A N‐Heterocyclic Carbene‐Supported Zinc Catalyst for the 1,2‐Regioselective Hydroboration of N‐Heteroarenes

Chemistry - A European Journal, Journal Year: 2023, Volume and Issue: 29(38)

Published: April 20, 2023

A fluorenyl-tethered N-heterocyclic carbene LH (LH=[(Flu)H-(CH2 )2 -NHCDipp ]) and its monoanionic version L- are explored in complexation with zinc towards the hydroboration of N-heteroarenes, carbonyl, ester, amide, nitrile under ambient condition. The N-heteroarenes exhibit high 1,2-regioselectivity which is justified by computational analyses. relative rates differently p-substituted (electron donating vs. withdrawing) pyridines also addressed. monodentate offers a better catalytic activity than chelating for steric reasons despite both giving three-coordinate complexes. mechanism involves Zn-H species at heart these processes trapped Ph2 CO. Computational studies suggest that barrier to form hydride complex comparable required following transfer pyridine.

Language: Английский

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Iron-Catalyzed Selective Hydroboration of CO₂ by Cooperative B–H Bond Activation

Organometallics, Journal Year: 2023, Volume and Issue: 42(10), P. 944 - 951

Published: May 9, 2023

We report a novel iron(II) complex supported by an anionic phosphanyl-iminopyridinate ligand, Cp*Fe(Cy2PN═C5H4N) (1), which shows remarkable catalytic activity in the selective hydroboration of CO2 with HBpin, producing boryl formate turnover frequency (TOF) ∼1176 h–1 at room temperature. This catalysis involves cooperative metal–ligand reactivity for H–B bond activation, affording key Fe(II)–H intermediate, Cp*FeH(Cy2PN(Bpin)C5H4N) (2), that binds Bpin moiety non-coordinated amino site. The very fast and formoxy production can be conveniently coupled to N-formylation amines, delivers variety formamides. In addition, reduction CH3OBpin stage was also achieved 1 HBpin under N2.

Language: Английский

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Amphoteric Zinc(II) Hydride Cations [ZnH]⁺: Effect of a Bipyridyl Ligand

Inorganic Chemistry, Journal Year: 2025, Volume and Issue: unknown

Published: April 23, 2025

Terminal zinc hydride cations [(Me2bpy)ZnH(L)][BArF4] (Me2bpy = 6,6'-dimethyl-2,2'-dipyridyl; ArF 3,5-(CF3)2C6H3; L THF, 1a; 4-(dimethylamino)pyridine, DMAP, 1b; pyridine, 1c; 4-(trifluoromethyl)pyridine, 1d) show Zn-H distances in the expected range, as exemplified by single-crystal X-ray diffraction for THF adduct 1a and pyridine 1c. With exception of labile 1a, ν(ZnH) stretching frequencies correlate with electron donating character ligand. The bond shows amphoteric behavior. Reaction ZnEt2 gives cationic ethyl complex [(Me2bpy)ZnEt(thf)][BArF4] (2a), while it undergoes CO2 insertion to form formato [(Me2bpy)Zn(OCHO)(thf)][BArF4] (3a). Thermolysis 3a at 80 °C dinuclear metalation product 4a, which is also formed photolysis 1a. acts a proton donor when treated N-heterocyclic carbene ItBu (ItBu 1,3-di-tert-butylimidazol-2-ylidene), giving imidazolium salt [ItBuH][BArF4], metal, Me2bpy. deprotonation occurs ZnCp*2 (Cp* pentamethylcyclopentadienyl) give dizinc(I) cation [(Me2bpy)Zn-ZnCp*(thf)][BArF4] (6a) Cp*H. Cp2MoH2 (Cp η5-cyclopentadienyl) leads heterobimetallic [(Me2bpy)Zn(μ-H)MoCp2]+[BArF4]- (7) under H2 elimination.

Language: Английский

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Hydrosilylation of nitriles and tertiary amides using a zinc precursor

Organic & Biomolecular Chemistry, Journal Year: 2024, Volume and Issue: 22(15), P. 3053 - 3058

Published: Jan. 1, 2024

A competent and selective hydrosilylation of nitriles tertiary amides catalyzed by zinc bis(hexamethyldisilazide) [Zn(HMDS) 2 ] under solvent-free mild conditions are reported, as a sustainable desirable alternative to existing methods.

Language: Английский

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A Robust C₃-Symmetric Aluminate Hydride for CO₂ Hydroboration Catalysis: Mechanistic Insights and Countercation Influence on Catalytic Performance

Inorganic Chemistry, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 22, 2025

The present study details the synthesis and characterization of a robust, monomeric Al–H aluminate supported by tridentate tris-phenolate ligand, isolated as [2][Li(THF)4] [2][N(nBu)4] salts, which were then exploited CO2 hydroboration catalysts. As initial reactivity studies, it was observed that nucleophilic anion in [2][C] (C = countercation [Li(THF)4]+ or [N(nBu)4]+) reacts fast with CO2, to afford corresponding Al-formate complexes [3][C], structurally characterized. Such anions potential reduction Salts [2–3][N(nBu)4] are efficient robust catalysts presence pinBH Me2S-BH3 hydroborane sources selectively formate-equivalent methanol-equivalent products (TON up 1920), depending on reaction conditions nature countercation. deduced from detailed DFT calculations, [3]− acts catalyst (for borane activation) but also an electrophile (through AlOCO carbon) allowing activation/functionalization thus catalysis occur, process thermodynamically driven stability products. anionic [2]− aluminates, resulting enhanced nucleophilicity (vs neutral analogues), may be crucial for catalytic activity. In contrast, according calculations performed model pinBH, processing via Al–O/B–H σ-bond metathesis appears kinetically unfavored. proposed mechanism involving electrophilic/nucleophilic dual-activation mode rationalizes importance [C]+ [2-3][C] activity selectivity, demonstrated higher performance vs [2][Li(THF)4].

Language: Английский

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Efficient Hydrosilylation of Carbonyls by Zinc Alkyl Complexes Supported by Flexible Amidophosphinochalcogenide Ligands

Organic & Biomolecular Chemistry, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 1, 2025

A facile mono- and di-hydrosilylation of various carbonyls is reported under mild reaction conditions to afford silyl ether-protected alcohols in a single step using novel zinc complexes supported by amidophosphinochalcogenide ligand moieties.

Language: Английский

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Designing γ-Carbonic Anhydrase as a Broad-Scope Metalloreductase with Ultrathermostability and Organic-Solvent Tolerance

ACS Catalysis, Journal Year: 2025, Volume and Issue: unknown, P. 8036 - 8048

Published: April 30, 2025

Language: Английский

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Solvent-free Zn (NSNO) complex-catalysed dihydroboration of nitriles

Chemical Communications, Journal Year: 2022, Volume and Issue: 58(59), P. 8266 - 8269

Published: Jan. 1, 2022

N-donors are the most commonly employed Lewis bases in ligand-assisted catalysis. A dimeric zinc complex (Zn-1) employing a tetradentate pyridine-thioether-anilido-aryloxide NSNO ligand (L) effects quantitative conversion of nitriles to corresponding double hydroborated products at 1 mol% catalyst loading. Variable Time Normalization Analysis kinetic studies showed first-order dependence with respect nitrile, pinacolborane and clear evidence for deactivation. plausible reaction pathway involves B-H bond activation by aryloxide (vs. anilido) donor.

Language: Английский

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PNP-type ligands enabled copper-catalyzed N-formylation of amines with CO₂ in the presence of silanes

Organic & Biomolecular Chemistry, Journal Year: 2022, Volume and Issue: 21(4), P. 832 - 837

Published: Dec. 22, 2022

The sustainable catalytic transformation of carbon dioxide into valuable fine chemicals with high efficiency is a global challenge as although CO2 an abundant, nontoxic, and feedstock it also the most important factor behind Greenhouse Effect. We describe herein PNP-type ligand-enabled copper-catalyzed N-formylation amines utilizing building block in presence hydrosilane reductant. Our current protocol featured newly synthesized ligands broad substrate scope under mild reaction conditions.

Language: Английский

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Bifunctional Activation of NHC‐Zinc Pre‐Catalyst for Effective Hydroboration of Quinolines and Nitriles

ChemCatChem, Journal Year: 2023, Volume and Issue: 15(20)

Published: July 17, 2023

Abstract Zinc dihydride complexes supported by bulky N‐heterocyclic carbenes (NHC) are efficient catalysts in hydroboration reactions. Herein, a set of zinc with an amino‐pyrrolide chelate (H L 1 ) and the small NHC ligand, 2,3‐dimethyl‐3,4‐dichloroimidazol‐2‐ylidene (DDI) was synthesized characterized. In particular, Zn(H 2 ( Zn4) displayed high activity catalytic nitrile dihydroboration using 0.01 mol % loading, quinoline 0.05 loading at room temperature. Stoichiometric reaction Zn4 4 equiv. pinacolborane (HBpin) produced ZnH Zn5 dissociated (Bpin) . Complex , generated situ this bifunctional catalyst activation step, shown to be more active than bis‐NHC analog previously reported examples ligands. addition, variable time normalization analysis (VTNA) showed first‐order dependence on [quinoline], [HBpin] [ ], revealing that single Zn−H is involved cycle, as also observed stoichiometric quinoline. VTNA indicated faces neither deactivation nor product inhibition.

Language: Английский

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