CF···cation interactions: alkali metal complexes of hexafluoro cage compound

Takemura, Hiroyuki; Nakashima, Sachiko; Kon, Noriyoshi; Inazu, Toshiyuki

doi:10.1016/s0040-4039(00)01022-4

Cited by 12 publications

(10 citation statements)

References 19 publications

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“…They are proportional to the interatomic distances between F and M + (Figure ); they shift to higher fields as the cations become smaller. A similar relationship was observed in the complexes, M + ⊂ 4 . Furthermore, a linear relationship is also observed between log K s of the complexes andcoupling constants J C - F in the 13 C NMR.…”

Section: Resultssupporting

confidence: 81%

“…As shown in Figure , an octet was observed in the spectrum of Cs + ⊂ 1 ( I ( 133 Cs) = 7/2, J = 54.9 Hz) at room temperature. An octet of the 19 F signal was also observed in Cs + ⊂ 4 at low temperatures . Only two such other examples are reported by Davidson et al, and they observed 19 F− 133 Cs spin coupling ( J Cs - F ≈ 58 Hz) in their fluorine-containing complexes .…”

Section: Resultsmentioning

confidence: 82%

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A Study of C−F···M⁺ Interaction: Alkali Metal Complexes of the Fluorine-Containing Cage Compound

et al. 2001

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The C-F.M(+) interaction was investigated by employing a cage compound 1 that has four fluorobenzene units. The NMR ((1)H, (13)C, and (19)F) spectra and X-ray crystallographic analyses of 1 and its metal complexes showed clear evidence of the interaction. Short C-F.M(+) distances (C-F.K(+), 2.755 and 2.727 A; C-F.Cs(+), 2.944 and 2.954 A) were observed in the crystalline state of K(+) subset 1 and Cs(+) subset 1. Furthermore, the C-F bond lengths were elongated by the interaction with the metal cations. By calculating Brown's bond valence, it is shown that the contribution of the C-F unit to cation binding is comparable or greater than the ether oxygen in the crystalline state. Representative spectroscopic changes implying the C-F.M(+) interaction were observed in the NMR ((1)H, (13)C, and (19)F) spectra. In particular, (133)Cs-(19)F spin coupling (J = 54.9 Hz) was observed in the Cs(+) complex.

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Section: Resultssupporting

confidence: 81%

Section: Resultsmentioning

confidence: 82%

A Study of C−F···M⁺ Interaction: Alkali Metal Complexes of the Fluorine-Containing Cage Compound

et al. 2001

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“…Interaction with Metal Cations. The presence of C−F···M + interaction can be qualitatively estimated by NMR spectra, and thus the interaction between NMR-observable metal cations and 1 and 2 was investigated. − The complexation study showed that metal cations can be classified into three groups as follows. In the first group, they form stable complexes (I), in the second group, the complexation is observable by NMR spectra (II), and in the third group, they are hydrolyzed and form protonated species, n H + ⊂ 1 , 2 (III).…”

Section: Resultsmentioning

confidence: 99%

“…Then, we had to estimate the quantitative data for the interaction, and this was achieved by the measurements of thermodynamic parameters of the cation inclusion process between alkali cations and 1 . As a result, the reaction gave relatively large − Δ H values (∼−16.1 kcal mo1 -1 ) . The values indicate that the interaction stabilizes the cations to an extent similar to that of crown ethers or cryptands in some cases (solvents in the measurements are different), and thus, the C−F···M + interaction was considered to be comparable to that of ether oxygen.…”

Section: Introductionmentioning

confidence: 99%

A Study of C−F···M⁺ Interaction: Metal Complexes of Fluorine-Containing Cage Compounds

et al. 2001

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The C-F...M(+) interaction was investigated by observation of the NMR spectroscopic changes and complexation studies between metal cations and the cage compounds 1 and 2 which have fluorobenzene units as donor atoms. As a result, the interaction was detected with all of the metal cations which form complexes with 1 and 2. The stability of the complexes of 1 and 2 was determined by the properties of the metal cations (ionic radii and degree of hydrolysis), not by the hard-soft nature of the cations. Crystallographic analyses of Tl(+) subset 1 and La(3+) subset 2 provided structural information (interatomic distances and bond angles), and the bond strengths, C-F...M(+), O...M(+), and N...M(+), were estimated by Brown's equation based on the structural data. Short C-F...Tl(+) (2.952-3.048 A) distances were observed in the complex Tl(+) subset 1. The C-F bond lengths in the complexes, Tl(+) subset 1 and La(3+) subset 2, are elongated compared to those of the metal-free compounds. Interestingly, no solvent molecules including water molecules were coordinated to La(3+) in the La(3+) subset 2. The stabilization energy of cation-dipole interaction was calculated on the basis of the data from X-ray crystallographic analysis, and it is roughly consistent with the (-)Delta H values estimated in solution. Thus, the C-F...M(+) interaction can be expressed by the cation-dipole interaction. This result explains the fact that compound 1 which has fluorine atom as hard donor strongly binds soft metals such as Ag(+) and Tl(+). Furthermore, it was concluded that the fluorobenzene unit has a poor electron-donating ability compared to that of ether oxygen or amine nitrogen, and thus the ratio of the coordination bond in C-F...M(+) is small. The specific and remarkable changes in the (1)H, (13)C, and (19)F NMR spectra were observed accompanied by the complexation between M(+) and the hosts 1 and 2. These spectral features are important tools for the investigation of the C-F...M(+) interaction. Furthermore, F.Tl(+) spin couplings were observed at room temperature in the Tl(+) subset 1, 2 (J(F-Tl) = 2914 Hz for Tl(+) subset 1 and 4558 Hz for Tl(+) subset 2), and these are clear and definitive evidence of the interaction.

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“…CS-MS is the only tool currently available that could demonstrate this structural integrity. Previous polydentate fluoride donors for sodium include a macrocyclic ligand designed by Takemura et al 12 In the future we will examine whether this behaviour is restricted to alkali metal ions, or whether clusters of d-block metals can be assembled using this cluster-ligand.…”

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Chemistry and supramolecular chemistry of chromium horseshoes

et al. 2008

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CF···cation interactions: alkali metal complexes of hexafluoro cage compound

Cited by 12 publications

References 19 publications

A Study of C−F···M⁺ Interaction: Alkali Metal Complexes of the Fluorine-Containing Cage Compound

A Study of C−F···M⁺ Interaction: Alkali Metal Complexes of the Fluorine-Containing Cage Compound

A Study of C−F···M⁺ Interaction: Metal Complexes of Fluorine-Containing Cage Compounds

Chemistry and supramolecular chemistry of chromium horseshoes

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CF···cation interactions: alkali metal complexes of hexafluoro cage compound

Cited by 12 publications

References 19 publications

A Study of C−F···M+ Interaction: Alkali Metal Complexes of the Fluorine-Containing Cage Compound

A Study of C−F···M+ Interaction: Alkali Metal Complexes of the Fluorine-Containing Cage Compound

A Study of C−F···M+ Interaction: Metal Complexes of Fluorine-Containing Cage Compounds

Chemistry and supramolecular chemistry of chromium horseshoes

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A Study of C−F···M⁺ Interaction: Alkali Metal Complexes of the Fluorine-Containing Cage Compound

A Study of C−F···M⁺ Interaction: Alkali Metal Complexes of the Fluorine-Containing Cage Compound

A Study of C−F···M⁺ Interaction: Metal Complexes of Fluorine-Containing Cage Compounds