The S-aryl substituted thionylphosphazene (Cl2PN)(2)[4-t-BuC6H4(O)SN] (1) was prepared by Friedel-Craft's reaction of NSOCl(NPCl2)(2) with tert-butylbenzene. When it reacted with excess KSO2F at 110 degrees C, the P-Cl bonds of I were fluorinated, yielding the tetrafluorothionylphosphazene, (F2PN)(2)[4-t-BuC6H4(O)SN] (2). An equimolar reaction of 2 with dilithiated 1,3-propanediol in THF at -78 degreesC resulted in the formation of the ansa-substituted compound CH2(CH2O)(2)[FPN](2)[4-t-BuC6H(O)SN] (3). The crystal structures of 2 and 3 were determined. In 3 the ansa ring is trans on the PNS heterocycle with respect to the aryl group. Reaction of 2 with the disiloxane (CF2CH2OSiMe3)(2), in the presence of catalytic amounts of CsF in THF at 90 degreesC, resulted in the formation of the dispiro compound [(CF2CH2O)(2)PN](2)[4-t-BuC6H4(O)SN] (4). Compounds 1-4 were characterized by IR, NMR (H-1,C-13,F-19, P-31), mass spectral, and elemental analyses.