Citation:
Abstract:
Reaction of the bicyclic sulfur-nitrogen heterocycles RC6H4CN5S3 (R=4-CH3O, 4-CH3, 4-H, 4-Cl, 4-CF3, 3-CF3) with PR'3 (R'=C6H5 or 4-CH3OC6H4) produces 3-phosphoraniminato-7-aryl-1,3,5-trithia-2,4,6,8-tetrazocines RC6H4CN4S3NPR'3. In all cases, only the endo-isomers were isolated and characterized by 1H, 31P, and 19F NMR as well as UV spectroscopy and X-ray crystallog. RB3LYP/6-311+G(d,p)// RB3LYP/6-31G(d,p) computations were undertaken to help explain the atom-exact syntheses via intermediates previously detected spectroscopically. Three reasonable intermediates have been computed as stationary points with energies consistent with the obsd. reaction path. Cyclic and square-wave voltammetry studies of RC6H4CN4S3NPR'3, using a glassy carbon working electrode in CH2Cl2 with 0.4 M [nBu4N][PF6], reveal two IRR redn. processes at RT in all cases at approx. -1.9 and -2.2 V, resp., and one IRR oxidn. process at approx. +1.0 V (vs. Fc+/0). [RC6H4CN4S3NPR'3]-. radical anions (R'=4-CH3OC6H4, R=4-CH3O, 4-H, 4-CF3) were detected at -50 °C in CH2Cl2 by using in situ electrolysis and simultaneous ESR spectroscopy: [4-RC6H4CN4S3NP(4-CH3OC6H4)3]-., estd. a(31P)=0.078 mT, a(14N1)=0.031 mT, a(14N2,3)=0.256 mT, a(14N4,5)=0.341 mT. The signals decay rapidly, but after the electrolysis is ended, a persistent EPR signal is always obtained with EPR parameters that match known 4-aryl-1,2,3,5-dithiadiazolyls, i.e., a(N)=0.51 mT and g=2.0105, which are consistent with the prodn. of [4-CF3-C6H4CN2S2]..