Infrared Spectroscopic and Theoretical Investigations of Group 13 Oxyfluorides OMF₂ and OMF (M=B, Al, Ga, In)

Abstract

Group 13 oxyfluorides OMF 2 were produced by the reactions of laser-ablated group 13 atoms M (M=B, Al, Ga and In) with OF 2 and isolated in excess neon or argon matrices at 5 K. These molecules were characterized by matrix-isolation infrared spectroscopy and isotopic substitution experiments in conjunction with quantum-chemical calculations. The calculations indicate that the OMF 2 molecules have a 2 B 2 ground state with C 2v symmetry. The computed molecular orbitals and spin densities show that the unpaired electron is mainly located at the terminal oxygen atom. Oxo monofluorides OMF were only observed in solid argon matrices and exhibit a linear structure in the singlet ground state. The MÀ O bonding in the OMF molecules can be rationalized as highly polar multiple bonds based on the calculated bond lengths and natural resonance theory (NRT) analyses. In particular, the molecular orbitals of OBF exhibit the character of a triple bond BÀ O resulting from two degenerate electron-sharing π bonds and an O!B dative σ bond formed by the oxygen 2p lone pair which donates electron density to the boron empty 2p orbital.