Next Article in Journal
Probing Active Sites on Metal-Free, Nitrogen-Doped Carbons for Oxygen Electroreduction: A Review
Next Article in Special Issue
Prominent Conductor Mechanism-Induced Electron Transfer of Biochar Produced by Pyrolysis of Nickel-Enriched Biomass
Previous Article in Journal
Synthesis and Characterization of Cationic Tetramethyl Tantalum(V) Complex
Previous Article in Special Issue
Study of Chemical and Morphological Transformations during Ni2Mo3N Synthesis via an Oxide Precursor Nitration Route
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Catalysts
Volume 8
Issue 11
10.3390/catal8110508
catalysts-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Application of POCOP Pincer Nickel Complexes to the Catalytic Hydroboration of Carbon Dioxide

by
Jie Zhang
*,
Jiarui Chang
,
Ting Liu
,
Bula Cao
,
Yazhou Ding
and
Xuenian Chen
*
School of Chemistry and Chemical Engineering, Henan Key Laboratory of Boron Chemistry and Advanced Energy Materials, Henan Normal University, Xinxiang 453007, China
*
Authors to whom correspondence should be addressed.
Catalysts 2018, 8(11), 508; https://doi.org/10.3390/catal8110508
Submission received: 1 October 2018 / Revised: 25 October 2018 / Accepted: 29 October 2018 / Published: 1 November 2018
(This article belongs to the Special Issue Ni-Containing Catalysts)
Browse Figures
Versions Notes

Abstract

:
The reduction of CO2 is of great importance. In this paper, different types of bis(phosphinite) (POCOP) pincer nickel complexes, [2,6-(R2PO)2C6H3]NiX (R = tBu, iPr, Ph; X = SH, N3, NCS), were applied to the catalytic hydroboration of CO2 with catecholborane (HBcat). It was found that pincer complexes with tBu2P or iPr2P phosphine arms are active catalysts for this reaction in which CO2 was successfully reduced to a methanol derivative (CH3OBcat) with a maximum turnover frequency of 1908 h−1 at room temperature under an atmospheric pressure of CO2. However, complexes with phenyl-substituted phosphine arms failed to catalyze this reaction—the catalysts decomposed under the catalytic conditions. Complexes with iPr2P phosphine arms are more active catalysts compared with the corresponding complexes with tBu2P phosphine arms. For complexes with the same phosphine arms, the catalytic activity follows the series of mercapto complex (X = SH) ≈ azido complex (X = N3) >> isothiocyanato complex (X = NCS). It is believed that all of these catalytic active complexes are catalyst precursors which generate the nickel hydride complex [2,6-(R2PO)2C6H3]NiH in situ, and the nickel hydride complex is the active species to catalyze this reaction.

1. Introduction

The development of effective chemical processes that catalytically convert carbon dioxide to valuable compounds has received a great deal of attention recently [1,2,3,4,5,6]. Of the various chemical transformations investigated, catalytic reduction of CO2 to methanol (MeOH) is of particular interest because the latter is a very important commodity chemical and can be used as a type of clean fuel. Over the last 20 years, great efforts have been made to reduce CO2 to MeOH or its derivatives [5,6,7,8,9,10,11,12,13]. Specifically, significant progress or breakthroughs have been achieved in metal catalyzed homogeneous conversion of CO2 to MeOH [14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29].
As an earth-abundant cost-effective late transition metal, nickel has been extensively used to catalyze a variety of chemical transformations since the last century. Nowadays, homogeneous nickel catalysis is becoming more and more important in modern synthetic chemistry because of the diverse novel catalytic reactivities of nickel complexes [30,31,32].
We have been interested in the chemistry of transition metal complexes bearing bis(phosphinite) (POCOP) pincer ligands [14,15,26,27,33,34,35,36,37,38]. Recently, we applied some POCOP pincer nickel thiolato complexes, [2,6-(R2PO)2C6H3]NiY (R = tBu, iPr; Y = SC6H4-p-OCH3, SC6H4-p-CH3, SPh, SC6H4-p-CF3, SCH2Ph), to the catalytic reduction of CO2 with catecholborane (HBcat) [27]. Carbon dioxide was effectively reduced to CH3OBcat under very mild conditions, and turnover frequencies (TOFs) up to 2400 h−1 were observed. Although POCOP pincer nickel hydrides are also good catalysts for this reaction under the same conditions [14,15,16], the catalytic activity of the nickel thiolato complexes are better than that of the corresponding nickel hydride complexes. It was concluded that the thiolato complexes may work as pre-catalysts with the in situ generated nickel hydride complexes being the real active species. The superior catalytic activity of the thiolato complexes may be due to some in situ generated thiolato species that act as co-catalysts. To confirm this speculation, we initiated a more extensive study for this hydroboration reaction. In this paper, we used different types of POCOP pincer ligated nickel complexes with different phosphine arms and different auxiliary ligands, [2,6-(R2PO)2C6H3]NiX (Scheme 1), to catalyze this reaction under the same conditions. It was found that pincer complexes with tBu2P or iPr2P arms are active catalysts and CO2 was reduced to CH3OBcat at room temperature under an atmospheric pressure of CO2. Turnover frequencies up to 1908 h−1 were observed. Complexes with iPr2P arms are more active catalysts compared with the corresponding complexes with tBu2P arms. For complexes with the same phosphine arms, the catalytic activity follows the series of mercapto complex (X = SH) ≈ azido complex (X = N3) >> isothiocyanato complex (X = NCS). The results are consistent with the speculation that these different types of pincer nickel complexes are catalyst precursors and the in situ generated pincer nickel hydrides are the actual active species to catalyze the hydroboration of carbon dioxide with catecholborane.

2. Results and Discussion

2.1. Synthesis and Characterization of the Ni Catalysts

Complexes 1a [37], 1b [38], 2a–c [35] and 3a–c [35] were synthesized as described in the literatures. Complex 1c has never been reported before and was synthesized by the reaction between [2,6-(Ph2PO)2C6H3]NiCl and NaSH in THF/methanol at room temperature (Scheme 2). As a new complex, 1c was fully characterized by nuclear magnetic resonance spectroscopy (NMR), Fourier Transform infrared spectroscopy (FTIR), X-ray crystallography and elemental analysis.
Complex 1c is an air-sensitive orange solid and is soluble in toluene and dichloromethane. The 1H, 13C{1H} and 31P{1H} NMR spectra of 1c were in good agreement with the structure depicted in Scheme 2. Complex 1c showed the expected spectra characteristics for a POCOP pincer ligated nickel complex [14,15,16,27,33,34,35,36,37,38,39,40,41,42]. Similar to other reported transition metal mercapto complexes [37,38,43,44,45], the 1H NMR resonance of the –SH proton of 1c appeared in a relatively high-field (−0.76 ppm) as a triplet. An H–P coupling constant of 19.7 Hz was observed. The 31P{1H} NMR spectrum of 1c displayed one singlet, implying an identical chemical environment for the two phosphine arms in solutions. The FTIR spectrum of 1c displayed a weak absorption at 2546 cm−1 which was attributed to the S–H stretching vibration.
Single crystals of 1c used for X-ray diffraction analysis were obtained by recrystallization in n-hexane/CH2Cl2 solution at −10 °C. The identity of the crystals was affirmed by 31P{1H} NMR spectroscopy. The diffraction experiment was carried out at 103 K using a Bruker SMART6000 CCD diffractometer (Bruker Corporation, Karlsruhe, Germany). The molecular structure of 1c is shown in Figure 1 and the selected bond lengths and angles are also provided.
As shown in Figure 1, the square-planar geometry for the Ni center of 1c is distorted; this is quite common for POCOP pincer nickel complexes [14,15,16,27,33,34,35,36,37,38,39,40,41,42]. Both the Cipso–Ni and Ni–S bond lengths in complex 1c are comparable to those of the related pincer nickel mercapto complexes with tBu2P or iPr2P arms [37,38]. This indicates that the Cipso–Ni and Ni–S bond strengths are not considerably affected by the substituents on the phosphine arms.

2.2. Catalytic Hydroboration of CO2 with HBcat

In order to check the catalytic activities, a NMR tube reaction was carried out for each of the nickel complexes. Typically, the nickel complex (0.01 mmol) was mixed with HBcat (0.3 mmol) in C6D6 (0.5 mL) in a NMR tube under a N2 atmosphere. Carbon dioxide was then introduced and the reaction was monitored by NMR spectra at room temperature. For complexes 1a, 1b, 2a, 2b and 3b, the 11B NMR spectra showed that HBcat was completely or partly consumed in 30 min. CH3OBcat and catBOBcat were formed as evidenced by the two singlets at 23.6 and 22.6 ppm [14,26,27,46,47] in the 11B NMR spectra (see Figure 2 for example, the representative 11B NMR spectra for the interactions of the nickel complexes with HBcat under CO2). The formation of CH3OBcat was also confirmed by the singlet at 3.36 ppm [14,26,27,46] in the 1H NMR spectra. Similar to the hydroboration of CO2 with HBcat using the related nickel thiolato complexes as the catalysts [27], the 31P{1H} NMR spectra were too complex to be understood—many unidentified species were shown. For complex 3a, no reaction was observed after 60 min at temperatures up to 60 °C as evidenced by the 31P{1H} NMR spectra. For complexes 1c, 2c and 3c, black precipitate developed in 10 min and the 31P{1H} NMR spectra showed that the original nickel complexes decomposed completely; neither CH3OBcat nor catBOBcat were detected by the NMR spectra.
The above NMR tube reactions indicate that complexes 1a, 1b, 2a, 2b and 3b are active catalysts for the hydroboration of CO2 with HBcat under mild conditions (Scheme 3).
Flask reactions were carried out to further evaluate the catalytic activities of these complexes. Typically, the nickel complex (0.01 mmol), HBcat (5 mmol) and C6(CH3)6 (0.02 mmol, internal standard) were dissolved in benzene-d6 (4 mL) under a nitrogen atmosphere. The solution was stirred at room temperature and CO2 was bubbled through the solution at the same time. The reaction was stopped after a large amount of white precipitate developed. The reaction mixture was filtered and the clear liquid was analyzed by NMR spectroscopy. When complexes 3a and 3b were used as the catalysts, no white precipitate developed and the reaction was stopped after 2 h.
The isolated white precipitate was confirmed to be catBOBcat [14,26,27,46,47]. The 11B NMR spectra of the clear reaction solutions indicated that HBcat was completely (for the reactions catalyzed 1a, 1b, 2a or 2b) or partly (for the reaction catalyzed by 3b) converted to CH3OBcat and catBOBcat. No product was detected for the reaction catalyzed by 3a. Based on the 1H NMR integrations of the CH3OBcat methyl resonance (3.36 ppm) and the C6(CH3)6 methyl resonance (2.11 ppm), turnover number (TON) was calculated for each of the reactions. Table 1 summarizes the results of the above catalytic reactions. A representative 1H NMR spectrum of the clear reaction solution that was used to determine the TON value is shown in Figure 3.
It can be seen from Table 1 that the mercapto and azido complexes have quite similar activities in catalyzing the hydroboration of CO2 with HBcat and the catalytic activities are comparable to those of the corresponding palladium [26] and nickel [27] thiolato complexes reported previously. Complexes with isopropyl-substituted phosphine arms are more active than the corresponding complexes with tert-butyl substituted phosphine arms. This is in good agreement with the previous observation for the hydroboration of CO2 with HBcat using the related nickel thiolato complexes as the catalysts [26,27]. Isothiocyanato complexes are far less active than the corresponding mercapto and azido complexes.
We previously reported that POCOP pincer ligated nickel mercapto complexes with tBu2P or iPr2P arms (1a and 1b) can interact with HBcat at room temperature to generate POCOP pincer nickel hydride species [38]. In order to obtain more information, we checked the interactions of the other complexes (1c, 2a–c and 3a–c) with HBcat. The nickel complexes were treated with an excess amount of HBcat in C6D6 at room temperature in a sealed NMR tube and the reactions were monitored by NMR. For the interaction of 2a or 2b with HBcat, the hydride species [2,6-(R2PO)2C6H3]NiH [48] was detected by the 31P{1H} NMR spectra in 20 min. For the interaction of 3b with HBcat, the hydride species was also observed in 2 h. However, no reaction was detected for the interaction of 3a with HBcat after 24 h. When 1c, 2c or 3c was treated with HBcat, black precipitate developed in 20 min and the original complex decomposed partly as evidenced by the 31P{1H} NMR spectra.
It should be noted that POCOP pincer nickel hydride species with entirely phenyl substituted phosphine arms cannot be synthesized because of the instability of this type of hydride complexes [48]. Therefore, the hydride species were not likely formed for the interaction of 1c, 2c or 3c with HBcat.
The above experimental results are consistent with the speculation that these different types of pincer nickel complexes are pre-catalysts for the hydroboration of CO2 with HBcat and the in situ generated pincer nickel hydrides are the actual active species to catalyze this reaction. Any POCOP pincer nickel complexes that can generate POCOP pincer nickel hydrides under the catalytic conditions are active catalysts for the hydroboration of CO2 with catecholborane. The easier the hydride species can be generated, the more active the catalyst. For the hydroboration of carbon dioxide with HBcat using pure nickel hydrides as the catalysts, less bulky substituents on the phosphine arms make the catalysts less active because of the formation of an inactive complex outside the catalytic cycle [14,15,16]. However, for the hydroboration of CO2 with HBcat using a pre-catalyst, such as POCOP pincer ligated nickel thiolato, mercapto, azido or isothiocyanato complex, the catalytic activity is also dependent on the ease or the difficulty to generate the active hydride species. Smaller substituents on the phosphine arms make it easier to generate the active hydride species, although other issues, such as the electronic nature of the substituents on the phosphine arms [39,49,50] and the bond disassociation energy of the Ni–S or Ni–N bond [34,35], may also play important roles. On the other hand, the in situ generated other species, such as thiolato, azido and isothiosyanato species, may act as co-catalysts for this hydroboration reaction.

3. Materials and Methods

3.1. General Information

All manipulations were performed under an inert gas atmosphere. Solvents were degassed and dried before use. C6D6 was distilled from sodium and benzophenone before use. A Bruker Advance 400 MHz spectrometer (Swiss Bruker Corporation, Faellanden, Switzerland) was used for the NMR studies. For 1H and 13C NMR spectra, the residual solvent resonances were used to calibrate the chemical shift values internally. For 31P and 11B NMR spectra, H3PO4 (85%) and BF3·Et2O were used, respectively, to reference the chemical shift (δ 0) externally. Complexes [2,6-(Ph2PO)2C6H3]NiCl] [51], 1a [37], 1b [38], 2a–c [35] and 3a–c [35] were prepared as described in the literatures.

3.2. Synthesis of [2,6-(Ph2PO)2C6H3]NiSH (1c)

THF (10 mL) and MeOH (10 mL) were added to a flask containing [2,6-(Ph2PO)2C6H3]NiCl (572 mg, 1 mmol) and NaSH (280 mg, 5 mmol). The flask was then sealed and the resulting mixture in the flask was stirred at room temperature. After 48 h, the reaction was stopped and the volatiles were removed under vacuum. The residue was extracted with toluene and filtered through a pad of Celite. Complex 1c was obtained as an orange solid (341 mg, 60% yield) after the solvent of the combined extractions were removed under vacuum. 1H NMR (400 MHz, benzene-d6, δ): 8.03–8.08 (m, 8H, ArH), 7.01 (t, 1H, ArH, JH–H = 6.9 Hz), 6.94–7.00 (m, 12H, ArH), 6.83 (d, 2H, ArH, JH–H = 6.9 Hz), −0.76 (t, 1H, SH, JH–P = 19.7 Hz). 13C{1H} NMR (101 MHz, benzene-d6, δ): 167.0 (t, ArC, JC–P = 11.4 Hz), 135.5 (s, ArC), 133.6 (t, ArC, JC–P = 24.0 Hz), 132.6 (t, ArC, JC–P = 7.2 Hz), 131.6 (s, ArC), 129.6 (s, ArC), 128.9 (t, ArC, JC–P = 5.8 Hz), 106.7 (t, ArC, JC–P = 7.2 Hz). 31P{1H} NMR (162 MHz, benzene-d6, δ): 152.9 (s). Selected data from FTIR (KBr disc, cm−1): 2546 (w), 1435 (s), 1106 (m), 838 (s). Anal. Calcd for C30H24NiO2P2S: C, 63.30; H, 4.25. Found: C, 63.07; H, 4.11.

3.3. X-ray Structure Determination of [2,6-(Ph2PO)2C6H3]NiSH (1c)

Single crystals of 1c used for X-ray diffraction analysis were obtained from n-hexane/CH2Cl2 solution at −10 °C. The identities of the resulting crystals were confirmed by 31P{1H} NMR spectroscopy before the X-ray diffraction analysis. The intensity data were collected at 103 K on a Bruker SMART6000 CCD diffractometer. A graphite-monochromated Mo Kα radiation (λ = 0.71073 Å) was used for the data collection. Details for the data processing and structure refinement were similar to our previously reported procedures [37]. A summary of crystallographic data and structure refinement for complex 1c is provided in Table 2.
CCDC 1869263 contains the supplementary crystallographic data for complex 1c. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre (The Cambridge Structural Database, Cambridge, UK).

3.4. Procedure for the Catalytic Hydroboration of CO2

Flask experiments for the catalytic hydroboration of carbon dioxide were carried out at room temperature under an atmospheric pressure of carbon dioxide in benzene-d6 with a catalyst-to-substrate ratio of 1:500. The nickel catalyst (0.01 mmol), HBcat (5.00 mmol), hexamethylbenzene (0.02 mmol) and benzene-d6 (4 mL) were mixed in a flame-dried 50 mL Schlenk flask under N2. Then CO2 was bubbled through the solution until a large amount of white precipitate developed. The mixture was stirred for an additional 2 min. The resulting white precipitate was then allowed to settle, and 0.6 mL of the clear liquid was transferred under nitrogen into a NMR tube. 11B and 1H NMR spectra were then recorded. The TON numbers were calculated based on the 1H NMR integrations of the CH3OBcat methyl resonance at 3.36 ppm and the C6(CH3)6 (internal standard) methyl resonance at 2.11 ppm. The conversions were calculated from the 11B NMR spectra.

4. Conclusions

In summary, we have applied three different types of POCOP pincer nickel complexes (i.e., mercapto complex, azido complex and isothiosyanato complex) to the catalytic hydroboration of carbon dioxide with catecholborane. CO2 was successfully reduced to a methanol derivative (CH3OBcat) under an atmospheric pressure of CO2 at room temperature with TOFs up to 1908 h−1. It was found that pincer complexes with isopropyl-substituted phosphine arms are more active than the corresponding complexes with tert-butyl substituted phosphine arms. Complexes with phenyl-substituted phosphine arms decomposed under the catalytic conditions and failed to catalyze the reactions. Of the three types of complexes, the isothiosyanato complex is far less active than the corresponding mercapto and azido complexes. It is concluded that all of these catalytically active complexes are catalyst precursors which generate the nickel hydride complex [2,6-(R2PO)2C6H3]NiH in situ under the catalytic conditions, and the nickel hydride complex is the active species to catalyze this reaction.

Author Contributions

Conceptualization, J.Z.; Methodology, J.Z.; Validation, J.Z. and X.C.; Investigation, J.C., T.L., B.C. and Y.D.; Resources, J.Z. and X.C.; Data curation, X.C.; Writing—Original Draft Preparation, J.C, T.L. and B.C.; Writing—Review and Editing, J.Z.; Visualization, J.Z.; Supervision, J.Z. and X.C.; Project Administration, J.Z. and X.C.; Funding Acquisition, J.Z. and X.C.

Funding

This research was funded by the National Natural Science Foundation of China, grant numbers 21571052 and 21771057.

Conflicts of Interest

The authors declare no conflict of interest. The funder had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

References

  1. Kortlever, R.; Shen, J.; Schouten, K.J.P.; Calle-Vallejo, F.; Koper, M.T.M. Catalysts and reaction pathways for the electrochemical reduction of carbon dioxide. J. Phys. Chem. Lett. 2015, 6, 4073–4082. [Google Scholar] [CrossRef] [PubMed]
  2. Costentin, C.; Roberta, M.; Savéant, J.-M. Catalysis of the electrochemical reduction of carbon dioxide. Chem. Soc. Rev. 2013, 42, 2423–2436. [Google Scholar] [CrossRef] [PubMed]
  3. Takeda, H.; Ishitani, O. Development of efficient photocatalytic systems for CO2 reduction using mononuclear and multinuclear metal complexes based on mechanistic studies. Coord. Chem. Rev. 2010, 254, 346–354. [Google Scholar] [CrossRef]
  4. Chong, C.C.; Kinjo, R. Catalytic hydroboration of carbonyl derivatives, imines, and carbon dioxide. ACS Catal. 2015, 5, 3238–3259. [Google Scholar] [CrossRef]
  5. Benson, E.E.; Kubiak, C.P.; Sathrum, A.J.; Smieja, J.M. Electrocatalytic and homogeneous approaches to conversion of CO2 to liquid fuels. Chem. Soc. Rev. 2009, 38, 89–99. [Google Scholar] [CrossRef] [PubMed]
  6. Wang, W.-H.; Himeda, Y.; Muckerman, J.T.; Manbeck, G.F.; Fujita, E. CO2 hydrogenation to formate and methanol as an alternative to photo- and electrochemical CO2 reduction. Chem. Rev. 2015, 115, 12936–12973. [Google Scholar] [CrossRef] [PubMed]
  7. Ali, K.A.; Abdullah, A.Z.; Mohamed, A.R. Recent development in catalytic technologies for methanol synthesis from renewable sources: A critical review. Renew. Sustain. Energy Rev. 2015, 44, 508–518. [Google Scholar] [CrossRef]
  8. Ganesh, I. Conversion of carbon dioxide into methanol—A potential liquid fuel: Fundamental challenges and opportunities (a review). Renew. Sustain. Energy Rev. 2014, 31, 221–257. [Google Scholar] [CrossRef]
  9. Fontaine, F.-G.; Courtemanche, M.-A.; Légaré, M.-A. Transition-metal-free catalytic reduction of carbon dioxide. Chem. Eur. J. 2014, 20, 2990–2996. [Google Scholar] [CrossRef] [PubMed]
  10. Habisreu-tinger, S.N.; Schmidt-Mende, L.; Stolarczyk, J.K. Photocatalytic reduction of CO2 on TiO2 and other semiconductors. Angew. Chem. Int. Ed. 2013, 52, 7372–7408. [Google Scholar] [CrossRef] [PubMed]
  11. Appel, A.M.; Bercaw, J.E.; Bocarsly, A.B.; Dobbek, H.; DuBois, D.L.; Dupuis, M.; Ferry, J.G.; Fujita, E.; Hille, R.; Kenis, P.J.A. Frontiers, opportunities, and challenges in biochemical and chemical catalysis of CO2 fixation. Chem. Rev. 2013, 113, 6621–6658. [Google Scholar] [CrossRef] [PubMed]
  12. Aresta, M.; Dibenedetto, A.; Angelini, A. Catalysis for the valorization of exhaust carbon: From CO2 to chemicals, materials, and fuels. Technological use of CO2. Chem. Rev. 2014, 114, 1709–1742. [Google Scholar] [CrossRef] [PubMed]
  13. Arakawa, H.; Aresta, M.; Armor, J.N.; Barteau, M.A.; Beckman, E.J.; Bell, A.T.; Bercaw, J.E.; Creutz, C.; Dinjus, E.; Dixon, D.A.; et al. Catalysis research of relevance to carbon management: Progress, challenges, and opportunities. Chem. Rev. 2001, 101, 953–996. [Google Scholar] [CrossRef] [PubMed]
  14. Chakraborty, S.; Zhang, J.; Krause, J.A.; Guan, H. An efficient nickel catalyst for the reduction of carbon dioxide with a borane. J. Am. Chem. Soc. 2010, 132, 8872–8873. [Google Scholar] [CrossRef] [PubMed]
  15. Chakraborty, S.; Zhang, J.; Patel, Y.J.; Krause, J.A.; Guan, H. Pincer-ligated nickel hydridoborate complexes: The dormant species in catalytic reduction of carbon dioxide with boranes. Inorg. Chem. 2013, 52, 37–47. [Google Scholar] [CrossRef] [PubMed]
  16. Chakraborty, S.; Patel, Y.J.; Krause, J.A.; Guan, H. Catalytic properties of nickel bis(phosphinite) pincer complexes in the reduction of CO2 to methanol derivatives. Polyhedron 2012, 32, 30–34. [Google Scholar] [CrossRef]
  17. Wesselbaum, S.; vom Stein, T.; Klankermayer, J.; Leitner, W. Hydrogenation of carbon dioxide to methanol by using a homogeneous ruthenium–phosphine catalyst. Angew. Chem. Int. Ed. 2012, 51, 7499–7502. [Google Scholar] [CrossRef] [PubMed]
  18. Huff, C.A.; Sanford, M.S. Cascade catalysis for the homogeneous hydrogenation of CO2 to methanol. J. Am. Chem. Soc. 2011, 133, 18122–18125. [Google Scholar] [CrossRef] [PubMed]
  19. Rezayee, N.M.; Huff, C.A.; Sanford, M.S. Tandem amine and ruthenium-catalyzed hydrogenation of CO2 to methanol. J. Am. Chem. Soc. 2015, 137, 1028–1031. [Google Scholar] [CrossRef] [PubMed]
  20. Tominaga, K.; Sasaki, Y.; Kawai, M.; Watanabe, T.; Saito, M. Ruthenium complex catalysed hydrogenation of carbon dioxide to carbon monoxide, methanol and methane. J. Chem. Soc. Chem. Commun. 1993, 0, 629–631. [Google Scholar] [CrossRef]
  21. Wesselbaum, S.; Moha, V.; Meuresch, M.; Brosinski, S.; Thenert, K.M.; Kothe, J.; vom Stein, T.; Englert, U.; Hölscher, M.; Klankermayer, J.; et al. Hydrogenation of carbon dioxide to methanol using a homogeneous ruthenium–triphos catalyst: From mechanistic investigations to multiphase catalysis. Chem. Sci. 2015, 6, 693–704. [Google Scholar] [CrossRef] [PubMed]
  22. Kothandaraman, J.; Goeppert, A.; Czaun, M.; Olah, G.A.; Prakash, G.K.S. Conversion of CO2 from air into methanol using a polyamine and a homogeneous ruthenium catalyst. J. Am. Chem. Soc. 2016, 138, 778–781. [Google Scholar] [CrossRef] [PubMed]
  23. Lu, Z.; Williams, T.J. Di(carbene)-supported nickel systems for CO2 reduction under ambient conditions. ACS Catal. 2016, 6, 6670–6673. [Google Scholar] [CrossRef]
  24. Bontemps, S.; Vendier, L.; Sabo-Etienne, S. Borane-mediated carbon dioxide reduction at ruthenium: Formation of C1 and C2 compounds. Angew. Chem. Int. Ed. 2012, 51, 1671–1674. [Google Scholar] [CrossRef] [PubMed]
  25. Hadlington, T.J.; Kefalidis, C.E.; Maron, L.; Jones, C. Efficient reduction of carbon dioxide to methanol equivalents catalyzed by two-coordinate amido–germanium(II) and−tin(II) hydride complexes. ACS Catal. 2017, 7, 1853–1859. [Google Scholar] [CrossRef]
  26. Ma, Q.-Q.; Liu, T.; Li, S.; Zhang, J.; Chen, X.; Guan, H. Highly efficient reduction of carbon dioxide with a borane catalyzed by bis(phosphinite) pincer ligated palladium thiolate complexes. Chem. Commun. 2016, 52, 14262–14265. [Google Scholar] [CrossRef] [PubMed]
  27. Liu, T.; Meng, W.; Ma, Q.-Q.; Zhang, J.; Li, H.; Li, S.; Zhao, Q.; Chen, X. Hydroboration of CO2 catalyzed by bis(phosphinite) pincer ligated nickel thiolate complexes. Dalton Trans. 2017, 46, 4504–4509. [Google Scholar] [CrossRef] [PubMed]
  28. Tamang, S.R.; Findlater, M. Cobalt catalysed reduction of CO2 via hydroboration. Dalton Trans. 2018, 47, 8199–8203. [Google Scholar] [CrossRef] [PubMed]
  29. Li, H.; Gonçalves, T.P.; Zhao, Q.; Gong, D.; Lai, Z.; Wang, Z.; Zheng, J.; Huang, K.-W. Diverse catalytic reactivity of a dearomatized PN3P*–nickel hydride pincer complex towards CO2 reduction. Chem. Commun. 2018, 54, 11395–11398. [Google Scholar] [CrossRef] [PubMed]
  30. Yu, D.-G.; Li, B.-J.; Shi, Z.-J. Exploration of new C−O electrophiles in cross-coupling reactions. Acc. Chem. Res. 2010, 43, 1486–1495. [Google Scholar] [CrossRef] [PubMed]
  31. Tasker, S.Z.; Standley, E.A.; Jamison, T.F. Recent advances in homogeneous nickel catalysis. Nature 2014, 509, 299–309. [Google Scholar] [CrossRef] [PubMed]
  32. Su, B.; Cao, Z.-C.; Shi, Z.-J. Exploration of earth-abundant transition metals (Fe, Co, and Ni) as catalysts in unreactive chemical bond activations. Acc. Chem. Res. 2015, 48, 886–896. [Google Scholar] [CrossRef] [PubMed]
  33. Zhang, J.; Medley, C.M.; Krause, J.A.; Guan, H. Mechanistic insights into C−S cross-coupling reactions catalyzed by nickel bis(phosphinite) pincer complexes. Organometallics 2010, 29, 6393–6401. [Google Scholar] [CrossRef]
  34. Zhang, J.; Adhikary, A.; King, K.M.; Krause, J.A.; Guan, H. Substituent effects on Ni–S bond dissociation energies and kinetic stability of nickel arylthiolate complexes supported by a bis(phosphinite)-based pincer ligand. Dalton Trans. 2012, 41, 7959–7968. [Google Scholar] [CrossRef] [PubMed]
  35. Li, H.; Meng, W.; Adhikary, A.; Li, S.; Ma, N.; Zhao, Q.; Yang, Q.; Eberhardt, N.A.; Leahy, K.M.; Krause, J.A.; et al. Metathesis reactivity of bis(phosphinite) pincer ligated nickel chloride, isothiocyanate and azide complexes. J. Organomet. Chem. 2016, 804, 132–141. [Google Scholar] [CrossRef] [Green Version]
  36. Ma, Q.-Q.; Liu, T.; Adhikary, A.; Zhang, J.; Krause, J.A.; Guan, H. Using CS2 to probe the mechanistic details of decarboxylation of bis(phosphinite)-ligated nickel pincer formate complexes. Organometallics 2016, 35, 4077–4082. [Google Scholar] [CrossRef]
  37. Zhang, J.; Liu, T.; Ma, Q.-Q.; Li, S.; Chen, X. A reaction of [2,6-(tBu2PO)2C6H3]NiSCH2Ph with BH3·THF: Borane mediated C–S bond cleavage. Dalton Trans. 2018, 47, 6018–6024. [Google Scholar] [CrossRef] [PubMed]
  38. Zhang, J.; Liu, T.; Wei, C.; Chang, J.; Ma, Q.-Q.; Li, S.; Ma, N.; Chen, X. The reactivity of mercapto groups against boron hydrides in pincer ligated nickel mercapto complexes. Chem. Asian J. 2018, 13. [Google Scholar] [CrossRef] [PubMed]
  39. Vabre, B.; Spasyuk, M.D.; Zargarian, D. Impact of backbone substituents on POCOP-Ni pincer complexes: A structural, spectroscopic, and electrochemical study. Organometallics 2012, 31, 8561–8570. [Google Scholar] [CrossRef]
  40. Vabre, B.; Petiot, P.; Declercq, R.; Zargarian, D. Fluoro and trifluoromethyl derivatives of POCOP-type pincer complexes of nickel: Preparation and reactivities in SN2 fluorination and direct benzylation of unactivated arenes. Organometallics 2014, 33, 5173–5184. [Google Scholar] [CrossRef]
  41. Hao, J.; Vabre, B.; Zargarian, D. POCOP-ligated nickel siloxide complexes: Syntheses, characterization, and reactivities. Organometallics 2014, 33, 6568–6576. [Google Scholar] [CrossRef]
  42. Lapointe, S.; Vabre, B.; Zargarian, D. POCOP-type pincer complexes of nickel: Synthesis, characterization, and ligand exchange reactivities of new cationic acetonitrile adducts. Organometallics 2015, 34, 3520–3531. [Google Scholar] [CrossRef]
  43. Buil, M.L.; Elipe, S.; Esteruelas, M.A.; Oñate, E.; Peinado, E.; Ruiz, N. Five-coordinate complexes MHCl(CO)(PiPr3)2 (M = Os, Ru) as precursors for the preparation of new hydrido- and alkenyl-metallothiol and monothio−β-diketonato derivatives. Organometallics 1997, 16, 5748–5755. [Google Scholar] [CrossRef]
  44. Vicic, D.A.; Jones, W.D. Room-temperature desulfurization of dibenzothiophene mediated by [(i-Pr2PCH2)2NiH]2. J. Am. Chem. Soc. 1997, 119, 10855–10856. [Google Scholar] [CrossRef]
  45. Di Vaira, M.; Peruzzini, M.; Stoppioni, P. Hydrochalcogenide and hydride hydrochalcogenide derivatives of rhodium. Inorg. Chem. 1991, 30, 1001–1007. [Google Scholar] [CrossRef]
  46. Courtemanche, M.A.; Legare, M.A.; Maron, L.; Fontaine, F.G. A highly active phosphine–borane organocatalyst for the reduction of CO2 to methanol using hydroboranes. J. Am. Chem. Soc. 2013, 135, 9326–9329. [Google Scholar] [CrossRef] [PubMed]
  47. Lang, A.; Knizek, J.; Nöth, H.; Schur, S.; Thomann, M. Beiträge zur chemie des bors. 237. Bis(benzo-l,3,2-dioxaborolanyl)oxid und 2-(o-hydroxyphenoxy)-benzo-l,3,2-dioxaborolan. Vorstufen zur synthese von catecholboran (benzo-l,3,2-dioxaborolan). Z. Anorg. Allg. Chem. 1997, 623, 901–907. [Google Scholar] [CrossRef]
  48. Chakraborty, S.; Krause, J.A.; Guan, H. Hydrosilylation of aldehydes and ketones catalyzed by nickel PCP-pincer hydride complexes. Organometallics 2009, 28, 582–586. [Google Scholar] [CrossRef]
  49. Castonguay, A.; Spasyuk, D.M.; Madern, N.; Beauchamp, A.L.; Zargarian, D. Regioselective hydroamination of acrylonitrile catalyzed by cationic pincer complexes of Nickel(II). Organometallics 2009, 28, 2134–2141. [Google Scholar] [CrossRef]
  50. Salah, A.B.; Zargarian, D. The impact of P-substituents on the structures, spectroscopic properties, and reactivities of POCOP-type pincer complexes of Nickel(II). Dalton Trans. 2011, 40, 8977–8985. [Google Scholar] [CrossRef] [PubMed]
  51. Gómez-Benítez, V.; Baldovino-Pantaleón, O.; Herrera-Álvarez, C.; Toscano, R.A.; Morales-Morales, D. High yield thiolation of iodobenzene catalyzed by the phosphinite nickel PCP pincer complex: [NiCl{C6H3-2,6-(OPPh2)2}]. Tetrahedron Lett. 2006, 47, 5059–5062. [Google Scholar] [CrossRef]
Catalysts 08 00508 sch001 550
Scheme 1. The nickel complexes used for the catalytic hydroboration of CO2 with HBcat.
Scheme 1. The nickel complexes used for the catalytic hydroboration of CO2 with HBcat.
Catalysts 08 00508 sch001
Catalysts 08 00508 sch002 550
Scheme 2. Synthesis of complex 1c.
Scheme 2. Synthesis of complex 1c.
Catalysts 08 00508 sch002
Catalysts 08 00508 g001 550
Figure 1. Thermal ellipsoid plots of complex 1c at the 50% probability level (hydrogen atoms are omitted for clarity). Selected bond lengths (Å) and angles (deg): Ni1–C1, 1.890(2); Ni1–P1, 2.1389(8); Ni1–P2, 2.1456(8); Ni1–S1, 2.1852(7); P1–Ni1–P2, 164.13(3); S1–Ni1–C1, 177.33(8); P1–Ni1–S1, 98.78(3); P2–Ni1–S1, 97.00(3).
Figure 1. Thermal ellipsoid plots of complex 1c at the 50% probability level (hydrogen atoms are omitted for clarity). Selected bond lengths (Å) and angles (deg): Ni1–C1, 1.890(2); Ni1–P1, 2.1389(8); Ni1–P2, 2.1456(8); Ni1–S1, 2.1852(7); P1–Ni1–P2, 164.13(3); S1–Ni1–C1, 177.33(8); P1–Ni1–S1, 98.78(3); P2–Ni1–S1, 97.00(3).
Catalysts 08 00508 g001
Catalysts 08 00508 g002 550
Figure 2. 11B NMR spectra for the interactions of the nickel complexes (0.01 mmol) with HBcat (0.3 mmol) in benzene-d6 (0.5 mL) under a CO2 atmosphere at room temperature. The spectra were recorded 30 min after carbon dioxide was introduced into the NMR tube. (left, interaction of complex 1b with HBcat; right, interaction of complex 3b with HBcat).
Figure 2. 11B NMR spectra for the interactions of the nickel complexes (0.01 mmol) with HBcat (0.3 mmol) in benzene-d6 (0.5 mL) under a CO2 atmosphere at room temperature. The spectra were recorded 30 min after carbon dioxide was introduced into the NMR tube. (left, interaction of complex 1b with HBcat; right, interaction of complex 3b with HBcat).
Catalysts 08 00508 g002
Catalysts 08 00508 sch003 550
Scheme 3. Catalytic hydroboration of CO2 with HBcat.
Scheme 3. Catalytic hydroboration of CO2 with HBcat.
Catalysts 08 00508 sch003
Catalysts 08 00508 g003 550
Figure 3. 1H NMR spectrum for the hydroboration of CO2 with HBcat catalyzed by complex 1a in benzene-d6.
Figure 3. 1H NMR spectrum for the hydroboration of CO2 with HBcat catalyzed by complex 1a in benzene-d6.
Catalysts 08 00508 g003
Table
Table 1. Turnover number (TON) and turnover frequency (TOF) obtained from the catalytic hydroboration of CO2 with HBcat catalyzed by [2,6-(R2PO)2C6H3]NiX complexes 1.
Table 1. Turnover number (TON) and turnover frequency (TOF) obtained from the catalytic hydroboration of CO2 with HBcat catalyzed by [2,6-(R2PO)2C6H3]NiX complexes 1.
CatalystXRTime (min)Conversion (%)TONTOF (h−1)
1aSHtBu30100450 ± 19900 ± 38
1bSHiPr15100465 ± 151860 ± 60
2aN3tBu30100480 ± 11960 ± 22
2bN3iPr15100477 ± 121908 ± 48
3aNCStBu120000
3bNCSiPr12068325 ± 17163 ± 9
1 Conditions: 0.01 mmol of catalyst, 5.0 mmol of HBcat, 0.02 mmol of C6(CH3)6 (internal standard); 4 mL of benzene-d6, 1 atm of CO2, room temperature; TONs (based on HBcat) were calculated from the 1H NMR spectra and averaged from two to three independent experiments; conversions were based on the 11B NMR spectra.
Table
Table 2. Summary of crystal data and structure refinement for complex 1c.
Table 2. Summary of crystal data and structure refinement for complex 1c.
Empirical formulaC30H24NiO2P2SVolume, Å32582.0(3)
Formula weight569.20Z4
Temp, K103(2)dcalc, g cm−31.464
Crystal systemMonoclinicλ, Å0.71073
Space groupP 1 21/c 1μ, mm−10.983
a, Å14.9995(10)No. of data collected29,194
b, Å9.9798(5)No. of unique data10,374
c, Å17.2488(12)Rint0.0895
α (°)90Goodness-of-fit on F21.003
β (°)90.195(3)R1, wR2 (I > 2σ(I))0.0583, 0.1182
γ (°)90R1, wR2 (all data)0.1111, 0.1411

Share and Cite

MDPI and ACS Style

Zhang, J.; Chang, J.; Liu, T.; Cao, B.; Ding, Y.; Chen, X. Application of POCOP Pincer Nickel Complexes to the Catalytic Hydroboration of Carbon Dioxide. Catalysts 2018, 8, 508. https://doi.org/10.3390/catal8110508

AMA Style

Zhang J, Chang J, Liu T, Cao B, Ding Y, Chen X. Application of POCOP Pincer Nickel Complexes to the Catalytic Hydroboration of Carbon Dioxide. Catalysts. 2018; 8(11):508. https://doi.org/10.3390/catal8110508

Chicago/Turabian Style

Zhang, Jie, Jiarui Chang, Ting Liu, Bula Cao, Yazhou Ding, and Xuenian Chen. 2018. "Application of POCOP Pincer Nickel Complexes to the Catalytic Hydroboration of Carbon Dioxide" Catalysts 8, no. 11: 508. https://doi.org/10.3390/catal8110508

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop