Electron spin resonance studies of a range of stannane radical cations

Abstract

Exposure of dilute solutions of stannanes in freon (CFCI,) at 77 K to 6oCo y-rays gave the parent radical cations. SnH, gave two well defined centres, both exhibiting very large hyperfine coupling to l17Sn and 119Sn. One, with CgV symmetry, showing strong coupling to a unique proton, is thought to have the unpaired electron confined to one Q Sn-H orbital with a large 5s contribution from tin. The other (C2" symmetry), with strong coupling to two equivalent protons, and formed initially in almost equal

Photoinduced Transformations in Low-Temperature Matrices Containing Radical Cations of Organotin Compounds

“…The occurrence of photostimulated reaction (2) (or similar thermally stimulated process upon heating the sample from 77 to 120 K) followed by reaction (3) makes it possible to explain apparent contradiction between the data reported by Walther et al [11] and those presented by Symons [9] and Hasegawa et al [10]. Indeed, matrix radical ions (whose reactions could lead to the generation of [(ëç 3 ) 4 ]~ followed by formation of methyl radicals) in SiCl 4 or CFCl 3 matrices containing Me 4 radical cations were preliminarily bleached in [11] and not bleached in [9,10].…”

“…1, curve c ) have a nuclear spin of I = 0 and a total abundance of ~83.7%, whereas the radical cations containing tin with odd mass numbers (Fig. 1, curve d ) are characterized by a total natural abundance of ≈ 16.3%, close magnetic moments, and the same nuclear spin ( I = 0.5).The ESR spectra of radical cations show isotropic hyperfine coupling to three equivalent protons and anisotropic hyperfine coupling to tin nuclei with odd mass numbers ( g ⊥ = 2.043, g || = 1.989; hyperfine coupling constants of ‡ ⊥ ( radical cations stabilized in the ë 3v symmetry conformation [9][10][11] (in particular, Hasegawa et al [10] reported the following set of parameters: Sn +.…”

“…Indeed, matrix radical ions (whose reactions could lead to the generation of [(ëç 3 ) 4 ]~ followed by formation of methyl radicals) in SiCl 4 or CFCl 3 matrices containing Me 4 radical cations were preliminarily bleached in [11] and not bleached in [9,10].…”

“…As indicated by Symons [9], Hasegawa et al [10], and Bonazzola et al [13], the Me 4 radical cation in a CFCl 3 matrix is stabilized in the C 3 v symmetry conformation. However, 1 this radical cation adopts the C 2 v symmetry in a SiCl 4 matrix [13].…”

“…An analysis of the EPR spectra of Me 4 and Me 6 ) radical cations led to the conclusion that the positive charge is localized at one of the Sn-C bonds in the former species [9][10][11] but is confined to the Sn-Sn bond in the latter radical cation [12]. As indicated by Symons [9], Hasegawa et al [10], and Bonazzola et al [13], the Me 4 radical cation in a CFCl 3 matrix is stabilized in the C 3 v symmetry conformation.…”