Stereoretentive Ligand Exchange Reactions of N-Fused Porphyrin

Sep 27, 2017 - Department of Chemistry and Biochemistry, Graduate School of Engineering, and the Center for Molecular Systems, Kyushu University, 744 ...
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Stereoretentive Ligand Exchange Reactions of N‑Fused Porphyrin Ruthenium(II) Complexes Hideaki Matsuo,† Motoki Toganoh,† Masatoshi Ishida,† Shigeki Mori,§ and Hiroyuki Furuta*,† †

Department of Chemistry and Biochemistry, Graduate School of Engineering, and the Center for Molecular Systems, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan § Advanced Research Support Center, Ehime University, Matsuyama 790-8577, Japan S Supporting Information *

ABSTRACT: The ligand exchange reactions of the ruthenium(II) complex of N-fused tetraphenylporphyrin, Ru(NFp)(CO)2Cl (2), with various anions were investigated. The chloride ligand of the isomers 2a−c was stereoretentively exchanged with bromide (Br−), iodide (I−), and acetate (AcO−) anions in toluene at 100 °C, structures of which were confirmed by 1H NMR as well as single crystal X-ray diffraction analysis. The silver (AgOAc, AgOTf) and boron (NaBPh4) reagents also afforded the corresponding stereoretentive products. On the other hand, the reaction with NaBH4 afforded the hydride complex Ru(NFp)(CO)2H (7) with low stereospecificity, showing a higher reactivity of 2c than other isomers. The ligand dissociation mechanism was proposed with the help of theoretical calculations on the plausible five-coordinated intermediates.

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group elements28−30 were synthesized successfully. The relevant ruthenium(II) complex of N-fused tetraphenylporphyrin (Ru(NFp)(CO)2Cl, 2)18 was also prepared by heating NFpH with [RuCl2(CO)3]2 in toluene (Scheme 1). The three isomers (diastereomers) (2a−c) were separated by silica gel column chromatography, and the structures were unambiguously characterized by X-ray crystallographic analysis. Due to the tight binding of NFp ligand with three nitrogen atoms, the complexes 2a−c were rather stable, and the isomerization did not proceed even at 100 °C in toluene. In this paper, the ligand exchange reactions of Ru(NFp)(CO)2Cl (2) were studied in detail. The chloride ligand (Cl−) was replaced by various nucleophilic anions (Br−, I−, Ph−, AcO−, TfO−), affording the corresponding NFp-ruthenium complexes, stereoretentively. In addition, Cl−H exchange reaction was also investigated by using NaBH4. Because of the tight binding of Ru metal to the asymmetric NFp ligand, the ruthenium complex 2 would provide a good reference for the ligand exchange mechanism of half-sandwich complexes like [CpRu(CO)2Cl]. A facile separation of each isomer by column chromatography would also make ruthenium NFp complex handling easier for the study.

INTRODUCTION Half-sandwich ruthenium complexes have gathered a lot of attention from the interest of their potential applications in various fields such as catalysts,1,2 molecular devices,3,4 medicinal chemistry,5,6 etc. A variety of half-sandwich derivatives including chiral ones have been synthesized by the ligand exchange reactions on the metal of half-sandwich complexes.2,7 For example, Noyori et al. reported the formation of chiral ruthenium hydride complex form its chloride precursor in the asymmetric hydrogenation reaction of ketons.8 For controlling the stereochemistry of chiral complexes with suppressing the isomerization or racemization at the metal center, understanding of the ligand exchange reactions is indispensable.9,10 The mechanistic study on the chiral half-sandwich complex with a cyclopentadienyl ligand [CpRuL1L2L3] revealed that the energy barrier of racemization depends on the associated ligands.11,12 On the other hand, in the porphyrinoid chemistry, the ruthenium ion is usually coordinated by the tetrapyrrole macrocyclic ligand to form a square planar or pyramidal structure because of the ionic size matching to the macrocyclic core.13 The sandwich or half-sandwich type of ruthenium (or iron) complexes are so far limited to the core-modified porphyrins such as porphycene,14 dithiaethyneporphyrin,15 and triphyrin.16 Recently, we have synthesized a new type of sandwich and half-sandwich ruthenium complexes17,18 using a unique porphyrinoid ligand, N-fused porphyrin (NFpH, 1),19,20 and studied the ligand rearrangement on the NFp platform.18 NFp serves as a planar, tridentate, monoanionic nitrogen ligand, which is isoelectronic as a cyclopentadienyl anion (Cp−) or trispyrazolylborate (Tp−). Accordingly, a wide variety of NFp complexes with transition metals17,18,21−27 as well as main © XXXX American Chemical Society

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RESULTS AND DISCUSSION Ligand Exchange Reactions of 2 with Various Anions. The complexes 2a−c were synthesized according to the previous report.18 Among three isomers, 2c was obtained as a major product (2a: 6%, 2b: 12%, 2c: 63%), and thus 2c was mainly subjected to the ligand exchange reactions (Scheme 2). Received: August 2, 2017

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DOI: 10.1021/acs.inorgchem.7b01972 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry Scheme 1. Synthesis of Isomers of Ru(NFp)(CO)2Cl (2a−c)18

Scheme 2. Stereoretentive Ligand Exchange Reactions of 2c

Figure 1. X-ray structures of 3c (a) and 3b (b). The thermal ellipsoids are described at the 50% probability level.

stereochemistry of the product would be governed kinetically rather than thermodynamically. When tetrabutylammonium iodide (n-Bu4NI) was used in place of n-Bu4NBr, the corresponding iodide complex Ru(NFp)(CO)2I (4c) was obtained in the same manner. The laser desorption mass analysis gave the peaks of m/z = 840 and 713, corresponding to [4c−2(CO)]+ and [4c−2(CO)−I]+, respectively. The 1H NMR spectrum of 4c showed almost identical signals as 3c, as expected from the stereoretentive ligand exchange reaction. Next, phenyl anion (i.e., benzenide) was subjected to the exchange reaction (Scheme 2, path b). By treating 2 (2a, 2b, or 2c, respectively) with sodium tetraphenylborate (NaBPh4) at 100 °C, Ru(NFp)(CO)2Ph (5) was obtained stereoretentively (5a: 83%, 5b: 65%, 5c: 87%). In this ligand exchange reaction, the sodium tetraphenylborate worked as a benzenide source similar to the palladium catalyzed cross-coupling reactions.31,32 IR spectra showed a set of CO stretching bands at 2023 and 1956 cm−1 (5a), 2021 and 1955 cm−1 (5b), 2010 and 1942 cm−1 (5c), respectively. These values are lower by 23−30 cm−1 than the corresponding chloride complex 2 (2046−1972 cm−1), which suggests a strong coordination of the benzenide ligand to the Ru center. In the 1H NMR spectra of 5b (and 5c), the three signals of the introduced phenyl group were observed in an upper-field region at δ = 5.22 (6.15) (2H, o-phenyl), 6.49 (6.77) (2H, m-phenyl), and 6.66 (6.83) ppm (1H, p-phenyl) due to the shielding effect of the NFp ligand. While the phenyl signals of 5b and 5c were observed as the sharp signals at room temperature, the corresponding signals of 5a were significantly broadened under the same conditions, suggesting slow rotation of the phenyl group of 5a. They became sharp at −50 °C possibly due to the stopped spinning on the NMR time scale, and the phenyl signals were observed in an unsymmetrical manner: δ = 2.86 and 6.28 (o-phenyl), 5.18 and 6.63 (mphenyl), and 6.10 ppm (p-ph). The slow rotation of the phenyl group of 5a compared to 5b and 5c would be explained

At first, the chloride-bromide exchange reaction was examined (Scheme 2, path a). When a mixture of 2c and tetrabutylammonium bromide (n-Bu4NBr) in 1,4-dioxane was heated at 100 °C, a new red color spot was gradually observed on a thin-layer chromatography (TLC) plate. Below 100 °C, such change was not observed. The product was isolated by silica gel column chromatography and identified as Ru(NFp)(CO)2Br (3c) by the several spectroscopic methods. For example, the 1H NMR spectrum of 3c shows a set of NFp signals being very similar to the starting material 2c. Laser ionization MS spectrum shows the peaks of m/z = 794 and 713, corresponding to [3c−2(CO)]+ and [3c−2(CO)−Br]+, respectively. The presence of two CO groups was confirmed by the observation of IR stretching bands at 2044 and 1985 cm−1 and the 13C NMR signals at δ = 192.1 and 192.5 ppm. Configuration of the ligands in 3c was determined by the preliminary single crystal X-ray diffraction analysis (Figure 1a). The newly introduced bromide ligand in 3c was in the same position as chloride in 2c. Thus, the chloride-bromide ligand exchange reaction of 2c underwent in a stereoretentive manner. Similarly, the reaction of 2b with n-Bu4NBr at 100 °C also gave the stereoretentive product 3b, whose structure was unambiguously identified by single crystal X-ray analysis (Figure 1b). In the density functional theory (DFT) calculations at the B3LYP/6-31SDD level, 3c is thermodynamically more stable than 3b by 0.29 kcal/mol (see Supporting Information). Nevertheless, 3c was not obtained in this reaction. Thus, B

DOI: 10.1021/acs.inorgchem.7b01972 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 2. Optimized structures of 5a−c.

reasonably by the steric circumstances. The optimized structures of 5a−c at the B3LYP/6-31SDD level are shown in Figure 2. While the phenyl group of 5b or 5c placed above the pyrrole ring, 5a placed above the rigid tripentacyclic moiety (yellow-colored), which would cause steric hindrance. Practically, the o-phenyl signals of 5a were more influenced by the shield effect of NFp ring current (av 4.48 ppm) of 5b (5.22 ppm) and 5c (6.15 ppm). Successively, the ligand exchange reaction of 2c with acetate anion (AcO−) was investigated using an excess amount of potassium acetate. In this reaction, a higher temperature was necessary to promote the ligand exchange, and at 150 °C, the complex 6c was formed along with 6a and 6b (76% yield in total, 6a:6b:6c = 1.05:0.72:1.00 determined from the NMR signals). At this temperature, isomerization of 2c to 2a and 2b occurred.18 As the result, the reaction afforded a mixture of isomers 6a−c. To avoid the isomerization at high temperature, halogen abstraction reaction of 2c with silver acetate (AgOAc) was attempted at 100 °C. Then, the reaction proceeded smoothly to afford a stereoretentive product Ru(NFp)(CO)2(OAc) (6c) in a high yield (96%). The complex 6c was alternatively synthesized from 2c in a stepwise manner, that is, treatments first with silver triflate (AgOTf) and then potassium acetate (Scheme 3). The first step proceeded at

Figure 3. X-ray structures of (a) 6a and (b) 6c. The thermal ellipsoids are described at the 50% probability level.

Hydride Complex Formation. Metal-hydride complexes, drawn as MHnLm, are important because of their significant reactivity as the catalyst for hydride insertion, metathesis, reductions, etc.8,33,34 Thus, hydride exchange reaction of RuNFP complex was attempted using various hydride sources. When a THF solution of 2 (isomeric mixture) was heated at 60 °C with sodium borohydride (NaBH4), formation of hydride complexes was suggested from the 1H NMR spectrum of the reaction mixture, where the highly upfield-shifted Ru−H signals were observed around δ = −13 ppm.35 After separation by silica gel column chromatography with CH2Cl2, Ru(NFp)(CO)2H (7c), and N-confused porphyrin (NCP)36−38 were obtained as major products in 21% and 47% yields, respectively (Scheme 4). Electrospray ionization mass spectrometry (ESI-MS) of 7c shows the peak of m/z = 771.13821, corresponding to the ruthenium hydride complex (calculated 12 C461H2914N416O2102Ru1 ([M + H+]) = 771.13340). The 1H NMR analysis of the recovered 2 (initial isomeric mixture ratio, 2a:2b:2c = 1.0:3.5:4.3) showed the ratio 2a:2b:2c = 1.0:1.7:0.13. The result indicates 2c was more reactive than the other isomers toward NaBH4. On the other hand, when the isolated 2c was used as the starting material to check the stereospecificity, formation of isomers 7a and 7b along with the major product 7c (7a: 7b: 7c = 0.5:0.06:1.0) was confirmed by the 1H NMR signals in the upfield hydride region. These results indicate that the Cl−H exchange reaction did not proceed stereospecifically. When sodium triacetoxyborohydride (NaBH(OAc)3), a weaker hydride than NaBH4, was used as a hydride source, the reaction did not occur even with an excess amount of reagent. In contrast, the reaction with NaH, a stronger hydride, resulted in the formation of NCP only. The different selectivity and reactivity of hydrides from that of other nucleophilic anions investigated above may suggest the intervening of different reaction pathways in the Cl−H exchange reactions, which remains to be solved.

Scheme 3. Two Synthetic Pathways of 6c

room temperature to afford an intermediate complex Ru(NFp)(CO)2(OTf). Formation of triflate compound was detected by the laser desorption mass analysis as m/z = 862 [2c-2(CO)]+. The second triflate-acetate ligand exchange step also proceeded below 100 °C due to the better leaving group nature of the triflate anion. The structures of 6a and 6c were unambiguously determined by single crystal X-ray analysis (Figure 3). C

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Inorganic Chemistry Scheme 4. Hydride Complex Formation from the Ligand Exchange Reaction of 2 with NaBH4

Figure 4. Ligand dissociation mechanism of 3c formation and its isomerization.

Figure 5. Energy profile for the rotation pathways of the dissociated intermediates 2′.

Meerwein−Ponndorf−Verley reduction reagent.40 Likewise, lithium ion may accept the lone pair of the chloride ligand and hydride-ruthenium interaction to make a six-membered ring intermediate (Figure S10). The least crowded 2c could easily form the intermediate. Regarding the stability of the hydride complex, 7c in the solid state was stable at room temperature, and no change was

7c was also obtained selectively by the reaction with lithium diisopropylamide (LDA) even when the mixture of three isomers of 2 was used. Isomeric pure 7c was selectively obtained from the mixture of the three isomers 2a−c. In the case of half-sandwich-type ruthenium-hydride complexes, RuCp(CO)2H was formed from RuCp(CO)2Cl with isopropanol and bases.39 LDA was known to serve as the D

DOI: 10.1021/acs.inorgchem.7b01972 Inorg. Chem. XXXX, XXX, XXX−XXX

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λmax (nm) of “c” type isomers are shifted to a shorterwavelength region: 2c (939.0) vs 2a (963.0) and 2b (950.0); 5c (925.0) vs 5a (953.0) and 5b (940.0); 6c (934) vs 6a (954) and 6b (949). Among 2−6, significantly large blue-shifts are observed with the electron-donating phenyl-substituted 5 and acetate compound 6. In contrast, bromide 3 and iodide 4 complexes show small differences from that of chloride compound 2. These data are consistent with the previous observation that the NFp ligand gets perturbations strongly from the trans-located ligands to the fused ring of NFp.18 The theoretical HOMO−LUMO energies of 2−6 and frontier orbitals of 5a−c as representatives are summarized in Table 2 and Figure 7, respectively. All of the LUMOs mainly

observed by 1H NMR even after one month. However, in the halogenated solvent like CH2Cl2, 7c was gradually changed to a ruthenium-halogen complex. Accordingly, the 1H NMR spectrum of 7c in CDCl3 gradually changed and almost converted into that of 2c after 91 h at room temperature. Reaction Mechanism. The stereoretentive ligand exchange reaction of Ru(NFp)(CO)2Cl with halide “X−” might be explained by the ligand dissociation mechanism (Figure 4). Namely, the chloride ligand is first released from 2 as Cl−, then an excess amount of nucleophilic halide attacks the coordinatively unsaturated Ru of the intermediate, [Ru(NFp)(CO)2]+ (2′). This intermediate could hold a pseudotetrahedral structure while maintaining the stereochemistry of the starting complex because of the high-energy barrier of the isomerization at 100 °C. A similar mechanism was suggested in the ligand exchange reactions of chiral half-sandwich ruthenium cyclopentadienyl complexes,7,10,41−44 although unsaturated intermediates were not detected in the spectral analyses.45 To gain the insight into the dissociated intermediate (2′), the activation energies of the ligand rotation of each step were calculated by the DFT methods (Figure 5). The energy profile shows the stereoretentive pseudotetrahedral-type intermediates (2a′−2c′) were preferred to the planar intermediates (2a′‡− 2c′‡). The estimated rotation energy barriers are within a range of 25−30 kcal/mol. These values are not sufficiently high to suppress the thermal isomerization at 100 °C.46 However, if the formation of 16e unsaturated intermediate 2′ was the ratedetermining step, then it is likely the cationic intermediate 2′ immediately reacts with a surrounding nucleophile present in an excess amount before ligand rotation. Of course, other mechanisms involving the seven-coordinated ruthenium complex intermediate or σ-bond metathesis cannot be ruled out at this moment.47−49 Absorption Properties of Complexes 2−6. The absorption spectra of a series of ruthenium-NFp complexes 2c−6c are shown in Figure 6, and the data are summarized in

Table 2. Calculated Energies (EHOMO, ELUMO, ΔEL−H) of 2−6 and Experimental HOMO−LUMO Gaps Estimated from λmax Values (in eV)

Br (3)

I (4)

Ph (5)

OAc (6)

963.0 950.0 939.0

− 952.5 938.0

− − 938.5

953.0 940.0 925.0

954.0 949.0 934.5

ΔEL−H

ΔEλmax

−2.95 −2.96 −2.97 −2.96 −2.97 −2.98 −3.01 −3.02 −3.03 −2.85 −2.85 −2.83 −2.93 −2.93 −2.93

2.00 2.06 2.09 1.99 2.05 2.09 1.98 2.03 2.07 2.04 2.07 2.11 2.04 2.08 2.09

1.29 1.31 1.32 − 1.30 1.32 − − 1.32 1.30 1.31 1.33 1.30 1.32 1.34

CONCLUSION In this study, the ligand exchange reactions of Ru(NFp)(CO)2Cl (2) with various anions were investigated. The chloride ligand of 2 was exchanged at 100 °C in the presence of bromide (Br−), iodide (I−), and acetate (AcO−) anions in toluene solution. By using the stereoisomers 2a−c, stereoretentive exchange reaction was demonstrated by the 1H NMR and single crystal X-ray structural analysis. The silver (AgOAc, AgOTf) and boron (NaBPh4) reagents also afford stereoretentive products. However, the reaction with NaBH4 afforded the hydride complex Ru(NFp)(CO)2H (7) with low stereospecificity, showing a higher reactivity of 2c than other isomers. The ligand dissociation mechanism was proposed with the help of theoretical calculations on the plausible five-coordinated intermediates. The facile synthesis of stereocontrolled NFpRu(II) complexes by the simple ligand exchange reactions

Table 1. Longest Wavelength of the Absorption Maximum (λmax, nm) of 2−6 in CH2Cl2 Cl (2)

ELUMO

−4.95 −5.02 −5.06 −4.95 −5.02 −5.06 −4.99 −5.06 −5.10 −4.89 −4.91 −4.95 −4.97 −5.01 −5.02

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Table 1. Basically, the spectra resemble that of NFp ligand.50,51 Comparing the longest wavelength of the Q-like band of each complex, corresponding to the HOMO−LUMO transition, the

a b c

EHOMO

2a 2b 2c 3a 3b 3c 4a 4b 4c 5a 5b 5c 6a 6b 6c

show the π-orbitals of NFp ligand with small contribution of metal d-orbitals or the other ligands. Meanwhile, HOMOs show the contribution of the introduced ligands as well as the NFp ligand and metal orbitals (Figures S11−S15). Among 5a− c, for example, the contributions of benzenide ligand in HOMO and HOMO−1 was seen in order of 5a > 5b > 5c. Accordingly, 5a has the highest HOMO energy (−4.89 eV), while 5b is moderate (−4.91 eV) and 5c is the lowest (−4.95 eV). On the other hand, the LUMO energies are almost same. Thus, the HOMO−LUMO gaps (ΔEL−H) were in order of a < b < c, which is consistent with the absorption properties.

Figure 6. UV−vis-NIR absorption spectra of 2c−6c in CH2Cl2.

isomer

compd

E

DOI: 10.1021/acs.inorgchem.7b01972 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 7. Kohn−Sham orbitals of 5a−c; LUMO (top), HOMO (middle), and HOMO−1 (bottom). found. Vibrational modes corresponding to imaginary frequency were consistent with the rotational mechanism discussed below. Ru(NFp)(CO)2Br (3). Ru(NFp)(CO)2Cl (2b or 2c, 6 mg, 7.5 μmol)18 in 1,4-dioxane (3 mL) was added in a Schlenk tube under argon. Then tetrabutylammonium bromide (n-Bu4NBr: 29 mg, 12 equiv) was added, and the solution was heated at 100 °C for 144 h. After cooling, the solvent was removed under vacuum. The residue was dissolved in dichloromethane (CH2Cl2) and subjected to the silica gel column chromatography with CH2Cl2 as eluent for separation. The first red fraction afforded Ru(NFp)(CO)2Br (3b, 3.0 mg, 47%; 3c, 2.9 mg, 45%). Unreacted starting material (2b or 2c) was recovered from the second fraction. 3b: 1H NMR (CDCl3, 500 MHz, ppm): δ 7.21 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.34 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.54 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.54−7.56 (m, 1H), 7.60−7.65 (m, 3H), 7.69 (d, J = 5.5 Hz, 1H, β-pyrrole), 7.71−7.82 (m, 10H), 7.96−7.97 (br, 2H), 8.26− 8.27 (m, 2H), 8.66 (d, J = 7.5 Hz, 2H), 8.68 (d, J = 5.0 Hz, 1H, βpyrrole), 9.19 (d, J = 6.0 Hz, 1H, β-pyrrole), 9.31 (s, 1H, 21-H); 13C NMR (CDCl3, 125 MHz, ppm): δ 113.5, 114.9, 118.6, 121.9, 125.5, 127.1, 127.7, 127.8, 127.9, 128.2, 128.6, 128.7, 128.8, 129.1, 129.6, 130.0, 131.2, 131.7, 132.6, 132.8, 134.8, 136.4, 137.5, 137.9, 138.4, 141.9, 143.3, 144.8, 147.9, 152.2, 152.5, 153.7, 158.3, 163.2, 192.3, 192.9; IR (powder, cm−1): 2043 (CO), 1983 (CO); UV−vis-NIR (CH2Cl2, λmax/nm, log ε): 352.0 (4.57), 523.0 (4.70), 860.5 (3.43), 952.5 (3.42); HRMS (ESI+): Found: m/z 851.04491, calcd for 12 C461H2881Br114N416O2102Ru1 (MH+): m/z 851.04187; Anal. calcd for 3b·0.1CH2Cl2: C, 64.59; H, 3.20; N, 6.54. Found: C, 64.79; H, 3.20; N, 6.57. 3c: 1H NMR (CDCl3, 500 MHz, ppm): δ 7.36 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.44 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.54−7.61 (m, 5H), 7.73−7.79 (m, 6H), 7.83−7.85 (m, 4H), 7.97 (br, 1H), 8.06−8.08 (m, 2H), 8.17−8.18 (m, 2H), 8.68 (d, J = 8.0 Hz, 2H), 8.86 (d, J = 4.5 Hz, 1H, β-pyrrole), 9.28 (d, J = 4.5 Hz, 1H, β-pyrrole), 9.34 (s, 1H, 21-H); 13 C NMR (CDCl3, 125 MHz, ppm): δ 112.2, 112.4, 119.5, 121.6, 125.3, 127.0, 127.6, 127.8, 128.2, 128.6, 128.6, 128.7, 128.8, 129.5, 129.8, 130.1, 130.4, 130.5, 132.2, 133.0, 133.6, 134.9, 136.5, 137.4, 138.2, 139.6, 139.9, 142.4, 144.7, 148.6, 152.5, 152.6, 153.3, 157.3, 163.7, 192.1, 192.5; IR (powder, cm−1): 2044 (CO), 1985 (CO); UV−vis-NIR (CH2Cl2, λmax/nm, log ε): 351.0 (4.60), 420.5 (4.34), 514.5 (4.74), 844.0 (3.41), 938.0 (3.39); HRMS (ESI+): Found: m/z 851.04532, calcd for 12C461H2881Br114N416O2102Ru1 (MH+): m/z 851.04187; Anal. calcd for 3c·0.3CH2Cl2: C, 63.61; H, 3.18; N, 6.41. Found: C, 63.47; H, 3.22; N, 6.47. Ru(NFp)(CO)2I (4c). 2c (10 mg, 12 μmol), tetrabutylammonium iodide (n-Bu4NI, 45 mg, 10 equiv), and toluene (2 mL) were added in a Schlenk tube under argon. Then the mixture was heated at 100 °C for 47 h. After cooling, the solvent was removed under vacuum. The residue was dissolved in CH2Cl2 and subjected to the silica gel column

would be attractive for use as asymmetric catalysts. Further study toward such direction is currently underway.

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EXPERIMENTAL SECTION

General. Commercially available solvents and reagents were used without further purification unless otherwise mentioned. Thin-layer chromatography (TLC) was carried out on aluminum sheets coated with silica gel 60 F254 (Merck). Preparative separation was performed by silica gel flash column chromatography (KANTO silica gel 60N, spherical, neutral, 40−50 μm), silica gel gravity column chromatography (KANTO silica gel 60N, spherical, neutral, 63-210 μm), and alumina column chromatography (γ-Alumina KCG-1525W, Sumitomo). 1H NMR spectra were recorded in CDCl3 solution on a JNMECX (500 MHz) FT-NMR spectrometer, and chemical shifts were reported relative to a residual proton of a deuterated solvent, CHCl3 (δ = 7.26) in ppm. 13C NMR spectra were recorded in CDCl3 solution on the same instrument at 125 MHz, and chemical shifts were reported relative to CDCl3 (δ = 77.00) in ppm. UV−vis-NIR absorption spectra were recorded on a Shimadzu UV-3150PC spectrometer at ambient temperature. Mass spectra were recorded on a Bruker Daltonics Autoflex-KK MALDI-TOF MS spectrometer. High-resolution mass spectra were recorded on a JEOL JMS-T100CS spectrometer (ESI-TOF mode). Cyclic voltammetry measurements were performed on a CH Instrument Model 620B (ALS) equipped with a Pt electrode. IR absorptions were recorded on FT/IR-4200 (JASCO). X-ray Crystallography. Single-crystal X-ray structural analyses were performed on a Saturn equipped with a CCD detector (Rigaku) using MoKα (multilayer mirror, monochromated, λ = 0.71069 Å) radiation. The data were corrected for Lorentz, polarization, and absorption effects. The structures were solved by the direct method of SHELXT 2014/552 and refined using the SHELXL-2016/653 program. All of the positional parameters and thermal parameters of nonhydrogen atoms were refined anisotropically on F2 by the full matrix least-squares method. Hydrogen atoms were placed at the calculated positions and refined riding on their corresponding carbon atoms. Calculation Details. All DFT calculations were achieved with a Gaussian 09 program package.54 The basis sets implemented in the program were used. The B3LYP density functional method was used with a 631SDD basis set for structural optimizations and frequency calculation. The 631SDD bases set is composed of 6-31G(d,p) for carbon, hydrogen, nitrogen, oxygen, chloride, and bromide and SDD for iodide and ruthenium. Initial structures for ground state were based on the X-ray structures, and those for transition state were arbitrarily constructed. Ground-state geometries were fully optimized and verified by the frequency calculations, where no imaginary frequency was found. Transition-state geometries were also verified by the frequency calculations, where only one imaginary frequency was F

DOI: 10.1021/acs.inorgchem.7b01972 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry chromatography with CH2Cl2 as eluent for separation. The first red fraction afforded Ru(NFp)(CO)2I (4c, 2.9 mg, 26%). Unreacted 2c was recovered from the second fraction. 4c: 1H NMR (CDCl3, 500 MHz, ppm): δ 7.35 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.42 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.53 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.57 (t, J = 6.8 Hz, 1H, p-H), 7.60−7.63 (m, 3H), 7.74− 7.79 (m, 5H), 7.83−7.86 (m, 4H, β-pyrrole and phenyl), 7.99 (br, 2H), 8.07 (d, J = 7.6 Hz, 2H), 8.19−8.20 (m, 2H), 8.69 (d, J = 7.6 Hz, m-ph), 8.86 (d, J = 4.5 Hz, 1H, β-pyrrole), 9.30 (d, J = 4.5 Hz, 1H, βpyrrole), 9.33 (s, 1H, 21-H); 13C NMR (CDCl3, 125 MHz, ppm): δ 112.1, 112.4, 119.7, 121.3, 125.1, 126.9, 127.4, 127.7, 128.3, 128.4, 128.5, 128.7, 129.3, 129.6, 129.8, 129.9, 130.3, 132.1, 132.9, 133.6, 134.8, 136.6, 137.3, 137.8, 140.0, 142.5, 144.5, 148.4, 153.2, 153.3, 153.4, 156.5, 163.6, 192.2, 193.1; IR (powder, cm−1): 2038 (CO), 1981 (CO); UV−vis-NIR (CH2Cl2, λmax/nm, log ε): 355.0 (4.66), 431.5 (4.24), 516.0 (4.77), 849.0 (3.42), 938.5 (3.39); HRMS (ESI+): Found: m/z 897.03485, calcd for 12C461H28127I114N416O2102 Ru1 (MH+): m/z 897.03004; Anal. calcd for 4c·0.4CH2Cl2·0.1C6H14: C, 60.16; H, 3.14; N, 5.97. Found: C, 60.07; H, 3.42; N, 5.83. Ru(NFp)(CO)2Ph (5). Sodium tetraphenylborate (5 equiv) was added to Ru(NFp)(CO)2Cl (2a, 10.3 mg, 2b, 15 mg or 2c, 8.6 mg) in chlorobenzene (2 mL) in a Schlenk tube under nitrogen at room temperature. Then the mixture was heated at 100 °C for 19 h. After cooling, the solvent was evaporated, and the residue was separated by silica gel column chromatography with CH2Cl2 as eluent. The first red fraction afforded Ru(NFp)(CO)2Ph (5: 5a, 9.0 mg, 83%, 5b, 10.3 mg, 65%, 5c, 7.9 mg, 87% yield), and the unreacted starting material (2a, 2b, 2c) was recovered from the second red fraction. 5a: 1H NMR (CDCl3, −50 °C, 500 MHz, ppm): δ 2.86 (d, J = 8.0 Hz, 1H, o-ph), 5.18 (t, J = 6.8 Hz, 1H, m-ph), 6.10 (t, J = 7.0 Hz, 1H, p-ph), 6.28 (d, J = 8.0 Hz, 1H, o-ph), 6.63 (t, J = 7.5 Hz, 1H, m-ph), 7.18 (d, J = 5.0 Hz, 1H, β-pyrrole), 7.41 (d, J = 3.5, 1H, β-pyrrole), 7.41 (d, β-pyrrole, 2H, ph), 7.52 (d, J = 3.0 Hz, 1H, β-pyrrole), 7.51− 7.35 (m, 1H), 7.57 (t, J = 8.3 Hz, 2H, ph), 7.65−7.69 (m, 3H, ph), 7.74 (t, J = 7.5 Hz, 2H, ph), 7.81 (t, J = 7.8 Hz, 2H, ph), 7.85−7.87 (m, 3H, ph), 7.86 (d, J = 4.5 Hz, 1H, β-pyrrole), 8.14 (d, J = 5.0 Hz, 1H, β-pyrrole), 8.23 (br, 2H, ph), 8.34 (d, J = 7.5 Hz, 1H, ph), 8.77 (d, J = 7.5 Hz, 2H, ph), 8.95 (d, J = 6.0 Hz, 1H, β-pyrrole), 9.47 (s, 1H, 21-H); 13C NMR (CDCl3, −50 °C, 125 MHz, ppm): δ 111.0, 112.9, 119.8, 120.2, 121.2, 124.0, 124.9, 126.0, 126.7, 127.1, 127.2, 127.6, 128.0, 128.2, 128.4, 128.6, 129.3, 129.4, 129.9, 130.3, 130.5, 133.1, 133.2, 133.7, 135.1, 136.7, 137.2, 137.4, 137.9, 138.6, 139.6, 141.8, 142.5, 145.8, 150.0, 151.7, 152.4, 152.9, 154.9, 158.6, 161.6, 195.9, 197.2; IR (powder, cm−1): 2023 (CO), 1956 (CO); UV−vis-NIR (CH2Cl2, λmax/nm, log ε): 354.5 (4.49), 448.5 (4.18), 525.0 (4.57), 862.0 (3.32), 953.0 (3.32); HRMS (ESI+): Found: m/z 847.16232, calcd for 12C521H3314N416O2102Ru1 (MH+): m/z 847.16470; Anal. calcd for 5a·0.2CH2Cl2·2.2C6H14: C, 74.63; H, 6.05; N, 5.32. Found: C, 74.88; H, 5.87; N, 5.02. 5b: 1H NMR (CDCl3, 500 MHz, ppm): δ 5.22 (d, J = 7.0 Hz, 2H, o-ph), 6.49 (t, J = 7.5 Hz, 2H, m-ph), 6.66 (t, J = 7.5 Hz, 1H, p-ph), 7.23 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.38 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.43 (d, J = 4.0 Hz, 1H, β-pyrrole), 7.49 (d, J = 6.5 Hz, 2H, ph), 7.53 (t, J = 7.5 Hz, 1H, ph), 7.60−7.67 (m, 6H), 7.73−7.76 (m, 5H), 7.90 (d, J = 4.0 Hz, 1H, β-pyrrole), 7.93 (br, 2H), 8.03 (br, 2H), 8.68 (d, J = 7.0 Hz, 2H, ph), 8.71 (d, J = 4.5 Hz, 1H, β-pyrrole), 8.97 (s, 1H, 21H), 9.20 (d, J = 5.5 Hz, 1H, β-pyrrole); 13C NMR (CDCl3, 125 MHz, ppm): δ 111.9, 113.4, 119.3, 120.9, 122.1, 124.5, 126.1, 126.2, 127.6, 128.1, 128.2, 128.3, 128.6, 128.9, 129.4, 129.9, 130.7, 131.2, 132.0, 132.7, 133.3, 135.2, 136.4, 137.6, 137.9, 138.9, 139.1, 140.3, 143.3, 145.2, 148.4, 152.7, 154.0, 154.2, 155.4, 157.8, 163.1, 196.7, 196.7; IR (powder, cm−1): 2021 (CO), 1955 (CO); UV−vis-NIR (CH2Cl2, λmax/nm, log ε): 352.5 (4.60), 413.5 (4.30), 528.0 (4.70), 848.0 (3.43), 940.0 (3.42); HRMS (ESI+): Found: m/z 847.16180, calcd for 12 C521H3314N416O2102Ru1 (MH+): m/z 847.16470; Anal. calcd for 5b· 0.5CH2Cl2: C, 70.98; H, 3.74; N, 6.31. Found: C, 70.90; H, 4.02; N, 6.14. 5c:1H NMR (CDCl3, 500 MHz, ppm): δ 6.15 (d, J = 6.5 Hz, 2H, oPhenyl ligand), 6.77 (t, J = 7.5 Hz, 2H, m-Phenyl ligand), 6.83 (t, J = 7.5 Hz, 1H, p-Phenyl ligand), 7.18 (d, J = 8.0 Hz, 2H, o-Ph), 7.31 (d, J

= 4.5 Hz, 1H, β-pyrrole), 7.41 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.43− 7.49 (m, 4H), 7.54−7.65 (m, 2H), 7.77−7.80 (m, 5H), 7.84−7.90 (m, 3H), 8.09−8.21 (m, 2H), 8.34 (d, J = 5.5 Hz, 2H, ph), 8.76 (d, J = 8.0 Hz, 2H, o-ph), 8.82 (d, J = 5.5 Hz, 1H, β-pyrrole), 9.24 (d, J = 4.5 Hz, 1H, β-pyrrole), 9.38 (s, 1H, 21-H); 13C NMR (CDCl3, 125 MHz, ppm): δ 111.9, 113.1, 119.6, 120.9, 122.5, 124.1, 126.2, 126.5, 127.2, 127.7, 127.9, 128.1, 128.4, 128.4, 128.7, 129.4, 129.5, 129.6, 130.0, 130.90, 131.8, 131.8, 132.7, 132.8, 135.4, 136.5, 138.1, 138.4, 138.4, 138.6, 140.3, 143.3, 145.8, 150.3, 151.8, 152.4, 154.7, 155.9, 157.4, 163.0, 196.5, 197.5; IR (powder, cm−1); 2010 (CO), 1942 (CO); UV−vis-NIR (CH2Cl2, λmax/nm, log ε): 352.5 (4.55), 523.0 (4.71), 647.0 (3.62), 834 (3.34), 925.0 (3.32); HRMS (ESI+): Found: m/z 847.16124, calcd for 12C521H3314N416O2102Ru1 (MH+): m/z 847.16470; Anal. calcd for 5c·0.4CH2Cl2: C, 71.53; H, 3.76; N, 6.37. Found: C, 71.40; H, 3.97; N, 6.07. Ru(NFP)(CO)2(OAc) (6). To a mixture of three isomers of 2 (10.0 mg, 12 μmol) in o-dichlorobenzene (3 mL), potassium acetate (61.0 mg, 50 equiv) was added, and the resulting solution was heated at 150 °C under Ar for 31 h. After cooling, the solvent was removed under reduced pressure, and the residue was subjected to the silica gel column chromatography with 1% methanol/CH2Cl2 as eluent. The fifth red fraction was evaporated to dryness and dried under vacuum to give a mixture of 6a, 6b, and 6c (8.9 mg in total, 86%). 6.5 mg of 6 was dissolved in 1% methanol/CH2Cl2 and repeatedly separated by HPLC with silica gel column (20 × 200 mm) using 1% methanol/CH2Cl2 (flow rate was 7.0 mL/min and monitored at 500 nm). The product mixture was separated into three fractions 6a (2.4 mg), 6b (1.2 mg), and 6c (2.0 mg). 6a: 1H NMR (CDCl3, 500 MHz, ppm): δ 0.52 (s, 3H), 7.12 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.33 (d, J = 4.0 Hz, 1H, β-pyrrole), 7.38 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.55 (t, 1H, J = 7.5), 7.60−7.65 (m, 3H), 7.69−7.75 (m, 4H), 7.76−7.79 (m, 2H), 7.81−7.84 (m, 4H), 7.88 (d, J = 4.5 Hz, 1H, β-pyrrole), 8.01 (s, 2H), 8.16−8.20 (m, 2H), 8.71 (d, J = 8.0 Hz, 2H, ph), 8.78 (d, J = 4.5 Hz, 1H, β-pyrrole), 9.21 (d, J = 4.5 Hz, 1H, β-pyrrole), 9.38 (s, 1H, 21-H); 13C NMR (CDCl3, 125 MHz, ppm): δ 21.4, 112.4, 112.8, 120.3, 120.8, 123.7, 126.2, 127.7, 128.3, 128.6, 128.7, 128.8, 129.3, 129.6, 129.7, 129.9, 130.0, 132.5, 133.1, 133.2, 134.2, 135.1, 136.4, 137.3, 137.7, 138.3, 140.3, 144.0, 145.4, 149.5, 153.2, 153.6, 154.3, 157.5, 160.6, 175.0, 193.2, 193.9; IR (powder, cm−1): 2043 (CO), 1980 (CO); UV−vis-NIR (CH2Cl2, λmax/nm, log ε): 354.0 (4.63), 522.0 (4.72), 652.0 (3.73), 861.0 (3.49), 954.0 (3.50); HRMS (ESI+): Found: m/z 829.14150, calcd for 12 C481H3114N416O4102Ru1 (MH+): m/z 829.13888; Anal. calcd for 6a· 0.3H2O: C, 68.79; H, 3.68; N, 6.69. Found: C, 68.54; H, 3.71; N, 6.66. 6b: 1H NMR (CDCl3, 500 MHz, ppm): δ 1.37 (s, 3H), 7.11 (d, J = 6.0 Hz, 1H, β-pyrrole), 7.36 (t, J = 3.8 Hz, 1H, β-pyrrole), 7.51 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.54 (t, J = 7.0 Hz, 1H), 7.59−7.63 (m, 4H), 7.70−7.76 (m, 5H), 7.78−7.85 (m, 5H), 7.96 (br, 2H), 8.20−8.21 (m, 2H), 8.65 (d, J = 8.0 Hz, 2H), 8.66 (d, J = 4.5 Hz, 1H, β-pyrrole), 9.16 (d, J = 4.5 Hz, 1H, β-pyrrole), 9.27 (s, 1H, 21-H); 13C NMR (CDCl3, 125 MHz, ppm): δ 29.8, 113.2, 114.2, 118.7, 121.9, 125.2, 126.9, 127.8, 127.9, 128.1, 128.4, 128.5, 128.6, 128.7, 129.2, 129.3, 129.5, 129.6, 129.9, 131.1, 131.6, 132.4, 132.7, 134.9, 136.5, 137.9, 138.1, 138.6, 140.5, 143.5, 144.9, 146.4, 152.3, 152.4, 152.8, 158.9, 164.3, 175.6, 193.6, 194.1; IR (powder, cm−1): 2042 (CO), 1982 (CO); UV−vis-NIR (CH2Cl2, λmax/nm, log ε): 359.0 (4.58), 419.0 (4.29), 526.0 (4.68), 856.5 (3.42), 949.0 (3.40); HRMS (ESI+): Found: m/z 829.14312, calcd for 12C481H3114N416O4102Ru1 (MH+): m/z 829.13888; Anal. calcd for 6b·0.6CH2Cl2·0.1C6H14: C, 66.59; H, 3.65; N, 6.31. Found: C, 66.58; H, 3.90; N, 6.06. 6c: 1H NMR (CDCl3, 500 MHz, ppm): δ 1.69 (s, 3H), 7.32 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.45 (d, J = 5.0 Hz, 1H, β-pyrrole), 7.53−7.56 (m, 2H), 7.61−7.64 (m, 3H), 7.74−7.78 (m, 5H), 7.82−7.83 (m, 3H), 7.85 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.89 (br, 2H), 8.14−8.16 (m, 4H), 8.66 (d, J = 7.5 Hz, 2H), 8.88 (d, J = 4.5 Hz, 1H, β-pyrrole), 9.25 (d, J = 4.5 Hz, 1H), 9.32 (s, 1H, 21-H); 13C NMR (CDCl3, 125 MHz, ppm): δ 22.6, 111.8, 112.4, 119.4, 121.6, 125.2, 126.7, 127.7, 128.0, 128.4, 128.6, 128.7, 129.55, 129.60, 130.0, 130.2, 130.8, 132.1, 132.7, 133.3, 134.9, 136.7, 137.6, 138.1, 138.6, 139.6, 142.5, 144.9, 148.9, 151.0, 151.5, 153.2, 158.3, 164.2, 176.2, 193.1, 193.4; IR (powder, G

DOI: 10.1021/acs.inorgchem.7b01972 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry cm−1): 2040 (CO), 1980 (CO); UV−vis-NIR (CH2Cl2, λmax/nm): 351.5 (4.58), 418.5 (4.35), 513.5 (4.72), 647.0 (3.63), 847.0 (3.41), 934.5 (3.39); HRMS (ESI+): Found: m/z 829.14063, calcd for 12 C481H3114N416O4102Ru1 (MH+): m/z 829.13888; Anal. calcd for 6c· 0.5CH2Cl2: C, 66.93; H, 3.59; N, 6.44. Found: C, 66.88; H, 3.63; N, 6.52. Synthesis of 6c via the Reaction with Silver Trifluoromethanesulfonate. To a toluene (2 mL) solution of 2c (5.2 mg, 6.5 μmol), silver trifluoromethanesulfonate (25 mg, 15 equiv) was added, and the mixture was stirred for 35 min at room temperature. Then, potassium acetate (17 mg, 27 equiv) was added, and the temperature was raised to 100 °C. After 5 h, the solvent was removed under reduced pressure, and the residue was subjected to the silica gel column chromatography with 1% methanol/CH2Cl2. The first red fractions afforded 6c (4.9 mg, 92%). Synthesis of 6c with Silver Acetate. To a 1,4-dioxane (2 mL) solution of 2c (10.0 mg, 12 μmol), silver acetate (23 mg, 10 equiv) was added, and the mixture was stirred for 22 h at 100 °C. The solvent was removed under reduced pressure, and the residue was subjected to the silica gel column chromatography with 1% methanol/CH2Cl2. The second red fraction afforded 6c (10.2 mg, 99%). Ru(NFp)(CO)2H (7). To a dry THF solution of N,N-diisopropylamine (1 mL, 7.1 mmol) in a Schlenk flask, 1.6 M n-BuLi in hexane (0.5 mL, 0.8 mmol) was added at 0 °C under argon, and the solution was stirred for 1 h. The freshly prepared LDA reagent (1 mL, 1.3 equiv) was then added to 5 mL of THF solution of 2 (100 mg, 0.12 mmol) in a Schlenk flask under N2. The resulting solution was heated at 60 °C for 18 h. After cooling, the reaction mixture was washed with CH2Cl2 and saturated NH4Cl aq, and the organic layer was separated. After evaporation, the residue was subjected to the silica-gel column chromatography with CH2Cl2/Hexane = 1/1 (v/v) as eluent. The first red fraction afforded a 15.7 mg of crude product. Precipitation from CH2Cl2 and hexane afforded 4.6 mg of 7c (4.8% yield). 45.9 mg of 2 was recovered. 7c: 1H NMR (CDCl3, 500 MHz, ppm): δ −13.17 (s, 1H, Ru−H), 7.31 (t, 2H), 7.46 (t, 1H), 7.56 (q, 1H), 7.58−7.60 (m, 2H), 7.75− 7.82 (m, 12H), 8.02 (s, 2H), 8.29 (d, J = 8.0 Hz, 2H, ph), 8.74−8.77 (m, 3H, β-pyrrole+ph), 9.21 (d, J = 6.0 Hz, 1H, β-pyrrole), 9.38 (s, 1H, 21 position H); UV−vis (CH2Cl2, λmax/nm): 356.5, 523.0, 646.5, 837.0, 923.0; MALDI-TOF-MS (m/z); 713.942, 1326.008, 1428.180; HRMS (ESI): Found 771.13821, calcd 12C461H2914N416O2102Ru1 (M + H) 771.13340; IR (CO/cm−1); 1942.9, 2014.3. Synthesis of 7 with Sodium Borohydride. To a dry THF solution (10 mL) of 2 (9.9 mg, 12 μmol, 2a: 2b: 2c = 1:3.5:4.3), 2.5 mL of 12 μM THF solution of sodium borohydride (5 equiv) was added in a Schlenk flask at 0 °C under nitrogen. The solution was stirred for 15.5 h with 60 °C heating. After cooling, the reaction mixture was washed with CH2Cl2 and saturated NH4Cl aq., and the organic layer was collected. After evaporation, the residue was subjected to the silica-gel column chromatography with CH2Cl2/ hexane = 1/1 (v/v) as eluent. The first red fraction afforded 7c in 2.0 mg (21% yield), and 3.0 mg of 2 was recovered.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Hiroyuki Furuta: 0000-0002-3881-8807 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The work was supported by the Grant-in-Aid (no. 15K13646 to H.F.; 16K05700 and 17H05377 to M.I.) from the Ministry of Education, Culture, Sports, Science and Technology of Japan. The financial support from a bilateral program between JSPS and the National Research Foundation (NRF) of South Africa is also acknowledged.

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REFERENCES

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S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.7b01972. 1 H and 13C NMR spectra of 3−6, X-ray crystallographic parameters of 3b, 3c, 6a, and 6c, Cartesian coordinates for the optimized structures (PDF) Accession Codes

CCDC 1560430−1560432 and 1560443 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/ cif or by emailing [email protected] or contacting H

DOI: 10.1021/acs.inorgchem.7b01972 Inorg. Chem. XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.inorgchem.7b01972 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ö .; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09, Revision C.01; Gaussian, Inc.: Wallingford, CT, 2009.

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DOI: 10.1021/acs.inorgchem.7b01972 Inorg. Chem. XXXX, XXX, XXX−XXX