ESR Spectra of the Fluorinated Silyl Radicals

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Abstract
Isotropic ESR spectra of · SiH2F, · SiHF2, and · SiF3 are reported. The radicals were produced by radiolysis of H3SiF, H2SiF2, and HSiF3 in an SF6 matrix. The hyperfine parameters in gauss are: for · SiH2F, aH=34.6, aF=55.2; for · SiHF2, aH=89.9, aF=77.8; and for · SiF3, aF=136.6, aSi=(−) 498.0. The large 29Si hyperfine constant for · SiF3 shows that the radical is strongly pyramidal, probably as a result of the high ionic character of the Si–F bonds. The proton hyperfine constants are believed to be positive and the parallel of · SiHF2 with · HPO2− (aH=82.5 G) is noted. The radical (CH3)2SiF · was also produced in liquid phase photolysis experiments and has the parameters aH=4.53 and aF=65.21 G.