Competition between Hydrogen Bonds and Lewis Acid-Base Interactions in the Equilibria between Bis(pentafluorophenyl)borinic Acid and Pyridine: Insights from NMR, Diffractometric and Computational Studies
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Daniela Maggioni
Abstract
1H and 19F NMR spectroscopy, X-ray diffractometry and DFT computations have been used for investigating the interaction between the Lewis base pyridine and bis(pentafluorophenyl)borinic acid Ar2BOH (1, Ar=C6F5). Previous studies showed that the latter species in solution exists as an equilibrium mixture of the monomer (1m) and a cyclic trimer (1t), in variable ratios, and that the trimer is stabilized in the presence of Lewis bases, by the formation of strong 1t···L hydrogen bonds. In the present case, upon addition of 0.33 equivalents of pyridine, low-temperature NMR spectra showed the formation of deprotonated 1t (anion 3), strongly hydrogen-bonded to the pyridinium cation Hpy+. The presence of this cation was confirmed by the high value of 1JHN (88 Hz). DFT computations confirmed the higher stability of the O-···H–N+ limit form over the neutral O–H···N one. Variable temperature NMR spectra showed that the Hpy+·3 ion pair has high conformational freedom. At temperatures higher than 260 K, 3 underwent reversible partial fragmentation to give 1m and the Lewis acid-base covalent adducts between pyridine and either 1m (2py), or its anhydride (5py). The fragmentation was perfectly reversible on lowering the temperature. The adduct 2py became the only species in solution in the presence of 1 equivalent of pyridine, showing that the Lewis basicity of pyridine plays the major role, at variance with what previously observed with other bases. Hydrogen bond interactions, however, promote the supramolecular organization of 2py in the form of a cyclic tetramer, as revealed by X-ray single crystal diffractometric analysis. The formation of the deprotonated trimer 3 was previously observed in the reaction of 1 with 1,8-bis(dimethylamino)naphtalene (DMAN). However the stepwise dearylation processes, which were dominant in the reactions with DMAN, have a very marginal role in the reaction with pyridine, due to its lower Brønsted basicity.
For Supplementary Material see online version. Supporting information available: details of the NMR spectroscopic characterization (Figs. S1–S4), computed chemical shifts (Table S1), details of the X-ray diffractometric analysis, and tables of geometrical parameters (Tables S2–S3).
© by Oldenbourg Wissenschaftsverlag, München, Germany
Articles in the same Issue
- Editorial
- Biography of Prof. Dr. Hans-Heinrich Limbach
- Alumni and long term guests of the Limbach group
- NMR and FT-IR Studies on the Association of Derivatives of Thymidine, Adenosine, and 6-N-Methyl-Adenosine in Aprotic Solvents
- Competition between Hydrogen Bonds and Lewis Acid-Base Interactions in the Equilibria between Bis(pentafluorophenyl)borinic Acid and Pyridine: Insights from NMR, Diffractometric and Computational Studies
- Energy Analysis of Competing Non-Covalent Interaction in 1:1 and 1:2 Adducts of Collidine with Benzoic Acids by Means of X-Ray Diffraction
- A TT Dinucleotide with a Nonionic Silyl Backbone: Impact on Conformation and H-Bond Mediated Base Pairing as Studied by Low-Temperature NMR
- Oxygen and Hydrogen Isotopic Preference in Hydration Spheres of Chloride and Sulfate Ions
- Ab Initio Study of Cooperative Effects in Complexes X:HBO:Z, with X, Z=LiH, HNC, HF, HCN, HCl, ClF, and HBO: Structures, Binding Energies, and Spin-Spin Coupling Constants across Intermolecular Bonds
- The Structure and Dynamic Properties of 1H-Pyrazole-4-Carboxylic Acids in the Solid State
- Acridine – a Promising Fluorescence Probe of Non-Covalent Molecular Interactions
- First Example of Hydrogen Bonding to Platinum Hydride
- Interaction of Hydrogen with a Cobalt(0001) Surface
- Immobilization and Characterization of RuCl2(PPh3)3 Mesoporous Silica SBA-3
- Secondary Isotope Effects on 13C and 15N Chemical Shifts of Schiff Bases Revisited
- Analysis of Nutation Patterns in Fourier-Transform NMR of Non-Thermally Polarized Multispin Systems
- The Structure of Supercooled Water and the Mechanism of Homogeneous Nucleation of Ice Ih
- Probing Small Protonated Water Clusters in Acetonitrile Solutions by 1H NMR
- Double Hydrogen Transfer in Low Symmetry Porphycenes
- Nuclear Spin Selective Torsional States: Implications of Molecular Symmetry
Articles in the same Issue
- Editorial
- Biography of Prof. Dr. Hans-Heinrich Limbach
- Alumni and long term guests of the Limbach group
- NMR and FT-IR Studies on the Association of Derivatives of Thymidine, Adenosine, and 6-N-Methyl-Adenosine in Aprotic Solvents
- Competition between Hydrogen Bonds and Lewis Acid-Base Interactions in the Equilibria between Bis(pentafluorophenyl)borinic Acid and Pyridine: Insights from NMR, Diffractometric and Computational Studies
- Energy Analysis of Competing Non-Covalent Interaction in 1:1 and 1:2 Adducts of Collidine with Benzoic Acids by Means of X-Ray Diffraction
- A TT Dinucleotide with a Nonionic Silyl Backbone: Impact on Conformation and H-Bond Mediated Base Pairing as Studied by Low-Temperature NMR
- Oxygen and Hydrogen Isotopic Preference in Hydration Spheres of Chloride and Sulfate Ions
- Ab Initio Study of Cooperative Effects in Complexes X:HBO:Z, with X, Z=LiH, HNC, HF, HCN, HCl, ClF, and HBO: Structures, Binding Energies, and Spin-Spin Coupling Constants across Intermolecular Bonds
- The Structure and Dynamic Properties of 1H-Pyrazole-4-Carboxylic Acids in the Solid State
- Acridine – a Promising Fluorescence Probe of Non-Covalent Molecular Interactions
- First Example of Hydrogen Bonding to Platinum Hydride
- Interaction of Hydrogen with a Cobalt(0001) Surface
- Immobilization and Characterization of RuCl2(PPh3)3 Mesoporous Silica SBA-3
- Secondary Isotope Effects on 13C and 15N Chemical Shifts of Schiff Bases Revisited
- Analysis of Nutation Patterns in Fourier-Transform NMR of Non-Thermally Polarized Multispin Systems
- The Structure of Supercooled Water and the Mechanism of Homogeneous Nucleation of Ice Ih
- Probing Small Protonated Water Clusters in Acetonitrile Solutions by 1H NMR
- Double Hydrogen Transfer in Low Symmetry Porphycenes
- Nuclear Spin Selective Torsional States: Implications of Molecular Symmetry
