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1.
Inorg Chem ; 60(18): 13811-13820, 2021 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-34043353

RESUMO

As prevalent cofactors in living organisms, iron-sulfur clusters participate in not only the electron-transfer processes but also the biosynthesis of other cofactors. Many synthetic iron-sulfur clusters have been used in model studies, aiming to mimic their biological functions and to gain mechanistic insight into the related biological systems. The smallest [2Fe-2S] clusters are typically used for one-electron processes because of their limited capacity. Our group is interested in functionalizing small iron-sulfur clusters with redox-active ligands to enhance their electron storage capacity, because such functionalized clusters can potentially mediate multielectron chemical transformations. Herein we report the synthesis, structural characterization, and catalytic activity of a diferric [2Fe-2S] cluster functionalized with two o-phenylenediamide ligands. The electrochemical and chemical reductions of such a cluster revealed rich redox chemistry. The functionalized diferric cluster can store up to four electrons reversibly, where the first two reduction events are ligand-based and the remainder metal-based. The diferric [2Fe-2S] cluster displays catalytic activity toward silylation of dinitrogen, affording up to 88 equiv of the amine product per iron center.


Assuntos
Proteínas Ferro-Enxofre/química , Nitrogênio/química , Fenilenodiaminas/química , Catálise , Proteínas Ferro-Enxofre/síntese química , Ligantes , Estrutura Molecular , Oxirredução
2.
Chem Soc Rev ; 49(4): 1209-1232, 2020 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-31984394

RESUMO

The development of homogeneous iron catalysts has been a prolific research field in recent years. Many catalytic reactions are no longer limited to noble metals. The use of N-heterocyclic carbenes (NHCs) as ancillary ligands has made substantial impact in noble metal catalysis and also started to gain popularity in iron catalysis in recent years. This review article surveys the recent literature on Fe-NHC-catalyzed chemical reactions, including C-C bond formation, reduction, and oxidation reactions.

3.
J Am Chem Soc ; 140(4): 1263-1266, 2018 01 31.
Artigo em Inglês | MEDLINE | ID: mdl-29320184

RESUMO

We report an unexpected rearrangement of a deprotonated picolyl-functionalized N-heterocyclic carbene (NHC) ligand from N,C-chelate to N,N-chelate in three-legged piano-stool Fe(II) and Ru(II) complexes. The reaction mechanism has been explored for one of the Fe(II) complexes. Experimental and computational studies suggest an unusual intermediate featuring a four-membered chelate ring, where the NHC and the α-carbon of one of the N-substituents coordinate to the Fe(II) center. A possible Fe-alkylidene intermediate has also been predicted by computations.

4.
Inorg Chem ; 57(6): 3054-3060, 2018 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-29494141

RESUMO

Herein we report our investigation into the mechanism of CO2 reduction by HBpin catalyzed by [Ru(CO)H(L)(PPh3)2] (2; L is the 4,5-diazafluorenyl ligand with a Bpin functional group at the 9-position) through computational studies using the model complex [Ru(CO)H(L)(PMe3)2] (A1). The reaction consists of four stages: (1) CO2 insertion into the C-B bond of A1 to form A4, (2) the reduction of A4 by HBpin to afford HCOOBpin (P2) and regenerate A1, (3) the reduction of P2 by HBpin to HCHO (P5), and (4) the reduction of P5 to CH3OBpin (P6). We found that Lewis adduct formation plays a key role in all stages of the mechanism, in that it forms more relaxed rings in the key transition states and makes the hydride more hydridic. Oftentimes, the hydride and Bpin moieties can transfer within the Lewis adducts in a concerted manner in our proposed hydride-shuttle mechanism. The energy spans for all stages of our proposed mechanism are within the range of 15.7-22.6 kcal/mol in terms of Gibbs free energy. In contrast, the direct hydroboration and σ-bond metathesis mechanisms proposed in the literature have extremely high energy barriers because of the highly strained four-membered rings in the transition states and the unactivated hydride in HBpin.

5.
Inorg Chem ; 56(19): 11956-11970, 2017 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-28898100

RESUMO

Complexes [MClCp*(HL)] (1[Fe]/1[Ru]) (where HL = 1-mesityl-3-(pyridin-2-ylmethyl)imidazol-2-ylidene) were synthesized from the reaction of in situ generated HL ligand and [FeClCp*(TMEDA)] (where TMEDA is N,N,N',N'-tetramethylethylenediamine) or [RuClCp*]4, respectively. The deprotonation of 1[Fe]/1[Ru] with 1 equiv of LiHMDS led to cyclometalation through the o-Me of the mesityl group, forming [MCp*(L-κC,κC',κN)] 2[Fe]/2[Ru]. The coordinatively unsaturated compounds [MCp*(HL)]BPh4 3[Fe]/3[Ru] were prepared from 1[Fe]/1[Ru] and halide scavenger NaBPh4. Complex 3[Ru] showed agostic interactions between the o-Me group of the mesityl moiety and the metal center in solution and the solid state. When the vacant coordination site of 3[Fe]/3[Ru] is occupied by CO, the resulting [MCp*(CO)(HL)]BPh4 4[Fe]/4[Ru] can be deprotonated with 1 equiv of KHMDS at the pyridylic position to afford complexes [MCp*L'(CO)] 5[Fe]/5[Ru], where the L'- ligand chelates to the metal center through the nitrogen donor atom of the dearomatized pyridine ring and the carbene carbon. Complex 2[Fe] reacted rapidly with CO to afford the simple ligand substitution product [FeCp*(L-κC,κC')(CO)] 6[Fe], where the L- acts as a bidentate chelating ligand through the carbene carbon and benzylic carbon. Under the same condition, the reaction of 2[Ru] with CO forms [RuCp*L″(CO)] 7[Ru], where the L″- ligand (an isomer of L- and L'-) chelates to the metal center through the carbene carbon and a pyridyl carbon. Complexes 3[Fe]/3[Ru] reversibly bind dinitrogen to form [MCp*(HL)(N2)]BPh4 8[Fe]/8[Ru]. 3[Ru] reversibly binds dihydrogen to give [MCp*(H2)(HL)]BPh4 9[Ru], while no reaction was observed between 3[Fe] and H2. The reaction of 3[Ru] with dioxygen led to the isolation of a stable side-on O2 complex [RuCp*(HL)(O2)]BPh4 10[Ru], while the reaction of 3[Fe] with dioxygen led to an intractable mixture of products.

6.
Org Biomol Chem ; 15(10): 2240-2245, 2017 Mar 08.
Artigo em Inglês | MEDLINE | ID: mdl-28230885

RESUMO

We report the synthesis and characterization of a zwitterionic indenylammonium compound and its carbon-centred reactivity towards reversible CO2 binding at ambient temperature through its formal insertion into a C-H bond as well as the catalytic hydroboration of CO2 to methanol derivatives.

7.
Angew Chem Int Ed Engl ; 56(22): 6317-6320, 2017 05 22.
Artigo em Inglês | MEDLINE | ID: mdl-28295865

RESUMO

We report a gem-specific homo- and cross-dimerization of terminal alkynes catalyzed by a well-defined iron(II) complex containing Cp* and picolyl N-heterocyclic carbene (NHC) ligands, and featuring a piano-stool structure. This catalytic system requires no additives and is compatible with a broad range of substrates, including those with polar functional groups such as NH and OH.

8.
Angew Chem Int Ed Engl ; 56(52): 16588-16592, 2017 12 22.
Artigo em Inglês | MEDLINE | ID: mdl-29108092

RESUMO

Diphenyldiazomethane reacts with HB(C6 F5 )2 and B(C6 F5 )3 , resulting in 1,1-hydroboration and adduct formation, respectively. The hydroboration proceeds via a concerted reaction involving initial formation of the Lewis adduct Ph2 CN2 BH(C6 F5 )2 . The highly sensitive adduct Ph2 CN2 (B(C6 F5 )3 ) liberates N2 and generates Ph2 CB(C6 F5 )3 . DFT computations reveal that formation of Ph2 CN2 B(C6 F5 )3 from carbene, N2 , and borane is thermodynamically favourable, suggesting steric frustration could preclude carbene-borane adduct formation and affect FLP-N2 capture.

9.
Nat Commun ; 15(1): 797, 2024 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-38280870

RESUMO

Exploration of molybdenum complexes as homogeneous hydrogenation catalysts has garnered significant attention, but hydrogenation of unactivated olefins under mild conditions are scarce. Here, we report the synthesis of a molybdenum complex, [Cp*Mo(Ph2PC6H4S-CH = CH2)(Py)]+ (2), which exhibits intriguing reactivity toward C2H2 and H2 under ambient pressure. This vinylthioether complex showcases efficient catalytic activity in the hydrogenation of various aromatic and aliphatic alkenes, demonstrating a broad substrate scope without the need for any additives. The catalytic pathway involves an uncommon oxidative addition of H2 to the cationic Mo(II) center, resulting in a Mo(IV) dihydride intermediate. Moreover, complex 2 also shows catalytic activity toward C2H2, leading to the production of polyacetylene and the extension of the vinylthioether ligand into a pendant triene chain.

10.
J Am Chem Soc ; 135(43): 16175-83, 2013 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-24069952

RESUMO

The 4,5-diazafluorenide ligand (L(-)) serves as an actor ligand in the formal insertion of CO2 into a C-H bond remote from the metal center. With the Ru(II) complex of L(-) as the starting point, Rh(III), Rh(I), and Cu(I) were used as spectator metal centers to tune the reactivity of the actor ligand toward CO2. In the case of Rh(III)-diazafluorenide a room temperature reversible activation of CO2 was observed, similar to the isoelectronic Ru(II) analogue. In the case of Rh(I)- and Cu(I)-diazafluorenide CO2 is trapped by the formation of dinuclear carboxylate complexes and diazafluorene (LH). The spectator metal center could even be replaced entirely with an organic group allowing for the first metal-free reversible tandem CO2 and C-H activation.

11.
Angew Chem Int Ed Engl ; 52(2): 710-3, 2013 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-23165755

RESUMO

A real turn-on: a luminescent lanthanide metal-organic framework shows strong and fast turn-on responses to N,N-dimethylformamide (DMF) vapor. The selective turn-on effect is triggered mainly by DMF-ligand interactions, along with the removal of quencher, water, from the metal coordination sphere.

12.
Chem Commun (Camb) ; 59(32): 4770-4773, 2023 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-37000520

RESUMO

Prompted by the recent stepwise mechanistic proposal for the Huisgen [3+2] cycloaddition reaction between enamine and α-diazo ester, where the nucleophilic addition of the enamine carbon onto the terminal nitrogen of diazo ester is crucial, we examined the possible use of N-heterocyclic olefins (NHOs) as highly electron-rich dipolarophiles in these reactions. The mesoionic NHOs derived from 1,2,3-triazoles undergo fast [4+1] cycloaddition to give 3-(triazolium-4-yl)-(3H)-pyrazol-4-olates at room temperature. The reaction mechanism has been explored through experimental and DFT computational studies.

13.
Inorg Chem ; 51(13): 7039-49, 2012 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-22686513

RESUMO

A novel multidentate ligand with 2,2'-dipyridylamine functionalities, 1,8-bis[4-(2,2'-dipyridylamino)phenylacetylenyl]anthracene (1), has been synthesized through a double Sonogashira coupling reaction and characterized by NMR spectroscopic, elemental, and X-ray diffraction analyses. Compound 1 can bind to either one metal center as a tetradentate ligand or two metal centers as a double-bidentate ligand. In the double-bidentate mode, the distance between the two metal centers may vary significantly. Compound 1 displays bright blue luminescence in the solid state and in solution with a quantum efficiency of 64% relative to 9,10-diphenylanthracene. While the dirhodium complex of 1 shows no luminescence, the two zinc complexes of 1 display blue luminescence with quantum efficiencies slightly lower than that of 1. Organic light-emitting devices (OLEDs) using 1 as the emitter show a maximum current efficiency of 7 cd/A.


Assuntos
2,2'-Dipiridil/análogos & derivados , Antracenos/química , Complexos de Coordenação/síntese química , Luminescência , 2,2'-Dipiridil/química , Antracenos/síntese química , Complexos de Coordenação/química , Ligantes , Modelos Moleculares , Estrutura Molecular
14.
Dalton Trans ; 51(24): 9191-9198, 2022 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-35642920

RESUMO

This Perspective article highlights the recent development of mesoionic N-heterocyclic olefins (mNHOs), where the exo-cyclic olefinic carbon is not bonded to strongly electron-withdrawing groups. The unquenched basicity and nucleophilicity of the exo-cyclic olefinic carbon make mNHOs strong σ-donors and enable unique reactivity patterns.

15.
Sci Adv ; 8(48): eabq7023, 2022 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-36459560

RESUMO

With numerous structurally diverse indoor contaminants, indoor transformation chemistry has been largely unexplored. Here, by integrating protein affinity purification and nontargeted mass spectrometry analysis (PUCA), we identified a substantial class of previously unrecognized indoor transformation products formed through gas-surface reactions with nitrous acid (HONO). Through the PUCA, we identified a noncommercial compound, nitrated bisphenol A (BPA), from house dust extracts strongly binding to estrogen-related receptor γ. The compound was detected in 28 of 31 house dust samples with comparable concentrations (ND to 0.30 µg/g) to BPA. Via exposing gaseous HONO to surface-bound BPA, we demonstrated it likely forms via a heterogeneous indoor chemical transformation that is highly selective toward bisphenols with electron-rich aromatic rings. We used 15N-nitrite for in situ labeling and found 110 nitration products formed from indoor contaminants with distinct aromatic moieties. This study demonstrates a previously unidentified class of chemical reactions involving indoor HONO, which should be incorporated into the risk evaluation of indoor contaminants, particularly bisphenols.

16.
Inorg Chem ; 50(21): 10614-22, 2011 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-21992701

RESUMO

The dinuclear Me(2)Pt(II) complexes of 3,4-bis(quinolin-8-yl)thiophene (1a), 3,4-bis(6 trifluoromethoxyquinolin-8-yl)thiophene (1b), and 3,4-bis(2-methylquinolin-8-yl)thiophene (1c) react with MeOTf (OTf = trifluoromethanesulfonate) to afford the corresponding chiral mononuclear five-coordinate Me(3)Pt(IV) complexes [PtMe(3)(1a)]OTf (3a), [PtMe(3)(1b)]OTf (3b), and [PtMe(3)(1c)]OTf (3c), respectively. [PtMe(3)(1c)]BAr(F)(4) (3d) (where BAr(F)(4) = [B{C(6)H(3)-3,5-(CF(3))(2)}(4)]) has also been synthesized for structural study. While 3a appears to be symmetric in solution and asymmetric in solid state, 3c and 3d are asymmetric in both solution and solid state. The chirality originates from interligand repulsion, rather than any unsymmetrical ligand. Variable-temperature NMR and computational studies suggest a ligand-twisting isomerization pathway for the interconversion of the enantiomers, rather than the rotational exchange of three CH(3) ligands on the metal center.

17.
Chem Commun (Camb) ; 57(83): 10927-10930, 2021 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-34596194

RESUMO

We report the dioxygenation of mesoionic N-heterocyclic olefins (mNHOs) using molecular dioxygen. For 1,2,3-triazole-derived mNHOs possessing a vinyl proton and at least one acidic C-H group, they are oxidized into the corresponding triazolium benzoate salts, whereas those without vinyl proton or an acidic C-H group are oxidized into triazolium oxide and ketones/aldehydes.

18.
Chem Commun (Camb) ; 57(50): 6137-6140, 2021 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-34042131

RESUMO

Mesoionic N-heterocyclic olefins (mNHOs) were first reported last year and their reactivity remains largely unexplored. Herein we report the reaction of unprotected mNHOs and organic azides as a novel synthetic route to a variety of pyrazolo[3,4-d][1,2,3]triazoles, an important structural motif in drug candidates and energetic materials. The only byproduct aniline can be easily recycled and converted back to the starting organic azide, in compliance with the green chemistry principle. The reaction mechanism has been explored through experimental and computational studies.

19.
Inorg Chem ; 49(5): 2026-8, 2010 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-20108943

RESUMO

Two novel ligands, 3,4-bis(quinolin-8-yl)thiophene and 3,4-bis[6-(trifluoromethoxyl)quinolin-8-yl]thiophene, and their corresponding diplatinum complexes have been synthesized and fully characterized. These two complexes feature the inverse sandwich structures and the eta(2)-C,C thiophenes on platinum centers.

20.
Dalton Trans ; 49(35): 12287-12297, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32840277

RESUMO

We report the syntheses of a family of tetrahedral iron complexes bearing a bulky redox active o-phenylenediamide ligand. The electronic structures of these complexes have been investigated by Mössbauer spectroscopy, magnetic susceptibility measurements, and X-ray crystallography.

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