Syntheses and experimental studies on the relative stabilities of spiro, ansa, and bridged derivatives of cyclic tetrameric fluorophosphazene

Reactions of (CF2CH2OSiMe3)(2) and CF2(CF2CH2OSiMe3)(2) with N4P4Fdelta (1) in a 1:2.5 molar ratio resulted in the formation of monospiro compounds [(CF2CH2O)(2)PN] (F2PN)(3) (2) and [CF2(CF2CH2O)(2)PN](F2PN)(3) (4) as well as the intermolecular bridged compounds F7N4P4OCH2CF2CF2CH2OP4N4F7 (3) and F7N4P4OCH2CF2CF2CF2CH2-OP4N4F7 (5). An equimolar reaction of dilithiated 1,3-propanediol with 1 resulted in the 1,3-ansa-substituted compound CH2(CH2O)(2)[P(F)N](2)(F2PN)(2) (6) as the major product in good yield. However, an analogous reaction of the dilithiated 1,3-propanedithiol with 1 gave only the spirocyclic compound CH2(CH2S)(2)(PN)(F2PN)(3) (8). The molecular structures of 2 and 6 were determined by single-crystal X-ray diffraction. In the presence of catalytic amounts of CsF in THF, the bridged compound 3 was converted to the spirocyclic compound 2 while the 1,3-ansa compound 6 under similar conditions transformed into the monospiro-substituted compound CH2(CH2O)(2)(PN)(F2PN)(3) (7). These transformations were monitored by time-dependent F-19 and P-31 NMR studies.