B-H···π Interaction: A New Type of Nonclassical Hydrogen Bonding

Area of Science:

• Inorganic Chemistry
• Supramolecular Chemistry
• Computational Chemistry

Background:

• Hydrogen bonding typically involves electronegative atoms like O, N, or F.
• Nonclassical hydrogen bonds are weaker and less understood.
• Boron hydride (B-H) bonds offer potential for novel hydrogen bonding interactions.

Purpose of the Study:

• To describe and experimentally realize nonclassical hydrogen bonding involving B-H···π interactions.
• To investigate these interactions in carborane complexes at ambient temperatures.
• To elucidate the nature and strength of B-H···π hydrogen bonds.

Main Methods:

• Quantum chemical predictions and calculations.
• Synthesis of iridium-carborane complexes.
• X-ray diffraction studies.
• (1)H NMR spectroscopy.

Main Results:

• Observation of B-H···π hydrogen bonds in gas-phase complexes (diborane-benzene, carborane-benzene).
• Experimental realization of B-H···π interactions in iridium-carborane complexes with phosphines at ambient temperatures.
• X-ray diffraction confirmed B-H···π distances of 2.40-2.76 Å.
• (1)H NMR spectroscopy showed characteristic high-field shifts (0.0–0.3 ppm) indicative of B-H···π bonding in solution.
• Computational analysis revealed electrostatic nature and significant force constants for the B-H···π interaction.

Conclusions:

• Nonclassical B-H···π hydrogen bonding is experimentally validated.
• These interactions are stable and observable in solution and gas phase.
• The strength of B-H···π bonds is comparable to conventional hydrogen bonds.