Article pubs.acs.org/Organometallics
Synthesis and Reactivity of Ruthenium Complexes Bearing ArsenicContaining Arsenic-Nitrogen-Arsenic-Type Pincer Ligand Yoshiaki Tanabe, Shogo Kuriyama, Kazuya Arashiba, Kazunari Nakajima, and Yoshiaki Nishibayashi* Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan S Supporting Information *
ABSTRACT: Dinuclear and mononuclear ruthenium complexes bearing an arsenic-containing arsenic-nitrogen-arsenic (ANA)-type pincer ligand are designed, prepared, and characterized by X-ray analyses. Both ruthenium complexes work as effective catalysts toward dehydrogenative transformations of alcohols.
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INTRODUCTION Recently, a series of tridentate chelating ligands that have been named “Pincer” have been applied to various transition metalcatalyzed transformations of organic molecules.1 Especially, phosphorus-containing pyridine-based PNP-type pincer ligands which coordinate to transition metals such as ruthenium, iridium, or palladium have been shown to catalyze dehydrogenation and related reactions.2 On the other hand, we have recently succeeded in constructing a new reaction system to convert molecular dinitrogen directly into ammonia catalyzed by a dinitrogen-bridged dimolybdenum complex, where tridentate PNP-type pincer ligand is introduced onto the molybdenum atoms and up to 52 equiv of ammonia have been produced based on the catalyst (26 equiv of ammonia based on the molybdenum atom) (Scheme 1).3−5 In this system, the
Chart 1. Molybdenum and Ruthenium Complexes with an ANA-Type Pincer Ligand: Introduction of Arsine Moieties to Pincer Ligand
Scheme 1. Molybdenum-Catalyzed Reduction of Molecular Dinitrogen into Ammonia under Ambient Conditions
choice and design of the ligands and their substituents to compromise the coordination sphere and to control their steric and electronic effects have been shown to be keys to the efficient coordination and activation of molecular dinitrogen. To expand our scope of designing pincer-type ligands, we next focused upon the use of an arsenic-containing arsenicnitrogen-arsenic (ANA)-type pincer ligand (Chart 1), where © 2014 American Chemical Society
Received: June 9, 2014 Published: September 9, 2014 5295
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phosphines in the PNP-type pincer ligand are substituted for arsines,6 because arsines are known to have similar coordination chemistry to phosphines but are also recognized to be more reluctant to oxidations, sterically bulkier, and poorer σ-donors and π-acceptors compared to phosphines, leading to contrasting steric and electronic effects on coordination spheres different from those of phosphines.7 In fact, we have synthesized a series of molybdenum−dinitrogen complexes bearing an arsenic-containing ANA-type pincer ligand 2,6bis[(di-tert-butylarsino)methyl]pyridine (tBuANA) which afford a stoichiometric amount of ammonia by the treatment with proton sources.6 This result prompted us to investigate the ability of the ANA-type pincer ligand, tBuANA, toward other transition metal complexes. Herein, we describe the preparation of a series of ruthenium complexes with an arsenic-containing ANA-type pincer ligand (Chart 1) and their catalytic activity toward acceptorless dehydrogenative transformations of alcohols. Typical results are described in this paper.
Figure 1. ORTEP drawing of 1a. Thermal ellipsoids are given at the 50% probability level. Hydrogen atoms and toluene molecules are omitted for clarity.
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RESULTS AND DISCUSSION Synthesis and Characterization of Dinitrogen-Bridged Diruthenium Complex and Mononuclear Ruthenium Hydridochloride Carbonyl Complex. When a toluene suspension of [RuCl2(PPh3)3] and 1.2 equiv of tBuANA was heated at 100 °C for 20 h under an atmospheric pressure of dinitrogen, dissociation of PPh3 was observed by 31P NMR spectrum, and the dinitrogen-bridged diruthenium complex [{RuCl2(tBuANA)}2(μ-N2)] (1a) was isolated in 29% yield (Scheme 2). 1H NMR spectrum of 1a exhibits a pair of triplet
and cis-[Mo(N2)2(tBuANA)] units are bridged by one dinitrogen ligand coordinated to molybdenum atoms in an end-on fashion to form a specific molecular configuration different from that of trans,trans-[{Mo(N2)2(tBuPNP)}2(μN2)] (Chart 1).3a,6 On the other hand, the bridging N(1)− N(2) bond distance of 1.108(5) Å (Table 1) in 1a is only 0.010 Å longer than that in free dinitrogen (1.0977 Å)9 and is slightly shorter than those reported for dinitrogen-bridge diruthenium(II) complexes (1.110−1.135 Å).8,10 This result suggests that the weaker electron-donating ability of the ANA-type pincer ligand weakens the π-back-donation of ruthenium atoms to dinitrogen ligand. In a similar reaction to the formation of 1a, mononuclear ruthenium hydridochloride carbonyl complex [RuHCl(CO)(tBuANA)] (2a) was obtained in 69% isolated yield by heating a toluene suspension of [RuHCl(CO)(PPh3)3] and 1.2 equiv of t BuANA at 100 °C for 20 h (Scheme 3). The 1H NMR spectrum of 2a exhibits a singlet peak at δ −15.4 assignable to the hydride coordinated to the ruthenium atom. Furthermore, two doublet resonances at δ 3.81 and 2.88 with JHH = 14.6 Hz due to methylene protons and two singlet resonances at δ 1.51 and 1.13 due to tert-butyl protons clearly indicates lack of a symmetry plane involving the ruthenium atom and the ANAtype pincer ligand. The values of the IR absorptions of 2a at 2031 and 1917 cm−1 assignable to the Ru−H and CO stretches, respectively, are similar to those observed at 2052 and 1906 cm−1 for the corresponding mononuclear ruthenium hydridochloride carbonyl complex [RuHCl(CO)(tBuPNP)] (2b)11 or those observed at 2075 and 1915 cm−1 for [RuH(CO)(NCMe)(tBuPNP)]PF6.12 The detailed molecular structure of 2a was finally determined by an X-ray analysis (Figure 2, Table 2), which indicates that the ruthenium center adopts a well-known octahedral coordination geometry including the ANA-type pincer ligand, hydride, chloride, and carbonyl ligands, where the carbonyl ligand is bound to the Ru(II) center trans to the pyridine nitrogen atom with the hydride and chloride ligands located trans to each other. Catalytic Dehydrogenation and Dehydrogenative Coupling Using Ruthenium Complexes with the ANAType Pincer Ligand as Catalysts. Milstein and co-workers previously reported that the ruthenium complexes bearing PNP-type pincer ligands such as 1b and 2b catalyzed the dehydrogenation of alcohols8,13 and dehydrogenative coupling reactions between alcohols and amines to afford imines.11,14 In
Scheme 2. Preparation of the Dinitrogen-Bridged Diruthenium Complex 1a
and doublet resonances assignable to the pyridine protons at δ 7.05 and 6.94, respectively, with two singlet resonances at δ 3.07 and 1.18 assignable to methylene and tert-butyl protons, respectively, suggesting that 1a was obtained as the sole product in contrast to the reaction of [RuCl2(PPh3)3] with the PNP-type pincer ligand 2,6-bis[(di-tert-butylphosphino)methyl]pyridine (tBuPNP) to afford a mixture of the mononuclear ruthenium−dinitrogen complex [RuCl2(N2)(tBuPNP)] and the dinitrogen-bridged diruthenium complex [{RuCl2(tBuPNP)}2(μ-N2)] (1b).8 The molecular structure of 1a was unambiguously determined by an X-ray analysis as depicted in Figure 1, which demonstrated that 1a has a symmetric structure where two trans-[RuCl2(tBuANA)] units are bridged by one dinitrogen ligand coordinated to ruthenium atoms in an end-on fashion trans to the pyridine nitrogen with two ruthenium atoms separated at 5.0258(5) Å. The two coplanar ruthenium tBuANA units are twisted around the almost linear Ru(1)−N(1)−N(2)−Ru(2) axis nearly perpendicularly with a dihedral angle of 88.76(1)° comparable to the value observed for 1b (86.1°).8 This is in contrast to the dinitrogen-bridged dimolybdenum complex trans,cis-[{Mo(N2)2(tBuANA)}2(μ-N2)], where trans-[Mo(N2)2(tBuANA)] 5296
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Table 1. Selected Bond Lengths (Å) and Angles (deg) for 1a·2C7H8 Ru(1)−As(1) Ru(1)−As(2) Ru(1)−Cl(1) Ru(1)−Cl(2) Ru(1)−N(1) Ru(1)−N(3) N(1)−N(2) As(1)−Ru(1)−As(2) As(1)−Ru(1)−Cl(1) As(1)−Ru(1)−Cl(2) As(1)−Ru(1)−N(1) As(1)−Ru(1)−N(3) As(2)−Ru(1)−Cl(1) As(2)−Ru(1)−Cl(2) As(2)−Ru(1)−N(1) As(2)−Ru(1)−N(3) Cl(1)−Ru(1)−Cl(2) Cl(1)−Ru(1)−N(1) Cl(1)−Ru(1)−N(3) Cl(2)−Ru(1)−N(1) Cl(2)−Ru(1)−N(3) N(1)−Ru(1)−N(3) Ru(1)−N(1)−N(2)
2.4770(6) 2.4795(7) 2.4232(12) 2.4064(12) 1.965(4) 2.092(3) 1.108(5) 162.499(18) 90.51(4) 89.28(4) 98.26(11) 81.38(10) 90.71(4) 89.48(4) 99.20(11) 81.16(10) 179.79(5) 89.93(10) 90.26(9) 90.09(10) 89.71(9) 179.59(14) 178.7(4)
Ru(2)−As(3) Ru(2)−As(4) Ru(2)−Cl(3) Ru(2)−Cl(4) Ru(2)−N(2) Ru(2)−N(4)
2.4745(7) 2.4760(7) 2.4173(14) 2.4148(14) 1.953(4) 2.091(4)
As(3)−Ru(2)−As(4) As(3)−Ru(2)−Cl(3) As(3)−Ru(2)−Cl(4) As(3)−Ru(2)−N(2) As(3)−Ru(2)−N(4) As(4)−Ru(2)−Cl(3) As(4)−Ru(2)−Cl(4) As(4)−Ru(2)−N(2) As(4)−Ru(2)−N(4) Cl(3)−Ru(2)−Cl(4) Cl(3)−Ru(2)−N(2) Cl(3)−Ru(2)−N(4) Cl(4)−Ru(2)−N(2) Cl(4)−Ru(2)−N(4) N(2)−Ru(2)−N(4) Ru(2)−N(2)−N(1)
163.77(3) 91.28(4) 89.13(4) 97.25(10) 82.14(11) 89.26(4) 89.97(4) 98.96(10) 81.65(11) 178.57(5) 90.17(11) 89.07(12) 91.14(11) 89.63(12) 179.01(16) 178.7(4)
every Ru−Cl bond) in 1,4-dioxane at 100 °C for 24 h in a closed system equipped with a rubber balloon capable of releasing dihydrogen gas (Table 3).8 When the dinitrogenbridged diruthenium complex with the ANA-type pincer ligand 1a was used as a catalyst, the dehydrogenation of the alcohol took place to afford acetophenone in 15% yield, corresponding to a turnover number of 15 based on the ruthenium atom (Table 3, run 1). The yield of acetophenone almost doubled (32%) when the mononuclear ruthenium hydridochloride carbonyl complex with the ANA-type pincer ligand 2a was used as a catalyst (Table 3, run 2). The yields of acetophenone were much higher when ruthenium complexes with the PNPtype pincer ligand 1b and 2b were used as catalysts (Table 3, runs 3 and 4). We have also examined the catalytic dehydrogenative coupling reaction between benzylalcohol and benzylamine to afford N-benzylidenebenzylamine (imine), where N-benzylbenzamide (amide) and benzyl benzoate (ester) can be formed as byproducts.11,14,15 The reaction was carried out in the presence of a catalyst (0.2 mol % for the dinuclear 1a and 1b, 0.4 mol % for the mononuclear 2a and 2b; i.e., 0.4 mol % for Ru atom) and NaOiPr as a base (4 equiv to the dinuclear 1a and 1b, 1 equiv to the mononuclear 2a and 2b; i.e., an equivalent of base for every Ru−Cl bond) in toluene under reflux conditions for 24 h in a closed system equipped with a rubber balloon capable of releasing dihydrogen gas (Table 4). When 1a was used as a catalyst, imine was almost exclusively obtained in 60% yield, corresponding to a turnover number of 151 (Table 4, run 1). The yield of imine was lower (46%) when 2a was used as a catalyst (Table 4, run 2). In contrast, the yields of imine were even higher (more than 70%) when 1b and 2b were used as catalysts (Table 4, runs 3 and 4), while yields of byproducts were much lower (less than 1%) when 1a was used as a catalyst (Table 4, run 1). Indeed, when the reaction was carried out for 72 h using 1a as a catalyst, imine was still obtained almost exclusively in 79% yield (Table 4, run 5).
Scheme 3. Preparation of the Mononuclear Ruthenium Hydridochloride Carbonyl Complex 2a
Figure 2. ORTEP drawing of 2a. Thermal ellipsoids are shown at the 50% probability level. Hydrogen atoms except for the hydride H(1) are omitted for clarity.
order to evaluate the effect of arsines on the reactivity of ruthenium centers, we next have examined the catalytic activity of the newly obtained ruthenium complexes with the ANA-type pincer ligand. The catalytic dehydrogenation of 1-phenylethanol into acetophenone was carried out in the presence of a catalyst (0.5 mol % for the dinuclear 1a and 1b, 1.0 mol % for the mononuclear 2a and 2b; i.e., 1.0 mol % for Ru atom) and NaOiPr as a base (4 equiv to the dinuclear 1a and 1b, 1 equiv to the mononuclear 2a and 2b; i.e., an equivalent of base for 5297
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Table 2. Selected Bond Lengths (Å) and Angles (deg) for 2a Ru(1)−As(1) Ru(1)−Cl(1) Ru(1)−C(1) O(1)−C(1) As(1)−Ru(1)−As(2) As(1)−Ru(1)−N(1) As(1)−Ru(1)−H(1) As(2)−Ru(1)−N(1) As(2)−Ru(1)−H(1) Cl(1)−Ru(1)−C(1) N(1)−Ru(1)−C(1) As(2)−Ru(1)−H(1)
2.4062(5) 2.5688(10) 1.821(4) 1.152(6) 160.03(2) 83.12(8) 85.3(16) 81.22(9) 82.8(16) 96.58(13) 178.18(14) 82.8(16)
Table 3. Catalytic Dehydrogenation of rac-1-Phenylethanol to Afford Acetophenone
runa
cat.
yield of ketone (%)b
TON based on Ru atomc
1 2 3 4
1a 2a 1b 2b
15 32 33 56
15 32 33 56
Ru(1)−As(2) Ru(1)−N(1) Ru(1)−H(1)
2.4090(6) 2.186(3) 1.61(4)
As(1)−Ru(1)−Cl(1) As(1)−Ru(1)−C(1) As(2)−Ru(1)−Cl(1) As(2)−Ru(1)−C(1) Cl(1)−Ru(1)−N(1) Cl(1)−Ru(1)−H(1) N(1)−Ru(1)−H(1) Ru(1)−C(1)−O(1)
99.48(3) 96.03(14) 91.47(3) 99.26(15) 85.16(8) 173.8(16) 91.5(14) 177.7(4)
worked as less effective catalysts than those bearing PNP-type pincer ligand 1b and 2b under the same reaction conditions. For example, a possible reaction pathway for the dehydrogenation of 1-phenylethanol catalyzed by 2a is shown in Chart 2.2,16 The exact reason has not yet been cleared until now; Chart 2. Possible Reaction Pathway for the Dehydrogenation of 1-Phenylethanol Using 2a as a Catalyst
a
Reaction conditions: catalyst 0.01 mmol of 1a or 1b, 0.02 mmol of 2a or 2b; 4 equiv of NaOiPr for 1a or 1b, 1 equiv of NaOiPr for 2a or 2b; rac-1-phenylethanol 2.0 mmol, 1,4-dioxane 1.0 mL. bDetermined by 1 H NMR using C6Me5H as an internal standard. cNumber of moles of rac-1-phenylethanol consumed to yield acetophenone per ruthenium atom.
Table 4. Catalytic Dehydrogenative Coupling of Benzylalcohol and Benzylamine to Afford NBenzylidenebenzylamine
run
a
1 2 3 4 5d
cat.
yield of imine (%)b
yield of amide (%)b
yield of ester (%)b
conversion of alcohol (%)b
1a 2a 1b 2b 1a
60 46 70 72 79
trace 12 4 11 0.9
0.3 15 17 14 1.3
61 73 91 97 81
however, we consider that the dearomatized species A, which is formed via deprotonation of 2a with base, may play an important role to promote the both catalytic transformations of alcohols. The presence of arsine instead of phosphine in the pincer ligand may have lowered the reaction rate to form the dearomatized species like A, where the arsine attached to the deprotonated methylene group unit may work as a weaker πacceptor compared to the phosphine known to be a stronger πacceptor as well as a better stabilizer for the formation of the dearomatized structure of A′, which has been isolated via the deprotonation of 2b with base and also shows high catalytic activity toward dehydrogenative coupling of alcohols and amines to afford imines.11
TON based on Ru atomc 151 114 176 181 197
(152) (184) (228) (242) (203)
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a
Reaction conditions: A mixture of 0.01 mmol of 1a or 1b (0.02 mmol of 2a or 2b), 4 equiv of NaOiPr for 1a or 1b (1 equiv of NaOiPr for 2a or 2b), 5.02 mmol of benzylalcohol, 5.04 mmol of benzylamine in 1.0 mL of toluene was refluxed for 24 h unless otherwise specified. b Determined by 1H NMR using C6Me5H as an internal standard. c Number of moles of benzylalcohol consumed to yield Nbenzylidenebenzylamine per ruthenium atom. Number of moles of benzylalcohol consumed to yield N-benzylidenebenzylamine, Nbenzylbenzamide, and benzyl benzoate are given in parentheses. d Refluxed for 72 h.
CONCLUSION We have designed, synthesized, and characterized the dinitrogen-bridged diruthenium complex and the mononuclear ruthenium hydridochloride carbonyl complex bearing an arsenic-containing ANA-type pincer ligand. These complexes are found to work as effective catalysts toward dehydrogenation and dehydrogenative coupling reactions of alcohols. Furthermore, 1a catalyzes dehydrogenative coupling of benzylalcohol and benzylamine to form imine rather selectively compared to the corresponding ruthenium complexes bearing the PNP-type pincer ligand. It must be noted that both 1a and 2a are rare examples of transition metal complexes bearing arsenic as a coordination atom to work as catalysts17 and are also
As shown above, the results of both dehydrogenation and dehydrogenative coupling reaction indicate that the ruthenium complexes bearing the ANA-type pincer ligand 1a and 2a 5298
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collected for the 2θ range of 5° to 55°. Intensity data were corrected for numerical (NUMABS) absorptions and for Lorentz and polarization effects and for secondary extinction (coefficient, 77 (12) for 2a).19 The structure solution and refinements were carried out by using CrystalStructure package.20 The positions of non-hydrogen atoms were determined by direct methods (SIR97 for 1a·2C7H8; SHELXS97 for 2a)21 and subsequent Fourier syntheses and were refined on F02 with all the unique reflections by full-matrix leastsquares with anisotropic thermal parameters except for the toluene carbon atoms which were solved isotropically as rigid groups in 1a· 2C7H8. All the hydrogen atoms were placed at the calculated positions with fixed isotropic parameters except for the toluene hydrogen atoms whose positions were not refined in 1a·2C7H8 and for the hydride atom (H(1)) which was determined on a peak in the difference Fourier maps and further refined isotropically in 2a. Goodness of fit indicator [Σw(F02 − Fc2)2/(Nobs − Nparams)]1/2 was all refined to the value of 1.000. Neutral atomic scattering factors and the values for Δf ′, Δf ″, and for the mass attenuation coefficients were taken from ref 22 with the inclusion of anomalous dispersion effects in Fc. Molecular structures of 1a·2C7H8 and 2a are depicted in Figures 1 and 2, and their metric features are summarized in Tables 1 and 2. Details of the crystals and data collection parameters are summarized in Table S1 of the Supporting Information.
comparable with the corresponding transition metal complexes bearing phosphorus as coordination atom in terms of their structures and reactivities. We believe that the substitution of arsenic for phosphorus can be a markworthy choice of the substituent effect to control catalytic activity. Further studies on the preparation and reactivity of related early and late transition metal complexes bearing pincer ligands including other ANAtype pincer ligands are currently under way.
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EXPERIMENTAL SECTION
General Methods. All manipulations were carried out under an atmosphere of dry dinitrogen in a VAC glovebox or using standard Schlenk techniques. THF, diethyl ether, toluene, and hexane were purified by passing through a purification system (Glass Contour). 2,6Bis[(di-tert-butylarsino)methyl]pyridine (tBuANA),6 2,6-bis[(di-tertbutylphosphino)methyl]pyridine (tBuPNP),18 [{RuCl2(tBuPNP)}2(μ-N2)],8 and [RuHCl(CO)(tBuPNP)]11 were prepared according to the literature procedures. 1-Phenylethanol, benzylalcohol, and benzylamine were dried and distilled before use. All the other dry solvents and reagents were obtained from commercial sources and used without further purification. 1H and 31P NMR spectra were recorded on a JEOL Excalibur 270 spectrometer (1H, 270 MHz; 31P, 109 MHz) at room temperature and were referenced to residual solvents (for 1H NMR) or an external standard (85% H3PO4 for 31P NMR). Elemental analyses were performed at the Microanalytical Center of The University of Tokyo or on an Exeter Analytical CE-440 elemental analyzer. IR spectra were recorded on a JASCO FT/IR 4100 Fourier transform infrared spectrophotometer. Preparation of [{RuCl2(tBuANA)}2(μ-N2)] (1a). A suspension of [RuCl2(PPh3)3] (191.5 mg, 0.199 mmol) and tBuANA (118.3 mg, 0.245 mmol) in toluene (5 mL) was stirred at 100 °C for 20 h under an atmospheric pressure of dinitrogen. The resultant dark red solution was dried in vacuo and washed with hexane, and the residue was recrystallized from toluene−hexane to afford efflorescent orange needle crystals of [{RuCl2(tBuANA)}2(μ-N2)]·2C7H8 (1a·2C7H8), which were further dried in vacuo to lose 1 equiv of toluene to give a yellow powder of 1a·C7H8 (41.6 mg, 0.029 mmol, 29% isolated yield). 1 H NMR (C6D6, δ): 7.05 (t, J = 8.5 Hz, 2H, 4-H of C5H3N), 6.94 (d, J = 8.5 Hz, 4H, 3- and 5-H of C5H3N), 3.07 (s, 8H, CH2), 1.18 (s, 72H, t Bu). Anal. Calcd for C53H94As4Cl4N4Ru2: C, 44.49; H, 6.62; N, 3.92. Found: C, 44.75; H, 7.12; N, 3.58. Preparation of [RuHCl(CO)(tBuANA)] (2a). A suspension of [RuHCl(CO)(PPh3)3] (95.5 mg, 0.100 mmol) and tBuANA (60.3 mg, 0.125 mmol) in toluene (5 mL) was stirred at 100 °C for 20 h. The resultant red solution was dried in vacuo and washed with hexane, and the residue was recrystallized from benzene−hexane to afford [RuHCl(CO)(tBuANA)] (2a) as yellow plate crystals (45.0 mg, 0.069 mmol, 69% isolated yield). 1H NMR (C6D6, δ): 6.79 (t, J = 7.7 Hz, 1H, 4-H of C5H3N), 6.54 (d, J = 7.7 Hz, 2H, 3- and 5-H of C5H3N), 3.81 (d, J = 14.6 Hz, 2H, CH2), 2.88 (d, J = 14.6 Hz, 2H, CH2), 1.51 (s, 18H, tBu), 1.13 (s, 18H, tBu), −15.4 (s, 1H, RuH). IR (KBr, cm−1): 2031 (m, RuH), 1917 (s, CO). Anal. Calcd for C24H44As2ClNORu: C, 44.42; H, 6.83; N, 2.16. Found: C, 44.60; H, 6.86; N, 2.08. Typical Procedure for the Catalytic Dehydrogenation of Alcohols. To a mixture of 1a·C7H8 (14.3 mg, 0.010 mmol) and NaOiPr (3.3 mg, 0.040 mmol) in 1,4-dioxane (1 mL) was added 1phenylethanol (245 mg, 2.00 mmol), and the mixture was heated at 100 °C for 24 h under an atmosphere of dinitrogen in a reflux condenser equipped with a rubber balloon capable of releasing dihydrogen gas. After cooling, the amount of acetophenone was analyzed by 1H NMR spectrum using pentamethylbenzene as an internal standard as well as by gas chromatography. Detailed results are summarized in Tables 3 and 4. X-ray Crystallography. Diffraction data for [{RuCl2(tBuANA)}2(μ-N2)]·2C7H8 (1a·2C7H8) and [RuHCl(CO)(tBuANA)] (2a) were collected at −75 °C on a Rigaku RAXIS RAPID imaging plate area detector with graphite-monochromated Mo−Kα radiation (λ = 0.71075 Å) with Varimax optics. Reflections were
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ASSOCIATED CONTENT
* Supporting Information S
Summarized crystallographic data of 1a·2C7H8 and 2a (Table S1) and CIF files for all these compounds. This material is available free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported by Grants-in-Aid for Scientific Research (Grant Nos. 26410110, 26288044, 26620075, and 26105708) from the Ministry of Education, Culture, Sports, Science and Technology of Japan (JSPS) and the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT). We also thank the Research Hub for Advanced Nano Characterization at The University of Tokyo.
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REFERENCES
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Organometallics
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dx.doi.org/10.1021/om5006116 | Organometallics 2014, 33, 5295−5300
