Organosilicon and ‐germanium Hydrides in Catalyst‐Free Hydrometallation Reactions

Jambor, Roman; Lyčka, Antonı́n

doi:10.1002/ejic.201700630

Cited by 13 publications

(8 citation statements)

References 80 publications

(64 reference statements)

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“…While hydroboration (Figure 1a) is arguably the most widely-studied class of hydroelementation reactions, catalyst or additivefree addition of E-H bonds to unsaturated substrates is now known for several other p-block element hydrides. [1][2][3][4][5][6][7][8][9][10] Besides rapid introduction of chemical complexity in molecular systems, such reactions have also been used for modular synthesis of functional inorganic materials. [11][12][13] Given the atom economy and broad scope of applications of such elementary reactions, the discovery and subsequent understanding of new hydroelementation processes is key to unlocking hitherto unknown synthetic methodologies.…”

Section: Introductionmentioning

confidence: 99%

Hydrostibination of Alkynes: A Radical Mechanism**

MacMillan

Marczenko

Johnson

et al. 2020

Chemistry A European J

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The addition of Sb-H bonds to alkynes was reported recently as a new hydroelementation reaction that exclusively yields anti-Markovnikov Z-olefins from terminal acetylenes. We examine four possible mechanisms that are consistent with the observed stereochemical and regiochemical outcomes. A comprehensive analysis of solvent, substituent, isotope, additive, and temperature effects on hydrostibination reaction rates definitively refutes three ionic mechanisms involving closed-shell charged intermediates. Instead the data support a fourth pathway featuring neutral radical Sb II and Sb III intermediates. Density Functional Theory (DFT) calculations are consistent with this model, predicting an activation barrier that is within 1 kcal/mol of the experimental value (Eyring analysis) and a rate limiting step that is congruent with experimental kinetic isotope effect. We therefore conclude that hydrostibination of arylacetylenes is initiated by the generation of stibinyl radicals, which then participate in a cycle featuring Sb II and Sb III intermediates to yield the observed Z-olefins as products. This mechanistic understanding will enable rational evolution of hydrostibination as a methodology for accessing challenging products such as E-olefins.

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Section: Introductionmentioning

confidence: 99%

Hydrostibination of Alkynes: A Radical Mechanism**

MacMillan

Marczenko

Johnson

et al. 2020

Chemistry A European J

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“…Carbon dioxide is one of the primary greenhouse gases and is mainly responsible for global warming. Although reducing its high concentrations in the air may be impractical, the use of this gas as a C 1 feedstock for the production of added-value compounds such as formic acid, methane, formaldehyde, and methanol is promising. − Germanium(II)- and tin(II)-based catalysts have been proven to be able to carry out hydrometalation reactions of carbonyl-containing compounds, including CO 2 . ,,− Hydrometalation of polar and nonpolar unsaturated bonds has great impact in both organic and inorganic synthesis. − In the present research, we have centered our attention on the hydroboration of CO 2 for the potential formation of formic acid by group 14 MG catalysts.…”

Section: Introductionmentioning

confidence: 83%

Formation of Formic Acid Derivatives through Activation and Hydroboration of CO₂ by Low-Valent Group 14 (Si, Ge, Sn, Pb) Catalysts

2020

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The chemistry of low-valent main group elements has attracted much attention in the past decade. These species are relevant because they have been able to mimic transition metal behavior in catalytic applications, with decreased material costs and diminished toxicity. In this contribution, we study the L 1 EH catalysts (E = Si(II), Ge(II), Sn(II), and Pb(II); L 1 = [ArNC(Me)CHC(Me)NAr] with Ar = 2,6-iPr 2 C 6 H 3 ) for the formation of formic acid derivatives through hydroboration of CO 2 . Detailed characterization of relevant structures on the potential energy surface enabled us to rationalize different paths for the hydroboration of CO 2 . Interestingly, it was found that according to the activation energies for the whole catalytic cycle, the process of transformation of CO 2 becomes more favored going down group 14. However, an effective energetic decrease for the process (taking as the reference the uncatalyzed reaction between CO 2 and HBpin) is evidenced just from the germanium analogue. The trend in reactivity found in the present study is a direct consequence of the change in the central main group element, enabling enhanced polar character of the E−H (L 1 EH in the CO 2 activation step) and E−O (metal formates in the hydroboration step) bonds as the atomic radius increases. The transient stabilization of reaction intermediates found in the hydroboration step was rationalized through the non-covalent interaction index (NCI) and symmetry-adapted perturbation theory (SAPT). This computational study highlights the reactivity trends in group-14based hydride catalysts in hydrometalation and posterior hydroboration to form formic acid intermediates. We hope that this study will motivate further experimental work in low-valent lead chemistry.

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“…Perhaps more importantly, the addition of B-H moieties can also be performed under catalyst-free conditions, which is virtually uncommon in the case of Si-H bond addition. 40,41 This extremely high reactivity mainly applies to non-hindered boranes. Unfortunately, such non-catalytic synthesis requires special precautions and often also harsh reaction conditions.…”

Section: Hydrosilylation and Hydroborationa Short Overviewmentioning

confidence: 99%

Hydrosilylation and hydroboration in a sustainable manner: from Earth-abundant catalysts to catalyst-free solutions

Kuciński

Hreczycho

2020

Green Chem.

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Organosilicon and ‐germanium Hydrides in Catalyst‐Free Hydrometallation Reactions

Cited by 13 publications

References 80 publications

Hydrostibination of Alkynes: A Radical Mechanism**

Hydrostibination of Alkynes: A Radical Mechanism**

Formation of Formic Acid Derivatives through Activation and Hydroboration of CO₂ by Low-Valent Group 14 (Si, Ge, Sn, Pb) Catalysts

Hydrosilylation and hydroboration in a sustainable manner: from Earth-abundant catalysts to catalyst-free solutions

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Organosilicon and ‐germanium Hydrides in Catalyst‐Free Hydrometallation Reactions

Cited by 13 publications

References 80 publications

Hydrostibination of Alkynes: A Radical Mechanism**

Hydrostibination of Alkynes: A Radical Mechanism**

Formation of Formic Acid Derivatives through Activation and Hydroboration of CO2 by Low-Valent Group 14 (Si, Ge, Sn, Pb) Catalysts

Hydrosilylation and hydroboration in a sustainable manner: from Earth-abundant catalysts to catalyst-free solutions

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Formation of Formic Acid Derivatives through Activation and Hydroboration of CO₂ by Low-Valent Group 14 (Si, Ge, Sn, Pb) Catalysts