Publications – N-Heterocyclic Carbenes
Inspired by the tautomeric relationship of imidazole and N-heterocyclic carbenes, we have been intrigued about the implications of such carbenes in metalloenzymes. Enzymes are the machinery of all biological transformations, and provide inspiration for designing artificial catalysts. New insights into the mode of action of enzymes is therefore instrumental for developing more competent synthetic catalysts as well as for better understanding natural systems. In collaboration with F. Paradisi (U Nottingham), we have begun to explore carbene binding to metalloenzymes. We have been focusing on blue copper proteins such as azurin and specific mutants of azurin to investigate the possibility of carbene bonding to the copper center, and to evaluate the effect that such bonding entails. While azurin is predominantly involved in electron transfer processes through reversible copper(II) reduction and oxidation, other blue copper proteins are catalytically active in redox transformations of substrates. Hence, these enzymes provide an attractive probe to explore the relevance of carbene bonding on the catalytic performance of the enzyme.
Independent synthesis of NHC-dithiolate ligand
This work focuses on the development of building blocks andreactions for the construction of a ligand type that has been shown to providemetal complexes possessing unique reactivity, N-heterocyclic carbene (NHC)ligands.
However, treatment of thecorresponding diamine/dithiol precursor in our case instead leads to thedithiazolium salt, where the carbon atom has inserted between the N and Satoms, rather than between the two N atoms.
N-Heterocyclic Carbenes as Ligands in Homogeneous Catalysis ..
It is not surprising that carbohydrate groups have been incorporated into NHC ligands to impose chirality, increase water solubility, and promote biocompatibility.
Substituted arene synthesis by 1,4-Addition
We were delighted to find that the use of 1,3‑bis(2,6‑diisopropylphenyl)imidazol-2‑ylidenechloride (IPr·HCl) afforded high molecular weight polymers with one of thelowest values of polydispersity reported to date for this molecular weightrange (1.09).
PDF Downloads : Oriental Journal of Chemistry
Such novel NHCs and their metal complexes show much promise in catalysis and medicinal chemistry.In this review, we focus on metal complexes that contain both an NHC ligand and a carbohydrate ligand, or have novel NHC ligands bearing pendant carbohydrate groups.
Tetrahydrofuran, anhydrous, ≥99.9%, inhibitor-free | …
N2 - Reaction of free dineopentyl-benzimidazoline-2-ylidene 1 (ligand: np2bimy) with (η3-cycloheptatriene)Mo(CO)3, molar ratio 3:1, provides the coordinatively unsaturated lateral-(np2bimy)2Mo(CO)3 complex 2. Crystal structure analysis of 2 reveals an almost ideal cis-square pyramidal geometry with tilted coordination of the metal, interplanar angles of the np2bimy ligands to the C4Mo plane of about 70° and significant bending of the N-heterocyclic carbene rings towards each other. Quantum chemical calculations (B97-D/6-31G(d)[Mo:cc-pVTZ-PP] level of theory) reproduce this peculiar structure and show it to be more stable by 36 kJ/mol than the second energy-minimum structure with trigonal bipyramidal geometry and the carbene ligands in the axial positions. Calculations indicated no significant Mo-C(II) back-bonding or interactions of the empty d-orbital with adjacent p-orbitals of the ligands, implying that the ligand distortions, tilted coordination and the occurrence of a free coordination site are caused by the spatial demand of the N-substituents.
Aerobic Copper-Catalyzed Organic Reactions - …
It is catalyzed mainly by group 10 metals, often stabilized by ligands like phosphines.
Since palladium complexes with bulky trialkylphosphines are good catalysts for the Suzuki crosscoupling and since NHC resemble basic phosphines we synthesized bis(NHC)palladium(0) complexes.