in the mole fraction range A^Os = 0.22-0.33 is considered a realistic description of the catalyst. However, the temperature of the melt should be in the range 400-500 °C, and furthermore the melt should be in contact with an S02/02/S03 gas mixture in order to correspond to the conditions of operation. Even in the absence of this redox mixture the complexes of vanadium(V) in the V205-K2S207 binary system might very well be analogous to the complexes formed during operation of the catalyst. The present results show that the dominating vanadium(V) complex in solution in the mole fraction range AV2o5 = 0.22-0.33 is probably the dimer (V02)2(S04)2S2074-. Furthermore, the results for the ternary V205-K2S207-K2S04 system show that the S2072-group is labile and that a ligand exchange forming (V02)2(S04)34-can take place. This lability might lead to an exchange of S2072-with S02 during the catalytic reaction, giving rise to the formation of the complex (V02)2(S04)2S022-as the initial step in the catalytic cycle. In this complex a two-electron transfer from S02 to the vanadium central atoms forming S03 and possibly a V(IV) complex might take place simultaneously.The redox and complex chemistry of vanadium in similar melts is under investigation.25-27 Furthermore, an extended calorimetric (25) Fehrmann, R.; Hansen, N. H.; Bjerrum, N. J.; Phillipsen, J.; Pedersen, E., to be submitted for publication.study involving temperatures other than 430 °C in the range 400-450 °C is under way;28 conductivity and density measurements are in progress.18
The reaction of benzamidine with S3N3C13 yields l-chloro-3,5-diphenyl-l,2,4,6-thiatriazine, whose molecular structure has been determined by X-ray crystallography; reduction of Ph2C2N3SCI with triphenylantimony yields the radical species (Ph2C2N3S). characterized by its e.s.r. spectrum.
The crystal and molecular structures of 1,2,7,9-tetrathia-3,6,8,10-tetra-aza-cyclophept(e)indene, a novel carbon–sulphur–nitrogen heterocycle based on the phenazulene ring system, are reported. Crystals of the compound are orthorhombic, space group Pbca, a = 7.1334(8), b = 14.761(2), c = 16.677(2) Å, V = 1756.0(3) Å3, Z = 8. The structure was solved by direct methods and refined by full-matrix least-squares procedures to a final R = 0.044 and Rw = 0.027. Molecules of the title compound consist of a five-membered [Formula: see text] ring and a seven-membered [Formula: see text] ring fused to a benzene ring. Internal structural parameters and the cell packing pattern suggest a dipolar charge distribution. The molecules are stacked in parallel planes in a head-to-tail fashion; the interplanar separation is 3.39 Å and the angle between the molecular planes and the a axis is 18°. The electronic spectrum of the molecule is discussed in relation to the perimeter model.
The reaction of (Me3SiN)Ph2PN(Ph)C(NSiMe3)2 with sulphur dichloride affords the 1,3,2,4,6-thiaphosphatriazine Ph2P(Ph)CN3SCI which, upon reduction with triphenylantimony, yields the corresponding thiaphosphatriazinyl radical [Ph2P(Ph)CN3S].; the e.s.r. spectrum of this radical reveals a spin distribution heavily localized over the (P)-N-S region of the ring.
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