Kinetics of alkali metal complex formation with cryptands in methanol

Cox, Brian G.; Schneider, Hermann; Stroka, Jadwiga

doi:10.1021/ja00483a019

Cited by 100 publications

(26 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This can most clearly be seen for complexes which have both terminal and bridging halogen atoms. (If both halogens in (6) 140.74 (25) 146.45 (40) 140.34 (15) 140.84 (20) 145.50 (17) 143.64 (10) 143.62 (56) 135.19 (3) 131.44 (21) 142.42 (40) 133.92 (1 1) 143.53 (12) 145.77 (20) 128.517 (28) …”

Section: Resultsmentioning

confidence: 99%

“…The reduction in ( a ) is commonly found in complexes with intermolecular secondary bridging, and is attributed to the weakening of that weak bonding as the crystals undergo thermal expansion. (The loss of secondary bonding lowers the NQR frequency less at higher temperatures [15].) It would appear that this effect is absent with the stronger symmetric bonding (enthalpies of dissociation of gaseous AI,X, are 44-60 kJ/mole [551).…”

Section: Secondary-bridging Adductsmentioning

confidence: 99%

See 1 more Smart Citation

Halogen‐Metal Secondary Bonding). An NQR Study in Mercury and Cadmium Halide Adducts of Polyethers

Wulfsberg

Weiß

1980

Ber Bunsenges Phys Chem

View full text Add to dashboard Cite

Chemische Bindung i Kernquadrupolresonanz I Kristallstruktur I MolekiilstrukturHalogen atoms bridge metal atoms by forming two M -X bonds of about equal length ("symmetric bridging", as in cadmium halide adducts of oxygen-donor ligands), or by forming two bonds of significantly different lengths ("secondary bridging", as mercuric halide adducts of the same ligands). Halogen (%, "Br, '"I) NQR spectra of the title and related complexes show characteristic differences for the two types of bridging. Bridging halogen atoms (in nontransition metal halides) have lower frequencies than do analogous terminal halogen atoms; if the bridging is symmetric, the lowering depends on the bridging angle and is quite variable; if the bridging is secondary, the lowering is less but relatively constant. Asymmetry parameters for symmetrically-bridging halogens are ofteii large and depend on the bridging angle; those of secondary-bridging halogens are small. The temperature dependence of the NQR frequencies of symmetric bridgng halogens is normal negative; that of secondary bridging halogens is less negative than for analogous terminal halogens, and may even be positive. Two Townes-Dailey treatments of secondary bridging have been developed: one assumes the use of sp hybrid orbitals by the halogen, and the other uses pure p orbitals for the secondary bond. Analysis of the data leads to a picture of the formation of a "typical" secondary bond: 0.03 electrons are polarized or transferred towards the metal atom from the halogen pr orbital, and the halogen acquires an additional 0.01 electron in the original M -X bond.Halogenatome bilden mit Metallatomen Briickenbindungen aus, wobei die beiden Bindungslangen ungefahr gleich sein konnen (,,symmetrische Briickenbindung", wie in Cd-halidaddukten mit Sauerstoff-Donorliganden) oder wesentlich ungleich lang sein konnen (,,sekundare Briickenbindung", wie in Hg-halidaddukten). Halogen ("CI, "Br, '271)-NQR-spektren der genannten und ahnlicher Komplexe zeigen fur die beiden Typen von Briickenbindung charakteristische Unterschiede. Halogenbriickenatome zeigen in Verbindungen mit Hauptgruppenmetallen niedrigere Frequenzen als die endstandigen Halogene. 1st die Briicke symmetrisch, so hangt die Frequenzabsenkung 475 empfindlich vom Bruckenwinkel ab. Sekundare Bruckenbindung ist weniger effektiv. Die Asymmetrieparameter symmetrischer Briickenhalogenatome sind meist hoch und vom Winkel abhangig; bei sekundarer Briickenbindung sind sie niedrig. Die Temperaturabhangigkeit der NQR-frequenzen symmetrischer Briickenhalogenatome ist normal, d. h. negativ: in sekundareren Bruckenbindungen ist sie schwacher negativ als die terminaler Halogenatome, ja manchmal positiv. Zwei verschiedene Berechnungen der sekundiren Bruckenbindung nach Townes und Dailey wurden durchgefiihrt: einmal werden sp-Hybrid-Orbitale am Halogen angenommen, im anderen Fall reine p-Orbitale. Daraus ergibt sich fur eine ,,typische" sekundare Bruckenbindung von Halogenen: 0.03 Elektronen aus dem py-Orbital des Halogens sind in Richtung Metallato...

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Secondary-bridging Adductsmentioning

confidence: 99%

Halogen‐Metal Secondary Bonding). An NQR Study in Mercury and Cadmium Halide Adducts of Polyethers

Wulfsberg

Weiß

1980

Ber Bunsenges Phys Chem

View full text Add to dashboard Cite

show abstract

“…Potentiometric measurements were carried out in Camlab potentiometer using the following electrochemical cell suggested by Cox et al [16]. Ag (S) /AgClO 4 , L, M nϩ //Et 4 NClO 4 2.5 ϫ 10 Ϫ2 mol dm Ϫ3 (1) //AgClO 4 10 Ϫ2 mol dm Ϫ3 /Ag (S) where L and M nϩ denote p-tert-butylcalix [4]arene tetradiisopropylacetamide and metal cations in solution, respectively.…”

Section: Thermodynamic Measurementsmentioning

confidence: 99%

Novel separation of thallium-201 using p-tert-butylcalix[4]arene derivative

Jammaz¹,

Amartey²,

Namor³

et al. 2000

Radiochimica Acta

View full text Add to dashboard Cite

Radioisotope separation / Thallium-201 / Lead-201 / Amides calix[4]arene / RadiopharmaceuticalSummary. p-tert-Butylcalix[4]arene tetradiisopropylacetamide was synthesized in 62% yield. Extraction experiments in the water:butan-1-ol solvent system at 298 K in the presence of p-tert-butylcalix [4]arene tetradiisopropylacetamide were performed. The selective extraction of Pb 2ϩ relative to Tl ϩ and Tl 3ϩ from the aqueous solution to the organic phase in the presence of the ligand at low hydrogen-ion concentration was demonstrated. The extraction of radioactive Pb 2ϩ , Tl ϩ and Tl 3ϩ by the same ligand was investigated as a function of the pH of the aqueous phase and the ligand concentration in the organic phase. The method appears to be very promising for use in the production of 201 Tl of pharmaceutical quality.

show abstract

“…They have been shown to form strong complexes with metal cations, including the lanthanides. The thermodynamics of cryptands with univalent and bivalent cations in water and non-aqueous media has been extensively discussed [6][7][8][9][10][11][12]. Some lanthanide complexes of cryptands have been isolated and their solid-state structure has been investigated by X-ray crystallography [13,14].…”

Section: Introductionmentioning

confidence: 99%

Solution thermodynamics of Lanthanide–Cryptand 222 complexation processes

Namor

Chahine

Jafou

et al. 2003

Journal of Coordination Chemistry

View full text Add to dashboard Cite

The thermodynamics of trivalent cations (Y 3þ , La 3þ , Pr 3þ , Nd 3þ , Eu 3þ , Gd 3þ , Tb 3þ , Ho 3þ , Er 3þ , Yb 3þ ) and cryptand 222 in acetonitrile at 298.15 K is discussed. Recent reports regarding the behavior of lanthanide(III) trifluoromethane sulfonate salts in acetonitrile are considered. Thus, the experimental work was carried out under conditions in which ions (M 3þ ) are predominantly in solution. Therefore, conductiometric titrations were carried out to establish the composition of the cation-cryptand 222 complexes and their ionic behavior in solution. Stability constants and derived standard Gibbs energies, enthalpies and entropies were determined by competitive titration microcalorimetry. Previously reported thermodynamic data for the complexation of cryptand 222 and a few lanthanide cations (La 3þ , Pr 3þ and Nd 3þ ) in acetonitrile are revisited. The medium effect on the stability of complex formation in acetonitrile relative to N,N-dimethylformamide is demonstrated. Thus, a drop in stability by a factor of 8 Â 10 10 is observed for the latter relative to the former solvent. The selectivity of cryptand 222 for these cations relative to La 3þ in acetonitrile is discussed.

show abstract

Kinetics of alkali metal complex formation with cryptands in methanol

Cited by 100 publications

References 3 publications

Halogen‐Metal Secondary Bonding). An NQR Study in Mercury and Cadmium Halide Adducts of Polyethers

Halogen‐Metal Secondary Bonding). An NQR Study in Mercury and Cadmium Halide Adducts of Polyethers

Novel separation of thallium-201 using p-tert-butylcalix[4]arene derivative

Solution thermodynamics of Lanthanide–Cryptand 222 complexation processes

Contact Info

Product

Resources

About