Negative hyperconjugation in hexachloro-3-cyclopentenylaminosulphenyl halides: Preparation and X-ray structure of C5Cl6NSBr and synthesis of C5Cl6NS+AsF6−

Abstract

The reaction of hexachlorocyclopentadiene with (NSCl)3 at 65 °C in the absence of a solvent produced hexachloro-3-cyclopentenylidenaminosulfenyl chloride, C5Cl6NSCl, in good yield. The derivatives C5Cl6NSX(X = Br, I, C5Cl6N, NPr2i, Ph) were prepared by treatment of C5Cl6NSCl with Me3SiBr, Me3SiI, Ph3Sb, iPr2NH, and Ph2Hg, respectively. The crystal structure of C5Cl6NSBr was determined by X-ray crystallography. Crystals of C5Cl6NSBr are triclinic, space group [Formula: see text] with a = 9.626(2), b = 9.810(2), c = 13.736(2) Å, α = 79.68(1), β = 88.62(1), γ = 74.73(1)°, Z = 4, final R and Rw values were0.075 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) and2.235(2) Å. 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)°. The unusual geometry of the < C=NSBr moiety is explained in terms of negative hyperconjugation (nN → σSBr*). A variable temperature 13C NMR of C5Cl6NSCl provides evidence for a fiuxional process (ΔG*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. Key words: hexachloro-3-cyclopentenylidenamino sulfides, crystal structure, hexachloro-3-cyclopentenylidenaminosulfenyl bromide.