REACTIONS OF N,N,N'-TRIS(TRIMETHYLSILYL)BENZAMIDINE WITH ORGANOCHALCOGEN HALIDES - FORMATION OF DIAZENES VIA THE RESONANCE-STABILIZED RADICALS PHCN2(EPH)2 AND THE X-RAY STRUCTURE OF PHCN2(SCCL3)3

The reactions of N,N,N'-tris(trimethylsilyl)benzamidine (1) with organosulfur chlorides in a 1:1 or 1:3 molar ratio in methylene dichloride produce the metathetical products PhC[N(SiMe3)2](NSR) [R = Ph, CCl3, 2,4-C6H3(NO2)2] or PhCN2(SR)3 [R = CCl3, 2,4-C6H3(NO2)2], respectively. The structure of PhCN2(SCCl3)3 (4b) was determined by X-ray crystallography. The crystals of 4b are triclinic, space group P1BAR, with a = 9.972 (2) angstrom, b = 10.517 (3) angstrom, c = 10.968 (3) angstrom, alpha = 109.75 (2)-degrees, beta = 93.31 (2)-degrees, gamma = 102.76 (2)-degrees, V = 1044.8 angstrom 3, and Z = 2. By contrast, the compound PhCN2(SPh)3 is thermally unstable and the reactions of 1 with PhECl (E = S, Se) in a 1:3 molar ratio in methylene dichloride produce the intensely colored diazenes trans-PhEN(Ph)CN = NC(Ph)NEPh. The ESR spectra of these reaction mixtures consist of a five-line (1:2:3:2:1) signal consistent with a radical mechanism involving the intermediate formation of the resonance-stabilized radicals PhC(NEPh)2. (E = S, g = 2.0071, a(N) = 0.575 mT; E = Se, g = 2.0201, a(N) = 0.59 mT). The reactions of 1 with RSeCl3 (R = Me, Ph) also yield the diazenes trans-RSeN(Ph)CN = NC(Ph)SeR (2a, R = Me; 2b, R = Ph). The reaction of 4-CF3C6H4CN2(SiMe3)3 with PhSCl in a 1:3 molar ratio produces the eight-membered ring (4-CF3C6H4)2C2N4S2Ph2, as a minor product, in addition to the isomeric diazene. The eight-membered rings Ph2C2N4S2R2 [R = CCl3, 2,4-(NO2)2C6H3] are obtained from the reaction of PhC(NSR)[N(SiMe3)2] with 2 molar equiv of PhSeCl.