Reducing CO<sub>2</sub> to Methanol Using Frustrated Lewis Pairs: On the Mechanism of Phosphine–Borane-Mediated Hydroboration of CO<sub>2</sub>

Courtemanche, Marc-André; Légaré, Marc‐André; Maron, Laurent; Fontaine, Frédéric‐Georges

doi:10.1021/ja5047846

Cited by 214 publications

(141 citation statements)

References 80 publications

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“…A recent study by Maron, Fontaine, and co-workers reveals that the reduction of HCO 2 Bcat (generated in situ) by HBcat to HCHO and catBOBcat does not necessarily need a metal catalyst. 19 Nevertheless, according to the DFT calculations, the kinetic barrier for the reduction of HCO 2 Bcat is lowered by 7.5 kcal/ mol when using catalyst 3. 18 Calculations also suggested that the insertion of HCO 2 Bcat crossed the highest kinetic barrier of the complete catalytic cycles.…”

Section: ■ Nickel Pocop-pincer Complexesmentioning

confidence: 93%

Nickel and Iron Pincer Complexes as Catalysts for the Reduction of Carbonyl Compounds

et al. 2015

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CONSPECTUS: The reductions of aldehydes, ketones, and esters to alcohols are important processes for the synthesis of chemicals that are vital to our daily life, and the reduction of CO 2 to methanol is expected to provide key technology for carbon management and energy storage in our future. Catalysts that affect the reduction of carbonyl compounds often contain ruthenium, osmium, or other precious metals. The high and fluctuating price, and the limited availability of these metals, calls for efforts to develop catalysts based on more abundant and less expensive first-row transition metals, such as nickel and iron. The challenge, however, is to identify ligand systems that can increase the thermal stability of the catalysts, enhance their reactivity, and bypass the one-electron pathways that are commonly observed for first-row transition metal complexes. Although many other strategies exist, this Account describes how we have utilized pincer ligands along with other ancillary ligands to accomplish these goals. The bis(phosphinite)-based pincer ligands (also known as POCOP-pincer ligands) create well-defined nickel hydride complexes as efficient catalysts for the hydrosilylation of aldehydes and ketones and the hydroboration of CO 2 to methanol derivatives. The hydride ligands in these complexes are substantially nucleophilic, largely due to the enhancement by the strongly trans-influencing aryl groups. Under the same principle, the pincer-ligated nickel cyanomethyl complexes exhibit remarkably high activity (turnover numbers up to 82,000) for catalytically activating acetonitrile and the addition of H−CH 2 CN across the CO bonds of aldehydes without requiring a base additive. Cyclometalation of bis(phosphinite)-based pincer ligands with low-valent iron species "Fe(PR 3 ) 4 " results in diamagnetic Fe(II) hydride complexes, which are active catalysts for the hydrosilylation of aldehydes and ketones. Mechanistic investigation suggests that the hydride ligand is not delivered to the carbonyl substrates but is important to facilitate ligand dissociation prior to substrate activation. In the presence of CO, the amine-bis(phosphine)-based pincer ligands are also able to stabilize lowspin Fe(II) species. Iron dihydride complexes supported by these ligands are bifunctional as both the FeH and NH moieties participate in the reduction of CO bonds. These iron pincer complexes are among the first iron-based catalysts for the hydrogenation of esters, including fatty acid methyl esters, which find broad applications in industry. Our studies demonstrate that pincer ligands are promising candidates for promoting the first-row transition metal-catalyzed reduction of carbonyl compounds with high efficiency. Further efforts in this research area are likely to lead to more efficient and practical catalysts. ■ INTRODUCTIONOne of the rapidly growing areas of research involves the development of first-row transition metal-based catalysts for chemical transformations. The need for such efforts has been motivated by the fact that prec...

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Section: ■ Nickel Pocop-pincer Complexesmentioning

confidence: 93%

Nickel and Iron Pincer Complexes as Catalysts for the Reduction of Carbonyl Compounds

et al. 2015

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“…A mechanistic investigation was carried out in order to better understand the efficiency of species 7 as a catalyst for the hydroboration of CO2 [41]. Using a computational study based on DFT, we were able to demonstrate that the hydroboration of the CO2 adduct of 7 following a classical pathway would have a very high barrier of activation of 55.7…”

Section: Investigating the Role Of Phosphinoboranes In The Catalytic mentioning

confidence: 99%

Design principles in frustrated Lewis pair catalysis for the functionalization of carbon dioxide and heterocycles

Fontaine

Courtemanche

Légaré

et al. 2017

Coordination Chemistry Reviews

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101

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This is the peer reviewed version of the following article: [Design Principles in Frustrated Lewis KeywordsFrustrated Lewis pairs, Ambiphilic molecules, Boron, Aluminum, Carbon dioxide, Methanol, C-H activation. Highlights 1.Phosphine-aluminum frustrated Lewis pairs (FLPs) can activate CO2 but show significant stability issues. 2.The Lewis acidity and basicity need to be fine-tuned to the desired reactivity for efficient FLP catalysis.3. FLP catalysts need to generate strong hydrides to reduce catalytically carbon dioxide. 4.Transition metal catalysis can serve as an inspiration for the design of metal-free catalysts for many transformations, including the borylation of heteroarenes. Graphical abstract AbstractThis account describes our work on the use of ambiphilic molecules as catalysts for the reduction of carbon dioxide. Starting with the discovery that aluminum ambiphilic species (Me2PCH2AlMe2)2 (1) and Al(C6H4-PPh3)3 (5) could coordinate CO2 but showed significant instability, we found that phosphinoborane Ph2P-2-Bcat-C6H4 (7) was an exceptional catalyst for the hydroboration of CO2 to methoxyboranes, a molecule that can be readily hydrolyzed to methanol. A mechanistic investigation allowed us to outline the similarities between the catalytic activity of frustrated Lewis pairs (FLPs) and that of transition metal complexes. We were able to extrapolate four important guidelines, described in this account, to synthesize efficient metal-free catalysts. We demonstrate that using these concepts it was possible to rationally design FLP catalysts for the C-H borylation of heteroarenes.

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“…Recently, systems containing frustrated Lewis pairs (FLPs) have been found as effective catalysts for H 2 activation678, CO 2 reduction91011 and hydrogenation121314 for the production of C1 fuels. As we know that a FLP contains both Lewis acid and base centers, and the most common active Lewis pairs are B/N, B/P, Al/N and Al/P.…”

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confidence: 99%

Be12O12 Nano-cage as a Promising Catalyst for CO2 Hydrogenation

Zhu

et al. 2017

Sci Rep

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An efficient conversion of CO2 into valuable fuels and chemicals has been hotly pursued recently. Here, for the first time, we have explored a series of M12x12 nano-cages (M = B, Al, Be, Mg; X = N, P, O) for catalysis of CO2 to HCOOH. Two steps are identified in the hydrogenation process, namely, H2 activation to 2H*, and then 2H* transfer to CO2 forming HCOOH, where the barriers of two H* transfer are lower than that of the H2 activation reaction. Among the studied cages, Be12O12 is found to have the lowest barrier in the whole reaction process, showing two kinds of reaction mechanisms for 2H* (simultaneous transfer and a step-wise transfer with a quite low barrier). Moreover, the H2 activation energy barrier can be further reduced by introducing Al, Ga, Li, and Na to B12N12 cage. This study would provide some new ideas for the design of efficient cluster catalysts for CO2 reduction.

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Reducing CO₂ to Methanol Using Frustrated Lewis Pairs: On the Mechanism of Phosphine–Borane-Mediated Hydroboration of CO₂

Cited by 214 publications

References 80 publications

Nickel and Iron Pincer Complexes as Catalysts for the Reduction of Carbonyl Compounds

Nickel and Iron Pincer Complexes as Catalysts for the Reduction of Carbonyl Compounds

Design principles in frustrated Lewis pair catalysis for the functionalization of carbon dioxide and heterocycles

Be12O12 Nano-cage as a Promising Catalyst for CO2 Hydrogenation

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Reducing CO2 to Methanol Using Frustrated Lewis Pairs: On the Mechanism of Phosphine–Borane-Mediated Hydroboration of CO2

Cited by 214 publications

References 80 publications

Nickel and Iron Pincer Complexes as Catalysts for the Reduction of Carbonyl Compounds

Nickel and Iron Pincer Complexes as Catalysts for the Reduction of Carbonyl Compounds

Design principles in frustrated Lewis pair catalysis for the functionalization of carbon dioxide and heterocycles

Be12O12 Nano-cage as a Promising Catalyst for CO2 Hydrogenation

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Reducing CO₂ to Methanol Using Frustrated Lewis Pairs: On the Mechanism of Phosphine–Borane-Mediated Hydroboration of CO₂