Attachment of molecular hydrogen to an isolated boron cation: an infrared and ab initio study

Authors

Viktoras Dryza, University Of Melbourne
Berwyck L. J Poad, University of WollongongFollow
Evan J. Bieske, University Of Melbourne

RIS ID

72174

Publication Details

Dryza, V., Poad, B. L. J. & Bieske, E. J. (2008). Attachment of molecular hydrogen to an isolated boron cation: An infrared and ab initio study. Journal of the American Chemical Society, 130 (39), 12986-12991.

Abstract

Structural properties of the B⁺−H₂ electrostatic complex are investigated through its rotationally resolved infrared spectrum in the H−H stretch region (3905−3975 cm⁻¹). The spectrum, which was obtained by monitoring B⁺ photofragments while the IR wavelength was scanned, is consistent with the complex having a T-shaped structure and a vibrationally averaged intermolecular separation of 2.26 Å, which decreases by 0.04 Å when the H₂ subunit is vibrationally excited. The H−H stretch transition of B⁺−H₂ is red-shifted by 220.6 ± 1.5 cm⁻¹ from that of the free H₂ molecule, much more than for other dihydrogen complexes with comparable binding energies. Properties of B⁺−H₂ and the related Li⁺−H₂, Na⁺−H₂, and Al⁺−H₂ complexes are explored through ab initio calculations at the MP2/aug-cc-pVTZ level. The unusually large red-shift for B⁺−H₂ is explained as due to electron donation from the H₂ σ_g bonding orbital to the unoccupied 2p_z orbital on the B⁺ ion.