SYNTHESIS AND STRUCTURE OF THE NORBORNENE ADDUCT OF 1,3,5,2,4,6-TRITHIATRIAZINIUM TETRACHLOROALUMINATE [C7H10.S3N3][ALCL4]

The treatment of (NSCl)3 with an excess of norbornene in dioxane at 0-degrees-C produces C7H10.S3N3Cl (1). The addition of AlCl3 or AgAsF6 to a solution of this adduct in SO2 yields [C7H10.S3N3]X [2a, X- = AlCl4-; 2b, X- = AsF6-]. The N-14 NMR spectra of 2a, 2b, and [S3N3Cl2]AlCl4 are reported. The norbornene ligand was shown by X-ray crystallography to be attached to the S3N3+ cation in 2a via two sulfur atoms to give the exo-beta isomer. The crystals of 2a are triclinic, space group P1BAR, with a = 7.3572 (14) angstrom, b = 9.9771 (15) angstrom, c = 11.1178 (12) angstrom, alpha = 71.561 (11)-degrees, beta = 85.320 (13)-degrees, gamma = 80.133 (14)-degrees, V = 762.4 (3) angstrom 3, and Z = 2. The least-squares refinement with anisotropic thermal parameters for all non-hydrogen atoms converged at R = 0.029 and R(w) = 0.035 for 2686 unique observed reflections. There are pronounced variations in the sulfur-nitrogen bond lengths in the S3N3 ring indicative of a structural weakness. The -N=S=N- unit [\d(S-N)\ = 1.549 (3) angstrom] is linked to the three-coordinate sulfur atoms of the SNS moiety [\d(S-N)\ = 1.627 (3) angstrom] by long S-N bonds [\d(S-N)\ = 1.709 (3) angstrom]. Attempts to detach norbornene from the S3N3 ring in 2a by heating or treatment with 2,3-dimethyl-1,4-butadiene resulted in loss of the -N=S=N- bridge to give the 2:1 adduct of norbornene and NS2+.