The transition metal-catalysed hydroboration reaction

Geier, Stephen J.; Vogels, Christopher M.; Melanson, Jennifer A.; Westcott, Stephen A.

doi:10.1039/d2cs00344a

Cited by 107 publications

(82 citation statements)

References 617 publications

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“…While the complexes highlighted in this Account demonstrate varied activity for (de)hydrogenation and hydrosilylation, many were found to be excellent hydroboration catalysts for different substrates. Although the literature is abundant with examples of hydroboration catalystsespecially for carbonylswe were keen to use this reaction as a platform for investigating the bifunctional potential of our [SNS] ligands. High activity for carbonyl hydroboration catalysis was found for both copper ( 18 , 19 ) and zinc complexes ( 20 , 21 ), as well as divalent 1 Mn .…”

Section: Carbonyl Hydroboration Catalysis and Divergent Mechanismsmentioning

confidence: 99%

Through the Looking Glass: Using the Lens of [SNS]-Pincer Ligands to Examine First-Row Metal Bifunctional Catalysts

Elsby

Baker

2023

Acc. Chem. Res.

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Metrics & MoreArticle Recommendations CONSPECTUS: Homogeneous catalysis is at the forefront of global efforts to innovate the synthesis of fine chemicals and achieve carbon-neutrality in energy applications. For decades, the push toward sustainable catalysis has focused on the development of first-row transition metal catalysts to supplant widespread use of precious metals. Metal−ligand cooperativity is an effective strategy to yield high-performing first-row metal molecular catalysts. Despite remarkable progress, state of the art catalysts often employ phosphorus-based ligands which are air-sensitive, potentially toxic, and on occasion offset the cost-savings of the metal. Thus, the development of simple and economical ligands composed of biomimetic donors should be a key focus that cannot be overlooked in the pursuit of sustainable catalyst candidates. This is an Account of our group's efforts to develop first-row transition metal complexes which use [SNS]-pincer ligands for bifunctional catalysis. We have synthesized two potentially tridentate ligands, one bearing an amido and two thioether donors [(S Me NS Me ), L1] and one which includes thiolate, imine, and thioether donors [(SNS Me ), L2], and used them as platforms upon which to explore the reaction pathways of first-row metals. The [SNS] ligand, L1, leads to formation of high-spin paramagnetic metal complexes of the type M(L1) 2 in which the 6-membered ring thioether donor is hemilabile (M = Mn, Fe, Co). This allows Mn(L1) 2 to function as a carbonyl hydroboration catalyst that operates by a novel hydride-free, inner-sphere reaction pathway. Exploring the reactivity of L2 with Fe and Ni revealed unique coordination chemistry and a variety of mono-, di-, tri-, and tetranuclear complexes enabled by bridging thiolates. Further studies showed L2 undergoes selective C aryl −S bond cleavage upon coordination to a metal with electronrich phosphine donors, yielding a new (CNS) 2− pincer ligand. The analogous reaction with L1 afforded a new (CNS Me ) − pincer ligand via both C aryl −S and benzylic C−H bond cleavage. In an attempt to prepare Fe(L2) 2 , we obtained instead an Fe(N 2 S 3 ) complex in which imine C−C bond formation affords a potentially hexadentate redox-active ligand. The Fe(N 2 S 3 ) complex is a selective catalyst for hydroboration of aldehydes and appears to operate through a complicated mechanism. In contrast, a mechanistic study of Mn(L2)(CO) 3 -photocatalyzed dihydroboration of nitriles indicated that both the flexibility of the κ 3 -SNS Me ligand (fac-vs mer-coordination) and ability of Mn to undergo a spin-state change are required to access low energy barriers for this transformation. To effectively compare the reactivity of the thiolate vs amido donor, we prepared two Cu complexes, Cu(L1)(IPr) and Cu(L2)(IPr) [IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene],showing that, while both served as carbonyl hydroboration catalysts, only the amido complex was an effective catalyst for carbonyl hydrosilylation. In addition, complexes of the...

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Section: Carbonyl Hydroboration Catalysis and Divergent Mechanismsmentioning

confidence: 99%

Through the Looking Glass: Using the Lens of [SNS]-Pincer Ligands to Examine First-Row Metal Bifunctional Catalysts

Elsby

Baker

2023

Acc. Chem. Res.

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“…7 In contrast to trigonal Cu-2 , 6 the molecular structures of both Ag-2 and Au-2 are linear with the Ag–S bond length (2.3477(7) Å) being slightly longer than Au–S (2.2981(7) Å). Interestingly, in contrast to Cu-1 and Cu-2 , neither Ag-1 nor Ag-2 or Au-2 catalysed the hydroboration of carbonyls, although other examples of effective catalysts with silver 8 and gold 9 have been reported. Unlike Cu-2 which forms two isomers in solution (proposed to be E - and Z -imine), 6 NMR spectra of Ag-2 and Au-2 indicated a single isomer for each.…”

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Coinage metal amido and thiolate SNS complexes: consequences of catalyst speciation in Cu(i)-catalysed carbonyl hydroboration

et al. 2023

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“…[1] Amongst the hydrofunctionalization reactions, hydroboration has proven to be a powerful reaction the generation of value-added reagents in organic synthesis. [2] This is in part due to the wide availability of boranes coupled with their high reactivity and selectivity towards unsaturated substrates. To date, many catalytic systems have been reported for hydroboration, with a large proportion being based on transition metals.…”

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“…To date, many catalytic systems have been reported for hydroboration, with a large proportion being based on transition metals. [2,3] However, it is Earth-abundant catalysts which are taking center stage, exhibiting high levels of activity in the hydroboration unsaturated C-C bonds. [4][5][6][7][8] Of these, iron has proved to be a popular catalyst system.…”

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Olefin Hydroboration catalyzed by an iron-borane complex

Grose

Willcox

2023

Preprint

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The transition metal-catalysed hydroboration reaction

Abstract: This review covers the development of the transition metal-catalysed hydroboration reaction, from its beginnings in the 1980s to more recent developments including earth-abundant catalysts and an ever-expanding array of substrates.

Cited by 107 publications

References 617 publications

Through the Looking Glass: Using the Lens of [SNS]-Pincer Ligands to Examine First-Row Metal Bifunctional Catalysts

Through the Looking Glass: Using the Lens of [SNS]-Pincer Ligands to Examine First-Row Metal Bifunctional Catalysts

Coinage metal amido and thiolate SNS complexes: consequences of catalyst speciation in Cu(i)-catalysed carbonyl hydroboration

Olefin Hydroboration catalyzed by an iron-borane complex

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