18130-74-0Relevant academic research and scientific papers
Enhancing the anion affinity of urea-based receptors with a Ru(terpy) 22+ chromophore
Baggi, Giorgio,Boiocchi, Massimo,Ciarrocchi, Carlo,Fabbrizzi, Luigi
, p. 5273 - 5283 (2013/06/26)
Covalent linking of a Ru(terpy)22+ substituent improves recognition and sensing properties of the urea subunit toward anions. Urea's anion affinity is enhanced by the electrostatic attraction exerted by the RuII cation and by the electron-withdrawing effect exerted by the entire polypyridine-metal complex. Such an enhancement of the anion affinity, which results from the combination of a through-space and a through-bond effect, is greater than that exerted by the classical neutral electron-withdrawing substituent nitrophenyl. Small yet significant modifications of π-π* and MLCT bands of the Ru(terpy)22+ chromophore, detected through UV-vis spectrophotometric titrations, allowed the determination of the constants for the formation of receptor-anion H-bond complexes in diluted MeCN solution. On 1H NMR titration experiments, carried out under more concentrated conditions, the interaction of a second Cl- ion was observed, taking place through an outer-sphere mechanism. The Ru(terpy) 22+ substituent favors the deprotonation of a urea N-H fragment on addition of a second equivalent of fluoride, with formation of HF2-.
The trans influence of F, Cl, Br and I ligands in a series of square-planar Pd(II) complexes. Relative affinities of halide anions for the metal centre in trans-[(Ph3P)2Pd(Ph)X]
Flemming, Jeffrey P.,Pilon, Mark C.,Borbulevitch, Oleg Ya.,Antipin, Mikhail Yu.,Grushin, Vladimir V.
, p. 87 - 98 (2008/10/08)
Single crystal X-ray diffraction studies of trans-[(Ph3P)2Pd(Ph)X] (X = F (1), Cl (2), Br (3), and I (4)) were carried out. The four structures split in two isostructural and isomorphous groups, namely orthorhombic for 1 and 2 (space group Pbca, Z = 8) and triclinic for 3 and 4 (space group P-1, Z=2). According to the Pd-C bond length, the trans influence of X within these pairs follows the trend Cl > F and I > Br. However, the trans influence of Cl is slightly stronger than that of Br. Both structural and 13C NMR studies revealed that electron-donating effects of (Ph3P)2PdX increase along the series X = I - for the Pd centre in [(Ph3P)2Pd(Ph)]+ were studied by 31P NMR in rigorously anhydrous CH2Cl2 solutions, and equilibrium constants and ΔG values were obtained for all possible combinations. The sequence F- > Cl- > Br- > I- is characteristic of halide preference for the Pd complexes. Dissolving 1 and PPN Cl in dry CH2Cl2 resulted in the release of 'naked' F- which fluorinated the solvent smoothly to give a mixture of CH2ClF and CH2F2 in high yield. When chloroform was used instead of CH2Cl2, dichlorocarbene was generated slowly, forming the corresponding cyclopropane in the presence of styrene. All observations were rationalized successfully in terms of the filled/filled effect and push/pull interactions.
Tetrafluorophosphite, PF4-, anion
Christe, Karl O.,Dixon, David A.,Mercier, Hélène P. A.,Sanders, Jeremy C. P.,Schrobilgen, Gary J.,Wilson, William W.
, p. 2850 - 2858 (2007/10/02)
N(CH3)4+PF4-, the first example of a PF4- salt, has been prepared from N(CH3)4F and PF3 using either CH3CN, CHF3, or excess PF3 as a solvent. The salt is a white, crystalline solid which is thermally stable up to 150 °C where it decomposes to N(CH3)3, CH3F, and PF3. The structure of the PF4- anion was studied by variable temperature 31P and 19F NMR spectroscopy, infrared and Raman spectroscopy, SCF, MP2, local and nonlocal density functional calculations, a normal coordinate analysis, and single-crystal X-ray diffraction. The anion possesses a pseudo trigonal bipyramidal structure with two longer axial bonds and an equatorial plane containing two shorter equatorial bonds and a sterically active free valence electron pair. In solution, it undergoes an intramolecular exchange process by the way of a Berry pseudorotation mechanism. The vibrational frequencies observed for PF4- in solid N(CH3)4PF4 are in excellent agreement with those calculated for free gaseous PF4-. The X-ray diffraction study tetragonal, space group P4?21m, a = 8.465(3) A?, c = 5.674(2) A?, Z = 2, R = 0.0723 for 268 observed [F ≥ σ(F)] reflections suffers from a 3-fold disorder with unequal occupancy factors for the equatorial fluorine atoms of PF4- but confirms its pseudo trigonal bipyramidal structure and the axial P-F bond length calculated for the free ion.
A comprehensive view of the gas-phase reaction of fluoride ions and acetic acid derivatives
Riveros, Jose M.
, p. 773 - 774 (2007/10/02)
The gas-phase reaction of F- with several acetic acid derivatives (MeCOX) is shown to proceed primarily by proton abstraction in the collision complex, rather than nucleophilic displacement, leading to the facile formation of FHX- or CH2CFO-.
