Synthesis and characterization of oligomeric and polymeric silver-imidazol-2-ylidene iodide complexes

Chen, Wanzhi; Liu, Fenghui

doi:10.1016/s0022-328x(03)00153-0

Cited by 106 publications

(19 citation statements)

References 19 publications

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“…All the bond lengths and bond angles are well in agreement with previously reported coumarin and/or mesityl substituted NHC complexes. − , In the extended crystal structure of the complex, a feeble π–π stacking interaction was observed between the benzo-fused rings of the adjacent coumarin rings with an interaction distance close to 4.1 Å. Accordingly, a set of considerable Ag–F, Ag–HC (mesityl,) and Ag–HC (coumarin) bonds were found to be operating with the interaction distance in the range 3.166–3.757 Å. , …”

Section: Resultssupporting

confidence: 88%

“…Accordingly, a set of considerable Ag−F, Ag−HC (mesityl,) and Ag−HC (coumarin) bonds were found to be operating with the interaction distance in the range 3.166− 3.757 Å. 26,27 Complex 8 (Figure 1) is a well-ordered structure consisting of 7,8-benzocoumarin and mesityl substitution on the imidazol-2-ylidene ring coordinated to a silver atom and an acetate counterion. Atoms of acetate ion are disordered over two sets, while the complex cation is an ordered structure with an inversion center at the metal atom.…”

Section: Resultsmentioning

confidence: 99%

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Novel Carbene Anchored Molecular Catalysts for Hydrogen Evolution Reactions

et al. 2021

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The development of low-cost molecular electrocatalysts for the HER from water remains scarce. The efficient electrocatalytic hydrogen evolution reactions (HER) with a series of sterically encumbered carbene ligated silver(I), gold(I) and nickel(II) complexes established here demonstrate the potential of molecular catalyst in hydrogen production from water. Tuning the benzannulation on the coumarin-substituted N-heterocyclic carbene (NHC) ligands afforded six new silver(I) (5–10), two new gold(I) (11 and 12), and two reported nickel(II) (13 and 14) NHC complexes, which differ by the steric bulk around the metal atom and the counterion. Benefiting from the desirable structure and appropriate porous morphology, complexes 6, 9, 10, and 11 exhibited significant electrocatalytic HER activity in acidic medium with an overpotential of −226.4, −445, −243 and −310 mV vs RHE, respectively, to drive a current density of 10 mA/cm2 when immobilized on glassy carbon electrode, which is analogous to that of several transition metal-based nanomaterials. The kinetic parameters such as Tafel slope value and exchange current density for the active complexes and the former observation authenticated the Volmer–Heyrovsky mechanism. Theoretical studies advocate the potential of developing novel series of carbene-ligated HER electrocatalysts based on the controlled ligand field following scalable and viable protocols.

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Section: Resultssupporting

confidence: 88%

Section: Resultsmentioning

confidence: 99%

Novel Carbene Anchored Molecular Catalysts for Hydrogen Evolution Reactions

et al. 2021

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“…Similar results have been communicated by Lee et al21b Configuration 2d has been previously reported for NHC carbene complexes of Ag with bridging halides involving a planar Ag 2 −halide 2 cluster. 6a, A “butterfly” configuration for Ag 2 I 2 has also been observed 6a, Ion-pair complexes ( 2f ) have been obtained in the reaction of N , N ‘-dimethylimidazolium iodide with Ag 2 O in DCM . Fluxional behavior between [R 2 NHC]−AgX and [(R 2 NHC) 2 −Ag] + [AgX 2 ] - species was observed in solution for most of the complexes 2a…”

Section: Resultssupporting

confidence: 83%

Mechanism of Formation of Silver N-Heterocyclic Carbenes Using Silver Oxide: A Theoretical Study

et al. 2007

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The reasons for the efficiency of the silver oxide route in the synthesis of Ag(I) N-heterocyclic carbene complexes have been investigated by means of DFT calculations. A general reaction system that incorporates two N,N-dimethyl imidazolium cations, two iodides as the counterions, Ag2O, and dichloromethane solvent was considered. Exploration of several pathways for the formation of the two silver−NHC cations gives a clear picture for the reaction mechanism. The favored route involves a barrierless and very exergonic deprotonation of the first imidazolium followed by a low barrier and also exergonic metalation, affording the first silver−NHC. The second imidazolium assists these two steps stabilizing intermediates and the transition state by the formation of a strong Cimidazolium−H···OAg hydrogen bond. The formed [R2NHC]−AgI then diffuses in the solution, while silver hydroxide deprotonates the second imidazolium salt in a slightly endergonic process. After metalation, the second silver−NHC is obtained. The overall reaction is thermodynamically driven, the conversion of two imidazolium salts to two silver carbenes entailing a system stabilization of more than 70 kcal mol-1. As the acid−base reaction between the imidazolium salt and the silver base plays a key role in the process, pK a calculations were performed to compare the basicity of the N-heterocyclic carbene with those of the silver bases Ag2O, AgOH, and AgOAc. From the pK a values obtained, the advantage of silver oxide in the generation of silver carbenes is attributed to its stronger basicity.

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“…Similar results have been communicated by Lee et al [41]. Ion-pair complexes have been obtained in the reaction of N,N-dimethylimidazoliumiodide with Ag 2 O in DCM [42]. Fluxional behavior between [R 2 NHC]-AgX and [(R 2 NHC) 2 -Ag] + [AgX 2 ] − species was observed in solution for most of the complexes [43].…”

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confidence: 85%