Hydroboration of Terminal Alkenes and <i>trans</i>‐1,2‐Diboration of Terminal Alkynes Catalyzed by a Manganese(I) Alkyl Complex

Weber, Stefan; Zobernig, Daniel; Stöger, Berthold; Veiros, Luı́s F.; Kirchner, Karl

doi:10.1002/anie.202110736

Cited by 34 publications

(33 citation statements)

References 67 publications

(11 reference statements)

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“… We also demonstrated that Mn(I)–alkyl complexes are capable of activating C–H bonds of terminal alkynes converting aromatic and aliphatic terminal alkynes efficiently and selectively into head-to-head Z -1,3-enynes and head-to-tail gem-1,3-enynes . Most recently, we showed that Mn(I)–alkyl complexes also catalyze the hydroboration of terminal alkenes (involving B–H bond activation) and the 1,2-diboration of terminal alkynes with pinacolborane (involving C–H bond activation) . Encouraged by these findings, we wondered if Si–H bonds may also be activated thereby initiating hydrosilylations and/or DS reactions of alkenes.…”

Section: Introductionmentioning

confidence: 89%

Manganese-Catalyzed Dehydrogenative Silylation of Alkenes Following Two Parallel Inner-Sphere Pathways

et al. 2021

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We report on an additive-free Mn(I)-catalyzed dehydrogenative silylation of terminal alkenes. The most active precatalyst is the bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn–alkyl bond to yield an acyl intermediate which undergoes rapid Si–H bond cleavage of the silane HSiR3 forming the active 16e– Mn(I) silyl catalyst [Mn(dippe)(CO)2(SiR3)] together with liberated butanal. A broad variety of aromatic and aliphatic alkenes was efficiently and selectively converted into E-vinylsilanes and allylsilanes, respectively, at room temperature. Mechanistic insights are provided based on experimental data and DFT calculations revealing that two parallel reaction pathways are operative: an acceptorless reaction pathway involving dihydrogen release and a pathway requiring an alkene as sacrificial hydrogen acceptor.

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Section: Introductionmentioning

confidence: 89%

Manganese-Catalyzed Dehydrogenative Silylation of Alkenes Following Two Parallel Inner-Sphere Pathways

et al. 2021

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“… 2021 60 24488 24492 . 2 Efficient and selective anti-Markovnikow hydroboration of terminal alkenes by a manganese alkyl carbonyl complex was reported. Furthermore, fully acceptorless trans-1,2-diboration of terminal alkynes, including mechanistic investigations, was presented .…”

Section: Key Referencesmentioning

confidence: 99%

“…Remarkably, we observed high reactivity and selectivity in the anti-Markovnikov hydroboration of alkenes ( Scheme 14 ). 2 It should be noted that, thus far, only manganese complexes in the oxidation state of +II were utilized for hydroboration reactions of alkenes and alkynes by the groups of Zhang and Zheng, 36 Thomas, 37 Karton and de Ruiter, 38 and Rueping. 39 An array of terminal alkenes was efficiently hydroborated, tolerating a broad variety of functional groups such as halides, ethers, esters, and amines with a catalyst loading of merely 0.25 mol % Mn4 for most substrates.…”

Section: Hydrofunctionalization Reactionsmentioning

confidence: 99%

Manganese Alkyl Carbonyl Complexes: From Iconic Stoichiometric Textbook Reactions to Catalytic Applications

Weber¹,

Kirchner²

2022

Acc. Chem. Res.

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Conspectus The activation of weakly polarized bonds represents a challenging, yet highly valuable process. In this context, precious metal catalysts have been used as reliable compounds for the activation of rather inert bonds for the last several decades. Nevertheless, base-metal complexes including cobalt, iron, or nickel are currently promising candidates for the substitution of noble metals in order to develop more sustainable processes. In the past few years, manganese(I)-based complexes were heavily employed as efficient catalysts for (de)hydrogenation reactions. However, the vast majority of these complexes operate via a metal–ligand bifunctionality as already well implemented for precious metals decades ago. Although high reactivity can be achieved in various reactions, this concept is often not applicable to certain transformations due to outer-sphere mechanisms. In this Account, we outline the potential of alkylated Mn(I)-carbonyl complexes for the activation of nonpolar and moderately polar E–H (E = H, B, C, Si) bonds and disclose our successful approach for the utilization of complexes in the field of homogeneous catalysis. This involves the rational design of manganese complexes for hydrogenation reactions involving ketones, nitriles, carbon dioxide, and alkynes. In addition to that, the reduction of alkenes by dihydrogen could be achieved by a series of well-defined manganese complexes which was not possible before. Furthermore, we elucidate the potential of our Mn-based catalysts in the field of hydrofunctionalization reactions for carbon–carbon multiple bonds. Our investigations unveiled novel insights into reaction pathways of dehydrogenative silylation of alkenes and trans -1,2-diboration of terminal alkynes, which was not yet reported for transition metals. Due to rational catalyst design, these transformations can be achieved under mild reaction conditions. Delightfully, all of the employed complexes are bench-stable compounds. We took advantage of the fact that Mn(I) alkyl complexes are known to undergo migratory insertion of the alkyl group into the CO ligand, yielding an unsaturated acyl intermediate. Hydrogen atom abstraction by the acyl ligand then paves the way to an active species for a variety of catalytic transformations which all proceed via an inner-sphere process. Although these textbook reactions have been well-known for decades, the application in catalytic transformations is still in its infancy. A brief historical overview of alkylated manganese(I)–carbonyl complexes is provided, covering the synthesis and especially iconic stoichiometric transformations, e.g., carbonylation, as intensively examined by Calderazzo, Moss, and others. An outline of potential future applications of defined alkyl manganese complexes will be given, which may inspire researchers for the development of novel (base-)metal catalysts.

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“…We have recently reported on the application of the Mn(I) alkyl complex fac -[Mn(dippe)(CO) 3 (CH 2 CH 2 CH 3 )] (dippe = 1,2-bis(di- iso -propylphosphino)ethane) ( Mn1 ) as precatalyst for the hydrogenation of ketones, 22 nitriles, 23 alkenes, 24 CO 2 , 25 the hydroboration and diboration of alkenes and alkynes, 26 the dehydrogenative silylation of alkenes, 27 and the dimerization and cross-coupling of terminal alkynes. 28 Inspired by these results, we wondered if Mn1 is also active in the semihydrogenation of alkynes.…”

Section: Introductionmentioning

confidence: 99%

E-Selective Manganese-Catalyzed Semihydrogenation of Alkynes with H₂ Directly Employed or In Situ-Generated

et al. 2022

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Selective semihydrogenation of alkynes with the Mn(I) alkyl catalyst fac -[Mn(dippe)(CO) 3 (CH 2 CH 2 CH 3 )] (dippe = 1,2-bis(di- iso -propylphosphino)ethane) as a precatalyst is described. The required hydrogen gas is either directly employed or in situ-generated upon alcoholysis of KBH 4 with methanol. A series of aryl-aryl, aryl-alkyl, alkyl-alkyl, and terminal alkynes was readily hydrogenated to yield E- alkenes in good to excellent isolated yields. The reaction proceeds at 60 °C for directly employed hydrogen or at 60–90 °C with in situ-generated hydrogen and catalyst loadings of 0.5–2 mol %. The implemented protocol tolerates a variety of electron-donating and electron-withdrawing functional groups, including halides, phenols, nitriles, unprotected amines, and heterocycles. The reaction can be upscaled to the gram scale. Mechanistic investigations, including deuterium-labeling studies and density functional theory (DFT) calculations, were undertaken to provide a reasonable reaction mechanism, showing that initially formed Z- isomer undergoes fast isomerization to afford the thermodynamically more stable E- isomer.

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Hydroboration of Terminal Alkenes and trans‐1,2‐Diboration of Terminal Alkynes Catalyzed by a Manganese(I) Alkyl Complex

Abstract: A Mn I -catalyzed hydroboration of terminal alkenes Scheme 1. Overview of manganese-based hydroboration catalysts.

Cited by 34 publications

References 67 publications

Manganese-Catalyzed Dehydrogenative Silylation of Alkenes Following Two Parallel Inner-Sphere Pathways

Manganese-Catalyzed Dehydrogenative Silylation of Alkenes Following Two Parallel Inner-Sphere Pathways

Manganese Alkyl Carbonyl Complexes: From Iconic Stoichiometric Textbook Reactions to Catalytic Applications

E-Selective Manganese-Catalyzed Semihydrogenation of Alkynes with H₂ Directly Employed or In Situ-Generated

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Hydroboration of Terminal Alkenes and trans‐1,2‐Diboration of Terminal Alkynes Catalyzed by a Manganese(I) Alkyl Complex

Abstract: A Mn I -catalyzed hydroboration of terminal alkenes Scheme 1. Overview of manganese-based hydroboration catalysts.

Cited by 34 publications

References 67 publications

Manganese-Catalyzed Dehydrogenative Silylation of Alkenes Following Two Parallel Inner-Sphere Pathways

Manganese-Catalyzed Dehydrogenative Silylation of Alkenes Following Two Parallel Inner-Sphere Pathways

Manganese Alkyl Carbonyl Complexes: From Iconic Stoichiometric Textbook Reactions to Catalytic Applications

E-Selective Manganese-Catalyzed Semihydrogenation of Alkynes with H2 Directly Employed or In Situ-Generated

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E-Selective Manganese-Catalyzed Semihydrogenation of Alkynes with H₂ Directly Employed or In Situ-Generated