Argentophilic Interactions in Solution: An EXAFS Study of Silver(I) Nitrene Transfer Catalysts

Mak, Choi L.; Bostick, Benjamín C.; Yassin, Nadine; Campbell, Michael G.

doi:10.1021/acs.inorgchem.8b00934

Cited by 14 publications

(9 citation statements)

References 23 publications

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“… [27] Crystallographic characterization of the catalyst showed a ligand‐bridged dimeric structure with a silver–silver distance of 2.842(2) Å, and the dinuclear complex could also be isolated by column chromatography after the aziridination reaction (Figure 11 d). Subsequent DOSY‐NMR and X‐ray absorption spectroscopy (XAS) studies further established that this catalyst exhibits a dimeric structure with a close silver–silver interaction in solvents such as dichloromethane [6c, 28] . The He group later demonstrated that the same catalyst was effective for intramolecular C–H amidation of carbamates and sulfamates (Figure 11 b), [29] and Bolm reported the use of this catalyst for the imination of sulfides and sulfoxides (Figure 11 c).…”

Section: Catalysis Employing Well‐defined Dinuclear Silver(i) Complexesmentioning

confidence: 97%

“… [30] In 2007, the He group reported an intermolecular C–H amination reaction with PhINNs as the oxidant, using a catalyst system of AgOTf and bathophenanthroline [31] . In this case, the X‐ray crystal structure again showed a dimeric structure, with a silver–silver distance of 3.386(1) Å; however, more detailed solution‐phase characterization using DOSY‐NMR and XAS later revealed that this catalyst exhibits a monomeric structure in solution [6c, 28] …”

Section: Catalysis Employing Well‐defined Dinuclear Silver(i) Complexesmentioning

confidence: 99%

“…We encourage researchers working in this field to be diligent about rigorous solution‐phase characterization, and to be cautious about using X‐ray crystallography as the sole source of structural information that informs mechanistic proposals or computational studies. Recent work has shown that detailed NMR studies, as well as less common techniques such as X‐ray absorption spectroscopy, can indeed provide a better understanding of the structures of silver catalysts in solution [6c, 32] …”

Section: Outlook and Conclusionmentioning

confidence: 99%

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Dinuclear Silver Complexes in Catalysis

2021

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Over the past two decades, there has been a substantial increase in the number of synthetically useful transformations catalyzed by silver. Across the range of silver‐catalyzed reactions that have been reported, dinuclear species often emerge as a common feature, either as the (pre‐)catalysts themselves or as intermediates during catalysis. This Minireview explores the role of dinuclear silver complexes in homogeneous catalysis, which we hope will aid in the development of improved design principles for silver catalysts.

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Section: Catalysis Employing Well‐defined Dinuclear Silver(i) Complexesmentioning

confidence: 97%

Section: Catalysis Employing Well‐defined Dinuclear Silver(i) Complexesmentioning

confidence: 99%

Section: Outlook and Conclusionmentioning

confidence: 99%

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Dinuclear Silver Complexes in Catalysis

2021

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“…Aziridines are important synthetic intermediates in organic synthesis, medicinal chemistry, and polymer chemistry, Catalytic approaches to their syntheses have rapidly expanded in recent years , . Transition metal‐catalyzed reactions involving nitrene transfer to alkenes have gained prominence in this regard , . Of these latter catalysts, copper(I) and silver(I) scorpionate complexes [tris(pyrazolyl)borates, (normal scorpionates, or Tp R , Scheme , top left), tris(pyrazolyl)methanes (Tpm R or C ‐scorpionates, Scheme , top right), certain C‐heteroscorpionates (Scheme , bottom left), and certain nitrogen‐confused C‐scorpionates (Scheme , bottom right)] have proven adept at catalytically affording aziridines from alkenes and various nitrene sources under mild conditions.…”

Section: Introductionmentioning

confidence: 99%

Silver(I) and Copper(I) Complexes of Semi‐Bulky Nitrogen‐Confused C‐Scorpionates

et al. 2020

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Two new sterically demanding nitrogen-confused C-scorpionate ligands with a bis(3,5-diisopropylpyrazol-1yl)methyl group bound to the 3-position of a normal pyrazole ( H L iPr2 ) or an N-toluenesulfonyl pyrazole ( Ts L iPr2 ) have been prepared. Reactions between the ligands ( x L iPr2 ) and silver trifluoromethanesulfonate, AgOTf, gave four new compounds of the types [Ag(Ts, 1b; x = H, 2b) depending on the initial metal:ligand ratio. Similarly, the reactions with [Cu(CH 3 CN) 4 ](PF 6 ) produce [a] Dr.to trap and spectroscopically characterize the nitrene intermediates {[(2-py)Bpm R3R5 ]Cu(NTs)} + in CH 2 Cl 2 at -78°C using (2-tBuSO 2 )C 6 H 4 I=NTs [34] as a soluble nitrene source. The spectroscopic and magnetic data were consistent with diamagnetic, singlet species at -78°C. Calculations showed ground state triplet but all spin states [ 1/3 Cu I -nitrene or 1/3 Cu II -N·(iminyl)] and nitrene binding modes (κ 1 N-, κ 2 N,O-) are thermally accessible. These intermediates were capable of stoichiometrically transferring a nitrene unit to a variety of substrates. Then, different {[(2-py)Bpm R3R5 ]Cu(CH 3 CN)}(PF 6 ) complexes were found to be capable catalysts for nitrene transfer to unsubstituted or p-substituted styrenes giving modest yields (> 65 %) of aziridine under mild ocnditions (PhI=NTs/CH 2 Cl 2 /295 K, 24 h).In a previous study, [27] eight complexes of the type [Ag( x L R ) n ](OTf ) (n = 1, 2 and x L R = H L, Ts L, H L*, and Ts L*) were characterized and evaluated for their ability to catalyze aziridination of styrene. Both ESI(+) MS and NMR spectroscopic studies indicated that the analytically pure [Ag( x L R ) n ](OTf ) compounds did not retain their structure in CH 3 CN rather were involved in multiple dynamic equilibria in solution. These dynamic processes remained in the fast exchange regime on the NMR timescale down to the freezing point of the solvent, thereby obfuscating structural information. These silver complexes of nitrogen-confused C-scorpionates showed no or very little capacity to participate in styrene aziridination using PhI= NTs in room temperature CH 2 Cl 2 . However, [Ag( x L R ) n ](OTf ) showed modest catalytic activity at 80°C in CH 3 CN when employing a nitrene generated in-situ from H 2 NTs and PhI(OAc). Interestingly, the bulkiest derivative [Ag( Ts L * ) 2 ](OTf ) was reported to have the highest activity giving 34 % yield of the desired N-tosyl aziridine. This observation prompted the current study to determine if further increasing steric bulk of the ligands would lead to an increase in catalytic activity of silver complexes. Herein we report on the preparation of two new semi-bulky nitrogen confused scorpionates, Ts L iPr2 and H L iPr2 and their silver(I) and copper(I) complexes. The copper(I) complexes were prepared to compare catalytic activity with their silver congeners, and possibly to demonstrate the generality of any trends in ligand sterics on catalytic activity. It was also hoped that the slower ligand exchange rates associated with the smaller copper(I) compared ...

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“…The non-covalent metal-metal interactions play a significant role in the emission [1,2] or catalytic [3][4][5] properties of the d 10 metal complexes. Dinuclear or trinuclear coinage metal complexes with bridging bis-or trisphosphine ligands represent a unique class of molecules occupying a position between mononuclear complexes and nanoparticles.…”

Section: Introductionmentioning

confidence: 99%

Dinuclear Silver(I) Nitrate Complexes with Bridging Bisphosphinomethanes: Argentophilicity and Luminescence

et al. 2020

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Two silver nitrate complexes with bisphosphines were obtained and characterized: [Ag(dcypm)]2(NO3)2 (1; dcypm = bis(dicyclohexylphosphino)methane) and [Ag(dppm)]2(Me2PzH)n(NO3)2 (n = 1, 2a; n = 2, 2b; dppm = bis(diphenylphosphino)methane, Me2PzH = 3,5-dimethylpyrazole). The steric repulsions of bulky cyclohexyl substituents prevent additional ligand coordination to the silver atoms in 1. Compounds obtained feature the bimetallic eight-member cyclic core [AgPCP]2. The intramolecular argenthophilic interaction (d(Ag···Ag) = 2.981 Å) was observed in complex 1. In contrast, the coordination of pyrazole led to the elongation of Ag···Ag distance to 3.218(1) Å in 2a and 3.520 Å in 2b. Complexes 1 and 2a possess phosphorescence both in the solution and solid state. Time-dependent density-functional theory (TD-DFT) calculations demonstrate the origin of their different emission profile. In the case of 1, upon excitation, the electron leaves the Ag–P bonding orbital and locates on the intramolecular Ag···Ag bond (metal-centered character). Complex 2a at room temperature exhibits a phosphorescence originating from the 3(M + LP+N)LPhCT state. At 77 K, the photoluminescence spectrum of complex 2a shows two bands of two different characters: 3(M + LP+N)LPhCT and 3LCPh transitions. The contribution of Ag atoms to the excited state in both complexes 2a and 2b decreased relative to 1 in agreement with the structural changes caused by pyrazole coordination.

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Argentophilic Interactions in Solution: An EXAFS Study of Silver(I) Nitrene Transfer Catalysts

Cited by 14 publications

References 23 publications

Dinuclear Silver Complexes in Catalysis

Dinuclear Silver Complexes in Catalysis

Silver(I) and Copper(I) Complexes of Semi‐Bulky Nitrogen‐Confused C‐Scorpionates

Dinuclear Silver(I) Nitrate Complexes with Bridging Bisphosphinomethanes: Argentophilicity and Luminescence

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