Picolinamide as a Directing Group on Metal Sandwich Compounds

Apr 20, 2017 - (11i, 11l) However, catalytic C–H activation using a removable directing group has remained a challenge on metal sandwich compounds, ...
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Picolinamide as a Directing Group on Metal Sandwich Compounds: sp2 C−H Bond Activation and sp3 C−H Bond Oxidation Susanta Hazra, Mayukh Deb, Jatinder Singh, and Anil J. Elias* Department of Chemistry, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110016, India S Supporting Information *

ABSTRACT: Palladium catalyzed bis-arylations, -alkylations, and -allylations on the Cp ring of iron and cobalt sandwich compounds have been achieved using the bidentate picolinamide directing group. This directing group along with catalytic Pd(OAc)2 was found to be highly efficient for C−H functionalization, giving up to 87% yields. The palladacyclic intermediate for the C−H activation of the Cp ring has been isolated and structurally characterized for the cobalt sandwich compound [η5C5H5]Co(η4-C4Ph4). Attempted C−H annulation reactions using picolinamide-derived sandwich compounds did not yield the expected annulated products and instead oxidized the Cp- and picolinamide-bound CH2 unit to aldehydes. Detailed studies on this novel and unprecedented oxidation indicated that this happens only with the assistance of the picolinamide directing group. We have also shown that the sp2 C−H functionalization and the sp3 C−H oxidation can be effectively carried out as a one-pot reaction.

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workers in 2007. 11a In addition, intermolecular C−H functionalization of ferrocene derivatives was reported by using a nonremovable directing group.11b,h Recently, palladiumcatalyzed intramolecular C−H arylation of ferrocene derivatives was reported separately by You, Gu, and Liu using external ligands.11i,l However, catalytic C−H activation using a removable directing group has remained a challenge on metal sandwich compounds, with only 8-aminoquinoline showing some promise.12 Therefore, the development of new methodologies for functionalization of metal sandwich compounds using readily available, inexpensive, and removable directing groups is considered to be highly desirable. The picolinamide directing group, first introduced by Daugulis in 2005, demonstrated excellent directing abilities that ensured a range of transformations on conventional aromatic as well as aliphatic organic compounds.13 In addition, picolinamide-directed carbon−heteroatom bond formations have also been achieved.14 However, no attempts have been made to introduce a picolinamide directing group on metal sandwich compounds for C−H bond activation. Herein, we present a Pd-catalyzed sp2 C−H arylation and alkylation of iron and cobalt sandwich compounds using picolinamide as the directing group (Scheme 1). We also demonstrate the easy removal of the picolinamide directing group by two methods: mainly, reductive cleavage by Zn/HCl and by hydrolysis using NaOH in ethanol. More interestingly, we report for the first time a novel methodology to remove the directing group via oxidation of an sp3 C−H bond to an

INTRODUCTION There has been a sustained interest in developing methodologies for multifunctionalization of the Cp ring of ferrocene due to numerous applications of such derivatives in pharmaceuticals,1 biosensors,2 and dendrimers3 as well as in catalysis,4 electrochemistry, and materials science.5 Recently, the design and development of ferrocene-based electroactive materials such as semiconductors, conducting polymers, and charge storage materials have been carried out.6 Due to its high air and moisture stability and ease of synthesis, the cobalt sandwich compound [η5-C5H5]Co(η4-C4Ph4) has become an excellent competitor to ferrocene and other sandwich compounds in many applications, especially in the design of chiral ligands for asymmetric catalysis.7 In addition, the electron donor capability of [η5-RCp]Co(η4 -C4Ph4) derivatives has also been utilized for realizing new luminescent materials and photovoltaic devices.8 The conventional approaches for functionalization of ferrocene include standard Friedel−Crafts and Vilsmeier reactions and the use of organolithium and organomercury reagents.9 These methods have some limitations, such as low functional group tolerance and requirement of excess reagent (RLi, RHg).11d,12b In the case of the sterically hindered cobalt sandwich compound [η5-C5H5]Co(η4-C4Ph4), even these methods were not found to be suitable for functionalization of the Cp ring.9j In the last two decades, transition-metalcatalyzed and directing-group-assisted highly site selective C−H functionalization has become a powerful methodology for many significant transformations in organic synthesis.10 These C−H functionalization studies have been extended to ferrocene and ruthenocene following the pioneering work by You and co© XXXX American Chemical Society

Received: February 23, 2017

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DOI: 10.1021/acs.organomet.7b00143 Organometallics XXXX, XXX, XXX−XXX

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Organometallics Scheme 1. Directing-Group-Assisted C−H Bond Activation of Iron and Cobalt Sandwich Compounds

Figure 1. Molecular structure of compound 1. Thermal ellipsoids are drawn at the 30% probability level. Hydrogen atoms have been omitted for clarity.

Scheme 3. Synthesis of Palladacycle Intermediates for the Cp C−H Activation of the Picolinamide-Derived Cobalt Sandwich Compound

membered palladacycle 3. Although spectral studies such as 1H and 13C NMR and IR on palladacycle 3 indicated the presence of CH3CN as a ligand, its identity could not be verified by X-ray diffraction studies. On reaction of palladacycle 3 with an equimolar amount of 3-bromopyridine, the new palladacycle 4 was obtained whose crystal structure indicated the presence of 3-bromopyridine as the fourth ligand in the square-planar palladium center (Figure 2).

aldehyde. To the best of our knowledge, this represents an unprecedented use of a picolinamide directing group for the oxidation of an sp3 CH2 unit bound to the Cp ring of metal sandwich compounds.

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RESULTS AND DISCUSSION The acyl chloride derivative of picolinic acid was prepared and reacted with the corresponding aminomethyl derivative of iron and cobalt sandwich compounds, which resulted in the formation of picolinamide-derived metal sandwich compounds in 76−82% yields (Scheme 2). These are highly air and Scheme 2. Synthesis of Picolinamides Based on Iron and Cobalt Sandwich Compoundsa

Figure 2. Molecular structure of compound 4. Thermal ellipsoids are drawn at the 30% probability level. Hydrogen atoms have been omitted for clarity.

a

A reaction of the palladacycle 3 with methyl iodide at 80 °C in dichloroethane as solvent gave the bis-methylated product 4a in 18% yield. However, when the solvent was changed to tertamyl alcohol, the yield of 4a was found to increase to 86%. This observation made us attempt the C−H activation reaction by using catalytic amounts of Pd(OAc)2. It was observed that 20 mol % of Pd(OAc)2 gave 4a with a maximum yield of 79%. The effect of reaction parameters was also optimized (Table S1 in the Supporting Information). On the basis of isolated yields, it was observed that tert-amyl alcohol was the most appropriate solvent for the reaction with Cs2CO3 as base at 80 °C (Scheme

Isolated yields are given.

moisture stable compounds and are soluble in many polar organic solvents. The cobalt sandwich derived picolinamide 1 was also structurally characterized (Figure 1). To determine the possibility of C−H activation of the Cp ring using the picolinamide directing group, we carried out the reaction of compound 1 with an equimolar amount of palladium acetate in a mixture of acetic acid and acetonitrile at 60 °C (Scheme 3). This resulted in the formation of the fiveB

DOI: 10.1021/acs.organomet.7b00143 Organometallics XXXX, XXX, XXX−XXX

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found to be unreactive under the optimized reaction conditions. 2-Fluoroiodobenzene did react but gave poor yields of the product 5i even after the reaction was carried out for 30 h (Chart 1). The syntheses of Cp-bis-alkylated iron and cobalt sandwich compounds have also been successfully carried out, the details of which are given in Chart 1. The compounds 4a and 5e were also structurally charecterized, and their structures are shown in Figures 3 and 4, respectively.

4). In the case of arylation, we observe that slightly better yields are obtained by increasing the reaction temperature to 100 °C: Scheme 4. Optimization of Reaction Conditions for C−H Functionalization

e.g., for 4d (87%). The reaction of palladacycle intermediates 3 and 4 with 4-iodoanisole also gave the bis-arylated product 4d in 90% and 84% yields, respectively. We were keen to explore the substrate scope for this C−H activation reaction. The reaction was found to work well with electron-rich iodoarenes as well as electron-poor iodoarenes and showed good tolerance toward functional groups present on the iodoarenes (Scheme 5). It was also observed that Scheme 5. Removal of Picolinamide Directing Group

Figure 3. Molecular structure of compound 4a. Thermal ellipsoids are drawn at the 30% probability level. Hydrogen atoms have been omitted for clarity.

iodoarenes were more suitable than bromoarenes, as a reaction using 4-bromoiodobenzene gave exclusively 4-bromo-substituted products (4e, 5e). Both meta- and para-substituted iodoarenes gave the bis-arylated products in moderate to good yields (Chart 1). It was observed that monosubstituted products are also formed in the reaction, but in very low yields (∼2%). On the other hand, substituted iodoarenes having ortho substituents such as OMe, NO2, and CO2Me were Chart 1. Substrate Scope with Regard to Alkyl and Aryl Iodides for the C−H Functionalization Reaction Given in Scheme 4 Figure 4. Molecular structure of compound 5e. Thermal ellipsoids are drawn at the 30% probability level. Hydrogen atoms have been omitted for clarity.

Two different methods were attempted for removing the picolinamide directing group after C−H functionalization. Selected examples of α,α-bis-alkylated and α,α-bis-arylated sandwich compounds were treated with (A) Zn with 1.5 M HCl at room temperature and (B) NaOH in ethanol at 80 °C.13a,14f,h The removal of picolinamide groups was found to readily occur, giving the substituted parent aminomethyl derivatives in 62−90% yield (Scheme 5). The Zn/HCl method gave better yields in comparison to the conventional NaOH/ EtOH method. C

DOI: 10.1021/acs.organomet.7b00143 Organometallics XXXX, XXX, XXX−XXX

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With a view to see whether both sp2 C−H bond functionalization and sp3 C−H bond oxidation could be carried out as a one-pot reaction, we performed C−H activation reactions with the picolinamides 1 and 2 using Pd(OAc)2 in tert-amyl alcohol under the optimized reaction conditions. After completion of the sp2 C−H bond functionalization, which was monitored by TLC, [RuCl2(p-cym)]2 and Cu(OAc)2 were added to the same reaction mixture and it was further heated to 80 °C for 10−12 h. Isolation and purification of the crude products by coloumn chromatography afforded bis-substituted aldehydes in 35−55% yields (Scheme 8). The molecular structure of the α,α-bis-methylated aldehyde of cobalt sandwich compound 8c was also determined by single-crystal X-ray diffraction studies and is shown in Figure 5. Mechanism for the C−H Functionalization of Metal Sandwich Compounds. A possible mechanism for bisarylation of picolinamide-based iron and cobalt sandwich compounds is depicted in Scheme 9. The presence of the picolinamide group has been found to be essential for the coordination of palladium with the substrates for C−H functionalization of the Cp ring. The coordination of Pd(II) through the nitrogen atom followed by elimination of AcOH results in the formation of intermediate I.12,13a In the presence of appropriate solvent and base, the Cp C−H bond in the vicinity of the Pd(II) center becomes activated, which results in the formation of palladacycle intermediate II.12,13a Next, oxidative addition of aryl iodide leads to the Pd(IV) intermediate III. Reductive elimination generates Pd(II) with transfer of the aryl group to the Cp ring (IV). C−H bond activation of the mono-aryl-substituted Cp ring followed by base-assisted elimination of HI and oxidative addition of a second molecule of aryl iodide leads to the Pd(IV) intermediate (VI).13g Repetition of the steps leads to the formation of the bis-arylated products. Mechanism for sp3 C−H Bond Oxidation. To investigate the possible reaction mechanism of the sp3 C−H bond oxidation, we have carried out a few control experiments, which are shown in Scheme 10. Since single-electron transfer (SET) is a possible step in the sp3 C−H oxidation reaction, we verified this possibility by the addition of a radical inhibitor. When compounds 1 and 2 were treated with 2,2,6,6-tetramethylpiperidine oxide (TEMPO) under the optimized reaction conditions, the yields of the aldehydes were found to decrease drastically, indicating that the reaction probably proceeds by a free radical process. Similar studies using TEMPO on C−C coupling reactions involving picolinamide-derived amino acids also showed drastic reduction in the yields.18,19 A picolinamide directing group does play a significant role in the oxidation reaction, as both the aminomethyl derivative and the benzamide derivative of metal sandwich compounds were found to be unreactive for the oxidation reaction under identical conditions (Scheme 10). On the basis of our observations and related studies from other groups,17−19 a possible catalytic cycle has been proposed, as shown in Scheme 11. First, a redox reaction take place in which Cu2+ oxidizes the Ru2+ complex to Ru3+ and itself becomes reduced to Cu+.17 Next, Ru3+ is coordinated with picolinamide to yield the intermediate IM1.18 After that, Cu+ abstracts an electron from C−H bond of IM1 to form the radical intermediate IM2. Subsequently, the radical species IM2 undergoes an intramolecular single-electron transfer (SET) to afford the iminium intermediate IM3, which undergoes hydrolysis to give the corresponding aldehydes 8 and 9.19

Carretero and co-workers in 2015 effectively carried out C− H olefination/annulation on aryl picolinamides using [RhCp*Cl2]2 along with Cu(OAc)2 and alkynes.15 Under similar reaction conditions but by using [RuCl2(p-cym)]2 with benzyl amine as the substrate, Urriolabeitia and co-workers also successfully carried out an alkyne annulation reaction.16 With a view to exploring an analogous alkyne annulation on our metal sandwich derived picolinamides, we have carried out a reaction of picolinamide 2 with diphenylacetylene by using [RuCl2(pcym)]2 as the catalyst along with Cu(OAc)2. Quite surprisingly, instead of formation of the annulated/olefinated product, we observed the formation of a metal sandwich aldehyde as the only product of this reaction. The reaction clearly indicated that the sp3 CH2 unit bound to the Cp ring is oxidized under these conditions (Scheme 6). A similar sp3 CH2 unit oxidation was observed in the case of the picolinamide-derived cobalt sandwich compound as well. Scheme 6. Attempted C−H Olefination/Annulation Reaction on Compound 2

To the best of our knowledge, this type of sp3 C−H bond oxidation to an aldehyde using a directing group has never been reported. This novel finding has the potential not only to remove the directing group after C−H functionalization but also to convert the aminomethyl derivatives to an aldehyde. Detailed studies were carried out for optimizing the reaction conditions and for maximizing the yields. It was found that [RuCl2(p-cym)]2 (5 mol %) along with Cu(OAc)2 (1 equiv) gave maximum yields (45−57%) for Cp bis-alkyl- and bis-arylsubstituted sandwich compounds (Scheme 7). Noticeble decomposition was observed in these reactions, which led to lesser than expected yields of the compounds. Scheme 7. Directing-Group-Assisted Ru-Catalyzed Oxidation of α,α-Bis-Substituted Picolinamides to the Corresponding Aldehydes

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Organometallics Scheme 8. One-Pot Synthesis of α,α-Bis-Substituted Aldehydes of Metal Sandwich Compounds

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CONCLUSIONS In summary, the syntheses of Cp multiply substituted iron and cobalt sandwich compounds have been efficiently carried out using picolinamide as a directing group and by using Pd(OAc)2 as a catalyst. The palladacycle intermediate of this reaction for the cobalt sandwich compound has been isolated and structurally characterized. Aryl iodides containing electrondonating as well as electron-withdrawing substituents were equally suitable for the reaction. We have also demonstrated the easy removal of the directing group after C−H functionalization by hydrolysis and reductive cleavage. More interestingly, for the first time, we report a novel methodology to remove the directing group by oxidation of the sp3 C−H bond to the corresponding aldehydes. This novel methodology and catalyst system can be applied to a variety of aryl- and alkylsubstituted sandwich compounds. We have also successfully

Figure 5. Molecular structure of compound 8c. Thermal ellipsoids are drawn at the 30% probability level. Hydrogen atoms have been omitted for clarity.

Scheme 9. Proposed Mechanism for Pd-Catalyzed Bis-Arylation of Metal Sandwich Compounds

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DOI: 10.1021/acs.organomet.7b00143 Organometallics XXXX, XXX, XXX−XXX

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combined the sp2 C−H functionalization and the sp3 C−H bond oxidation as a one-pot reaction. Attempts to extend sp3 C−H oxidation to aryl picolinamide under identical reaction conditions were unsuccessful and will require more detailed studies. Possible mechanisms have been proposed for the C−H activation and the C−H oxidation, which need to be verified further by detailed mechanistic studies.

Scheme 10. Control Experiments for Ru-Catalyzed Oxidation of sp3 C−H Bonds

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EXPERIMENTAL SECTION

General Information. All manipulations of the compounds used were carried out using standard Schlenk techniques under a nitrogen atmosphere. All solvents were freshly distilled and used. Ferrocenecarboxylic acid, ferrocenecarboxamide, ferrocenylmethylamine, the sodium salt of carbomethoxycyclopentadiene, and tris(triphenylphosphine)cobalt chloride, as well as carboxylic acid, carboxamide, and aminomethyl derivatives of [η5-C5H4]Co(η4C4Ph4) were prepared according to literature procedures.7k,l,20 Dimethyl carbonate, triphenylphosphine, oxalyl chloride (Spectrochem), picolinic acid, palladium acetate (Alfa Aesar), iodoarenes, and iodoalkenes were used as received. 1H and 13C NMR spectra were recorded on a Bruker Spectrospin DPX-300 NMR spectrometer at 300 and 75.47 MHz, respectively. Mass spectra were recorded on a Bruker Micro-TOF QII quadrupole time-of-flight (Q-TOF) mass spectrometer. X-ray diffraction studies of crystals mounted on a capillary were carried out on a Bruker AXS SMART-APEX diffractometer equipped with CCD area detector (Kα = 0.71073 Å, graphite monochromator).21,22 Frames were collected at T = 298 K by ω, ϕ, and 2θ rotation with a full quadrant data collection strategy (four domains each with 600 frames) at 10 s per frame with SMART.23 The measured intensities were reduced to F2 and corrected for absorption with

Scheme 11. Proposed Mechanism for Ru-Catalyzed sp3 C−H Bond Oxidation of Metal Sandwich Compounds

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Organometallics SAINT.23 Structure solution and refinement were carried out with the SHELXTL package by direct methods.24 Non-hydrogen atoms were refined anisotropically. All hydrogen atoms were included in idealized positions, and a riding model was used for the refinement. Images were created with the program Diamond.25 General Procedure for Synthesis of Picolinamides of Metal Sandwich Compounds. Picolinic acid (0.18 g, 1.50 mmol) and triethylamine (0.30 mL, 3.00 mmol) were dissolved in dry DCM (15 mL). The solution was cooled to 0 °C followed by addition of ethyl chloroformate (0.16 g, 1.50 mmol). The solution was then stirred for 15 min in an ice bath. Afterward, the aminomethyl derivative of iron and cobalt sandwich compounds (1 mmol) were dissolved in dry DCM and were added dropwise using a syringe into the reaction mixture. The solution was warmed to room temperature and stirred for 24 h. Afterward, the solution was concentrated under vacuum and the crude product was purified through column chromatography on neutral alumina using hexane/ethyl acetate (70:30) as eluent. [η5-(CH2R)C5H4]Co(η4-C4Ph4) (R = picolinamido) (1): red crystalline solid; yield 0.51 g (82%). Mp: 143−145 °C. Anal. Found: C, 78.25; H, 5.05; N, 4.62. Calcd for C40H31N2CoO: C, 78.17; H, 5.08; N, 4.56. IR (ν, cm−1): 1677 (CO), 3387 (NH). 1H NMR (300 MHz, CDCl3): δ 8.46 (s, 1H), 8.11−8.13 (d, J = 6 Hz, 1H), 7.76−7.83 (m, 2H), 7.37−7.49 (m, 9H), 7.16−7.25 (m, 12H), 4.67 (s, 2H), 4.61 (s, 2H), 3.98 (s, 2H). 13C NMR (75 MHz, CDCl3): δ 164.02, 149.81, 147.91, 137.24, 136.12, 122.21−128.8, 95.09, 83.02, 42.21. HRMS: m/z 615.1845, calcd for C40H32CoN2O [M + H]+ 615.1841. [η5-(CH2R)C5H4]Fe(η5-C5H5) (R = picolinamido) (2): yellow crystalline solid; yield 0.20 g (76%). Mp: 136−138 °C. Anal. Found: C, 63.75; H, 5.07; N, 8.78. Calcd for C17H16FeN2O: C, 63.77; H, 5.04; N, 8.75. IR (ν, cm−1): 1657 (CO), 3339, 3491(NH). 1H NMR (300 MHz, CDCl3): δ 8.56 (s, 1H), 8.21−8.36 (m, 2H), 7.84−7.86 (d, 1H), 7.39−7.42 (m, 1H), 4.31 (s, 3H), 4.23 (s, 6H), 4.14 (s, 2H). 13C NMR (75 MHz, CDCl3): δ 163.50, 148.06, 137.32, 126.09, 122.24, 83.45, 82.42, 69.77, 35.73. HRMS: m/z 343.0490, calcd for C17H16FeN2NaO [M + Na]+ 343.0504. General Procedure for Bis-Alkylation of [η5-(CH2R)C5H2]Co(η4-C4Ph4) (R = Picolinamido). One equivalent of cobalt sandwich compound derived picolinamide 1 (0.06 g, 0.10 mmol), Pd(OAc)2 (20 mol %), Cs2CO3 (2 equiv), and alkyl iodide or allyl bromide (4 equiv) were added to tert-amyl alcohol in a screw-capped vial having a magnetic bead and were heated at 80−90 °C for 12−24 h. The reaction was monitored by TLC. After completion, the reaction mixture was dried under vacuum and the crude product was purified through column chromatography using silica and hexane/ethyl acetate (90/10) as eluent. 2,5-Bis(methyl)-η5-(CH2R)C5H2]Co(η4-C4Ph4) (R = picolinamido) (4a): orange crystalline solid; yield 51 mg (79%). Mp: 135−137 °C. Anal. Found: C, 78.45; H, 5.45; N, 4.40. Calcd for C42H35N2CoO: C, 78.49; H, 5.49; N, 4.36. 1H NMR (300 MHz, CDCl3): δ 8.44 (s, 1H), 8.13 (d, 1H), 7.81 (d, 2H), 7.40−7.76 (m, 9H), 7.22−7.36 (m, 12H), 4.35 (s, 2H), 3.98 (s, 2H), 1.61 (s, 6H). 13C NMR (75 MHz, CDCl3): δ 163.57, 147.90, 137.21, 135.96, 128.06−128.66 (m), 126.09, 125.94, 122.15, 93.05, 83.32, 74.05, 33.73, 10.37. HRMS: m/z 643.2152, calcd for C42H36CoN2O [M + H]+ 643.2154. 2,5-Bis(ethyl)-η5-(CH2R)C5H2]Co(η4-C4Ph4) (R = picolinamido) (4b): yellow semisolid; yield 28 mg (42%). 1H NMR (300 MHz, CDCl3): δ 8.43 (s, 1H), 8.14 (d, 1H), 7.76−7.81 (d, 2H), 7.40−7.46 (m, 9H), 7.21−7.33 (m, 12H), 4.50 (s, 1H), 4.42 (s, 1H), 3.99 (s, 2H), 2.08−2.12 (q, 2H), 1.91−1.93 (q, 2H), 0.82 (t, 6H); 13C NMR (75 MHz, CDCl3): δ 163.57, 147.90, 137.21, 135.96, 128.06−128.66 (m), 126.09, 125.94, 122.15, 93.05, 83.32, 74.05, 33.73, 20.74, 10.29; HRMS: m/z 671.2465, calcd For C44H40CoN2O [M + H]+ = 671.2467. 2,5-Bis(allyl)-η5-(CH2R)C5H2]Co(η4-C4Ph4) (R = picolinamido) (4c): yellow solid; yield 25 mg (38%). Mp: 128−130 °C. Anal. Found: C, 79.55; H, 5.68; N, 4.02. Calcd for C46H39N2CoO: C, 79.52; H, 5.66; N, 4.03. 1H NMR (300 MHz, CDCl3): δ 8.42 (s, 1H), 8.09 (d, J = 9 Hz, 1H), 7.79−7.82 (t, 2H), 7.42−7.59 (m, 9H), 7.25 (m, 12H), 5.58 (q, 2H), 4.77 (dd, J = 15 Hz, 4H), 4.42 (s, 2H), 3.99 (d, 2H), 2.86 (dd, J = 6 Hz, 4H). 13C NMR (75 MHz, CDCl3): δ 163.31, 147.89,

137.07, 135.84, 128.09−128.64 (m), 126.30, 125.82, 122.08, 115.48, 95.68, 83.23, 74.24, 33.32, 22.68, 14.09. HRMS: m/z 695.2470, calcd for C46H40CoN2O [M + H]+ 695.2467. General Procedure for Bis-Arylation of [η5-(CH2R)C5H4]Co(η4C4Ph4) (R = Picolinamido). One equivalent of cobalt sandwich compound derived picolinamide 1 (0.06 g, 0.10 mmol), Pd(OAc)2 (20 mol %), Cs2CO3 (2 equiv), and aryl iodide (2.5 equiv) were added to tert-amyl alcohol in a screw-capped vial having a magnetic bead and heated at 80−100 °C for 12−24 h. The reaction was monitored by TLC, and after completion, the reaction mixture was dried under vacuum and the crude product was purified through column chromatography using silica and hexane/ethyl acetate (80/20) as eluent. 2,5-(4-OMeC6H4)2-η5-(CH2R)C5H2]Co(η4-C4Ph4) (R = picolinamido) (4d): red crystalline solid; yield 72 mg (87%). Mp: 144−145 °C. Anal. Found: C, 78.45; H, 5.15; N, 3.42. Calcd for C54H43N2CoO3: C, 78.44; H, 5.24; N, 3.39. 1H NMR (300 MHz, CDCl3): δ 8.39 (s, 1H), 8.09−8.16 (m, 2H), 7.98 (m, 1H), 6.98−7.37 (m, 25H), 6.49−6.58 (m, 4H), 5.07 (s, 2H), 4.39 (s, 2H), 3.79 (s, 6H). 13C NMR (75 MHz, CDCl3): δ 163.59, 158.33, 147.98, 137.12, 135.17, 128.06−128.77, 126.27, 125.92, 113.60, 99.87, 83.01, 75.33, 55.32, 35.73. HRMS: m/z 849.2502, calcd for C54H43CoN2O3Na [M + Na]+ 849.2497. 2,5-(4-BrC6H4)2-η5-(CH2R)C5H2]Co(η4-C4Ph4) (R = picolinamido) (4e): yellow solid; yield 57 mg (63%). Mp: 142−143 °C. Anal. Found: C, 67.51; H, 4.08; N, 3.09. Calcd for C52H37N2Br2CoO: C, 67.55; H, 4.03; N, 3.03. 1H NMR (300 MHz, CDCl3): δ 8.33 (s, 1H), 8.07−8.10 (d, 1H), 7.91 (s, 1H), 7.78- 7.81 (t, 1H), 7.08−7.75 (m, 25H), 6.82− 6.85 (d, 4H), 5.06 (s, 2H), 4.30 (s, 2H). 13C NMR (75 MHz, CDCl3): δ 163.68, 148.90, 137.52, 135.31, 128.06−128.37 (m), 126.17, 123.12, 122.00, 99.39, 85.01, 35.43. 2,5-(4-CF3C6H4)2-η5-(CH2R)C5H2]Co(η4-C4Ph4) (R = picolinamido) (4f): yellow-orange solid; yield 62 mg (68%). Mp: 139−140 °C. Anal. Found: C, 71.85; H, 4.18; N, 3.12. Calcd for C54H37N2CoOF6: C, 71.84; H, 4.13; N, 3.10. 1H NMR (300 MHz, CDCl3): δ 8.30 (s, 1H), 8.2 (d, 2H), 8.05 (t, 1H) 7.22- 7.33 (m, 16H), 7.05−7.17 (m, 13H), 5.18 (s, 2H), 4.37 (s, 2H). 13C NMR (75 MHz, CDCl3): δ 163.60, 147.90, 137.72, 134.31, 128.06−128.57 (m), 126.17, 125.12, 122.00, 99.09, 84.01, 35.73. HRMS: m/z 925.1998, calcd for C54H37CoN2O1F6Na [M + Na]+ 925.2034. 2,5-(4-NO2C6H4)2-η5-(CH2R)C5H2]Co(η4-C4Ph4) (R = picolinamido) (4g): orange-red solid; yield 55 mg (60%). Mp: 144−146 °C. Anal. Found: C, 75.39; H, 4.58; N, 3.32. Calcd for C52H37N2CoO5: C, 75.36; H, 4.50; N, 3.38. 1H NMR (300 MHz, CDCl3): δ 8.35 (s, 1H), 8.22 (d, 2H), 8.09 (t, 1H), 7.17- 7.29 (m, 16H), 7.11−7.21 (m, 13H), 5.12 (s, 2H), 4.35 (s, 2H). 13C NMR (75 MHz, CDCl3): δ 163.64, 147.90, 137.72, 134.31, 128.16−128.67 (m), 126.17, 125.12, 122.06, 99.19, 84.11, 35.71. 2,5-(3-CO2MeC6H4)2-η5-(CH2R)C5H2]Co(η4-C4Ph4) (R = picolinamido) (4h): orange solid; yield 57 mg (58%). Mp: 140−142 °C. Anal. Found: C, 76.15; H, 4.98; N, 3.13. Calcd for C56H43N2CoO5: C, 76.18; H, 4.91; N, 3.17. IR (ν, cm−1) 1721, 1673 (CO), 3446, 3396 (NH). 1H NMR (300 MHz, CDCl3): δ 8.38 (s, 1H), 8.10−8.16 (m, 2H), 7.78−7.87 (m, 4H), 7.01- 7.57 (m, 26H), 5.24 (s, 2H), 4.5 (s, 2H), 3.71 (s, 6H). 13C NMR (75 MHz, CDCl3): δ 165.53, 163.66, 150.03, 148.14, 141.72, 137.33, 129.23, 126.09, 125.14, 122.25, 93.80, 85.38, 68.58, 52.37, 38.44. HRMS: m/z 905.2399, calcd for C56H43CoN2O5Na [M + Na]+ 905.2396. General Procedure for Bis-Alkylation of [η5-(CH2R)C5H4]Fe(η5-C5H5) (R = Picolinamido). One equivalent of picolinamide 2 (0.03 g, 0.10 mmol), Pd(OAc)2 (20 mol %), Cs2CO3 (2 equiv), and alkyl iodide or allyl bromide (4 equiv) were added to tert-amyl alcohol in a screw-capped vial having a magnetic bead and heated at 80−90 °C for 5−10 h. The reaction was monitored by TLC. After completion, the reaction mixture was dried under vacuum and the crude product was purified through column chromatography using silica and hexane/ ethyl acetate (90/10) as eluent. 2,5-Bis(methyl)-η5-(CH2R)C5H4]Fe(η5-C5H5) (R = picolinamido) (5a): yellow-orange semisolid; yield 26 mg (74%). 1H NMR (300 MHz, CDCl3): δ 8.43 (s, 1H), 8.14−8.16 (dd, 2H), 7.76−7.78 (m, 1H), 7.31−7.34 (d, J = 9 Hz, 1H), 4.36 (d, J = 9 Hz, 2H), 3.95−4.07 (m, 7H), 1.93 (s, 6H). 13C NMR (75 MHz, CDCl3): δ 163.50, 149.94, G

DOI: 10.1021/acs.organomet.7b00143 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics

2,5-(2-FC6H6)2-η5-(CH2R)C5H2]Fe(η5-C5H5) (R = picolinamido) (5i): orange-red crystalline solid; yield 6 mg (12%). Mp: 135−137 °C. Anal. Found: C, 68.59; H, 4.34; N, 5.60. Calcd for C29H22N2FeOF2: C, 68.52; H, 4.36; N, 5.51. 1H NMR (300 MHz, CDCl3): δ 8.43 (s, 1H), 8.33 (s, 1H), 8.14−8.19 (m, 5H), 7.88 (t, 1H), 7.69−7.72 (m, 4H), 7.41−7.43 (t, 1H), 4.84 (s, 2H), 4.67−4.69 (s, 2H), 4.23 (s, 5H); 13C NMR (75 MHz, CDCl3): δ 163.84, 147.93, 141.56, 137.31, 129.23, 126.15 125.14, 122.10, 88.01, 80.12, 71.98, 69.89, 36.58. General Procedure for the Removal of the Picolininamide Directing Group. Bis-aryl or bis-alkyl picolinamides were dissolved in a THF/H2O (1/1) mixture and stirred at room temperature for 15 min. Afterward 0.1 mL of 1.5 M HCl and Zn dust (15 equiv) were added to the solution and this mixture was then stirred at room temperature for 2−3 h. The reaction was monitored by TLC, and after completion, the mixture was extracted with aqueous NaOH solution, the organic layer dried over Na2SO4, and the crude product purified through column chromatography on basic aluminum oxide using DCM/MeOH (95/5) as eluent. A NaOH/EtOH hydrolysis reaction was also carried out (Scheme 5) on a selected example to compare the yields. 2,5-(4-OMeC6H4)2-η5-(CH2NH2)C5H2]Co(η4-C4Ph4) (6a): orange solid; yield 22 mg (85%). Mp: 128−129 °C. Anal. Found: C, 78.09; H, 6.05; N, 2.10. Calcd for C43H40NCoO2: C, 78.05; H, 6.09; N, 2.12. 1 H NMR (300 MHz, CDCl3): δ 7.21−7.32 (m, 12H), 6.89−7.08 (m, 12H), 6.57−6.60 (dd, 4H), 4.86 (s, 2H), 3.86 (s, 6H), 3.61 (s, 2H), 1.45 (br, 2H). 13C NMR (75 MHz, CDCl3): δ 158.55, 135.49, 126.06−129.53, 113.62, 82.27, 75.02, 55.27, 30.33. 2,5-Bis(methyl)-η5-(CH2NH2)C5H2]Co(η4-C4Ph4) (6b): orange solid; yield 27 mg (87%). Mp: 128−130 °C. Anal. Found: C, 80.79; H, 5.69; N, 2.60. Calcd for C36H30CoN: C, 80.73; H, 5.65; N, 2.62. 1H NMR (300 MHz, CDCl3): δ 7.25−7.28 (m, 12H), 7.39−7.48 (m, 8H), 4.64 (s, 2H), 4.58 (s, 6H), 1.61 (s, 6H). 13C NMR (75 MHz, CDCl3): δ 136.31, 126.28−128.73, 83.31, 82.79, 60.39, 30.20, 14.20. HRMS: m/z 521.1682, calcd for C36H30Co [M − NH2]+ 521.1674. 2,5-(4-OMeC6H4)2-η5-(CH2NH2)C5H2]Fe(η5-C5H5) (7a): orange solid; yield 18 mg (85%). Mp: 135−136 °C. Anal. Found: C, 70.05; H, 6.02; N, 3.12. Calcd for C25H25FeNO2: C, 70.27; H, 5.90; N, 3.28. 1H NMR (300 MHz, CDCl3): δ 7.50−7.53 (d, J = 9 Hz, 4H), 6.89−6.92 (d, J = 9 Hz, 4H), 4.47 (s, 2H), 4.08 (s, 5H), 3.84 (s, 6H). 13C NMR (75 MHz, CDCl3): δ 158.38, 137.18, 130.13, 89.05, 80.52, 71.54, 68.55, 55.27, 30.33. HRMS: m/z 427.1239, calcd for C25H25FeNO2 [M]+ 427.1229. 2,5-Bis(methyl)-η5-(CH2NH2)C5H2]Fe(η5-C5H5) (7b): yellow semisolid; yield 17 mg (90%). 1H NMR (300 MHz, CDCl3): δ 3.90−3.93 (m, 7H), 3.66 (s, 2H), 1.96 (s, 6H); 1.43 (br, 2H). 13C NMR (75 MHz, CDCl3): δ 82.35, 69.56, 67.19, 38.44, 13.11. HRMS: m/z 227.0519, calcd for C13H15Fe [M − NH2]+ 227.0517. General Procedure for the Removal of the Picolininamide Directing Group via Oxidation of sp3 C−H Bond. Bis-aryl or bisalkyl picolinamides were dissolved in tert-amyl alcohol and stirred at room temperature for 15 min. Afterward [RuCl2(p-cym)]2 (5 mol %) and Cu(OAc)2 (1 equiv) were added to the solution, and this mixture was then heated at 80 °C for 10−12 h. The reaction was monitored by TLC, and after completion, the mixture was dried over vacuum and the crude product was purified through column chromatography on silica gel using hexane/ethyl acetate (80/20) as eluent. 2,5-(4-OMeC6H4)2-[η5-C5H2-CHO]Co(η4-C4Ph4) (8a): orange crystalline solid; yield 21 mg (50%). Mp: 158−160 °C. Anal. Found: C, 79.89; H, 5.34; N, 0.00. Calcd for C48H37CoO3: C, 79.99; H, 5.17; N, 0.00. 1H NMR (300 MHz, CDCl3): δ 9.67 (s, 1H), 7.28 (m, 4H), 7.22−7.28 (m, 7H), 7.04−7.14 (m, 13H), 6.66 (d, J = 9 Hz, 4H), 5.16 (s, 2H), 3.84 (s, 6H). 13C NMR (75 MHz, CDCl3): δ 191.28, 158.87, 134.34, 130.87, 128.06−128.77 (m), 126.86, 125.18, 113.18, 103.14, 87.65, 55.30. HRMS: m/z 721.2149, calcd for C48H38CoO3 [M + H]+ 721.2147. 2,5-(4-BrC6H4)2-[η5-C5H2−CHO]Co(η4-C4Ph4) (8b): orange solid; yield 25 mg (57%). Mp: 165−167 °C. Anal. Found: C, 67.58; H, 4.06; N, 0.00. Calcd for C46H31CoOBr2: C, 67.50; H, 3.82; N, 0.00. 1H NMR (300 MHz, CDCl3): δ 9.58 (s, 1H), 7.10−7.17 (m, 5H), 7.03− 7.06 (m, 19H), 6.85−6.88 (m, 4H), 5.11 (s, 2H). 13C NMR (75 MHz,

148.06, 137.32, 126.09, 122.24, 83.45, 82.45, 69.77, 67.50, 35.73, 13.25. HRMS: m/z 348.0914, calcd for C19H20FeN2O [M]+ 348.0919. 2,5-Bis(ethyl)-η5-(CH2R)C5H4]Fe(η5-C5H5) (R = picolinamido) (5b): yellow-orange semisolid; yield 17 mg (45%). 1H NMR (300 MHz, CDCl3): δ 8.43 (s, 1H), 8.16 (d, J = 9 Hz, 1H), 8.00 (s, 1H), 7.76− 7.79 (m, 1H), 7.31−7.34 (d, J = 9 Hz, 1H), 4.33 (d, J = 3 Hz, 2H),3.95−4.19 (m, 7H), 2.28−2.36 (q, 4H), 1.26−1.29 (t, 6H). 13C NMR (75 MHz, CDCl3): δ 163.70, 150.02, 148.15, 137.35, 126.11, 122.27, 90.24, 85.36, 69.49, 67.85, 38.43, 20.74, 14.99. HRMS: m/z 399.1135, calcd for C21H24FeN2ONa [M + Na]+ 399.1130. [2,5-Bis(allyl)-η5-(CH2R)C5H4]Fe(η5-C5H5) (R = picolinamido) (5c): yellow-orange semisolid; yield 15 mg (40%). 1H NMR (300 MHz, CDCl3): δ 8.47 (s, 1H), 8.46 (d, J = 12 Hz, 1H), 8.00 (s, 1H), 7.72− 7.79 (m, 1H), 7.29−7.33 (d, J = 12 Hz, 1H), 5.89 (q, 2H), 4.95 (d, 4H), 4.33 (d, J = 3 Hz, 2H), 3.95−4.29 (m, 7H), 3.086 (d, J = 6 Hz, 4H). HRMS: m/z 400.1226, calcd for C23H24FeN2O [M]+ 400.1233. General Procedure for Bis-Arylation of [η5-(CH2R)C5H4]Fe(η5C5H5) (R = Picolinamido). One equivalent of ferrocenyl picolinamide 2 (0.03 g, 0.10 mmol), Pd(OAc)2 (20 mol %), Cs2CO3 (2 equiv), and aryl iodide (2.5 equiv) were added to tert-amyl alcohol in a screwcapped vial having a magnetic bead and heated at 80−110 °C for 12− 20 h. The reaction was monitored by TLC, and after completion, the reaction mixture was dried under vacuum and the crude product was purified through column chromatography using silica and hexane/ ethyl acetate (70/30) as eluent. 2,5-(4-OMeC6H4)2-η5-(CH2R)C5H2]Fe(η5-C5H5) (R = picolinamido) (5d): red semisolid; yield 41 mg (77%). 1H NMR (300 MHz, CDCl3): δ 8.42−8.44 (m, 2H), 8.16−8.19 (d, J = 9 Hz, 1H), 7.80−7.81 (m, 1H), 7.47−7.50 (m, 5H), 6.80−6.83 (d, 4H) 4.55−4.61 (m, 4H), 4.19 (s, 5H), 3.76 (s, 6H). 13C NMR (75 MHz, CDCl3): δ 163.44, 158.38, 149.86, 148.03, 137.18, 130.13, 129.50, 125.98, 122.04, 89.05, 80.52, 71.54, 68.55, 55.27, 36.80. HRMS: m/z 532.1461, calcd for C31H28FeN2O3 [M]+ 532.1444. 2,5-(4-BrC6H4)2-η5-(CH2R)C5H2]Fe(η5-C5H5) (R = picolinamido) (5e): orange crystalline solid; yield 35 mg (60%). Mp: 138−140 °C. Anal. Found: C, 55.29; H, 3.58; N, 4.40. Calcd for C29H22N2FeOBr2: C, 55.27; H, 3.52; N, 4.45. 1H NMR (300 MHz, CDCl3): δ 8.44 (s, 1H), 8.18 (s, 1H), 8.15 (d, J = 6 Hz, 1H), 7.84 (t, 1H), 7.40 (s, 9H), 4.60−4.62 (m, 4H), 4.19 (s, 5H). 13C NMR (75 MHz, CDCl3): δ 163.69, 149.99, 148.16, 137.36, 126.13, 122.25, 85.34, 68.67, 38.44. HRMS: m/z 627.9451, calcd for C29H22FeN2OBr2 [M]+ 627.9443, [M + 2] 629.9430, [M + 4] 631.9407. 2,5-(4-NO2C6H4)2-η5-(CH2R)C5H2]Fe(η5-C5H5) (R = picolinamido) (5f): red crystalline solid; yield 39 mg (57%). Mp: 140−142 °C. Anal. Found: C, 61.73; H, 3.68; N, 9.73. Calcd for C29H22N4FeO5: C, 61.94; H, 3.94; N, 9.66. IR (ν, cm−1): 1672 (CO), 1511, 1338 (NO2). 1H NMR (300 MHz, CDCl3): δ 8.42 (d, 1H), 8.41 (s, 1H), 8.18 (d, 1H), 7.82−7.84 (m, 1H), 7.54−7.71 (m, 4H), 7.40−7.42 (m, 4H), 7.38 (t, 1H) 4.67−4.74 (m, 4H), 4.26 (s, 5H). 13C NMR (75 MHz, CDCl3): δ 163.84, 147.93, 141.56, 137.31, 129.23, 126.15, 125.14, 122.10, 88.01, 80.12, 71.98, 69.89, 36.56. HRMS: m/z 562.0923, calcd for C29H22FeN4O5 [M]+ 562.0934. 2,5-Bis(4-CF3C6H4)2-η5-(CH2R)C5H2]Fe(η5-C5H5) (R = picolinamido) (5g): orange crystalline solid; yield 41 mg (64%). Mp: 129−131 °C. Anal. Found: C, 61.13; H, 3.68; N, 4.65. Calcd for C31H22N2FeOF6: C, 61.20; H, 3.65; N, 4.60. 1H NMR (300 MHz, CDCl3): δ 8.42 (d, 1H), 8.41 (s, 1H), 8.18 (d, 1H), 7.82−7.84 (m, 1H), 7.54−7.71 (m, 4H), 7.40−7.42 (m, 4H), 7.38 (t, 1H) 4.67−4.74 (m, 4H), 4.26 (s, 5H). 13C NMR (75 MHz, CDCl3): δ 163.84, 147.93, 141.56, 137.31, 129.23, 126.15 125.14, 122.10, 88.01, 80.12, 71.98, 69.89, 36.56. HRMS: m/z 608.0983, calcd for C31H22FeN2OF6 [M]+ 608.0980. 2,5-(3-CO2MeC6H4)-η5-(CH2R)C5H2]Fe(η5-C5H5) (R = picolinamido) (5h): orange crystalline solid; yield 36 mg (55%). Mp: 136−138 °C. Anal. Found: C, 67.39; H, 4.84; N, 4.71. Calcd for C33H28N2FeO5: C, 67.36; H, 4.80; N, 4.76. 1H NMR (300 MHz, CDCl3): δ 8.33−8.38 (m, 2H), 8.09−8.19 (m, 3H), 7.64−7.82 (m, 5H), 7.18−7.32 (m, 3H), 4.65−4.66 (s, 2H), 4.50−4.54 (s, 2H), 4.17 (s, 5H), 3.81(s, 6H). 13C NMR (75 MHz, CDCl3): δ 165.53, 163.66, 150.03, 148.14, 141.72, 137.33, 129.23, 126.09 125.14, 122.25, 93.80, 85.38, 68.58, 52.37, 38.44. H

DOI: 10.1021/acs.organomet.7b00143 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics CDCl3): δ 191.12, 134.86, 129.28, 128.06−128.56 (m), 126.37, 92.54, 88.81, 76.73. 2,5-Bis(methyl)-[η5-C5H2−CHO]Co(η4-C4Ph4) (8c): orange solid; yield 12 mg (56%). Mp: 161−162 °C. Anal. Found: C, 80.52; H, 5.84; N, 0.00. Calcd for C36H29CoO: C, 80.59; H, 5.45; N, 0.00. IR (ν, cm-1) 1670 (CO). 1H NMR (300 MHz, CDCl3): δ 9.63 (s, 1H), 7.38−7.52 (m, 12H), 7.17−7.23 (m, 8H), 4.55 (s, 2H), 1.86 (s, 6H). 13 C NMR (75 MHz, CDCl3): δ 191.62, 134.89, 130.01, 129.83− 128.14 (m), 126.91, 96.15, 90.21, 88.59, 75.92, 68.20, 10.84. HRMS: m/z 537.1612, calcd for C36H30CoO [M + H]+ 537.1623. 2,5-(4-OMeC6H4)2-η5-(CHO)C5H2]Fe(η5-C5H5) (9a): red solid; yield 10 mg (45%). Mp: 145−148 °C dec. Anal. Found: C, 70.49; H, 5.24; N, 0.00. Calcd for C25H22FeO3: C, 70.44; H, 5.20; N, 0.00. 1H NMR (300 MHz, CDCl3): δ 10.25 (s, 1H), 7.50−7.53 (d, J = 9 Hz, 4H), 6.89−6.92 (d, J = 9 Hz, 4H), 4.84 (s, 2H), 4.20 (s, 5H), 3.84 (s, 6H). 13 C NMR (75 MHz, CDCl3): δ 193.44, 159.46, 139.08, 133.46, 122.18, 82.24, 71.54, 68.55, 55.34. HRMS: m/z 449.0796, calcd for C25H22FeNaO3 [M + Na]+ 449.0811. 2,5-(4-BrC6H4)2-η5-(CHO)C5H2]Fe(η5-C5H5) (9b): orange-red solid; yield 11 mg (55%). Mp: 157−158 °C. Anal. Found: C, 52.79; H, 3.08; N, 0.00. Calcd for C23H16FeOBr2: C, 52.72; H, 3.08; N, 0.00. 1H NMR (300 MHz, CDCl3): δ 10.25 (s, 1H), 7.48 (s, 8H), 4.91 (s, 2H), 4.26 (s, 5H). 13C NMR (75 MHz, CDCl3): δ 193.44, 139.05, 133.45, 92.05, 89.05, 69.67, 68.55. HRMS: m/z 544.8806, calcd for C23H16FeBr2NaO [M + Na]+ 544.8812. 2,5-Bis(methyl)-η5-(CHO)C5H2]Fe(η5-C5H5) (9c): red solid; yield 12 mg (45%). Mp: 154−156 °C. Anal. Found: C, 64.65; H, 6.02; N, 0.00. Calcd for C13H14FeO: C, 64.50; H, 5.83; N, 0.00. 1H NMR (300 MHz, CDCl3): δ 10.29 (s, 1H), 4.34 (s, 2H), 4.12 (s, 5H), 2.04 (s, 6H). 13C NMR (75 MHz, CDCl3): δ 194.63, 87.03, 75.62, 72.04, 70.70, 14.07. HRMS: m/z 265.0286, calcd for C13H14FeNaO [M + Na]+ 265.0286. Crystal Structure Determination. Suitable crystals of compounds were obtained by slow evaporation of their saturated solutions in suitable solvent mixtures. Single-crystal diffraction studies were carried out on a Bruker SMART APEX CCD diffractometer with a Mo Kα (λ = 0.71073 Å) sealed tube. All crystal structures were solved by direct methods. The program SAINT (version 6.22) was used for integration of the intensity of reflections and scaling. The program SADABS was used for absorption correction. The crystal structures were solved and refined using the SHELXTL (version 6.12) package.24 All hydrogen atoms were included in idealized positions, and a riding model was used. Non-hydrogen atoms were refined with anisotropic displacement parameters. Selected bond distances and angles for all the compounds are given in the Tables S5−S10 in the Supporting Information.

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S.H., M.D., and J.S. thank the UGC of India for research fellowships. We thank the DST-FIST and IIT D for funding the single-crystal X-ray diffractometer and HRMS facilities at IIT Delhi.

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(1) (a) Cass, A. E. G.; Davis, G.; Francis, G. D.; Hill, H. A. O.; Aston, W. G.; Higgins, I. J.; Plotkin, E. V.; Scott, L. D. L.; Turner, A. P. F. Anal. Chem. 1984, 56, 667−671. (b) Dubar, F.; khalife, J.; Brocard, J.; Dive, D.; Biot, C. Molecules 2008, 13, 2900−2907. (c) Kreidenweiss, A.; Kremsner, P. G.; Dietz, L.; Mordmuller, B. Am. J. Trop. Med. Hyg. 2006, 75, 1178−1181. (d) van Staveren, D. R.; Metzler-Nolte, N. Chem. Rev. 2004, 104, 5931. (e) Delhaes, L.; Biot, C.; Berry, L.; Delcourt, P.; Macieijewski, L. A.; Camus, D.; Brocard, J. S.; Dive, D. ChemBioChem 2002, 3, 418−420. (f) Braga, S. S.; Silva, A. M. S. Organometallics 2013, 32, 5626−5630. (g) Hillard, E.; Vessieres, A.; Thouin, L.; Jaouen, G.; Amatore, C. Angew. Chem. 2006, 118, 291− 294; Angew. Chem., Int. Ed. 2006, 45, 285−288. (2) (a) Sun, R.; Wang, L.; Yu, H.; Abdin, Z.; Chen, Y.; Huang, J.; Tong, R. Organometallics 2014, 33, 4560−4573. (b) Miyaji, H.; Kim, D. S.; Chang, B. Y.; Park, E.; Park, S. M.; Ahn, K. H. Chem. Commun. 2008, 753−755. (c) Xie, S.; Zang, J.; Yuan, Y.; Chi, Y.; Yuan, R. Chem. Commun. 2015, 51, 3387−3390. (d) Arivazhagan, C.; Borthakur, R.; Ghosh, S. Organometallics 2015, 34, 1147−1155. (3) (a) Dai, L. − X.; Tu, T.; You, S. − L.; Deng, W. − P.; Hou, X. − L. Acc. Chem. Res. 2003, 36, 659−667. (b) Gomez Arrayas, R. G.; Adrio, J.; Carretero, J. C. Angew. Chem., Int. Ed. 2006, 45, 7674−7715. (c) Atkinson, R. C. J.; Gibson, V. C.; Long, N. J. Chem. Soc. Rev. 2004, 33, 313−328. (d) Blaser, H.-U.; Federsel, H.-J. Asymmetric Catalysis on Industrial Scale: Challenges, Approaches and Solutions; Wiley-VCH: Weinheim, Germany, 2010. (e) Newman, S. G.; Lautens, M. J. Am. Chem. Soc. 2011, 133, 1778−1780. (f) Nomura, H.; Richards, C. J. Chem. - Asian J. 2010, 5, 1726−1740. (g) Overman, L. E.; Owen, C. E.; Pavan, M. M.; Richards, C. J. Org. Lett. 2003, 5, 1809−1812. (h) Stevens, A. M.; Richards, C. J. Organometallics 1999, 18, 1346− 1348. (i) Nomura, H.; Richards, C. J. Chem. - Eur. J. 2007, 13, 10216− 10224. (j) Prasad, R. S.; Anderson, C. E.; Richards, C. J.; Overman, L. E. Organometallics 2005, 24, 77−81. (k) Cass, A. E. G.; Davis, G.; Francis, G. D.; Hill, H. A. O.; Aston, W. G.; Higgins, I. J.; Plotkin, E. V.; Scott, L. D. L.; Turner, A. P. F. Anal. Chem. 1984, 56, 667−671. (l) Colacot, T. J. Chem. Rev. 2003, 103, 3101−3118. (m) Marquarding, D.; Klusacek, H.; Gokel, G.; Hoffmann, P.; Ugi, I. J. Am. Chem. Soc. 1970, 92, 5389−5393. (n) Hu, X. − P.; Chen, H.-L.; Zheng, Z. Adv. Synth. Catal. 2005, 347, 541−548. (o) Toma, S.; Csizmadiova, J.; Meciarova, M.; Sebesta, R. Dalton Trans. 2014, 43, 16557−16579. (4) (a) Astruc, D.; Ornelas, C.; Ruiz, J. Chem. - Eur. J. 2009, 15, 8936−8944. (b) Hudson, R. D. A. J. Organomet. Chem. 2001, 637-639, 47−69. (c) Astruc, D.; Rapakousiou, A.; Wang, Y.; Djeda, R.; Diallo, A.; Ruiz, J.; Ornelas, C. J. Coord. Chem. 2014, 67, 3809−3821. (d) Dietrich, S.; Nicolai, A.; Lang, H. J. Organomet. Chem. 2011, 696, 739−747. (5) (a) Geiger, W. E. Organometallics 2007, 26, 5738−5765. (b) Kawai, T.; Iwakura, C.; Yoneyama, H. Electrochim. Acta 1989, 34, 1357−1361. (c) Tamura, K.; Akutagawa, N.; Satoh, M.; Wada, J.; Masuda, T. Macromol. Rapid Commun. 2008, 29, 1944−1949. (d) Miller, J. S. Chem. Rev. 1988, 88, 201−220. (e) Togni, A. In Ferrocenes; Homogeneous Catalysis, Organic Synthesis, Materials Science; Hayashi, T., Ed.; Wiley-VCH: Weinheim, Germany, 2008. (f) Wiles, D. M.; Cooney, J. D. Textile Chemist and Colorist 1969, 1, 52−57. (6) (a) Li, Y.; Josowicz, M.; Tolbert, L. M. J. Am. Chem. Soc. 2010, 132, 10374−10382. (b) Sarhan, Y.; Nouchi, A.E.-W.; Izumi, T. Tetrahedron 2003, 59, 6353−6362. (c) Foucher, D. A.; Tang, B.-Z.; Manners, I. J. Am. Chem. Soc. 1992, 114, 6246−6248. (d) Matsuura, Y.; Matsukawa, K. Chem. Phys. Lett. 2006, 428, 321−325. (e) Matsuura, Y.; Matsukawa, K. Chem. Phys. Lett. 2007, 436, 224−227. (f) Hu, B.; Debruler, C.; Rhodes, Z.; Liu, T. L. J. Am. Chem. Soc. 2017, 139, 1207−1214. (g) Ding, Y.; Zhao, Y.; Yu, G. Nano Lett. 2015, 15, 4108−

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.7b00143. Experimental data and crystallographic data, including selected bond lengths and angles (PDF) Crystallographic data (CIF)

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REFERENCES

AUTHOR INFORMATION

Corresponding Author

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

Anil J. Elias: 0000-0001-9980-5076 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors thank the DST of India for financial assistance in the form of research grant to A.J.E (DST EMR/2015/000285). I

DOI: 10.1021/acs.organomet.7b00143 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics

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DOI: 10.1021/acs.organomet.7b00143 Organometallics XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.organomet.7b00143 Organometallics XXXX, XXX, XXX−XXX