Negative hyperconjugation in hexachloro-3-cyclopentenylaminosulphenyl halides: Preparation and X-ray structure of C 5 Cl 6 NSBr and synthesis of C 5 Cl 6 NS + AsF 6

• Published in: Canadian journal of chemistry Vol. 69; no. 6; pp. 1022 - 1027
• Main Authors: Apblett, Allen, Chivers, Tristram, Fait, James F., Vollmerhaus, Rainer
• Format: Journal Article
• Language: English
• Published: 01.06.1991
• ISSN: 0008-4042; 1480-3291
• DOI: 10.1139/v91-150

The reaction of hexachlorocyclopentadiene with (NSCl) 3 at 65 °C in the absence of a solvent produced hexachloro-3-cyclopentenylidenaminosulfenyl chloride, C 5 Cl 6 NSCl, in good yield. The derivatives C 5 Cl 6 NSX(X = Br, I, C 5 Cl 6 N, NPr 2 i , Ph) were prepared by treatment of C 5 Cl 6 NSCl with Me 3 SiBr, Me 3 SiI, Ph 3 Sb, i Pr 2 NH, and Ph 2 Hg, respectively. The crystal structure of C 5 Cl 6 NSBr was determined by X-ray crystallography. Crystals of C 5 Cl 6 NSBr 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 R w 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 C 5 Cl 6 NSBr 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 (n N  → σ SBr *). A variable temperature 13 C NMR of C 5 Cl 6 NSCl provides evidence for a fiuxional process (ΔG* 298  = 68.1 ± 1.2 kJ mol −1 ) in solution. The dark purple compound C 5 Cl 6 NS + AsF 6 − was synthesized from the reaction of C 5 Cl 6 NSCl and AgAsF 6 in SO 2 . Key words: hexachloro-3-cyclopentenylidenamino sulfides, crystal structure, hexachloro-3-cyclopentenylidenaminosulfenyl bromide.