ELECTRON SPIN RESONANCE AND STRUCTURE OF BF2 RADICAL

The BF2 radical has been detected and its structure determined from observation of the electron spin resonance of γ-irradiated molecules of BF2 trapped in the xenon matrix at 4.2°K. Hyperfine structure of both B and F was resolved and analyzed. The isotropic coupling constants are: for 10B, 277.98 Me/sec; for 11B, 826.24 Me/sec; and for 19F, 532 Me/sec.Analysis of the hyperfine structure shows that the unpaired electron is in the a system, that 93% of the electron spin density is in a nonbonding s p2 hybrid on the B, and that the remaining 7% is in hybridized bonding orbitals of the two F atoms. The sp2 hybrid of the unpaired electron on the B has 44% 2s character and 56% 2p character. This orbital is in the molecular plane. The bond angle derived from the hybridization is 112°.