E.S.R. spectra and structure of the halogermane radical anions

E.S.R. spectra of GeH3 X - (X = Br, I) radical anions consisting of the hyperfine structure from one halogen X and three equivalent hydrogens were observed with γ-irradiated solid solutions of tetramethylsilane (TMS) containing GeH3 X. The spectra were compared with those assigned to the congeneric radical anions SiH3 X - having structures of trigonal bipyramid. In the latter spectra, hyperfine structures due to one halogen and one hydrogen in the axial positions of SiH3 X - were observed, while splittings due to the other two hydrogens in the equatorial positions were unresolved. Thus, in contrast to the result for SiH3 X -, the presence of the three equivalent hydrogens indicates that the GeH3 X - radical anions have structures of C 3v symmetry. The geometric and electronic structures of GeH3 X - were compared with those of CH3 --- X - adducts formed in acetonitrile and SiH3 X - radical anions generated in TMS.