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Papangelis E, Pelzer K, Gourlaouen C, Armspach D, Braunstein P, Danopoulos AA, Bailly C, Tsoureas N, Gerokonstantis DT. New Pyridine Dicarbene Pincer Ligands with Ring Expanded NHCs and their Nickel and Chromium Complexes. Chem Asian J 2024; 19:e202400169. [PMID: 38619064 DOI: 10.1002/asia.202400169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Revised: 04/14/2024] [Accepted: 04/15/2024] [Indexed: 04/16/2024]
Abstract
The pincer complexes [NiIIBr(CNC)]Br (4), [CrIIIBr3(CNC)] (5 a) and [CrIIIBr2.3Cl0.7(CNC)] (5 b), where CNC=3,3'-(pyridine-2,6-diyl)bis(1-mesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene), were obtained from the novel ligand CNC, generated in situ from the precursor (CHNCH)Br2 and [NiIIBr2(PPh3)2] or from [CrII{N(SiMe3)2}2(THF)2] and (CHNCH)Br2 by aminolysis, respectively. The tetrahedrally distorted square planar (τ4≅0.30) geometry and the singlet ground state of Ni in 4 were attributed to steric constraints of the CNC backbone. Computational methods highlighted the dependence of the coordination geometry and the singlet-triplet energy difference on the size of the N-substituent of the tetrahydropyrimidine wingtips and contrasted it to the situation in 5-membered imidazolin-2-ylidene pincer analogues. The octahedral CrIII metal center in 5 a and 5 b is presumably formed after one electron oxidation from CH2Cl2. 4/MAO and 5 a/MAO were catalysts of moderate activity for the oligomerization and polymerization of ethylene, respectively. The analogous (CH^N^CH)Br2 precursor, where (CH^N^CH)=3,3'-(pyridine-2,6-diylbis(methylene))bis(1-mesityl-3,4,5,6-tetrahydropyrimidin-1-ium), was also prepared, however its coordination chemistry was not studied due to the inherent instability of the resulting free C^N^C ligand.
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Affiliation(s)
- Evangelos Papangelis
- Inorganic Chemistry Laboratory, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Zografou, 15771, Athens, Greece
| | - Katrin Pelzer
- Equipe Confinement Moléculaire et Catalyse, Institut de Chimie de Strasbourg, UMR 7177 CNRS, Université de Strasbourg, 4, rue Blaise Pascal, CS-90032, 67081, Strasbourg Cedex, France
| | - Christophe Gourlaouen
- Laboratoire de Chimie Quantique, Institut de Chimie de Strasbourg, UMR 7177 CNRS, Université de Strasbourg, 4, rue Blaise Pascal, CS-90032, 67081, Strasbourg Cedex, France
| | - Dominique Armspach
- Equipe Confinement Moléculaire et Catalyse, Institut de Chimie de Strasbourg, UMR 7177 CNRS, Université de Strasbourg, 4, rue Blaise Pascal, CS-90032, 67081, Strasbourg Cedex, France
| | - Pierre Braunstein
- Equipe Confinement Moléculaire et Catalyse, Institut de Chimie de Strasbourg, UMR 7177 CNRS, Université de Strasbourg, 4, rue Blaise Pascal, CS-90032, 67081, Strasbourg Cedex, France
| | - Andreas A Danopoulos
- Inorganic Chemistry Laboratory, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Zografou, 15771, Athens, Greece
| | - Corinne Bailly
- Fédération de Chimie "Le Bel" -, UAR2042, BP 296R8, 1, rue Blaise Pascal, 67008, Strasbourg Cedex, France
| | - Nikolaos Tsoureas
- Inorganic Chemistry Laboratory, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Zografou, 15771, Athens, Greece
| | - Dimitrios Triantafyllos Gerokonstantis
- Laboratory of Analytical Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Zografou, 15771, Athens, Greece
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Fogos WF, Lessa MD, de Carvalho da Silva F, de Carneiro JWM. Mechanistic insights into C(sp 2)-H activation in 1-Phenyl-4-vinyl-1H-1,2,3-triazole derivatives: a theoretical study with palladium acetate catalyst. J Mol Model 2024; 30:183. [PMID: 38782773 DOI: 10.1007/s00894-024-05987-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Accepted: 05/17/2024] [Indexed: 05/25/2024]
Abstract
CONTEXT The activation of C-H bonds is a fundamental process in synthetic organic chemistry, which enables their replacement by highly reactive functional groups. Coordination compounds serve as effective catalysts for this purpose, as they facilitate chemical transformations by interacting with C-H bonds. A comprehensive understanding of the mechanism of activation of this type of bond lays the foundation for the development of efficient protocols for cross-coupling reactions. We explored the activation of C(sp2)-H bonds in 1-Phenyl-4-vinyl-1H-1,2,3-triazole derivatives with CH3, OCH3, and NO2 substituents in the para position of the phenyl ring, using palladium acetate as catalyst. The studied reaction is the first step for subsequent conjugation of the triazoles with naphthoquinones in a Heck-type reaction to create a C-C bond. The basic nitrogen atoms of the 1,2,3-triazole coordinate preferentially with the cationic palladium center to form an activated species. A concerted proton transfer from the terminal vinyl carbon to one of the acetate ligands with low activation energy is the main step for the C(sp2)-H activation. This study offers significant mechanistic insights for enhancing the effectiveness of C(sp2)-H activation protocols in organic synthesis. METHODS All calculations were performed using the Gaussian 09 software package and density functional theory (DFT). The structures of all reaction path components were fully optimized using the CAM-B3LYP functional with the Def2-SVP basis set. The optimized geometries were analyzed by computing the second-order Hessian matrix to confirm that the corresponding minimum or transition state was located. To account for solvent effects, the Polarizable Continuum Model of the Integral Equation Formalism (IEFPCM) with water as the solvent was used.
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Affiliation(s)
- Wagner F Fogos
- Department of Inorganic Chemistry, Institute of Chemistry, Fluminense Federal University, Niterói, Brazil.
| | - Milena D Lessa
- Department of Inorganic Chemistry, Institute of Chemistry, Fluminense Federal University, Niterói, Brazil
| | - Fernando de Carvalho da Silva
- Department of Organic Chemistry, Institute of Chemistry, Fluminense Federal University, Outeiro de São João Batista-, Niterói, RJ, 24020-141, Brazil
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Höhn V, Feuerstein W, Rehak FR, Kehry M, Lebedkin S, Kappes MM, Klopper W, Breher F. Non-Palindromic C∧C∧P Platinum and Palladium Pincer Complexes Showing Intense Phosphorescence via Direct Spin-Forbidden S 0 → T 1 Excitation. Inorg Chem 2023; 62:15627-15640. [PMID: 37682719 DOI: 10.1021/acs.inorgchem.3c02339] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/10/2023]
Abstract
The synthesis of C∧C∧P pre-ligands based on a dicyclohexylphosphine-substituted biphenyl framework is reported. The pre-ligands form the respective non-palindromic pincer complexes of PtII and PdII via double oxidative addition and subsequent comproportionation or C-H activation. The complexes of PtII as well as PdII emit similar green phosphorescence efficiently in the solid state, the former also in solution albeit with less intensity. The most fascinating photophysical feature, however, is a direct singlet-triplet (S0 → T1) excitation of this phosphorescence in the spectral window between the emission and the major singlet-singlet UV absorption. The S0 → T1 excitation spectra show a rich vibronic pattern, which is especially pronounced for the solid samples at cryogenic temperatures. The molar extinction of the lowest-energy singlet-triplet absorption band of the homologous Pt and Pd complexes as well as that of the Pt complex with a different (NHC) ancillary ligand were determined in tetrahydrofuran solutions. Quantum efficiencies of triplet formation (by intersystem crossing) via the "standard" excitation pathway S0 → Sn → T1 were determined for the Pt complexes and found to be different in dependence of the ancillary ligand.
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Affiliation(s)
- Verena Höhn
- Karlsruhe Institute of Technology (KIT), Institute of Inorganic Chemistry, Engesserstraße 15, 76131 Karlsruhe, Germany
| | - Wolfram Feuerstein
- Karlsruhe Institute of Technology (KIT), Institute of Inorganic Chemistry, Engesserstraße 15, 76131 Karlsruhe, Germany
| | - Florian R Rehak
- Karlsruhe Institute of Technology (KIT), Institute of Physical Chemistry, Fritz-Haber-Weg 2, 76131 Karlsruhe, Germany
| | - Max Kehry
- Karlsruhe Institute of Technology (KIT), Institute of Physical Chemistry, Fritz-Haber-Weg 2, 76131 Karlsruhe, Germany
| | - Sergei Lebedkin
- Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Manfred M Kappes
- Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Wim Klopper
- Karlsruhe Institute of Technology (KIT), Institute of Physical Chemistry, Fritz-Haber-Weg 2, 76131 Karlsruhe, Germany
| | - Frank Breher
- Karlsruhe Institute of Technology (KIT), Institute of Inorganic Chemistry, Engesserstraße 15, 76131 Karlsruhe, Germany
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He F, Gourlaouen C, Pang H, Braunstein P. Experimental and Theoretical Study of Ni II - and Pd II -Promoted Double Geminal C(sp 3 )-H Bond Activation Providing Facile Access to NHC Pincer Complexes: Isolated Intermediates and Mechanism. Chemistry 2022; 28:e202200507. [PMID: 35543286 PMCID: PMC9401054 DOI: 10.1002/chem.202200507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Indexed: 11/11/2022]
Abstract
We report the first examples of metal-promoted double geminal activation of C(sp3 )-H bonds of the N-CH2 -N moiety in an imidazole-type heterocycle, leading to nickel and palladium N-heterocyclic carbene complexes under mild conditions. Reaction of the new electron-rich diphosphine 1,3-bis((di-tert-butylphosphaneyl)methyl)-2,3-dihydro-1H-benzo[d]imidazole (1) with [PdCl2 (cod)] occurred in a stepwise fashion, first by single C-H bond activation yielding the alkyl pincer complex [PdCl(PCsp 3 H P)] (3) with two trans phosphane donors and a covalent Pd-Csp 3 bond. Activation of the C-H bond of the resulting α-methine Csp 3 H-M group occurred subsequently when 3 was treated with HCl to yield the NHC pincer complex [PdCl(PCNHC P)]Cl (2). Treatment of 1 with [NiBr2 (dme)] also afforded a NHC pincer complex, [NiBr(PCNHC P)]Br (6), but the reactions leading to the double geminal C-H bond activation of the N-CH2 -N group were too fast to allow identification or isolation of an intermediate analogous to 3. The determination of six crystal structures, the isolation of reaction intermediates and DFT calculations provided the basis for suggesting the mechanism of the stepwise transformation of a N-CH2 -N moiety in the N-CNHC -N unit of NHC pincer complexes and explain the key differences observed between the Pd and Ni chemistries.
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Affiliation(s)
- Fengkai He
- School of Chemistry and Chemical EngineeringYangzhou UniversityYangzhou225009JiangsuP. R. China) E-mail: s
- Laboratoire de Chimie de CoordinationInstitut de Chimie (UMR 7177 CNRS)Université de Strasbourg4 rue Blaise Pascal67081StrasbourgFrance
| | - Christophe Gourlaouen
- Laboratoire de Chimie QuantiqueInstitut de Chimie (UMR 7177 CNRS)Université de Strasbourg4 rue Blaise Pascal67081StrasbourgFrance
| | - Huan Pang
- School of Chemistry and Chemical EngineeringYangzhou UniversityYangzhou225009JiangsuP. R. China) E-mail: s
| | - Pierre Braunstein
- Laboratoire de Chimie de CoordinationInstitut de Chimie (UMR 7177 CNRS)Université de Strasbourg4 rue Blaise Pascal67081StrasbourgFrance
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