B₂(BO)₂ ²-Diboronyl Diborene: A Linear Molecule with A Triple Boron-Boran Bond

Journal Article · Wed Feb 27 04:00:00 EST 2008 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/ja0771080· OSTI ID:951868

Li, Si-Dian; Zhai, Hua Jin; Wang, Lai S

We have produced and investigated an unique boron oxide cluster, B₄O₂-, using photoelectron spectroscopy and ab initio calculations. Relatively simple and highly vibrationally resolved PES spectra were obtained at two photon energies (355 and 193 nm). The electr on affinity of neutral B₄O₂ was measured to be 3.160 ± 0.015 eV. Two excited states were observed for B₄O₂ at excitation energies of 0.48 and 0.83 eV above the ground state. Three vibrational modes were resolved in the 355 nm spectrum for the ground state of B₄O₂ with frequencies of 350 ± 40, 1530 ± 30, and 2040 ± 30 cm^-1. Ab initio calculations showed that neutral B₄O₂ (D_∞h, ³Σ_g-) and anionic B₄O₂- (D_∞h, ²Π_u) both possess highly stable linear structures (O≡B-B=B-B≡O), which can be viewed as a B₂ dimer bonded to two terminal boronyl groups. The lowest nonlinear structures are at least 1.5 eV higher in energy. The calculated electron detachment energies from the linear B₄O₂-and the vibrational frequencies agree well with the experimental results. The three observed vibrational modes are due to the B-B, B=B, and B≡O symmetric stretching vibrations, respectively, in the linear B₂(BO)₂. Chemical bonding analyses revealed that the HOMO of B₂(BO)₂, which is half-filled, is a bonding π orbital in the central B₂ unit. Thus, adding two electrons to B₂(BO)2 leads to a B≡B triple bond in [O≡B-B≡B-B≡O]^2-. Possibilities for stabilizing B₂(BO)₂^2- in the form of B₂(BO)₂Li₂ are considered computationally and compared with other valent isoelectronic, triple bonded species, B₂H₂Li₂, B₂H₂^2-, and C₂H₂. The high stability of B₂(BO)₂^2- suggests that it may exist as a viable building block in the condensed phase.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 951868
• Report Number(s): PNNL-SA-58283; 3227a; KP1704020
• Journal Information: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 8 Vol. 130; ISSN JACSAT; ISSN 0002-7863
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
AFFINITY
BONDING
BORON OXIDES
DIMERS
ELECTRON DETACHMENT
ELECTRONS
EXCITATION
EXCITED STATES
Environmental Molecular Sciences Laboratory
GROUND STATES
PHOTOELECTRON SPECTROSCOPY
PHOTONS
SPECTRA
STABILITY