Magnetic resonance. X. Spectroscopy of carbanions and the effect of ion pairing on chemical shifts

Grutzner, John B.; Lawlor, J. M.; Jackman, L. M.

doi:10.1021/ja00762a023

Cited by 90 publications

(19 citation statements)

References 4 publications

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“…Table 3 shows our 1 H and 13 C NMR data for LiCPh 3 at 299 K in THF. These data are in good agreement with those reported by Sandel and Freedam,39a and later by Jackman et al39b The 13 C chemical shift of the anionic carbon, δ = 90.1 ppm, is found at higher frequency than that of the sp 3 ‐hybridized precursor, δ = 57.3 ppm, in analogy with the known 13 C data for the ipso ‐carbon atom of phenyllithium43 and other metalated phenyl derivatives 44. The low‐frequency shift of C‐4 is consistent with delocalization of some negative charge into the phenyl rings.…”

Section: Resultssupporting

confidence: 93%

⁷Li, ³¹P, and ¹H Pulsed Gradient Spin‐Echo (PGSE) Diffusion NMR Spectroscopy and Ion Pairing: On the Temperature Dependence of the Ion Pairing in Li(CPh₃), Fluorenyllithium, and Li[N(SiMe₃)₂] amongst Other Salts

Fernández

Martínez‐Viviente

Breher

et al. 2005

Chemistry A European J

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7Li, 31P, and 1H variable-temperature pulsed gradient spin-echo (PGSE) diffusion methods have been used to study ion pairing and aggregation states for a range of lithium salts such as lithium halides, lithium carbanions, and a lithium amide in THF solutions. For trityllithium (2) and fluorenyllithium (9), it is shown that ion pairing is favored at 299 K but the ions are well separated at 155 K. For 2-lithio-1,3-dithiane (13) and lithium hexamethyldisilazane (LiHMDS 16), low-temperature data show that the ions remain together. For the dithio anion 13, a mononuclear species has been established, whereas for the lithium amide 16, the PGSE results allow two different aggregation states to be readily recognized. For the lithium halides LiX (X = Br, Cl, I) in THF, the 7Li PGSE data show that all three salts can be described as well-separated ions at ambient temperature. The solid state structure of trityllithium (2) is described and reveals a solvent-separated ion pair formed by a [Li(thf)4]+ ion and a bare triphenylmethide anion.

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Section: Resultssupporting

confidence: 93%

⁷Li, ³¹P, and ¹H Pulsed Gradient Spin‐Echo (PGSE) Diffusion NMR Spectroscopy and Ion Pairing: On the Temperature Dependence of the Ion Pairing in Li(CPh₃), Fluorenyllithium, and Li[N(SiMe₃)₂] amongst Other Salts

Fernández

Martínez‐Viviente

Breher

et al. 2005

Chemistry A European J

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“…Previously substantial agreement had been found between our uv-visible study of triphenylmethyl alkali metal salts (1) and a corresponding 'H nmr study (2) regarding the dependence of contact and solveilt separated ion pair equilibria on the nature of the cation, solvent, and temperature.…”

Section: Discussionsupporting

confidence: 82%

“…The results could be compared with a RLi.2THF and RLi.4THF. Study (7) of the 1,1,4,4-parallel study of these carbanion systems by 'H nmr tetraphenylbutane dianion, P~,CCH,CH,~P~,, in spectroscopy (2).…”

mentioning

confidence: 99%

Spectrophotometric study of ion pairing in diphenylmethyl alkali metals salts

Buncel¹,

Menon²,

Colpa³

1979

Can. J. Chem.

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. Can. J. Chem. 57,999 (1979). A spectrophotometric study of diphenylmethyllithium (DPM-Li+) and diphenylmethylpotassjum WPM-K+) in ethereal solvents has yielded information on ion pairing and solvation phenomena in these carbanion systems. Different spectral absorptions are observed, characteristic of two types of contact ion pairs (unsolvated and partially solvated) as well as the solvent separated ion pair species, on varying the cation and solvent. This contrasts with our previous observations with triphenylmethyl alkali metal salts where only contact and solvent separated ion pairs were observed. The effect of 18-crown-6 polyether and the effect of temperature changes on the ion pairing equilibria are evaluated. Thermodynamic parameters are obtained for equilibria pertaining to the DPM-Li+/THF and DPM-Li+/DME systems. The results are discussed in relation to literature reports on ion pairing in these systems as derived from nmr studies. Comparison with triphenylmethyl alkali metal salts yields information relating to delocalization and steric effects on ion pairing. E. BUNCEL, B. C. MENON et J. P. COLPA. Can. J. Chem. 57,999 (1979). Une etude spectrophotomktrique du diphenylmkthyllithium (DPM-Li+) et du diphknylmkthylpotassium (DPM-K+) dans des solvants kthkres a fournit des informations concernant les paires d'ions et la solvatation dans ces systemes carbanioniques. Lorsqu'on a fait varier le cation et le solvant, on a observe diverses absorbtions spectrales qui sont caracteristiques de deux types de paires d'ions de contact (non-solvatk et partiellement solvate) de m2me que des paires d'ions skparks par le solvant. Ces resultats different de ceux obtenus au cours de nos travaux antkrieurs avec les sels triphenylmkthyles de mktaux alcalins alors qu'on avait observe uniquement la prksence de paires d'ions de contact ou skparks par le solvant. On a Bvaluk I'effet de polykther-6 couronne-18 et de changements de temperature sur les tquilibres des paires d'ion. On a obtenu des paramktres thermodynamiques pour l'kquilibre relatif aux systemes DMP-Li+/THF et DMP-Li+/DME. On discute des resultats en fonction de rapports, parus dans la litterature, concernant les paires d'ions preseiltes dans ces systemes qui sont basks sur des etudes rmn. Une comparaison avec des sels triphknylmethyles de metaux alcalins fournit des informations concernant les effets stbiques et la dklocalisation sur le pairage des ions.[Traduit par le journal]In our study of triphenylmethyllithium (TPM-Li') parison of our results. The necessity of investigating and triphenylmethylpotassium (TPM-K') in ether-ion-pairing phenomena by different experimental eal solvents by uv-visible spectroscopy, it was found techniques has been emphasized (5). An earlier that these carbanion alkali metal salts showed spectrophotometric study (6) of 1,l-diphenylhexylspectral behaviour characteristic of contact or lithium in THF or di-n-propyl ether and benzene solvent-separated ion pairs, depending on the nature or hexane mixtures was interpreted in terms of of the...

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“…Thus, the 1 H NMR spectrum of 6 in [D 6 ]benzene shows a singlet signal at δ ϭ 2.06 due to the CH 3 protons of the pentamethylcyclopentadienyl ligand and a set of signals typical for the fluorenide anion [40,41] in the aromatic region. The proton signals of the CH 3 O groups of the DME ligand appear as a broad multiplet, significantly high-field shifted, while the signals for the CH 2 protons keep their normal position.…”

Section: Resultsmentioning

confidence: 99%

Fluorenyl andansa-Dimethylsilylbis(fluorenyl) Derivatives of Divalent Ytterbium and Samarium − Synthesis and Structure of the First Mixed-Ligand LnII Classic Sandwich Complex (C13H9)(C5Me5)Yb(DME)

Kirillov

Dechert

Schumann

et al. 2001

Eur. J. Inorg. Chem.

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Novel fluorenyl complexes of divalent ytterbium (C13H9)2Yb(L)n [L = THF, n = 2 (1); L = DME, n = 1 (2)] have been prepared by reaction of YbI2(THF)2 with 2 equiv. of C13H9K as well as by reaction of (C10H8)Yb(THF)2 with fluorene in THF. Oxidation of 1 by tBuN=CHCH=NtBu (DAD) resulted in the formation of (C13H9)2Yb(DAD) (3). The reaction of {YbI(DME)2]2(µ‐C10H8)} (4) with fluorene did not give (C13H9)YbI(DME) (5), but the redistribution products YbI2(DME) and 2. The first mixed‐ligand sandwich complex of a divalent lanthanide metal (C13H9)(C5Me5)Yb(DME) (6) was prepared in a one‐pot reaction of 4 with C5Me5H and C13H9K in DME. ansa‐Me2Si(C13H8)2Yb(THF) (7) and ansa‐Me2Si(C13H8)2Sm(THF)4 (8) were obtained by treatment of the appropriate LnII iodides with ansa‐Me2Si(C13H9)2K2 in THF. The molecular structures of 1 and 6 were determined by single‐crystal X‐ray diffraction.

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Magnetic resonance. X. Spectroscopy of carbanions and the effect of ion pairing on chemical shifts

Cited by 90 publications

References 4 publications

⁷Li, ³¹P, and ¹H Pulsed Gradient Spin‐Echo (PGSE) Diffusion NMR Spectroscopy and Ion Pairing: On the Temperature Dependence of the Ion Pairing in Li(CPh₃), Fluorenyllithium, and Li[N(SiMe₃)₂] amongst Other Salts

⁷Li, ³¹P, and ¹H Pulsed Gradient Spin‐Echo (PGSE) Diffusion NMR Spectroscopy and Ion Pairing: On the Temperature Dependence of the Ion Pairing in Li(CPh₃), Fluorenyllithium, and Li[N(SiMe₃)₂] amongst Other Salts

Spectrophotometric study of ion pairing in diphenylmethyl alkali metals salts

Fluorenyl andansa-Dimethylsilylbis(fluorenyl) Derivatives of Divalent Ytterbium and Samarium − Synthesis and Structure of the First Mixed-Ligand LnII Classic Sandwich Complex (C13H9)(C5Me5)Yb(DME)

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Magnetic resonance. X. Spectroscopy of carbanions and the effect of ion pairing on chemical shifts

Cited by 90 publications

References 4 publications

7Li, 31P, and 1H Pulsed Gradient Spin‐Echo (PGSE) Diffusion NMR Spectroscopy and Ion Pairing: On the Temperature Dependence of the Ion Pairing in Li(CPh3), Fluorenyllithium, and Li[N(SiMe3)2] amongst Other Salts

7Li, 31P, and 1H Pulsed Gradient Spin‐Echo (PGSE) Diffusion NMR Spectroscopy and Ion Pairing: On the Temperature Dependence of the Ion Pairing in Li(CPh3), Fluorenyllithium, and Li[N(SiMe3)2] amongst Other Salts

Spectrophotometric study of ion pairing in diphenylmethyl alkali metals salts

Fluorenyl andansa-Dimethylsilylbis(fluorenyl) Derivatives of Divalent Ytterbium and Samarium − Synthesis and Structure of the First Mixed-Ligand LnII Classic Sandwich Complex (C13H9)(C5Me5)Yb(DME)

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⁷Li, ³¹P, and ¹H Pulsed Gradient Spin‐Echo (PGSE) Diffusion NMR Spectroscopy and Ion Pairing: On the Temperature Dependence of the Ion Pairing in Li(CPh₃), Fluorenyllithium, and Li[N(SiMe₃)₂] amongst Other Salts

⁷Li, ³¹P, and ¹H Pulsed Gradient Spin‐Echo (PGSE) Diffusion NMR Spectroscopy and Ion Pairing: On the Temperature Dependence of the Ion Pairing in Li(CPh₃), Fluorenyllithium, and Li[N(SiMe₃)₂] amongst Other Salts