Related Experiment Video
Updated: Oct 14, 2025
06:31
Preparation of SNS CobaltII Pincer Model Complexes of Liver Alcohol Dehydrogenase
Published on: March 19, 2020
7.3K
Transition metal complexes bearing atropisomeric saturated NHC ligands
Mariia Savchuk1, Lucas Bocquin1, Muriel Albalat1
1Aix Marseille Univ, CNRS, Centrale Marseille, iSm2, Marseille, France.
Chirality
|November 5, 2021
Summary
Chiral N-heterocyclic carbene (NHC) metal complexes were synthesized and resolved into enantiomers. Their catalytic activity in asymmetric synthesis was investigated, revealing no direct correlation between configurational stability and enantioselectivity.
Area of Science:
- Organometallic Chemistry
- Asymmetric Catalysis
- Chiral Ligand Design
Background:
- N-heterocyclic carbenes (NHCs) are versatile ligands in organometallic chemistry.
- Axial chirality can be induced in metal-NHC complexes through restricted rotation of substituents.
- Developing enantiopure catalysts is crucial for asymmetric synthesis.
Purpose of the Study:
- To synthesize chiral transition metal-NHC complexes from achiral precursors.
- To resolve these complexes into their respective enantiomers.
- To investigate the relationship between configurational stability and catalytic performance in asymmetric reactions.
Main Methods:
- Synthesis of chiral metal-NHC complexes (Pd, Cu, Ag, Au, Rh).
- Resolution of enantiomers using preparative chiral high-performance liquid chromatography (HPLC).
- Determination of enantiomerization barriers and evaluation in asymmetric intramolecular α-arylation of amides.
Main Results:
- Enantiopure metal-NHC complexes were obtained with high enantiopurity (>99% ee) and good yields.
- Enantiomerization barriers were influenced by the NHC backbone and the coordinated metal.
- Palladium-NHC precatalysts showed that high configurational stability does not guarantee high enantioselectivity in catalysis.
Conclusions:
- Axial chirality in metal-NHC complexes can be effectively controlled and resolved.
- The study highlights the complexity of structure-activity relationships in asymmetric catalysis.
- Configurational stability is not the sole determinant of enantioselective potential in these precatalysts.
Related Concept Videos
01:19Complexation Equilibria: The Chelate Effect
733
In complexation reactions, metal atoms or cations interact with ligands to form donor-acceptor adducts called metal complexes. Ligands that bind through one donor site are monodentate, ligands with two donor sites are bidentate, and those with more than two donor sites are polydentate ligands. For example, ethylene diamine is a bidentate ligand that binds through two nitrogen donor atoms, forming a five-membered ring. EDTA is a polydentate ligand that binds through four oxygen and two nitrogen...
733
02:51Metal-Ligand Bonds
22.1K
The hemoglobin in the blood, the chlorophyll in green plants, vitamin B-12, and the catalyst used in the manufacture of polyethylene all contain coordination compounds. Ions of the metals, especially the transition metals, are likely to form complexes.
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
22.1K
01:09Complexation Equilibria: Factors Influencing Stability of Complexes
538
In complexation reactions, metal cations are the electron pair acceptors, and the ligands are the electron pair donors. The stability of the metal complexes depends primarily on the complexing ability of the central metal ion and the nature of the ligands. Generally, the complexing ability of the metal ion depends on the size and charge of the ion. As the metal ion size increases, the stability of the metal complexes decreases, provided that the valency of the metal ion and the ligands remain...
538
02:34Structural Isomerism
20.1K
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can...
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can...
20.1K
01:07Ladder Diagrams: Complexation Equilibria
448
Ladder diagrams are useful for evaluating equilibria involving metal-ligand complexes. The vertical scale of the ladder diagram represents the concentration of unreacted or free ligand, pL. The horizontal lines on the scale depict the log of stepwise formation constants for metal-ligand complexes and indicate the dominant species in all the regions.
The formation constant, K1, for the formation of Cd(NH3)2+ complex from cadmium and ammonia is 3.55 × 102. Log K1 (i.e. pNH3) is 2.55, and...
The formation constant, K1, for the formation of Cd(NH3)2+ complex from cadmium and ammonia is 3.55 × 102. Log K1 (i.e. pNH3) is 2.55, and...
448
02:42Valence Bond Theory
9.8K
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
9.8K