An ESR study of the reaction of silver atoms with B2F4 under matrix isolation conditions

Abstract

Diboron tetrafluoride has been found by ESR to complex with silver atoms when the species are deposited together in hydrocarbon matrices at 77 K in a rotating cryostat. The major feature in the ESR spectra of the deposit in adamantane and cyclohexane matrices (Ag ∶ B2F4 ∶ matrix ratio of ∼1 ∶ 5 ∶ 500) was an almost isotropic set of two doublets of 13 (or possibly 15)-line multiplets. The two sets of doublets arise from the almost equally abundant 107Ag and 109Ag isotopes with I = 1/2. The multiplets on each silver line indicate hyperfine interaction with either four equivalent 11B nuclei (I = 3/2) or two equivalent 11B nuclei and four equivalent 19F nuclei. Multiplets from the less abundant 10B isotope (19.8%, I = 3) were not resolvable. The almost isotropic multiplets are best simulated as axial spectra with |A∥|(11B) = 17.5 MHz and |A⊥|(11B) = 14.1 MHz and Aiso(107Ag) = 1371.0 MHz. The complex is either [Ag(B2F4)2] or [Ag(B2F4)]. Assuming that A∥ and A⊥ are both positive, the total spin density is calculated to be 0.85 in [Ag(B2F4)2] and 0.80 in [Ag(B2F4)]. The most likely structures together with density function calculations on these two possibilities are discussed.