POLY(ALKYL/ARYLOXOTHIAZENES) - INORGANIC POLYMERS WITH A SULFUR(VI)-NITROGEN BACKBONE - SYNTHESIS, CHARACTERIZATION, AND THEORETICAL CALCULATIONS

N-Silylsulfonimidates [Me3SiN=S(O)(R1)OR2,3] with appropriate R2 groups have been found to undergo thermally induced condensation to produce the sulfur(VI)-nitrogen backbone polymers poly(alkyl-or aryloxothiazenes), [N=S(O)R1]n 4 and 5. Polymers 4 and 5 represent the first alkyloxothiazene polymers and the first characterized aryloxothiazene polymers. Modeled after the well-known condensation of N-silylphosphoranimines to poly(phosphazenes), the polycondensation of 3 to 4 appears to be a fairly general reaction. The design and novel synthesis of 3 are described in a companion article. The thermal condensation of 3 is catalyzed by Lewis acids and bases such as BF3.Et2O, AlCl3, fluoride ion, and phenoxide ion. Additionally, 3 can be quantitatively desilylated with methanol(without side reactions) to the ''free'' sulfonimidates [HN=S(O)(R1)OR2,7]. The free sulfonimidates, in turn, condense rapidly and quantitatively (at rates approximately two orders of magnitude faster and at temperatures 20 to 40-degrees-C lower, than 3) to poly-(oxothiazenes). The polymers have been characterized by gel permeation chromatography, NMR spectroscopy, thermoanalytical methods, and by elemental microanalysis. Theoretical calculations indicate a cis-trans helical conformation for poly(methyloxothiazene) 4a to be the most stable conformation. A major difference with phosphazene structure geometry is indicated by a near-tetrahedral N-S-N bond angle of 103-degrees.