Structure of bis(4-methylpyridine)hydrogen(I) tetraphenylborate

Glidewell, C.; Holden, H. D.

doi:10.1107/s0567740882003732

Cited by 14 publications

(8 citation statements)

References 6 publications

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“…Upon crystallization from a CH 2 Cl 2 or THF solution layered with pentane, only the more polar 5 ·OTf began to crystallize. This result contrasts with the behavior of related compounds where a proton was trapped, for example, between two pyridine or imidazole moieties . Changing the counterion to PF 6 and using more polar solvents such as THF or a THF/MeCN mixture did not lead to the isolation of the desired product.…”

Section: Resultscontrasting

confidence: 58%

Palladium Phosphino-Iminolate Complexes as Metalloligands for Coinage Metals: A Versatile, Ambivalent Behavior

2005

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Reactivity studies with the bis-chelated Pd(II) phosphino-iminolate complex [Pd(dmba)(κ2-P,O-PPh2NC(O)Me)] (2) (dmba = orthometalated dimethylbenzylamine) have shown that it readily reacts as a metalloligand with electrophilic complexes of the coinage metals, selectively via the nitrogen atom of the P,O chelate. After examining its reaction with AgOTf (OTf = SO3CF3), which afforded the first 1-D coordination polymer containing Ag−Pd bonds, [{Ag(2)}OTf] n (3·OTf), we have examined and compared its reactions with H+, Au(PPh3)+, [AuCl(THT)], [Au(THT)]BF4, and [Cu(NCMe)4]BF4. Depending on the nature of the electrophilic metal reagent used, the interaction between the iminolate N atom of 2 and the electrophile can be formally described as a dative bond involving its lone pair, which would formally place the positive charge of the complex more on the coinage metal, or as a more covalent interaction resulting in an increased carbon−oxygen bond order and thus in the pos/baitive charge being more localized on the Pd(II) center. In the former case, the metalloligand formally behaves as a two-electron, L-type donor, whereas in the latter, as a one-electron, X-type donor ligand. This ambivalent behavior explains the formation of the heterobimetallic complexes (6) and ([Au(PPh3)(2)]OTf) or (7·BF4), respectively. Double substitution of the d10 metal center by 2 afforded the Pd/Au/Pd and Pd/Cu/Pd heterotrinuclear complexes (8·BF4) and (9·BF4), respectively. The complexes 2, 5·OTf, 6, 7·BF4, 8·BF4·2CH2Cl2, and 9·BF4 have been structurally characterized by X-ray diffraction.

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Section: Resultscontrasting

confidence: 58%

Palladium Phosphino-Iminolate Complexes as Metalloligands for Coinage Metals: A Versatile, Ambivalent Behavior

2005

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“…For compound 20 , analogous to the bis(pyridine) complexes discussed previously, a short, 2.61 Å, N–N distance was detected by X‐ray (Fig. ) along with an unusually broad N–H stretch vibration at 2500 cm −1 , consistent with a weak HB . The N–H–N proton was found at the center of inversion without residual electron density close to the nitrogens.…”

Section: Halogen Bond Symmetry In the Solid Statementioning

confidence: 54%

“…It was suggested to be centered between equal donors in a single‐well potential (Figs and ) . Despite the lack of experimental evidence, the term “short‐strong hydrogen bond” has been coined and widely spread . The symmetry and exceptional strength of such HBs has, however, been questioned by Perrin, triggering vigorous discussions by Limbach and Singleton for example .…”

Section: Introductionmentioning

confidence: 99%

Halogen bond symmetry: the N–X–N bond

Hakkert

Erdélyi

2014

J of Physical Organic Chem

147

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Halogen bonding is the attractive interaction of an electrophilic region of a halogen with a nucleophile. Its geometry, energy, and dominantly electrostatic nature resemble that of the hydrogen bond. Halogen bond strength critically depends on the electron deficiency of the halogen. Accordingly, halonium ions that bear a formal positive charge are the strongest halogen bond donors known so far. Halonium ions, similar to H + , are capable of simultaneously interacting with two Lewis bases. The structure and properties of the resulting three-center halogen bonds are reviewed herein, based on their spectroscopic and computational data, with the emphasis being placed on one representative example, the [N-XÀN] + interaction. The iodine and bromine-centered systems form symmetric three-center-four-electron halogen bonds that have comparable orbital and electrostatic contributions and a large extent of charge delocalization. Their formation yields significant stabilization. The [N-Cl-N] + bond is computationally predicted to resemble the symmetry of the three-center bond of the heavier halogens, whereas the fluorine-centered halogen bond is predicted to be asymmetric, and thus behave more similar to the analogous, asymmetric three-center [NÀHÀN] + hydrogen bond. Experimental confirmation of the latter predictions remains to be accomplished, along with studies of the possible influence of the disorder of the local environment on halogen bond symmetry, and investigations in the gaseous phase. The electronic structure and the geometry of three-center halogen bonds are of fundamental interest, and also of practical importance, for example due to the occurrence of three-centered halogen bonds in synthetic reagents.

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“…The existence of the pyridine H-bonded dimer [Reaction 2(b)] has been previously demonstrated in organic solvent by vibrational spectroscopy (Tayyari et al, 2010), isotope exchange NMR (Schah-Mohammedi et al, 2000), and single crystal X-ray crystallography (Minshall et al, 1978;Glidewell et al, 1982;Bramme and Zhao, 1995). However, this dimer species has not been studied in aqueous solution.…”

Section: Resultsmentioning

confidence: 99%

Hydrogen Bonded Pyridine Dimer: A Possible Intermediate in the Electrocatalytic Reduction of Carbon Dioxide to Methanol

Yan

Bocarsly

2014

Aerosol Air Qual. Res.

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Previously, electrogenerated pyridinyl was implicated as a catalyst for the reduction of CO 2 to methanol. However, recent quantum mechanical calculations of both the homogeneous redox potential for the pyridinium/pyridinyl redox couple (900 mV more negative than experimentally reported) and the pK a of the reduced pyridinyl species (~27) have led to the proposal that the homogeneous reduction of pyridinium does not play a role in the observed catalytic reduction of CO 2 to methanol. In contrast, a more complete consideration of the reaction including the realization that pyridinium reduction is tightly coupled to H 2 evolution, produces a calculated redox potential in agreement with the experimental findings. In reexamining this system, it is found that aqueous solutions containing a near equimolar mixture of pyridine and pyridinium (i.e., solution pH near the pyridinium pK a = 5.2) contain a substantial concentration of a hydrogen-bonded dimer formed by the generation of a N-H···N bond containing one strong NH bond and one elongated NH bond. This species has been identified by X-ray diffraction of crystals grown in aqueous media from pyridine/pyridinium mixtures, and can be observed directly in solution using Raman spectroscopy. DFT (density functional theory) calculations indicate that the pK a for this species is ~22, a value that is consistent with a proton exchange capability. This suggests that this hydrogen bonded dimer may be the pre-electrocatalyst for the observed activation of CO 2 .

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Structure of bis(4-methylpyridine)hydrogen(I) tetraphenylborate

Cited by 14 publications

References 6 publications

Palladium Phosphino-Iminolate Complexes as Metalloligands for Coinage Metals: A Versatile, Ambivalent Behavior

Palladium Phosphino-Iminolate Complexes as Metalloligands for Coinage Metals: A Versatile, Ambivalent Behavior

Halogen bond symmetry: the N–X–N bond

Hydrogen Bonded Pyridine Dimer: A Possible Intermediate in the Electrocatalytic Reduction of Carbon Dioxide to Methanol

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