ESR Investigations of the Radicals {Li(3)[E(N(t)Bu)(3)](2)}(*) (E = S, Se) and the Radical Anions SO(x)()(N(t)Bu)(3)(-)(x)()(*)(-) (x = 1, 2).

Abstract

The air oxidation of the cluster compounds [Li(2)E(N(t)Bu)(3)](2) (E = S, Se) in toluene produces deep blue (E = S) or green (E = Se) solutions. The ESR spectra of these solutions consist of a septet (1:3:6:7:6:3:1) of decuplets. The simulation of these spectra shows that the secondary hyperfine splitting results from interaction of the unpaired electron with three equivalent (7)Li ions consistent with the formation of the neutral radicals {Li(3)[E(N(t)Bu)(3)](2)}(*) (4a, E = S, g = 2.0039, a((14)N) = 5.69 G, a((7)Li) = 0.82 G; 4b, E = Se, g = 2.00652, a((14)N) = 5.41 G, a((7)Li) = 0.79 G). Over a period of 25 h the seven line pattern of 4b is replaced first by a five line (1:2:3:2:1) spectrum (g = 2.009, a((14)N) = 13.4 G) and, subsequently, by a three line (1:1:1) spectrum (g = 2.00946, a((14)N) = 15.4 G, a((77)Se) = 4.3 G), neither of which exhibit (7)Li hyperfine splitting. These spectra are tentatively assigned to the radical anions SeO(N(t)Bu)(2)(*)(-) and SeO(2)(N(t)Bu)(*)(-), respectively. The cluster {Li(2)[O(2)S(N(t)Bu)]}(n)() (3) is prepared by the reaction of sulfur dioxide with 2 equiv of LiNH(t)Bu in toluene. The air oxidation of toluene solutions of {Li(2)[OS(N(t)Bu)(2)]}(6) (2a) or 3 produces deep blue species. In the former case the initial ESR spectrum is a 1:2:3:2:1 quintet (g = 2.009, a((14)N) = 13.3 G) which, after 16 h, evolves into a 1:1:1 triplet (g = 2.0088, a((14)N) = 15.9 G). The same triplet is observed in the ESR spectrum of oxidized solutions of 3 leading to the assignments OS(N(t)Bu)(2)(*)(-) and O(2)S(N(t)Bu)(*)(-) for the quintet and triplet, respectively. The disproportionation 2OS(N(t)Bu)(2)(*)(-) --> O(2)S(N(t)Bu)(*)(-) + S(N(t)Bu)(3)(*)(-) is indicated by the changes observed for the ESR spectra of oxidized solutions of 2a.