Fluorinated ansa substituted cyclophosphazenes endo-FcCH(2)P(S)(CH2O)(2)[P(F)N](2)(F2PN) [Fc = ferrocenyl] (1) and exo-FcCH(2)P(S)(CH2O)(2)[P(F)N](2)(F2PN) (2) readily transform to the spirocyclic compound [FcCH(2)P(S)(CH2O)(2)PN]-(F2PN)(2) (3) not only in the presence of CsF but also with non-fluorinated bases such as CS2CO3, K2CO3, KOBut, Et3N, DABCO, DBN, and DBU. The analogous tetrachloro ansa compound exo-FcCH(2)P(S)(CH2O)(2)[P(Cl)N](2)(Cl2PN) (5), however, did not transform to the chlorinated spiro compound (6) in the presence of these bases. With excess of CsF, P-Cl bonds of 5 were found to undergo fluorination leading to the formation of 2, which transformed to spirocyclic compound 3. Time dependent P-31 NMR spectroscopy was used to monitor this transformation. Crystal structure studies on the ansa substituted compounds 4 and 5 have shown weak bonding interactions involving C-(HCl)-Cl-..., C-(HO)-O-..., and C-(HS)-S-... interactions.