salicylaldehyde, 4-(diethylamino)-2hydroxybenzaldehyde, 2-hydroxy-4-methoxybenzaldehyde, 2-hydroxy5-methoxybenzaldehyde, 5-chloro-2-hydroxybenzaldehyde, 5-bromo2-hydroxybenzaldehyde, and 2-hydroxyethyl disulfide were purchased from Alfa. Sodium bis(trimethylsilyl)amide was purchased from Acros. 1 H and 13C NMR spectra were recorded on a Varian Unity Inova-600 (600 MHz for 1H and 150 MHz for 13C) or a Varian Mercury-400 (400 MHz for 1H and 100 MHz for 13C) spectrometer with chemical shifts given in ppm from internal tetramethylsilane or the central line of CDCl3. Gel permeation chromatography (GPC) measurements were performed on a Jasco PU-2080 plus system equipped with a RI2031 detector using THF (high-performance liquid chromatography grade) as an eluent (flow rate of 1.0 mL min−1 at 40 °C). The chromatographic column was Phenomenex Phenogel 5 μm and 103 Å, and the calibration curve used to calculate Mn(GPC) was produced from polystyrene standards. The GPC results were calculated using the Scientific Information Service Corporation chromatography data solution, 3.1 edition. X-ray Crystallographic Studies. Single crystals of complexes [LHNa(THF)]2 and [L4‑ClNa(THF)]2 were obtained from their saturated THF solutions. Suitable crystals were immersed in FOMBLINY under a N2 atmosphere and mounted on an Oxford Xcalibur Sapphire-3 CCD Gemini diffractometer employing graphitemonochromated Mo Kα radiation (λ = 0.710 73 Å), and the intensity data were collected with ω scans. Data collection and reduction were performed with the CrysAlisPro software,24 and the absorptions were corrected by the SCALE3 ABSPACK multiscan method.25 The spacegroup determination was based on a check of the Laue symmetry and systematic absences, and it was confirmed using the structure solution. The structure was solved and refined with the SHELXTL package.26 All non-H atoms were located from successive Fourier maps, and H atoms were refined using a riding model. Anisotropic thermal parameters were used for all non-H atoms, and fixed isotropic parameters were used for H atoms. Synthesis of LHH. A mixture of salicylaldehyde (1.832 g, 15 mmol) and N-(2-aminobenzyl)-N-cyclohexyl-N-methylamine (3.275 g, 15 mmol) was refluxed in toluene (50 mL) with a Dean−Stark condenser

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CONCLUSION We synthesized a series of dimeric and five-coordinated sodium complexes bearing NNO-tridentate Schiff base ligands to catalyze the polymerization of L-LA. All complexes demonstrated high efficiency toward the ROP of L-LA. Electrondonating substituents on ancillary ligands showed a higher catalytic activity than did the electron-withdrawing groups during polymerization. Among the sodium complexes, [L4‑OMeNa]2 with the OMe group showed the highest catalytic activity with a conversion of 95% and excellent controllability under the conditions of 0 °C, toluene (25 mL), [L-LA]0 = 0.1 M, and [L-LA]0:[cat.]:[BnOH] = 100:1:2. Kinetic studies revealed a first-order dependence on [L-LA], [sodium complex], and [BnOH]. Furthermore, the activation energy G


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Inorganic Chemistry

6.93 (m, 1H, J = 8.8 Hz, ArH), 6.84 (m, 1H, ArH), 6.77 (d, 1H, J = 2.4 Hz, ArH), 6.66 (m, 1H, ArH), 3.64 (s, 2H, CH2), 2.44−2.36 (m, 1H, CyH), 2.12 (s, 3H, NCH3), 1.78 (d, 2H, J = 11.6 Hz, CyH), 1.67 (d, 2H, J = 11.6 Hz, CyH), 1.51 (d, 1H, J = 12.8 Hz, CyH), 1.22−0.94 (m, 5H, CyH). 13C NMR (toluene-d8, 100 MHz): δ 161.35 (ArCOH), 160.36 (CHN), 147.77 (ArCN), 134.71, 132.85, 131.54, 130.58, 127.92, 127.02, 123.42, 120.54, 119.04, 118.30 (ArC), 62.90 (Cy-CH), 54.89 (CH2), 36.75 (NCH3), 28.79, 26.76, 26.39 (CyCH2). Anal. Calcd for C21H25ClN2O (356.89): C, 70.67; H, 7.06; N, 7.85. Found: C, 71.03; H, 6.79; N, 8.25. ESI-MS. Calcd for C21H25ClN2O: m/z 356.2. Found: m/z 357.3 ([M + H]+). Synthesis of L4‑BrH. A method similar to that for LHH except with 5-bromo-2-hydroxybenzaldehyde was used. Yield: 5.78 g (96%). 1H NMR (toluene-d8, 400 MHz): δ 13.39 (s, 1H, OH), δ7.71 (s, 1H, CHN), 7.46 (m, 1H, ArH), 7.11−6.97 (m, 4H, ArH), 6.71 (d, 1H, J = 8.8 Hz, ArH), 6.66 (m, 1H, ArH), 3.63 (s, 2H, CH2), 2.44−2.36 (m, 1H, CyH), 2.11 (s, 3H, NCH3), 1.78 (d, 2H, J = 11.6 Hz, CyH), 1.68 (d, 2H, J = 11.6 Hz, CyH), 1.51 (d, 1H, J = 12.8 Hz, CyH), 1.22−0.94 (m, 5H, CyH). 13C NMR (toluene-d8, 100 MHz): δ 161.26 (ArCOH), 160.79 (CHN), 147.74 (ArCN), 135.65, 134.71, 134.55, 130.59, 127.88, 127.03, 121.18, 119.44, 118.30, 110.32 (ArC), 62.91 (CyCH), 54.90 (CH2), 36.76 (NCH3), 28.81, 26.77, 26.40 (CyCH2). Anal. Calcd for C21H25BrN2O (401.34): C, 62.85; H, 6.28; N, 6.98. Found: C, 63.08; H, 6.02; N, 6.68. ESI-MS. Calcd for C21H25BrN2O: m/z 400.1. Found: m/z 401.3 ([M + H]+). Synthesis of [LHNa]2. To a rapidly stirred suspension of LHH (3.22 g, 10 mmol) in THF (40.0 mL) was slowly added sodium bis(trimethylsilyl)amide (1.83g, 10 mmol). The mixture was stirred at −95 °C for 3 h and then was returned to room temperature for 12 h. Volatile materials were removed under vacuum to give a yellow oil. Then it was washed with hexane (20 mL), and a light-yellow powder was obtained after filtration. Yield: 2.48 g (72%). 1H NMR (toluened8, 400 MHz): δ 7.97 (s, 1H, CHN), 7.09−6.90 (m, 4H, ArH), 6.75 (s, 1H, ArH), 6.69 (d, 1H, ArH, J = 7.4 Hz), 6.35 (t, 1H, J = 6.9 Hz, ArH), 6.18 (s, 1H, ArH), 3.34 (s, 2H, CH2), 2.03 (s, 3H, N(CH3)), 1.55−1.44 (m, 5H, CyH), 1.28−1.22 (m, 1H, CyH), 0.92−0.87 (m, 5H, CyH). 13C NMR (toluene-d8, 100 MHz): δ 172.41 (ArCONa), 167.08 (CHN), 155.16 (ArCN), 137.03, 133.11, 131.02, 129.72, 129.13, 123.93, 123.76, 123.55, 121.18, 111.73 (ArC), 60.92 (CyCH), 54.16 (CH2), 38.58 (NCH3), 32.02, 26.46, 25.86 (CyCH2). Mp: 161.6 °C. Anal. Calcd for C21H25N2NaO (344.43): C, 73.23; H, 7.32; N, 8.13. Found: C, 73.60; H, 7.17; N, 7.78. Synthesis of [L5‑NEt2Na]2. A method similar to that for [LHNa]2 except L5‑NEt2H was used. Yield: 1.41 g (34%). 1H NMR (toluene-d8, 400 MHz): δ 7.94 (s, 1H, CHN), 7.15−7.05 (m, 2H, ArH), 7.01− 6.95 (m, 2H, ArH), 6.89 (t, 1H, J = 7.2 Hz, ArH), 6.63 (d, J = 7.9 Hz, 1H, ArH), 5.92 (d, 1H, J = 8.8 Hz, ArH), 3.55 (s, 2H, CH2), 3.04 (d, 4H, J = 6.9 Hz, ArNCH2), 2.36 (s, 1H, CyH), 2.19 (s, 3H, N(CH3)), 1.70 (d, 2H, CyH), 1.56 (d, 2H, J = 10.8 Hz, CyH), 1.41 (d, 1H, J = 13.0 Hz, CyH), 1.17−0.99 (m, 3H, CyH), 0.96 (t, 6H, J = 6.9 Hz, ArNCH2CH3), 0.90−0.80 (m, 2H, CyH). 13C NMR (toluene-d8, 100 MHz): δ 175.27 (ArCONa), 166.53 (CHN), 156.48 (ArCN), 152.78, 139.38, 131.59, 130.12, 129.39, 122.77, 121.32, 115.37, 104.29, 99.28 (ArC), 60.09 (CyCH), 56.42 (CH2), 44.22 (ArNCH2), 37.80 (NCH3), 27.92, 26.45, 26.37 (CyCH2), 13.31 (ArNCH2CH3). Mp: 137.3 °C. Anal. Calcd for C25H34N3NaO (415.55): C, 72.26; H, 8.25; N, 10.11. Found: C, 71.38; H, 7.42; N, 9.71. Synthesis of [L5‑OMeNa]2. A method similar to that for [LHNa]2 except with L5‑OMeH was used. Yield: 2.44 g (65%). 1H NMR (toluened8, 400 MHz): δ 7.90 (s, 1H, CHN), 7.09 (m, 2H, ArH), 6.95−6.84 (m, 3H, ArH), 6.59 (m, 1H, ArH), 6.23 (m, 1H, ArH), 3.40 (s, 5H, ArOMe and CH2), 2.24 (s, 1H, CyH), 2.09 (s, 3H, N(CH3)), 1.63 (s, 2H, CyH), 1.55 (s, 2H, CyH), 1.41 (s, 1H, CyH), 0.97−0.83 (m, 5H, CyH). 13C NMR (toluene-d8, 100 MHz): δ 164.66 (ArCOMe), 164.35 (ArCONa), 161.85 (CHN), 148.47 (ArCN), 134.45, 133.65, 130.36, 127.83, 126.19, 118.43, 113.78, 107.39, 101.21 (ArC), 62.97 (CyCH), 54.70 (ArOMe and CH2), 36.91 (NCH3), 28.88, 26.82, 26.44 (CyCH2). Mp: 120.2 °C. Anal. Calcd for C22H27N2NaO2 (374.45): C, 70.57; H, 7.27; N, 7.48. Found: C, 70.25; H, 6.90; N, 7.28.

for 1 day. Volatile materials were removed under vacuum to give a yellow oil. Yield: 4.59 g (95%). 1H NMR (toluene-d8, 400 MHz): δ 13.43 (s, 1H, OH), 8.05 (s, 1H, CHN), 7.50 (d, 1H, J = 6.5 Hz, ArH), 7.18−6.90 (m, 5H, ArH), 6.69−6.66 (m, 2H, ArH), 3.67 (s, 2H, CH2), 2.40 (t, 1H, J = 12 Hz, CyH), 2.13 (s, 3H, N(CH3)), 1.79 (d, 2H, J = 10.9 Hz, CyH), 1.66 (d, 2H,J = 11.6 Hz, CyH), 1.50 (d, 1H, J = 12.5 Hz, CyH), 1.28−0.85 (m, 5H, CyH). 13C NMR (toluene-d8, 100 MHz): δ 162.71 (ArCOH), 162.06 (CHN), 148.33 (ArCN), 134.60, 133.11, 132.42, 130.40, 127.84, 126.62, 119.87, 118.75, 118.40, 117.67 (ArC), 62.94 (CyCH), 54.70 (CH2), 36.84 (NCH3), 28.84, 26.77, 26.39 (CyCH2). Anal. Calcd for C21H26N2O (322.44): C, 78.22; H, 8.13; N, 8.69. Found: C, 78.27; H, 7.50; N, 9.01. ESI-MS. Calcd for C21H26N2O: m/z 322.2. Found: m/z 323.3 ([M + H]+). Synthesis of L5‑NEt2H. A mixture of 4-(diethylamino)-2-hydroxybenzaldehyde (2.899 g, 15 mmol) and N-(2-aminobenzyl)-Ncyclohexyl-N-methylamine(3.275 g, 15 mmol) was stirred and refluxed in toluene (50 mL) with a Dean−Stark condenser for 1 week. Volatile materials were removed under vacuum to give an orange oil. Yield: 5.99 g (92%). 1H NMR (toluene-d8, 400 MHz): δ 13.92 (s, 1H, OH), 8.16 (s, 1H, CHN), 7.71−7.50 (m, 1H, ArH), 7.15−6.92 (m, 3H, ArH), 6.86−6.76 (m, 1H, ArH), 6.33 (d, 1H, J = 2.4 Hz, ArH), 6.05 (d, 1H, J = 8 Hz, ArH), 3.81 (s, 2H, CH2), 2.86 (q, 4H, J = 7.1 Hz, ArN(CH2CH3)2), 2.58−2.37 (m, 1H, CyH), 2.20 (s, 3H, N(CH3)), 1.87 (d, 2H, J = 11.8 Hz, CyH), 1.68 (d, 2H, J = 12.4 Hz, CyH), 1.51 (d, 1H, J = 12.6 Hz, CyH), 1.43−0.91 (m, 5H, CyH), 0.82 (t, 6H, J = 7.1 Hz, ArN(CH2CH3)2). 13C NMR (toluene-d8, 100 MHz): δ 164.57 (ArCOH), 161.36 (CHN), 151.74 (ArCNEt2), 149.17 (ArCN), 133.97, 130.13, 129.26, 128.44, 125.55, 118.31, 110.25, 103.53, 98.50 (ArC), 62.99 (CyCH), 54.44 (CH2), 44.39 (ArN(CH2CH3)2), 37.09 (NCH3), 28.93, 26.84, 26.45 (CyCH2), 12.61 (ArN(CH2CH3)2). Anal. Calcd for C25H35N3O (393.56): C, 76.29; H, 8.96; N, 10.68. Found: C, 76.11; H, 9.05; N, 10.35. ESI-MS. Calcd for C25H28N2O: m/z 393.3. Found: m/z 394.2 ([M + H]+). Synthesis of L5‑OMeH. A method similar to that for LHH except with 2-hydroxy-4-methoxybenzaldehyde was used. Volatile materials were removed under vacuum to give a yellow oil. Yield: 5.02 g (95%). 1 H NMR (toluene-d8, 400 MHz): δ 13.97 (s, 1H, OH), 8.04 (s, 1H, CHN), 7.53 (m, 1H, ArH), 7.13 (s, 1H, ArH), 7.11 (s, 1H, ArH), 6.87 (d, 1H, J = 8.8 Hz, ArH), 6.71 (m, 1H, ArH), 6.55 (d, 1H, J = 2.4 Hz, ArH), 6.40, 6.38 (d, 1H, J = 2.4 Hz, ArH), 3.72 (s, 2H, CH2), 3.21 (s, 3H, OCH3), 2.48−2.40 (m, 1H, CyH), 2.17 (s, 3H, NCH3), 1.84 (d, 2H, J = 11.6 Hz, CyH), 1.69 (d, 2H, J = 11.6 Hz, CyH), 1.52 (d, 1H, J = 12.8 Hz, CyH), 1.26−0.98 (m, 5H, CyH). 13C NMR (toluened8, 100 MHz): δ 164.66 (ArCOMe), 164.35 (ArCOH), 161.86 (CH N), 148.47 (ArCN), 134.45, 133.65, 130.36, 127.83, 126.19, 118.43, 113.78, 107.39, 101.21 (ArC), 62.97 (CyCH), 54.71 (ArOMe and CH2), 36.91 (NCH3), 28.88, 26.82, 26.44 (CyCH2). Anal. Calcd for C22H28N2O2(352.47): C, 74.97; H, 8.01; N, 7.95. Found: C, 74.90; H, 7.49; N, 8.14. ESI-MS. Calcd for C22H28N2O2: m/z 352.2. Found: m/z 353.3 ([M + H]+). Synthesis of L4‑OMeH. A method similar to that for LHH except with 2-hydroxy-5-methoxybenzaldehyde was used. Yield: 5.11 g (96%). 1 H NMR (toluene-d8, 400 MHz): δ 12.95 (s, 1H, OH), 8.02 (s, 1H, CHN), 7.65−7.44 (m, 1H, ArH), 7.10 (m, 2H, ArH), 7.03−6.91 (m, 1H, ArH), 6.71 (m, 2H, ArH), 6.57 (m, 1H, ArH), 3.69 (s, 2H, CH2), 3.37 (s, 3H, OCH3), 2.64−2.24 (m, 1H, CyH), 2.14 (s, 3H, NCH3), 1.80 (d, 2H, J = 10.7 Hz, CyH), 1.67 (d, 2H, J = 11.5 Hz, CyH), 1.51 (d, 1H, J = 12.3 Hz, CyH), 1.29−0.85 (m, 5H, CyH). 13C NMR (toluene-d8, 100 MHz): δ 162.58 (ArCOMe), 156.21 (ArCOH), 152.49 (CHN), 148.41 (ArCN), 134.62, 130.40, 127.82, 126.63, 125.07, 120.32, 119.46, 118.38, 115.64 (ArC), 62.98 (Cy-CH), 55.23 (ArOMe), 54.66 (CH2), 36.86 (NCH3), 28.84, 26.77, 26.40 (CyCH2). Anal. Calcd for C22H28N2O2: C, 74.97; H, 8.01; N, 7.95. Found: C, 74.69; H, 8.38; N, 8.15. ESI-MS. Calcd for C22H28N2O2: m/z 352.2. Found: m/z 353.3 ([M + H]+). Synthesis of L4‑ClH. A method similar to that for LHH except with 5-chloro-2-hydroxybenzaldehyde was used. Volatile materials were removed under vacuum to give a yellow oil. Yield: 5.09 g (95%). 1H NMR (toluene-d8, 400 MHz): δ 13.37 (s, 1H, OH), 7.74 (s, 1H, CHN), 7.47 (m, 1H, ArH), 7.08 (s, 1H, ArH), 7.10 (s, 1H, ArH), H


Inorganic Chemistry

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Synthesis of [L4‑OMeNa]2. Used a method similar to that for [LHNa]2 except L4‑OMeH was used. Yield: 2.65 g (75%). 1H NMR (toluene-d8, 400 MHz): δ 7.92 (s, 1H, CHN), 7.22−6.84 (m, 3H, ArH), 6.67 (d, J = 6.8 Hz, 1H, ArH), 6.55 (s, 2H, ArH), 6.11 (s, 1H, ArH), 3.48 (s, 3H, ArOMe), 3.33 (s, 2H, CH2), 2.12 (s, 1H, CyH), 2.05 (s, 3H, N(CH3)), 1.58 (s, 4H, CyH), 1.44 (d, J = 9.6 Hz, 1H, CyH), 0.95−0.85 (m, 5H, CyH). 13C NMR (toluene-d8, 100 MHz): δ 167.77 (ArCOMe), 166.54 (ArCONa), 155.25 (CHN), 147.54 (ArCN), 137.14, 131.04, 129.82, 124.37, 123.94, 122.40, 121.61, 121.15, 118.92 (ArC), 61.02 (Cy-CH), 55.95 (ArOMe), 54.15 (CH2), 38.59 (NCH3), 27.98, 26.68, 26.30 (CyCH2). Mp: 153.6 °C. Anal. Calcd for C22H27N2NaO2: C, 70.57; H, 7.27; N, 7.48. Found: C, 71.15; H, 6.96; N, 7.49. Synthesis of [L4‑ClNa]2. A method similar to that for [LHNa]2 except with L4‑ClH was used. Yield: 3.07 g (81%). 1H NMR (toluened8, 400 MHz): δ 7.62 (s, 1H, CHN), 7.18−6.76 (m, 4H, ArH), 6.75−6.59 (m, 1H, ArH), 6.43 (d, J = 7.2 Hz, 1H, ArH), 6.04−5.65 (m, 1H, ArH), 3.21 (s, 2H, CH2), 1.97 (s, 3H, N(CH3)), 1.55−1.44 (m, 6H, CyH), 0.87 (s, 5H, CyH). 13C NMR (toluene-d8, 100 MHz): δ 161.35 (ArCOH), 160.36 (CHN), 147.77 (ArCN), 134.71, 132.85, 131.54, 130.58, 127.92, 127.02, 123.42, 120.54, 119.04, 118.30 (ArC), 62.90 (CyCH), 54.89 (CH2), 36.75 (NCH3), 28.79, 26.76, 26.39 (CyCH2). Mp: 168.3 °C. Anal. Calcd for C21H24ClN2NaO (378.87): C, 66.57; H, 6.38; N, 7.39. Found: C, 66.80; H, 6.72; N, 7.06. Synthesis of [L4‑BrNa]2. A method similar to that for [LHNa]2 except with L4‑BrH was used. Yield: 3.09 g (73%). 1H NMR (toluened8, 400 MHz): δ 7.57 (s, 1H, CHN), 7.00 (m, 5H, ArH), 6.55−6.23 (m, 1H, ArH), 6.06−5.59 (m, 1H, ArH), 3.19 (s, 2H, CH2), 1.95 (s, 3H, N(CH3)), 1.5−1.47 (m, 6H, CyH), 0.94−0.85 (m, 5H, CyH). 13C NMR (toluene-d8, 100 MHz): δ 161.26 (ArCOH), 160.79 (CHN), 147.74 (ArCN), 135.65, 134.71, 134.55, 130.59, 127.88, 127.03, 121.18, 119.44, 118.30, 110.32 (ArC), 62.91 (CyCH), 54.90 (CH2), 36.76 (NCH3), 28.81, 26.77, 26.40 (CyCH2). Mp: 163.1 °C. Anal. Calcd for C21H24BrN2NaO (423.32): C, 59.58; H, 5.71; N, 6.62. Found: C, 59.92; H, 5.59; N, 6.74. General Procedures for the Polymerization of L-LA. A typical polymerization procedure was exemplified by the synthesis of entry 4 (Table 2) using complex [L4‑OMeNa]2 as a catalyst. The polymerization conversion was analyzed by1H NMR spectroscopic studies. A mixture of 0.005 mmol of BnOH/1 mL of toluene (1.0 mL) was added to a mixture of complex [L4‑OMeNa]2 (0.025 mmol), and 24 mL of toluene was added to L-LA (0.36 g, 2.5 mmol), followed by cooling to 0 °C. After the solution was mixed and then stirred for 30 s at 0 °C, the reaction was then quenched by adding a drop of isopropanyl alcohol; the polymer was precipitated by pouring the solution into n-hexane (30.0 mL) to give white solids. The white solid was dissolved in CH2Cl2 (5.0 mL), and then n-hexane (70.0 mL) was added to give a white crystalline solid. Yield: 0.26 g (74%).

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ACKNOWLEDGMENTS This study is supported by Kaohsiung Medical University “Aim for the top 500 universities grant” under Grant KMUDT103007, the NSYSU−KMU Joint Research Project (Grant NSYSUKMU 104-P006), and the Ministry of Science and Technology (Grants MOST 104-2113-M-037-010 and 1042113-M-005-015-MY3). We thank the Center for Research Resources and Development at Kaohsiung Medical University for instrumentation and equipment support.

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REFERENCES

(1) (a) Sutar, A. K.; Maharana, T.; Dutta, S.; Chen, C.-T.; Lin, C.-C. Chem. Soc. Rev. 2010, 39, 1724−1746. (b) Dean, R. K.; Reckling, A. M.; Chen, H.; Dawe, L. N.; Schneider, C. M.; Kozak, C. M. Dalton Trans. 2013, 42, 3504−3520. (c) Roşca, S.-C.; Roşca, D.-A.; Dorcet, V.; Kozak, C. M.; Kerton, F. M.; Carpentier, J.-F.; Sarazin, Y. Dalton Trans. 2013, 42, 9361−9375. (2) (a) Radano, C. P.; Baker, G. L.; Smith, M. R. J. Am. Chem. Soc. 2000, 122, 1552−1553. (b) Ovitt, T. M.; Coates, G. W. J. Am. Chem. Soc. 2002, 124, 1316−1326. (c) Majerska, K.; Duda, A. J. Am. Chem. Soc. 2004, 126, 1026−1027. (d) Li, G.; Lamberti, M.; Pappalardo, D.; Pellecchia, C. Macromolecules 2012, 45, 8614−8620. (e) Reisberg, S. H.; Hurley, H. J.; Mathers, R. T.; Tanski, J. M.; Getzler, Y. D. Y. L. Macromolecules 2013, 46, 3273−3279. (f) Pilone, A.; Press, K.; Goldberg, I.; Kol, M.; Mazzeo, M.; Lamberti, M. J. Am. Chem. Soc. 2014, 136, 2940−2943. (3) (a) Chisholm, M. H.; Eilerts, N. W.; Huffman, J. C.; Iyer, S. S.; Pacold, M.; Phomphrai, K. J. Am. Chem. Soc. 2000, 122, 11845−11854. (b) Huang, Y.; Wang, W.; Lin, C.-C.; Blake, M. P.; Clark, L.; Schwarz, A. D.; Mountford, P. Dalton Trans. 2013, 42, 9313−9324. (c) Garcés, A.; Sánchez-Barba, L. F.; Fernández-Baeza, J.; Otero, A.; Honrado, M.; Lara-Sánchez, A.; Rodríguez, A. M. Inorg. Chem. 2013, 52, 12691− 12701. (d) Yi, W.; Ma, H. Inorg. Chem. 2013, 52, 11821−11835. (e) Gallegos, C.; Tabernero, V.; Garcıá -Valle, F. M.; Mosquera, M. E. G.; Cuenca, T.; Cano, J. Organometallics 2013, 32, 6624−6627. (f) Gao, Y.; Dai, Z.; Zhang, J.; Ma, X.; Tang, N.; Wu, J. Inorg. Chem. 2014, 53, 716−726. (g) Xie, H.; Mou, Z.; Liu, B.; Li, P.; Rong, W.; Li, S.; Cui, D. Organometallics 2014, 33, 722−730. (4) (a) Darensbourg, D. J.; Choi, W.; Karroonnirun, O.; Bhuvanesh, N. Macromolecules 2008, 41, 3493−3502. (b) Clark, L.; Deacon, G. B.; Forsyth, C. M.; Junk, P. C.; Mountford, P.; Townley, J. P.; Wang, J. Dalton Trans. 2013, 42, 9294−9312. (5) (a) Williams, C. K.; Breyfogle, L. E.; Choi, S. K.; Nam, W.; Young, V. G.; Hillmyer, M. A.; Tolman, W. B. J. Am. Chem. Soc. 2003, 125, 11350−11359. (b) Piedra-Arroni, E.; Ladavière, C.; Amgoune, A.; Bourissou, D. J. Am. Chem. Soc. 2013, 135, 13306−13309. (c) Honrado, M.; Otero, A.; Fernández-Baeza, J.; Sánchez-Barba, L. F.; Garcés, A.; Lara-Sańchez, A.; Rodrıǵuez, A. M. Organometallics 2014, 33, 1859−1866. (d) Wang, H.; Yang, Y.; Ma, H. Macromolecules 2014, 47, 7750−7764. (6) (a) Dove, A. P.; Gibson, V. C.; Marshall, E. L.; Rzepa, H. S.; White, A. J. P.; Williams, D. J. J. Am. Chem. Soc. 2006, 128, 9834− 9843. (b) Wang, L.; Poirier, V.; Ghiotto, F.; Bochmann, M.; Cannon, R. D.; Carpentier, J.-F.; Sarazin, Y. Macromolecules 2014, 47, 2574− 2584. (7) Whitehorne, T. J. J.; Schaper, F. Inorg. Chem. 2013, 52, 13612− 13622. (8) Biernesser, A. B.; Li, B.; Byers, J. A. J. Am. Chem. Soc. 2013, 135, 16553−16560. (9) (a) Pietrangelo, A.; Knight, S. C.; Gupta, A. K.; Yao, L. J.; Hillmyer, M. A.; Tolman, W. B. J. Am. Chem. Soc. 2010, 132, 11649− 11657. (b) Bakewell, C.; White, A. J. P.; Long, N. J.; Williams, C. K. Inorg. Chem. 2013, 52, 12561−12567. (c) Aluthge, D. C.; Xu, C.; Othman, N.; Noroozi, N.; Hatzikiriakos, S. G.; Mehrkhodavandi, P. Macromolecules 2013, 46, 3965−3974. (10) Wang, L.; Fadlallah, S.; Bellini, C.; Orione, C.; Dorcet, V.; Carpentier, J.-F.; Sarazin, Y. Organometallics 2015, 34, 1321−1327.

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Inorganic Chemistry

Chem. Soc. 2003, 125, 11291−11298. (c) Wu, J.; Pan, X.; Tang, N.; Lin, C.-C. Eur. Polym. J. 2007, 43, 5040−5046. (d) Alaaeddine, A.; Thomas, C. M.; Roisnel, T.; Carpentier, J.-F. Organometallics 2009, 28, 1469−1475. (e) Chen, H.-L.; Dutta, S.; Huang, P.-Y.; Lin, C.-C. Organometallics 2012, 31, 2016−2025. (18) (a) Li, B.-Y.; Yao, Y.-M.; Wang, Y.-R.; Zhang, Y.; Shen, Q. Polyhedron 2008, 27, 709−716. (b) Yao, L.; Wang, L.; Pan, X.; Tang, N.; Wu, J. Inorg. Chim. Acta 2011, 373, 219−225. (c) Lu, W.-Y.; Hsiao, M.-W.; Hsu, S. C. N.; Peng, W.-T.; Chang, Y.-J.; Tsou, Y.-C.; Wu, T.Y.; Lai, Y.-C.; Chen, Y.; Chen, H.-Y. Dalton Trans. 2012, 41, 3659− 3667. (d) Ghosh, S.; Chakraborty, D.; Varghese, B. Eur. Polym. J. 2015, 62, 51−65. (e) García-Valle, F. M.; Estivill, R.; Gallegos, C.; Cuenca, T.; Mosquera, M. E. G.; Tabernero, V.; Cano, J. Organometallics 2015, 34, 477−487. (19) (a) Deacon, G. B.; Feng, T.; Hockless, D. C. R.; Junk, P. C.; Skelton, B. W.; Smith, M. K.; White, A. H. Inorg. Chim. Acta 2007, 360, 1364−1369. (b) Przybylski, P.; Pyta, K.; Ratajczak-Sitarz, M.; Katrusiak, A.; Brzezinski, B. Struct. Chem. 2008, 19, 983−995. (c) Li, B.-Y.; Yao, Y.-M.; Wang, Y.-R.; Zhang, Y.; Shen, Q. Polyhedron 2008, 27, 709−716. (20) Hammett, L. P. J. Am. Chem. Soc. 1937, 59, 96−103. (21) (a) Wider, G.; Dotsch, V.; Wuthrich, K. J. Magn. Reson., Ser. A 1994, 108, 255−258. (b) Valentini, M.; Pregosin, P. S.; Rüegger, H. Organometallics 2000, 19, 2551−2555. (c) Stamps, J. P.; Ottink, B.; Visser, J. M.; van Duynhoven, J. P. M.; Hulst, R. J. Magn. Reson. 2001, 151, 28−31. (d) Barrett, A. G. M.; Casely, I. J.; Crimmin, R.; Hill, M. S.; Lachs, J. R.; Mahon, M. F.; Procopiou, P. A. Inorg. Chem. 2009, 48, 4445−4453. (22) Witzke, D. R.; Narayan, R.; Kolstad, J. J. Macromolecules 1997, 30, 7075−7085. (23) Yu, T.-L.; Wu, C.-C.; Chen, C.-C.; Huang, B.-H.; Wu, J.; Lin, C.C. Polymer 2005, 46, 5909−5917. (24) CrysAlisPro, version 1.171; Agilent Technologies: Santa Clara, CA, 2009. (25) CrysAlisPro SCALE3 ABSPACK, a scaling algorithm for empirical absorption correction using spherical harmonics; Oxford Diffraction, Agilent Technologies: Santa Clara, CA, 2005. (26) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Crystallogr. 2008, 64, 112−122.

(11) (a) Kratsch, J.; Kuzdrowska, M.; Schmid, M.; Kazeminejad, N.; Kaub, C.; Oñ a-Burgos, P.; Guillaume, S. M.; Roesky, P. W. Organometallics 2013, 32, 1230−1238. (b) Bakewell, C.; White, A. J. P.; Long, N. J.; Williams, C. K. Inorg. Chem. 2015, 54, 2204−2212. (12) (a) Liang, L.-C.; Lin, S.-T.; Chien, C.-C. Inorg. Chem. 2013, 52, 1780−1786. (b) Su, C.-K.; Chuang, H.-J.; Li, C.-Y.; Yu, C.-Y.; Ko, B.T.; Chen, J.-D.; Chen, M.-J. Organometallics 2014, 33, 7091−7100. (c) Turner, Z. R.; Buffet, J.-C.; O’Hare, D.. (d) Stopper, A.; Press, K.; Okuda, J.; Goldberg, I.; Kol, M. Inorg. Chem. 2014, 53, 9140−9150. (13) (a) Nie, K.; Gu, W.; Yao, Y.; Zhang, Y.; Shen, Q. Organometallics 2013, 32, 2608−2617; Organometallics 2010, 39, 6832. (b) Bakewell, C.; White, A. J. P.; Long, N. J.; Williams, C. K. Angew. Chem., Int. Ed. 2014, 53, 9226−9230. (c) Yang, S.; Nie, K.; Zhang, Y.; Xue, M.; Yao, Y.; Shen, Q. Inorg. Chem. 2014, 53, 105−115. (d) Mou, Z.; Liu, B.; Liu, X.; Xie, H.; Rong, W.; Li, L.; Li, S.; Cui, D. Macromolecules 2014, 47, 2233−2241. (14) (a) Chen, H.-Y.; Zhang, J.; Lin, C.-C.; Reibenspies, J. H.; Miller, S. A. Green Chem. 2007, 9, 1038−1040. (b) Phomphrai, K.; Pracha, S.; Phonjanthuek, P.; Pohmakotr, M. Dalton Trans. 2008, 23, 3048−3050. (c) Peng, Y.-L.; Huang, Y.; Chuang, H.-J.; Kuo, C.-Y.; Lin, C.-C. Polymer 2010, 51, 4329−4335. (d) Huang, Y.; Tsai, Y.-H.; Hung, W.C.; Lin, C.-S.; Wang, W.; Huang, J.-H.; Dutta, S.; Lin, C.-C. Inorg. Chem. 2010, 49, 9416−9425. (e) Calvo, B.; Davidson, M. G.; GarcíaVivo, D. Inorg. Chem. 2011, 50, 3589−3595. (f) Chen, L.; Jia, L.; Cheng, F.; Wang, L.; Lin, C.-C.; Wu, J.; Tang, N. Inorg. Chem. Commun. 2011, 14, 26−30. (g) Zhang, J.; Wang, C.; Lu, M.; Yao, Y.M.; Zhang, Y.; Shen, Q. Polyhedron 2011, 30, 1876−1883. (h) Wang, L.; Pan, X.; Yao, L.; Tang, N.; Wu, J. Eur. J. Inorg. Chem. 2011, 5, 632− 636. (i) Zhang, J.; Jian, C.; Gao, Y.; Wang, L.; Tang, N.; Wu, J. Inorg. Chem. 2012, 51, 13380−13389. (j) Lu, W.-Y.; Hsiao, M.-W.; Hsu, S. C. N.; Peng, W.-T.; Chang, Y.-J.; Tsou, Y.-C.; Wu, T.-Y.; Lai, Y.-C.; Chen, Y.; Chen, H.-Y. Dalton Trans. 2012, 41, 3659−3667. (k) Zhang, J.; Xiong, J.; Sun, Y.; Tang, N.; Wu, J. Macromolecules 2014, 47, 7789− 7796. (l) Xiong, J.; Zhang, J.; Sun, Y.; Dai, Z.; Pan, X.; Wu, J. Inorg. Chem. 2015, 54, 1737−1743. (15) (a) Nomura, N.; Aoyama, T.; Ishii, R.; Kondo, T. Macromolecules 2005, 38, 5363−5366. (b) Chai, Z. Y.; Zhang, C.; Wang, Z. X. Organometallics 2008, 27, 1626−1633. (c) Liu, J.; Iwasa, N.; Nomura, K. Dalton Trans. 2008, 3978−3988. (d) Arbaoui, A.; Redshaw, C.; Hughes, D. L. Chem. Commun. 2008, 4717−4719. (e) Iwasa, N.; Fujiki, M.; Nomura, K. J. Mol. Catal. A: Chem. 2008, 292, 67−75. (f) Range, S.; Piesik, D. F.-J.; Harder, S. Eur. J. Inorg. Chem. 2008, 2008, 3442−3451. (g) Pappalardo, D.; Annunziata, L.; Pellecchia, C. Macromolecules 2009, 42, 6056−6062. (h) Iwasa, N.; Katao, S.; Liu, J.; Fujiki, M.; Furukawa, Y.; Nomura, K. Organometallics 2009, 28, 2179−2187. (i) Nimitsiriwat, N.; Gibson, V. C.; Marshall, E. L.; Elsegood, M. R. J. Dalton Trans. 2009, 3710−3715. (j) Jones, M. D.; Davidson, M. G.; Keir, C. G.; Hughes, L. M.; Mahon, M. F.; Apperley, D. C. Eur. J. Inorg. Chem. 2009, 2009, 635−642. (k) Di Iulio, C.; Jones, M. D.; Mahon, M. F.; Apperley, D. C. Inorg. Chem. 2010, 49, 10232−10234. (16) (a) Nimitsiriwat, N.; Marshall, E. L.; Gibson, V. C.; Elsegood, M. R. J.; Dale, S. H. J. Am. Chem. Soc. 2004, 126, 13598−13599. (b) Lewiński, J.; Horeglad, P.; Dranka, M.; Justyniak, I. Inorg. Chem. 2004, 43, 5789−5791. (c) Chen, H. Y.; Tang, H. Y.; Lin, C.-C. Macromolecules 2006, 39, 3745−3752. (d) Nimitsiriwat, N.; Gibson, V. C.; Marshall, E. L.; Elsegood, M. R. J. Inorg. Chem. 2008, 47, 5417− 5424. (e) Hung, W. C.; Huang, Y.; Lin, C. C. J. Polym. Sci., Part A: Polym. Chem. 2008, 46, 6466−6476. (f) Hung, W.-C.; Lin, C.-C. Inorg. Chem. 2009, 48, 728−734. (g) Darensbourg, D. J.; Karroonnirun, O. Inorg. Chem. 2010, 49, 2360−2371. (h) Darensbourg, D. J.; Karroonnirun, O. Macromolecules 2010, 43, 8880−8886. (i) Darensbourg, D. J.; Karroonnirun, O. Organometallics 2010, 29, 5627− 5634. (j) Darensbourg, D. J.; Karroonnirun, O.; Wilson, S. J. Inorg. Chem. 2011, 50, 6775−6787. (k) Matsubara, K.; Terata, C.; Sekine, H.; Yamatani, K.; Harada, T.; Eda, K.; Dan, M.; Koga, Y.; Yasuniwa, M. J. Polym. Sci., Part A: Polym. Chem. 2012, 50, 957−966. (17) (a) Nomura, N.; Ishii, R.; Akakura, M.; Aoi, K. J. Am. Chem. Soc. 2002, 124, 5938−5939. (b) Zhong, Z.; Dijkstra, P. J.; Feijen, J. J. Am. J


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