The use of alkall-metal fluorides as nucleophiles in oprotlc solvents has received much attention lately. The fluoride ion can cause reaction in two ways: cleavage (as in the case of $205F22 and P203F43) or addition (as in the case of COF24 and FSNS). We are reporting preliminary evidence of both the above reactions oocuring in an unsaturated phasphorus-nltrogen system, using trlmeric phasphonltrilic fluoride as the substrate. Addition did indeed occur when cesium fluoride was reacted with a slight excess of P3N3F 6 (based on a 1:1 reactant ratio) in anhydrous acetonitrile at ambient temperature. The white, hydroscopic odduct (CsP3N3F7) was isolated in quantitative yield by evaporation of the solvent. (Anal. Calcd: Cs 33.2, P 23.2, N 10.5, F 33.2, Equiv. Wt. 400.9; Found: Cs 33.4, P 23.1, N 10.2, F 32.6, Equiv. Wt. 403). Based on infrared evidence, the same product was obtained whether or not a large excess of either reagent was used. Thus cleavage of the P~'43 framework into small fragments apparently did not occur. Conductivity measurements of the salt in nitramethane demonstrated that i t was a 1:1 electrolyte (a plot o f . / ~ . ~ ¢ vs gave a slope of 250). 6 To date, the literature shows that the reaction between PsN~6 and a nucleophile (such as phenyllithlum) results in replacement of halogen by the phenyl group. An earlier article by Bode and Bach s reported that treatment of P3N3CI 6 by phenylmagnesium bromide and hydrochloric acid yielded Ph7PsN3H-HBr. This reaction not only replaced the halogens with phenyl group~ but also cleaved the ring to yield a linear species related in principle to structure II shown below. Although the structure of the anion PsN3F7is not known, two possibilities appear attractive: simple addition of fluoride ion to glve the cyclic anion I, or addition and cleavage to the linear structure II.