Silver Complexes of Cyclic Hexachlorotriphosphazene

The first solid‐state structures of complexed P 3 N 3 X 6 (X=halogen) are reported for X=Cl. The compounds were obtained from P 3 N 3 Cl 6 and Ag[Al(OR) 4 ] salts in CH 2 Cl 2 /CS 2 solution. The very weakly coordinating anion with R=C(CF 3 ) 3 led to the salt Ag(P 3 N 3 Cl 6 ) 2 + [Al(OR) 4 ] − ( 1 ), but the more strongly coordinating anion with R′=C(CH 3 )(CF 3 ) 2 gave the molecular adduct (P 3 N 3 Cl 6 )AgAl(OR′) 4 ( 3 ). Crystals of [Ag(CH 2 Cl 2 )(P 3 N 3 Cl 6 ) 2 ] + [Al(OR) 4 ] − ( 2 ), in which Ag + is coordinated by two phosphazene and one CH 2 Cl 2 ligands, were isolated from CH 2 Cl 2 solution. The three compounds were characterized by their X‐ray structures, and 1 and 3 also by NMR and vibrational spectroscopy. Solution and solid‐state 31 P NMR investigations in combination with quantum chemically calculated chemical shifts show that the 31 P NMR shifts of free and silver‐coordinated P 3 N 3 Cl 6 differ by less than 3 ppm and indicate a very weakly bound P 3 N 3 Cl 6 ligand in 1 . The experimental silver ion affinity (SIA) of the phosphazene ligand was derived from the solid‐state structure of 3 . The SIA shows that (PNCl 2 ) 3 is only a slightly stronger Lewis base than P 4 and CH 2 Cl 2 , while other ligands such as S 8 , P 4 S 3 , toluene, and 1,2‐Cl 2 C 2 H 4 are far stronger ligands towards the silver cation. The energetics of the complexes were assessed with inclusion of entropic, thermal, and solvation contributions (MP2/TZVPP, COSMO). The formation of the cations in 1 , 2 , and 3 was calculated to be exergonic by Δ r G °(CH 2 Cl 2 )=−97, −107, and −27 kJ mol −1 , respectively. All prepared complexes are thermally stable; formation of P 3 N 3 Cl 5 + and AgCl was not observed, even at 60 °C in an ultrasonic bath. Therefore, the formation of P 3 N 3 Cl 5 + was investigated by quantum chemical calculations. Other possible reaction pathways that could lead to the successful preparation of P 3 N 3 X 5 + salts were defined.