NEGATIVE HYPERCONJUGATION IN HEXACHLORO-3-CYCLOPENTENYLAMINOSULPHENYL HALIDES - PREPARATION AND X-RAY STRUCTURE OF C5CL6NSBR AND SYNTHESIS OF C5CL6NS+ ASF6-

The reaction of hexachlorocyclopentadiene with (NSCl)3 at 65-degrees-C in the absence of a solvent produced hexachloro-3-cyclopentenylidenaminosulfenyl chloride, C5Cl6NSCl, in good yield. The derivatives C5Cl6NSX(X = Br, I, C5ClN,NPr2i,Ph) were prepared by treatment of C5Cl6NSCl with Me3SiBr, Me3SiI, Ph3Sb, (i)Pr2NH, and Ph2Hg, respectively. The crystal structure of C5Cl6NSBr was determined by X-ray crystallography. Crystals of C5Cl6NSBr are triclinic, space group P1BAR with a = 9.626(2), b = 9.810(2), c = 13.736(2) angstrom, alpha = 79.68(1), beta = 88.62(1), gamma = 74.73(1)-degrees, Z = 4, final R and R(w) values were 0.075 and 0.063, respectively, for 4850 unique observed reflections. The > C = NSBr moiety adopts a syn conformation and there are two different molecules of C5Cl6NSBr in the asymmetric units. The bond lengths are d(C = N) = 1.278(8) and 1.253(8), d(N-S) = 1.560(6) and 1.569(6), and d(S-Br) = 2.229(2) and 2.235(2) angstrom. The bond angles at nitrogen are 146.7(4) and 148.6(4) and those at sulfur are 116.8(2) and 116.5(2)-degrees. The unusual geometry of the < C = NSBr moiety is explained in terms of negative hyperconjugation (n(N) --> sigma-SBr*). A variable temperature C-13 NMR of C5Cl6NSCl provides evidence for a fluxional process (DELTA-G*298 = 68.1 +/- 1.2 kJ mol-1) in solution. The dark purple compound C5Cl6NS+ AsF6- was synthesized from the reaction of C5Cl6NSCl and AgAsF6 in SO2.