NCN-Type Pincer Complexes of Subporphyrinatoboron(III

May 30, 2017 - The first NCN-type subporphyrin pincer complexes 3Pd and 3Pt have been synthesized via Suzuki coupling of 2,13-diborylsubporphyrin with...
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NCN-Type Pincer Complexes of Subporphyrinatoboron(III) Masaaki Kitano, Takayuki Tanaka, and Atsuhiro Osuka* Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan S Supporting Information *

ABSTRACT: The first NCN-type subporphyrin pincer complexes 3Pd and 3Pt have been synthesized via Suzuki coupling of 2,13-diborylsubporphyrin with 2-iodopyridine, followed by metalation with PdCl2(MeCN)2 or K2PtCl4, respectively. 2,13-Diiminosubporphyrin 4 was also prepared via formylation of 2,13-dilithiosubporphyrin followed by imination with aniline but was found to be unsuitable as a precursor of organometallic species. The complexes 3Pd and 3Pt displayed perturbed optical properties presumably due to the d(metal)π(subporphyrin) orbital interactions.

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INTRODUCTION A new boron-containing ring-contracted porphyrinoid, subporphyrinatoboron(III) (hereafter referred to “subporphyrin”), was first reported in 2006.1,2 Since then, there has been considerable progress in the development of the synthetic chemistry of subporphyrins that allows for the creation of various derivatives such as meso-aryl-substituted,3 meso-alkylsubstituted,4 β-alkyl-substituted,5 meso-free,6 pyrrole-reduced,7 and pyrrole-modified subporphyrins.8 In addition, subporphyrins have been increasingly recognized as a new class of functional dyes in light of the high tunability of their optical and electronic properties by meso substituents. Interesting examples are highly fluorescent (ΦF = 0.6) subporphyrin, two modes of twisted intramolecular charge transfer, and high photon-to-current conversion efficiency in a dye-sensitized solar cell.9 As another functional molecule, pincer-type transition-metal complexes of subporphyrins may be attractive, since porphyrinbased pincer complexes have been known as unique and effective catalysts (Chart 1).10,11 Actually, NCN-type porphyrin pincer complexes 1M and PCP-type complexes 2M have been demonstrated to act as effective catalysts for some C−C bond forming reactions. It is also noteworthy that the metalations at the peripheral pincer site induced significant structural and electronic perturbation of porphyrins. Thus, it occurred to us that a pincer complex of subporphyrin might be an interesting target not only as a novel catalyst but also as the first example of organometallic subporphyrin pigments with perturbed electronic and optical properties. In this paper, we designed two subporphyrins 3 and 4 bearing two 2-pyridyl groups and phenyliminyl groups at positions adjacent to the free meso position. Using these subporphyrins, we examined their conversions to NCN-type pincer complexes of subporphyrin, 3M and 4M.

Chart 1. Porphyrin and Subporphyrin Pincer Complexes

reaction and its conversion to 2,13-diiodosubporphyrin 6 by a Cu-mediated halogen exchange reaction.12 These compounds are good precursors for the designed pincer ligands, and actually 2,13-bis(2-pyridyl)subporphyrin 3 was synthesized via a Suzuki coupling of 5 with 2-iodopyridine under palladium catalysis in 70% yield (Scheme 1). The 1H NMR spectrum of 3 exhibits a singlet at 10.20 ppm due to the meso proton, two singlets at 8.44 and 8.18 ppm due to the β-protons, a set of multiple signals of β-pyridyl and meso-aryl protons, and two upfield-shifted doublets of B-tolyl protons at 6.17 and 4.73 ppm as a consequence of the diatropic ring-current effect arisen from

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Special Issue: Tailoring the Optoelectronic Properties of Organometallic Compounds with Main Group Elements

RESULTS AND DISCUSSION Recently we reported the facile preparation of 2,13-bis(pinacolatoboryl)subporphyrin 5 by an Ir-catalyzed direct borylation © XXXX American Chemical Society

Received: February 20, 2017

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DOI: 10.1021/acs.organomet.7b00130 Organometallics XXXX, XXX, XXX−XXX

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Organometallics Scheme 1. Synthesis of 2,13-Disubstituted Subporphyrins

Figure 1. X-ray crystal structures of (a) 3 and (b) 4. Thermal ellipsoids are scaled to 50% probability. Solvent molecules are omitted for clarity.

from dichloromethane/n-hexane. The structure of 4 was unambiguously determined by an X-ray analysis (Figure 1b). The two imine segments are almost coplanar with the subporphyrin core, enough to have a cavity for metal complexation. The bowl-depth value (1.42 Å) is similar to that of 3. The X-ray structure of diformylsubporphyrin 9 was also revealed (Figure S3-1 in the Supporting Information). All of the structural features of 9 are similar to those of 4. Then, reactions of 3 and 4 with metal salts were investigated (Scheme 2). Treatment of 3 with dichloropalladium(II) Scheme 2. Synthesis of Subporphyrin Pincer Complexes

a 14π aromatic circuit. The structure of 3 was finally shown by X-ray diffraction analysis (Figure 1a). In the solid state, one 2-pyridyl group attached at the β-position is roughly coplanar with the subporphyrin plane defined by the three neighboring carbons adjacent to the pyridyl group with a dihedral angle of 7.4°, while the other is tilted by about 42.7°. The bowl-depth value is calculated to be 1.40 Å.13 As another promising ligand for an NCN-type pincer complex, we prepared diiminosubporphyrin 4, which would be formed via imination of 2,13-diformylsubporphyrin 9. However, a direct formylation on a subporphyrin core has never been achieved so far, and we thus examined the halogen− lithium exchange reaction of β,β′-diiodosubporphyrin 6 according to the procedure for the in situ generation of β-porphyrinyllithium.14 Diiodide 6 was treated with n-butyllithium at −80 °C to generate dilithium 7, the existence of which was confirmed by a deuterium exchange experiment to give 8-D in 84% yield. Then, treatment of DMF with 7 afforded β,β′-diformylsubporphyrin 9 in 66% yield. Imination with 10 equiv of aniline in the presence of magnesium sulfate gave 4 in high yield, which was easily hydrolyzed by atmospheric water or on a silica gel column but was obtained in pure form by filtration of the reaction mixture followed by recrystallization

acetonitrile complex in the presence of sodium acetate in toluene at 80 °C successfully afforded the desired palladium pincer complex 3Pd in 59% yield. Similarly, the reaction of 3 with potassium tetrachloroplatinate(II) gave platinum pincer complex 3Pt in 45% yield. In contrast, reactions of 4 with metal salts under the same conditions did not give any complexes, merely resulting in the decomposition of 4 probably due to the instability of the imine groups. High-resolution atmosphericpressure-chemical-ionization time-of-flight mass spectrometry (HR-APCI-TOF-MS) revealed the parent peaks for 3Pd and 3Pt at m/z 803.1602 (calcd for C46H3311BN5102Pd35Cl m/z B

DOI: 10.1021/acs.organomet.7b00130 Organometallics XXXX, XXX, XXX−XXX

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Organometallics 803.1579 [M]−) and at 895.2157 (calcd for C46H3311BN5194Pt35Cl m/z 895.2152 [M]−), respectively, indicating that a chloride is attached on the metal as the fourth ligand in addition to two pyridines and the subporphryin meso carbon. The 1H NMR spectra of 3Pd and 3Pt showed similar but consistent signals, exhibiting two singlets due to the subporphyrin β-protons at 8.13 and 8.05 ppm for 3Pd and 8.00 and 7.98 ppm for 3Pt and four signals in the range of 10.2−7.1 ppm due to the 2-pyridyl protons, one of which was shifted significantly downfield (10.08 ppm for 3Pd and 10.13 ppm for 3Pt) because of the adjacent nitrogen− metal bond (Figure 2). Importantly, a signal of 3 ascribable to the

Figure 3. DFT optimized structures of (a) 3Pd and (b) 3Pt calculated at the B3LYP/6-311G(d) (for C, H, N, B, and Cl) + SDD (for Pd and Pt) level.

Figure 2. 1H NMR spectra of (a) 3Pd and (b) 3Pt measured in CDCl3 at room temperature. Figure 4. UV/vis absorption spectra of 3 (black), 3Pd (red), and 3Pt (blue) in CH2Cl2.

meso proton disappeared in 3Pd and 3Pt. Broad 11B NMR peaks were observed at −14.9 ppm for 3Pd and −14.7 ppm for 3Pt. Although we have tried to grow single crystals of 3Pd and 3Pt for a long time, a tiny fiberlike crystal of 3Pd was only obtained by the vapor diffusion method, from which we obtained a preliminary crystal structure of 3Pd (Figure S3-2 in the Supporting Information). On the basis of this preliminary structure, the structural optimizations have been conducted with the Gaussian 09 package at the level of B3LYP/6-311G(d) (for C, H, N, B, and Cl) + SDD (for Pd and Pt) (Figure 3 and details in Figures S5-1 and S5-2 in the Supporting Information). The peripheral metals take a nearly square-planar geometry; the distances between the metal atom and the mean plane constructed by C1N1N2Cl were 0.052 Å for 3Pd and 0.067 Å for 3Pt, and the summations of the surrounding bond angles were 362.47° for 3Pd and 361.90° for 3Pt. The meso-carbon (C1)metal bond length is calculated to be 1.996 Å for 3Pd, which is slightly longer than those of porphyrin pincer complexes 1MPd (1.977 Å for 1NiPd, 1.969 Å for 1CuPd, and 1.972 Å for 1HPd).11a The calculated C1Pt length is 1.994 Å. Due to the pincer-type metal complexations, the bowl-depth values of the core subporphyrin become slightly larger, being 1.47 and 1.49 Å for 3Pd and 3Pt, respectively. UV/vis absorption spectra of 3, 3Pd, and 3Pt are shown in Figure 4. Subporphyrin 3 displayed a slightly red shifted Soret-like band at 405 nm and a Q-like band at 488 nm in comparison with those of β-unsubstituted subporphyrin 8. The NCN-pincer complexes 3Pd and 3Pt exhibited broad and

split Soret-like bands at 417 and 449 nm for 3Pd and at 422 and 466 nm for 3Pt. The Q-like bands were remarkably red shifted, reaching to 592 and 627 nm for 3Pd and 3Pt, respectively. Similar spectral features were observed for the porphyrin pincer complexes and were ascribed to the orbital interaction between the π orbital on the meso carbon and d orbital on the metal.11a,f,h,15 Indeed, distinct stabilizations in LUMOs of 3Pd and 3Pt were calculated because of the decent interactions between the subporphyrin π orbital and the metal d orbital. The degree of d−π interaction may lead to different HOMO−LUMO gaps (ΔE = 1.94 eV for 3Pd and ΔE = 1.80 eV for 3Pt),16 which highlighted the importance of introducing a transition metal onto the periphery of the subporphyrin. While subporphyrin 3 displayed fluorescence at 562 nm with ΦF = 0.04, 3Pd and 3Pt were nonfluorescent presumably due to the heavy atom effect.17

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CONCLUSIONS In summary, the NCN-type subporphyrin pincer complexes 3Pd and 3Pt have been successfully obtained for the first time. A new method to prepare β-formyl and β-imino subporphyrins has been also developed by using β-lithiated subporphyrin as a key reactant. At the present stage, our attempts to use 3Pd and 3Pt as catalysts were unsuccessful,18 but these new subporphyrins might have potential for catalytic use as well as C

DOI: 10.1021/acs.organomet.7b00130 Organometallics XXXX, XXX, XXX−XXX

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Organometallics

ethyl acetate. The organic phase was washed with saturated NaHCO3 aqueous solution and brine and then dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure. The crude product was purified by silica gel chromatography (eluent dichloromethane). A red fraction was collected and recrystallized from dichloromethane/n-hexane to give the desired subporphyrins as red solids. B-Tolyl(2,13-dideuterated-5,10-bis(p-tolyl)subporphyrinato)boron(III) (8-D). According to the general procedure, subporphyrin 8-D was obtained in 84% yield. 1 H NMR (600 MHz, CDCl3): δ (ppm) 8.82 (s, 1H, meso-H), 8.11 (s, 2H, β), 8.08 (s, 2H, β), 7.94 (d, J = 7.8 Hz, 4H, meso-Ar-ortho), 7.49 (d, J = 7.8 Hz, 4H, meso-Ar-meta), 6.12 (d, J = 7.8 Hz, 2H, B-Armeta), 4.52 (d, J = 8.0 Hz, 2H, B-Ar-ortho), 2.57 (s, 6H, meso-Ar-Me), and 1.76 (s, 3H, B-Ar-Me). HRMS (APCI-TOF, positive mode): m/z 516.2580 (calcd for C36H27D211BN3 516.2581 [M + H]+). B-Tolyl(2,13-diformyl-5,10-bis(p-tolyl)subporphyrinato)boron(III) (9). According to the general procedure, subporphyrin 9 was obtained in 66% yield. 1 H NMR (600 MHz, CDCl3): δ (ppm) 10.75 (s, 2H, formyl-H), 9.80 (s, 1H, meso-H), 8.53 (s, 2H, β), 8.20 (s, 2H, β), 7.91 (d, J = 7.8 Hz, 4H, meso-Ar-ortho), 7.54 (d, J = 7.8 Hz, 4H, meso-Ar-meta), 6.22 (d, J = 8.0 Hz, 2H, B-Ar-meta), 4.68 (d, J = 8.0 Hz, 2H, B-Ar-ortho), 2.60 (s, 6H, meso-Ar-Me), and 1.82 (s, 3H, B-Ar-Me). 11B NMR (193 MHz, CDCl3): δ (ppm) −15.5 (s, 1B). 13C NMR (150 MHz, CDCl3): δ (ppm) 187.4, 141.8, 140.5, 139.4, 138.8, 136.1, 133.2, 132.4, 129.8, 128.9, 128.0, 127.5, 127.4, 124.2, 123.9, 104.6, 21.5, and 20.9. HRMS (APCI-TOF, positive mode): m/z 570.2346 (calcd for C38H2911BN3O2 570.2354 [M + H]+). UV−vis (in CH2Cl2): λ [nm] (ε [M−1 cm−1]) 332 (21000), 405 (77000), 417 (77000), 530 (9000). Fluorescence (in CH2Cl2, λex 405 nm): λmax [nm] 609, ΦF = 0.08. B-Tolyl(2,13-bis(phenyliminomethyl)-5,10-bis(p-tolyl)subporphyrinato)boron(III) (4). A solution of subporphyrin 9 (45.0 mg, 75.4 μmol), aniline (68.7 μL, 754 μmol), and magnesium sulfate (4.5 mg, 37.4 μmol) in dry THF (1.50 mL) was stirred at reflux under Ar. After 12 h, the reaction mixture was filtered and the solvent was removed under reduced pressure. The crude product was recrystallized from dichloromethane/n-hexane repeatedly to give 4 (44.3 mg, 81%) as red solids. 1 H NMR (600 MHz, CDCl3): δ (ppm) 10.09 (s, 1H, meso-H), 9.27 (s, 2H, imine), 8.45 (s, 2H, β), 8.17 (s, 2H, β), 7.96 (d, J = 7.8 Hz, 4H, meso-Ar-ortho), 7.52 (d, J = 7.8 Hz, 4H, meso-Ar-meta), 7.49−7.43 (m, 8H, NPh), 7.30 (t, J = 7.3 Hz, 2H, NPh), 6.22 (d, J = 8.0 Hz, 2H, B-Ar-meta), 4.74 (d, J = 8.0 Hz, 2H, B-Ar-ortho), 2.59 (s, 6H, meso-ArMe), and 1.82 (s, 3H, B-Ar-Me). 11B NMR (193 MHz, CDCl3): δ (ppm) −16.0 (s, 1B). 13C NMR (150 MHz, CDCl3): δ (ppm) 154.5, 152.5, 141.4, 141.3, 140.0, 138.2, 135.6, 134.0, 133.2, 132.6, 129.7, 129.4, 129.0, 127.2, 126.4, 123.7, 122.9, 122.2, 121.3, 105.0, 21.5, and 20.9. HRMS (APCI-TOF, positive mode): m/z 720.3274 (calcd for C50H3911BN5 = 720.3301 [M + H]+). UV−vis (in CH2Cl2): λ [nm] (ε [M−1 cm−1]) 316 (29000), 414 (104000), 499 (13000), 529 (13000). Fluorescence (in CH2Cl2, λex 414 nm): λmax [nm] 594, ΦF = 0.07. B-Tolyl(2,13-bis(2-pyridyl)-5,10-bis(p-tolyl)subporphyrinato)boron(III) (3). A solution of 2,13-bis(pinacolatoboryl)subporphyrin 5 (160 mg, 209 μmol), 2-iodopyridine (0.22 mL, 2.07 mmol), 2-(dicyclohexylphosphino)-2′,6′-dimethoxybiphenyl (34.4 mg, 83.6 μmol), tris(dibenzylideneacetone)dipalladium(0) (38.3 mg, 41.8 μmol), and tripotassium phosphate (266 mg, 1.25 mmol) in dry THF (4.10 mL) and water (0.10 mL) was deoxygenated via three freeze−pump−thaw cycles and then stirred at reflux under Ar. After 24 h, the reaction mixture was quenched with water and the product was extracted with dichloromethane. The organic phase was washed with brine and then dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure. The crude product was chromatographed on silica gel (eluent dichloromethane/n-hexane/diethyl ether 1/2/1). A red fraction was collected and recrystallized from dichloromethane/methanol to give 3 (97.3 mg, 70%) as red solids.

novel optical materials. Structural deformation by the peripheral metalation and perturbed electronic state due to the metal d−π interactions are of particular importance in this report.

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EXPERIMENTAL SECTION

General Information. If not stated otherwise, all reactions and manipulations were carried out under an atmosphere of dry nitrogen using Schlenk techniques. All reagents and solvents were of commercial reagent grade and were used without further purification unless where noted. THF was purified with a solvent purification system before use. Toluene and DMF were distilled from CaH2 and P2O5, respectively. SPhos (Aldrich, 97%), Pd2(dba)3 (Aldrich 97%), NIS (Wako, 97%), PdCl2(MeCN)2 (Wako, 98%), and K2PtCl4 (Wako, 98%) were used as obtained from commercial suppliers. A 1.6 M n-BuLi solution in hexane was purchased from Nacalai tesque. The purity of synthesized samples has been established by NMR spectroscopy. 1H and 13C NMR spectra were recorded on a JEOL delta-600 spectrometer, and chemical shifts were reported on the δ scale in ppm using the residual solvent as the internal standard for 1H (δ 7.26 ppm in CDCl3) and for 13C (δ 77.16 ppm in CDCl3) and BF3· OEt2 as the external reference for 11B (δ 0.00 ppm in CDCl3). Spectroscopic grade solvents were used for all spectroscopic studies without further purification. UV/visible absorption spectra were recorded on a Shimadzu UV-2550 spectrometer. Fluorescence spectra were recorded on a Shimadzu RF-5300PC spectrometer. Absolute fluorescence quantum yields were determined on a HAMAMATSU C9920-02S instrument. High-resolution atmospheric-pressure-chemical-ionization time-of-flight mass-spectroscopy (HR-APCI-TOF-MS) data were recorded on a BRUKER micrOTOF model using positive or negative mode. X-ray data were taken at −180 °C with a Rigaku XtaLAB P200 apparatus using a PILATUS 100 K/R two-dimensional detector with Cu Kα radiation (λ = 1.54187 Å). The structures were solved by direct methods (SIR-97) and refined by the SHELXL-97 program. Thin-layer chromatography (TLC) was performed with silica gel 60 F254. Preparative separations were performed by silica gel chromatography (Wako gel C-300). B-Tolyl(2,13-diiodo-5,10-bis(p-tolyl)subporphyrinato)boron(III) (6). A solution of 2,13-bis(pinacolatoboryl)subporphyrin 5 (150 mg, 196 μmol), N-iodosuccinimide (97.0 mg, 431 μmol), and CuI (82.1 mg, 431 μmol) in dry DMF (18 mL) and toluene (9 mL) was stirred at 80 °C. After 3 h, the reaction was quenched with water, and the product was extracted with ethyl acetate. The organic phase was washed with saturated NaHCO3 aqueous solution and brine and then dried over anhydrous Na2SO4. The solvent was removed under reduced pressure. The crude product was purified by silica gel chromatography (eluent CH2Cl2/n-hexane 1/3). A yellow fraction was collected and recrystallized from CH2Cl2/MeOH to give 6 (147 mg, 98%) as orange solids. 1 H NMR (600 MHz, CDCl3): δ (ppm) 8.59 (s, 1H, meso-H), 8.24 (s, 2H, β), 8.13 (s, 2H, β), 7.88 (d, J = 8.0 Hz, 4H, meso-Ar-ortho), 7.49 (d, J = 8.0 Hz, 4H, meso-Ar-meta), 6.17 (d, J = 8.0 Hz, 2H, B-Armeta), 4.57 (d, J = 8.0 Hz, 2H, B-Ar-ortho), 2.57 (s, 6H, meso-Ar-Me), and 1.79 (s, 3H, B-Ar-Me). 11B NMR (193 MHz, CDCl3): δ (ppm) − 15.8 (s, 1B); 13C NMR (150 MHz, CDCl3): δ (ppm) 144.4, 141.4, 141.0, 138.2, 135.7, 133.9, 133.2, 129.6, 129.2, 128.8, 127.2, 122.9, 120.7, 103.9, 81.0, 21.5, and 20.9. HRMS (APCI-TOF, positive mode): m/z 766.0423 (calcd for C36H2711BN3I2 766.0388 [M + H]+). UV−vis (in CH2Cl2): λ [nm] (ε [M−1 cm−1]) 316 (22000), 390 (136000), 476 (12000), 503 (7000). Fluorescence (in CH2Cl2, λex 390 nm): ΦF < 0.01. General Procedure for Preparation and Reaction of Subporphyrinyllithium. A solution of subporphyrin 6 (50 mg, 65.3 μmol) in dry THF (1.25 mL) was cooled to −80 °C under Ar. After 10 min, nBuLi (1.6 M solution in n-hexane, 0.13 mL, 208 μmol) was slowly added, and then the reaction mixture was stirred at −80 °C. After 1 h, D2O or DMF (about 0.2 mL) was added to the resulting solution. After being stirred for 1 h at room temperature, the reaction mixture was quenched with water, and the product was extracted with D

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Organometallics H NMR (600 MHz, CDCl3): δ (ppm) 10.20 (s, 1H, meso-H), 8.89 (d, J = 5.0 Hz, 2H, β-pyridine), 8.44 (s, 2H, β), 8.23 (d, J = 7.8 Hz, 2H, β-pyridine), 8.18 (s, 2H, β), 7.98 (d, J = 7.8 Hz, 4H, meso-Arortho), 7.86 (m, 2H, β-pyridine), 7.51 (d, J = 7.8 Hz, 4H, meso-Armeta), 7.31 (m, 2H, β-pyridine), 6.17 (d, J = 7.9 Hz, 2H, B-Ar-meta), 4.73 (d, J = 7.9 Hz, 2H, B-Ar-ortho), 2.58 (s, 6H, meso-Ar-Me), and 1.79 (s, 3H, B-Ar-Me). 11B NMR (193 MHz, CDCl3): δ (ppm) −15.8 (s, 1B). 13C NMR (150 MHz, CDCl3): δ (ppm) 154.5, 150.4, 140.9, 139.8, 137.7, 136.9, 135.8, 135.3, 134.5, 133.3, 129.5, 129.2, 129.1, 127.1, 127.0, 123.4, 122.3, 120.8, 120.0, 107.5, 21.5, and 20.9. HRMS (APCI-TOF, positive mode): m/z 668.2992 (calcd for C46H3511BN5 668.2988 [M + H]+). UV−vis (in CH2Cl2): λ [nm](ε [M−1 cm−1]) 316 (26000), 405 (121000), 488 (13000). Fluorescence (in CH2Cl2, λex 405 nm): λmax [nm] 562, ΦF = 0.04. Subporphyrin Pd Pincer Complex (3Pd). A solution of subporphyrin 3 (20.0 mg, 30.0 μmol), dichlorobis(acetonitrile)palladium(II) (8.6 mg, 33.1 μmol), and sodium acetate (2.7 mg, 32.9 μmol) in toluene (1.58 mL) was stirred at 80 °C under Ar. After 30 min, the solvent was removed under reduced pressure. The crude product was chromatographed on silica gel (eluent dichloromethane/ diethyl ether/methanol 1/1/0.03). A green fraction was collected and recrystallized from CH2Cl2/n-hexane to give 3Pd (14.4 mg, 59%) as black solids. 1 H NMR (600 MHz, CDCl3): δ (ppm) 10.08 (d, J = 6.0 Hz, 2H, β-pyridine), 8.21 (d, J = 7.8 Hz, 2H, β-pyridine), 8.13 (s, 2H, β), 8.05 (s, 2H, β), 7.91 (d, J = 7.8 Hz, 4H, meso-Ar-ortho), 7.87 (t, J = 8.3 Hz, 2H, β-pyridine), 7.50 (d, J = 7.8 Hz, 4H, meso-Ar-meta), 7.25 (m, 2H, β-pyridine), 6.22 (d, J = 8.0 Hz, 2H, B-Ar-meta), 4.91 (d, J = 8.0 Hz, 2H, B-Ar-ortho), 2.58 (s, 6H, meso-Ar-Me), and 1.80 (s, 3H, B-Ar-Me). 11 B NMR (193 MHz, CDCl3): δ (ppm) −14.9 (s, 1B). 13C NMR (150 MHz, CDCl3): δ (ppm) 156.8, 152.0, 142.0, 141.3, 138.6, 137.8, 136.0, 135.6, 135.5, 134.2, 133.0, 129.6, 129.2, 127.3, 123.2, 123.1, 121.7, 119.8, 116.2, 21.5, and 20.9. HRMS (APCI-TOF, negative mode): m/z 803.1602 (calcd for C46H3311BN5102Pd35Cl 803.1579 [M]−). UV−vis (in CH2Cl2): λ [nm] (ε [M−1 cm−1]) 417 (58000), 449 (35000), 501 (7000), 547 (6000), 592 (8000). Fluorescence (in CH2Cl2, λex 417 nm): ΦF < 0.01. Subporphyrin Pt Pincer Complex (3Pt). A solution of subporphyrin 3 (20.0 mg, 30.0 μmol), potassium tetrachloroplatinate(II) (13.7 mg, 33.0 μmol), and sodium acetate (2.7 mg, 32.9 μmol) in dry DMF (0.65 mL) and toluene (0.65 mL) was stirred at 100 °C under Ar. After 5 h, the solvent was removed under reduced pressure. The crude product was chromatographed on silica gel (eluent dichloromethane/diethyl ether/methanol 1/1/0.03). A green fraction was collected and recrystallized from ether/n-hexane to give 3Pt (12.0 mg, 45%) as black solids. 1 H NMR (600 MHz, CDCl3): δ (ppm) 10.13 (d, J = 5.5 Hz, 2H, β-pyridine), 8.16 (d, J = 6.8 Hz, 2H, β-pyridine), 8.00 (s, 2H, β), 7.98 (s, 2H, β), 7.88−7.86 (m, 6H, β-pyridine and meso-Ar-ortho), 7.48 (d, J = 7.8 Hz, 4H, meso-Ar-meta), 7.17 (t, J = 7.3 Hz, 2H, β-pyridine), 6.26 (d, J = 7.8 Hz, 2H, B-Ar-meta), 5.06 (d, J = 7.8 Hz, 2H, B-Arortho), 2.56 (s, 6H, meso-Ar-Me), and 1.82 (s, 3H, B-Ar-Me). 1B NMR (193 MHz, CDCl3): δ (ppm) −14.7 (s, 1B). 13C NMR (150 MHz, CDCl3): δ (ppm) 156.9, 153.4, 142.1, 141.2, 138.5, 137.6, 136.2, 135.5, 134.4, 133.5, 132.9, 129.5, 129.3, 127.4, 123.6, 123.1, 122.0, 119.0, 115.7, 104.3, 21.5, and 21.0. HRMS (APCI-TOF, negative mode): m/z 895.2157 (calcd for C46H3311BN5194Pt35Cl 895.2152 [M]−). UV−vis (in CH2Cl2): λ [nm] (ε [M−1 cm−1]): 309 (32000), 422 (46000), 466 (26000), 627 (9000). Fluorescence (in CH2Cl2, λex 422 nm): ΦF < 0.01. 1

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Coordinates of optimized geometries (XYZ) Coordinates of optimized geometries (XYZ) Accession Codes

CCDC 1436050, 1436052, and 1533351 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 by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Author

*E-mail for A.O.: [email protected]. ORCID

Atsuhiro Osuka: 0000-0001-8697-8488 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by JSPS KAKENHI Grant Numbers 25220802, 26620081, and 26810021. M.K. acknowledges a JSPS Fellowship for Young Scientists.

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REFERENCES

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.7b00130. NMR spectroscopic data, crystallographic data, UV/vis absorption and emission spectra, DFT calculations, and cyclic voltammograms (PDF) E

DOI: 10.1021/acs.organomet.7b00130 Organometallics XXXX, XXX, XXX−XXX

Article

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DOI: 10.1021/acs.organomet.7b00130 Organometallics XXXX, XXX, XXX−XXX