Spin-state crossover in photo-catalyzed nitrile dihydroboration <i>via</i> Mn-thiolate cooperation

Elsby, Matthew R.; Oh, Chang-Jin; Son, Mina; Kim, Scott Y. H.; Baik, Mu‐Hyun; Baker, R. Tom

doi:10.1039/d2sc04339d

Cited by 9 publications

(8 citation statements)

References 108 publications

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“…A portion of the resulting reaction mixture was then dissolved in C 6 D 6 and transferred to an NMR tube, and the 1 H NMR spectrum was recorded. All diborylamine products were characterized by comparison with their previously reported 1 H NMR spectra. ,− As no side products were observed, the dihydroborated product yield was calculated based on integrals compared to the starting nitrile.…”

Section: Methodsmentioning

confidence: 99%

“…57 Indeed, in our recent work on Mn-catalyzed nitrile dihydroboration, we found that thiolate donors activated HBpin by simple coordination, without B−H transfer to the metal. 50 Synthesis of phosphido-bridged complex 6 revealed the ease of pyridine ring dissociation in the NNN ligand, and the lack of reactivity of 6 with HBpin can also be attributed to weak B−P bonds (ca. 64 kcal/mol).…”

Section: ■ Conclusionmentioning

confidence: 99%

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Comparing B–H Bond Activation in Ni^IIX(NNN)-Catalyzed Nitrile Dihydroboration (X = Anionic N-, C-, O-, S-, or P-donor)

Ataie

Baker

2022

Inorg. Chem.

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One of the key steps in many metal complex-catalyzed hydroboration reactions is B–H bond activation, which results in metal hydride formation. Anionic ligands that include multiple lone pairs of electrons, in cooperation with a metal center, have notable potential in redox-neutral B–H bond activation through metal–ligand cooperation. Herein, using an easily prepared NpyridineNimineNpyrrolide ligand (L2)−, a series of divalent NiIIX(NNN) complexes were synthesized, with X = bromide (2), phenoxide (3), thiophenoxide (4), 2,5-dimethylpyrrolide (5), diphenylphosphide (6), and phenyl (7). The complexes were characterized using 1H and 13C NMR spectroscopy, mass spectrometry, and X-ray crystallography and employed as precatalysts for nitrile dihydroboration. Superior activity of the phenoxy derivative (3) [vs thiophenoxy (4) or phenyl (7)] suggests that B–H bond activation occurs at the Ni–X (vs ligand Ni–Npyrrolide) bond. Furthermore, stoichiometric treatment of 2–7 with a nitrile showed no reaction, whereas stoichiometric reactions of 2–7 with pinacolborane (HBpin) gave the same Ni–H complex for 2, 3, and 5. Considering that only 2, 3, and 5 successfully catalyzed nitrile dihydroboration, we suggest that the catalytic cycle involves a conventional inner sphere pathway initiated by substrate insertion into Ni–H.

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Section: Methodsmentioning

confidence: 99%

Section: ■ Conclusionmentioning

confidence: 99%

Comparing B–H Bond Activation in Ni^IIX(NNN)-Catalyzed Nitrile Dihydroboration (X = Anionic N-, C-, O-, S-, or P-donor)

Ataie

Baker

2022

Inorg. Chem.

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“…To access a diamagnetic monoligated complex of manganese, MnBrCO 5 was treated with L2 and LiHMDS to give Mn(κ 3 -SNS Me )(CO) 3 ( 17 ) which was also not observed to undergo C aryl –S bond cleavage, even upon heating at 100 °C (Scheme B). Surprisingly, in 17 , the L2 ligand is coordinated in a facial manner, which speaks to the flexibility of this ligand despite its 5- and 6-membered ring combination …”

Section: Exploring Coordination Chemistry Of [Sns] Ligands With First...mentioning

confidence: 98%

“…While our M-[SNS] complexes demonstrated high activity as carbonyl hydroboration catalysts, we observed unremarkable reactivity with alkenes, imines, alkynes, etc . When checking for M-hydride formation in the reaction of Mn( L2 )(CO) 3 ( 17 ) with HBpin, we serendipitously observed the dihydroboration of acetonitrile- d 3 solvent . Optimization studies demonstrated that efficient catalysis required the use of a coordinating solvent (THF) and continuous irradiation with UV light.…”

Section: Nitrile Dihydroboration Catalysismentioning

confidence: 99%

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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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Pd/S cooperativity: from stoichiometric activation of Si−H bonds to catalytic hydrosilylation

Clerc,

Humbert,

Mallet‐Ladeira

et al. 2024

ChemistryEurope

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With the aim to explore metal‐ligand cooperation across Pd−S linkages, we designed a quinoline‐based PNS tridentate ligand and prepared Pd(II) complexes thereof. Optimal solubility and stability of the dicationic complex [(PNS)Pd(II)]22+ IV2 were achieved with B(C6F5)4– as counter‐anion. It adopts a thiolate‐bridged dimeric structure with a (PdS)2 core, but readily activates hydrosilanes across the Pd−S linkage. The resulting mononuclear Pd(II) hydride [(PNSSiR3)Pd(II)H]+ VI was characterized by multi‐nuclear NMR spectroscopy and the Si−H bond coordination/activation was studied computationally. Complex IV2 was found to efficiently catalyze the hydrosilylation of alkynes, internal as well as terminal, with good stereo and regioselectivity.

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Spin-state crossover in photo-catalyzed nitrile dihydroboration via Mn-thiolate cooperation

Abstract: The role of a phosphine-free SNS-pincer ligand in metal–ligand cooperative hydroboration catalysis was investigated. The bifunctional thiolate donor and spin-state change to high-spin Mn are crucial to accessing low-energy activation barriers.

Cited by 9 publications

References 108 publications

Comparing B–H Bond Activation in Ni^IIX(NNN)-Catalyzed Nitrile Dihydroboration (X = Anionic N-, C-, O-, S-, or P-donor)

Comparing B–H Bond Activation in Ni^IIX(NNN)-Catalyzed Nitrile Dihydroboration (X = Anionic N-, C-, O-, S-, or P-donor)

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

Pd/S cooperativity: from stoichiometric activation of Si−H bonds to catalytic hydrosilylation

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Spin-state crossover in photo-catalyzed nitrile dihydroboration via Mn-thiolate cooperation

Abstract: The role of a phosphine-free SNS-pincer ligand in metal–ligand cooperative hydroboration catalysis was investigated. The bifunctional thiolate donor and spin-state change to high-spin Mn are crucial to accessing low-energy activation barriers.

Cited by 9 publications

References 108 publications

Comparing B–H Bond Activation in NiIIX(NNN)-Catalyzed Nitrile Dihydroboration (X = Anionic N-, C-, O-, S-, or P-donor)

Comparing B–H Bond Activation in NiIIX(NNN)-Catalyzed Nitrile Dihydroboration (X = Anionic N-, C-, O-, S-, or P-donor)

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

Pd/S cooperativity: from stoichiometric activation of Si−H bonds to catalytic hydrosilylation

Contact Info

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Comparing B–H Bond Activation in Ni^IIX(NNN)-Catalyzed Nitrile Dihydroboration (X = Anionic N-, C-, O-, S-, or P-donor)

Comparing B–H Bond Activation in Ni^IIX(NNN)-Catalyzed Nitrile Dihydroboration (X = Anionic N-, C-, O-, S-, or P-donor)