Protonation of N-heterocyclic carbene ligand coordinated to copper(I): Coordination mode of imidazolium cation as a function of counterion as determined by solid-state structures

Blue, Elizabeth D.; Gunnoe, T. Brent; Petersen, Jeffrey L.; Boyle, Paul D.

doi:10.1016/j.jorganchem.2006.09.051

Cited by 22 publications

(20 citation statements)

References 41 publications

(54 reference statements)

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“…[56] Furthermore, p coordination of naked Cu + is perfectly consistent with well-established concepts for metal-ion coordination, [49,[57][58][59][60] and indeed, crystallographic evidence for h 1 -, h 2 -, and h 6 -coordination of Cu I to arenes [61][62][63][64][65] exists, including examples for preferential p-rather than O-binding of Cu I to p-benzoquinones. [66,67] As the second part of our model system, we investigated…”

Section: A C H T U N G T R E N N U N G (Phoh)]supporting

confidence: 78%

The Phenoxy/Phenol/Copper Cation: A Minimalistic Model of Bonding Relations in Active Centers of Mononuclear Copper Enzymes

Milko

Roithová

Schröder

et al. 2008

Chemistry A European J

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The "bare" complex [Cu(PhOH)(PhO)](+) with a phenol (PhOH) and a phenoxy (PhO) ligand bound to copper is studied both experimentally and computationally. The binding energies and structure of this complex are probed by mass spectrometry, infrared multi-photon dissociation, and DFT calculations. Further, the monoligated complexes [Cu(PhO)](+) and [Cu(PhOH)](+) are investigated for comparison. DFT calculations on the [Cu(PhOH)(PhO)](+) complex predict that a phenolate anion interacts with copper(II) preferentially through the oxygen atom, and the bonding is associated with electron transfer to the metal center resulting in location of the unpaired electron at the aromatic moiety. Neutral phenol, on the other hand, interacts with copper preferentially through the aromatic ring. The same arrangements are also found in the monoligated complexes [Cu(PhO)](+) and [Cu(PhOH)](+). The calculations further indicate that the bond strength between the copper atom and the oxygen atom of the phenoxy radical is weakened by the presence of neutral phenol from 2.6 eV in bare [Cu(PhO)](+) to 2.1 eV in [Cu(PhOH)(PhO)](+).

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Section: A C H T U N G T R E N N U N G (Phoh)]supporting

confidence: 78%

The Phenoxy/Phenol/Copper Cation: A Minimalistic Model of Bonding Relations in Active Centers of Mononuclear Copper Enzymes

Milko

Roithová

Schröder

et al. 2008

Chemistry A European J

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“…A reaction of 1 and 2 (1:1) in THF led to the formation of backbone‐functionalized imidazolium triflate 3 along with 1,3‐(2,6‐diisopropylphenyl)‐imidazolium triflate 4 , a conjugated acid of carbene 1 , in about 9:1 ratio (Scheme ). Compound 3 was isolated in a pure form (61 % yield) by recrystallization of the crude mixture by slow evaporation of n ‐hexane to a saturated THF solution of it.…”

Section: Resultsmentioning

confidence: 99%

“…The calculated N1ÀC1 and N2ÀC1 bond lengths, 1.323(3) and 1.333(2) ,r espectively, suggest that the positive chargei sd elocalized over the two Na toms.Asimilars ituation was found in compound 4 (1.324(4) and 1.333 (4) ). [12] The backbone C2ÀC3 bond length in compound 3 was 1.357 (3) ,w hich is slightly largert han that of corresponding bond length in compound 4 (1.333 (5) ).…”

Section: Introductionmentioning

confidence: 90%

“…In doing so, we have developed method fort he in situ generation of free N-alkyl CAAC.T his opens up the synthetic preparation of this new family of CAACs, which is extremely important as they are expected to have widely different properties in comparison to their N-aryl-substituted analogues;a situation that has already been proveninN HCs. [11] Results and Discussion Ar eactiono f 1 and 2 (1:1) in THFled to the formation of backbone-functionalized imidazolium triflate 3 along with 1,3-(2,6diisopropylphenyl)-imidazolium triflate 4, [12] ac onjugated acid of carbene 1,i na bout9:1 ratio (Scheme 1). Compound 3 was isolated in ap ure form (61 %y ield) by recrystallization of the crude mixture by slow evaporation of n-hexanet oasaturated THF solution of it.…”

Section: Introductionmentioning

confidence: 99%

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“Abnormal” Addition of NHC to a Conjugate Acid of CAAC: Formation of N‐Alkyl‐Substituted CAAC

Mandal

Dolai

Kalita

et al. 2018

Chemistry A European J

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The addition reactions of N-heterocyclic carbenes (NHCs) are mostly known to occur through the carbenic centre (C2), which leads to a "normal" adduct. Herein, we report the "abnormal" addition of NHC 1 (1,3-(2,6-iPr C H )-imidazole-2-ylidene) to a conjugate acid of cyclic (alkyl)(amino)carbene 2 (CAAC =1-iPr-3,3,5,5-Me -pyrrolinium triflate). Mechanistic study revealed that this reaction proceeded through the in situ formation of 1,3-(2,6-iPr C H )-imidazolium cation 4 and N-iPr-substituted CAAC 5 followed by the oxidative addition of compound 5 across the C4-H bond (alias backbone C-H) of compound 4. The in situ formation of compound 5 was also proven by the oxidative addition of it to the N-H group of iPrNH . DFT calculations also supported the mechanistic findings. A different methodology for the in situ generation of compound 5 by using TMPLi is also described.

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“…In our continued interest in creating simplerd erivatives of nitrogen compounds that might act as ionicliquids [2] motivated us to synthesize the title compound andelucidateits crystal structure by means of adiffraction study. Exampleso fi midazolium-baseds ulfonates haveb een characterized structurallybefore [3][4][5].The title compoundisthe para-toluene-sulfonatesalt of bisimidazole.The asymmetric unit contains half ac ation and ac omplete anion. Thel east-squares planes as defined by the non-hydrogen atomso ft he two heterocyclic moieties, respectively the phenylgroup on the one hand and one of the heterocy-clic rings on the other hand, intersect at an angle of 84.48(4)°.…”

Section: Discussionmentioning

confidence: 99%

Crystal structure of bis(imidazolium) para-toluenesulfonate, C20H22N4O6S2

Moleko

Tshentu

Hosten

et al. 2015

Zeitschrift Für Kristallographie - New Crystal Structures

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Source of materialThecompoundwas prepared upon reacting the neutral nitrogencontaining compound with iron(III)-para-toluenesulfonatehexahydrate in methanol. Crystals suitable for the diffraction study were obtained upon evaporation of the solvent at ambient conditions. Experimental detailsCarbon-bound Hatomswere placed in calculated positions (C-H 0.95 Å) and were included in the refinementinthe riding model approximation, with U iso (H) setto1.2U eq (C). The Hatoms of the methyl group were allowed to rotate with afixed angle around the C-C bond to best fit the experimental electron density (HFIX 137 in the SHELX program suite [10]), with U iso (H) setto1.5U eq (C). Nitrogen-bound Ha tomsw ere placed in calculated positions (N-H 0.88 Å) and were included in the refinement in the riding model approximation, with U iso (H) setto1.2U eq (N). DiscussionPerfluorinated hydrocarbons ionic liquids have attracted much attention as versatilereactionmedia over thepast decades. Aprerequisitefor the suitability of asalttoact as ionic liquid is its low melting pointthat is conveniently achieved by the introduction of long perfluoroalkylalkyl chainsinto simple nitrogen-containing organic moieties and crystallizing theresulting cations by means of bulkier anions suchastosylate [1]. In our continued interest in creating simplerd erivatives of nitrogen compounds that might act as ionicliquids [2] motivated us to synthesize the title compound andelucidateits crystal structure by means of adiffraction study. Exampleso fi midazolium-baseds ulfonates haveb een characterized structurallybefore [3][4][5].The title compoundisthe para-toluene-sulfonatesalt of bisimidazole.The asymmetric unit contains half ac ation and ac omplete anion. Thel east-squares planes as defined by the non-hydrogen atomso ft he two heterocyclic moieties, respectively the phenylgroup on the one hand and one of the heterocy-clic rings on the other hand, intersect at an angle of 84.48(4)°. Intracyclic angles in the cation span arange of 106.93(11)-108.99(11)°with the smallest angle found on one of the "terminal" carbon atomsand the largest angle on one of the nitrogen atoms. The S-O bond lengths are measured in between 1.4355(10)-1.4738(11) Åw ith the shortest bond length observed for the oxygen atom that does not participate in any intermolecu-larc ontacts( videi nfra). In comparisont oo ther tosylateswhose metricalparameters have been deposited with the Cambridge Structural Database [6],t hese values are in good agreementwiththe most commonones observed. In the crystal, classical hydrogen bonds of the N-H×××Otype are observed next to C-H×××Ocontacts whose range invariably falls below the sum of van-der-Waals radii of the atomsparticipating in them [7].The classical hydrogen bonds involve all NH groups as donors and are directed towards two different oxygen atomsofthe tosylate anion as acceptors.The C-H×××Ocontacts are supported by one of the CH groups of the cation and -exclusively -only have one of the two oxygen atomsasacceptors that is also engaged in the clas...

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Protonation of N-heterocyclic carbene ligand coordinated to copper(I): Coordination mode of imidazolium cation as a function of counterion as determined by solid-state structures

Cited by 22 publications

References 41 publications

The Phenoxy/Phenol/Copper Cation: A Minimalistic Model of Bonding Relations in Active Centers of Mononuclear Copper Enzymes

The Phenoxy/Phenol/Copper Cation: A Minimalistic Model of Bonding Relations in Active Centers of Mononuclear Copper Enzymes

“Abnormal” Addition of NHC to a Conjugate Acid of CAAC: Formation of N‐Alkyl‐Substituted CAAC

Crystal structure of bis(imidazolium) para-toluenesulfonate, C20H22N4O6S2

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