PREPARATION OF SENSNSE(ASF6)2 AND STRUCTURAL CHARACTERIZATION OF THE 6-PI ELECTRON-RICH AROMATIC SENSNSE2+

Highly crystalline SeNSNSe(AsF6)2 was prepared by the oxidation of (SeNSNSe)2(AsF6)2 with AsF5 in liquid SO2. The X-ray crystal structure was determined which consists of discrete planar SeNSNSe2+ cations and AsF6- anions with significant cation-anion interactions. The average Se-N [1 .70(2)], S-N [1.59(1)] and Se-Se [2.310(2) angstrom] bond distances are consistent with the removal of the unpaired electron from the pi* singly occupied molecular orbital of the 7-pi SeNSNSe.+. The Se-77 [-70-degrees-C, delta(Me2Se) = 2411.7, nu-1/2 = 10.2 Hz] and N-14 NMR [r.t., 6(MeNO2) = -72.5, nu-1/2 = 690 Hz] and Raman spectrum in AsF, solution are all consistent with retention of the ring structure in solution. The reaction of Se4(AsF6)2 and S4N4 was reinvestigated and found to give appreciable amounts of (SNSNS)2(AsF6)2 and (SeNSN)2(AsF6)2 as well as the reported (SeNSNSe)2(AsF6)2. A pure sample of (SeNSNSe)2(AsF6)2 was prepared by reduction of SeNSNSe(AsF6)2 with CsN3.