Hydroboration of carbon dioxide with pinacolborane catalyzed by various aluminum hydrides: a comparative mechanistic study

Li, Caiqin; Leng, Geng; Li, Weiyi

doi:10.1039/d2cy01024k

Cited by 4 publications

(2 citation statements)

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“…Our group has a long-standing interest in exploring the chemistry of cationic complexes of group 13 elements and has previously reported on low-coordinated boron and aluminum cations and investigated their catalytic activity. , Interestingly, the activity of cationic species has been found to be far superior to similar neutral congeners; very recently, this has also been computationally verified by Koley and co-workers. , Inspired by the remarkable activity of these cations, herein we target the hydroboration of imines and alkynes under milder reaction conditions catalyzed by three coordinated cationic Al complexes, [ L AlH] + [HB(C 6 F 5 ) 3 ] − ( 1 ), [ L AlH] + [B(C 6 F 5 ) 4 ] − ( 2 ), and [ L AlMe] + [B(C 6 F 5 ) 4 ] − ( 3 ). Efficient conversion of imines and alkynes was observed with catalysts 3 and 2 , respectively.…”

Section: Introductionmentioning

confidence: 99%

Hydroboration of Imines and Alkynes Catalyzed by Electronically Unsaturated Aluminum Hydride and Methyl Aluminum Cations

et al. 2023

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Aluminum hydride cations, [LAlH] + [HB(C 6 F 5 ) 3 ] − (1) and [LAlH] + [B(C 6 F 5 ) 4 ] − (2), and the methyl aluminum cation, [LAlMe] +), due to their electronic and coordinative unsaturation at the Al center, exhibit high Lewis acidity and have been exploited for catalytic hydroboration (using HBpin/HBcat) of a variety of imines and alkynes. These catalysts, under mild reaction conditions, afford excellent yields of the respective products. Thorough mechanistic investigations have been performed using a series of stoichiometric experiments and successful isolation of the key intermediates was accomplished. The obtained results demonstrate the predominant Lewis acid activation mechanism over the pathways previously reported for covalent aluminum complexes catalyzed hydroboration of imines. The title cations form Lewis adducts with imines which are thoroughly characterized via multinuclear NMR measurements. For the hydroboration of alkynes, a detailed mechanistic study with the most efficient catalyst 2 supports the formation of a novel cationic aluminum alkenyl complex [LAl−C(Et)�CH(Et)] + [B(C 6 F 5 ) 4 ] − (7) via the hydroalumination reaction between the Al−H cation 2 and 3-hexyne. Similarly, hydroalumination of an unsymmetric internal alkyne 1-phenyl-1-propyne with 2 occurs regioselectively, leading to the formation of [LAl−C(Me)�CH(Ph)] + [B(C 6 F 5 ) 4 ] − (8). These unique cationic aluminum alkenyl complexes have been isolated and well characterized by multinuclear 1-D and 2-D NMR measurements. These alkenyl complexes further act as catalytically active species to carry forward the hydroboration reaction via the Lewis acid activation pathway.

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Section: Introductionmentioning

confidence: 99%

Hydroboration of Imines and Alkynes Catalyzed by Electronically Unsaturated Aluminum Hydride and Methyl Aluminum Cations

et al. 2023

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“…The renewed interest in molecular aluminum hydrides and the use of Lewis acid borane sources like pinacolborane have resulted in the obtainment of methoxy derivatives in a catalytic manner (Figure ). − Our exploration in understanding the elementary reactions in CO 2 hydrosilylation in the presence of aluminum hydride [(2-Me 2 CH 2 C 6 H 4 )(H)Al(μ-H)] 2 ( 1 ) and [Ph 3 C][B(3,5-C 6 H 3 Cl 2 ) 4 ] ( 2 ) − led us to stumble upon a catalytically active [(2-Me 2 NCH 2 C 6 H 4 )(3,5-C 6 H 3 Cl 2 )Al(μ-H) 2 B(3,5-C 6 H 3 Cl 2 ) 2 ] ( 4 ) (Figure ). Herein, we present detailed experimental and computational results deciphering the role of the aluminum center in CO 2 reduction and that of the boron center in synergistic Si–H activation.…”

Section: Introductionmentioning

confidence: 99%

Quest for Active Species in Al/B-Catalyzed CO₂ Hydrosilylation

Bisht,

Sharma,

Kannan

et al. 2023

Inorg. Chem.

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We demonstrate the catalytic role of aluminum and boron centers in aluminum borohydride [(2-Me2CH2C6H4)(C6H5)Al(μ-H)2B(C6H5)2] (6) during carbon dioxide (CO2) hydrosilylation. Preliminary investigations into CO2 reduction using [(2-Me2NCH2C6H4)(H)Al(μ-H)]2 (1) and [Ph3C][B(3,5-C6H3Cl2)4] (2) in the presence of Et3SiH and PhSiH3 resulted in CH2(OSiR3)2 and CH3OSiR3, which serve as formaldehyde and methanol surrogates, respectively. In pursuit of identifying the active catalytic species, three compounds, B(3,5-C6H3Cl2)3 (3), [(2-Me2NCH2C6H4)(3,5-C6H3Cl2)Al(μ-H)2B(3,5-C6H3Cl2)2] (4), and [(2-Me2NCH2C6H4)2Al(THF)][B(3,5-C6H3Cl2)4] (5), were isolated. Among compounds 2–5, the highest catalytic conversion was achieved by 4. Further, 4 and 6 were prepared in a straightforward method by treating 1 with 3 and BPh3, respectively. 6 was found to be in equilibrium with 1 and BPh3, thus making the catalytic process of 6 more efficient than that of 4. Computational investigations inferred that CO2 reduction occurs across the Al–H bond, while Si–H activation occurs through a concerted mechanism involving an in situ generated aluminum formate species and BPh3.

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Synthesis and structural characterization of 2,2′:6,2″-Terpyridine zinc Formate: Hydroboration and hydrosilylation of CO2 and carbonyl compounds

Loo,

de la Mora,

Parkin

2024

Polyhedron

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Hydroboration of carbon dioxide with pinacolborane catalyzed by various aluminum hydrides: a comparative mechanistic study

Abstract: In this work, density functional theory (DFT) calculations was performed to probe the catalytic viability of various neutral, cationic and anionic aluminum hydrides (AlH) in the hydroboration of CO2 with...

Cited by 4 publications

References 76 publications

Hydroboration of Imines and Alkynes Catalyzed by Electronically Unsaturated Aluminum Hydride and Methyl Aluminum Cations

Hydroboration of Imines and Alkynes Catalyzed by Electronically Unsaturated Aluminum Hydride and Methyl Aluminum Cations

Quest for Active Species in Al/B-Catalyzed CO₂ Hydrosilylation

Synthesis and structural characterization of 2,2′:6,2″-Terpyridine zinc Formate: Hydroboration and hydrosilylation of CO2 and carbonyl compounds

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Hydroboration of carbon dioxide with pinacolborane catalyzed by various aluminum hydrides: a comparative mechanistic study

Abstract: In this work, density functional theory (DFT) calculations was performed to probe the catalytic viability of various neutral, cationic and anionic aluminum hydrides (AlH) in the hydroboration of CO2 with...

Cited by 4 publications

References 76 publications

Hydroboration of Imines and Alkynes Catalyzed by Electronically Unsaturated Aluminum Hydride and Methyl Aluminum Cations

Hydroboration of Imines and Alkynes Catalyzed by Electronically Unsaturated Aluminum Hydride and Methyl Aluminum Cations

Quest for Active Species in Al/B-Catalyzed CO2 Hydrosilylation

Synthesis and structural characterization of 2,2′:6,2″-Terpyridine zinc Formate: Hydroboration and hydrosilylation of CO2 and carbonyl compounds

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About

Quest for Active Species in Al/B-Catalyzed CO₂ Hydrosilylation