Synthesis, Crystal Structures and Properties of the Trimetaphosphimates Na 2 M(PO 2 NH) 3 · 2H 2 O with M = K, Tl

The double salt disodium thallium(I) tri‐μ‐imidocyclotriphosphate dihydrate, Na 2 Tl(PO 2 NH) 3 · 2H 2 O, was obtained by evaporation of combined, equimolar, aqueous solutions of Na 3 (PO 2 NH) 3 · 4H 2 O and TlOOCCH 3 . The structure determination of the pseudo‐merohedrally twinned crystals of Na 2 Tl(PO 2 NH) 3 · 2H 2 O was performed by single‐crystal X‐ray methods ( $P{\bar 1}$ , no. 2, a = 799.1(2), b = 799.3(2), c = 864.6(2) pm, α = 76.83(3)°, β = 83.81(3)°, γ = 77.57(3)°, Z = 2). In the crystal structure the trimetaphosphimate ring shows a chair conformation and two cyclic anions are connected to each other by six N‐H···O hydrogen bonds. The [(PO 2 NH) 3 ] 3− pairs are interconnected in a three‐dimensional network building strands along [1–10] by coordination to the sodium ions, with several coordinating bonds to the thallium ions and further hydrogen bonds. According to an ELF‐calculation, there is no stereochemical influence of the 6s 2 ‐electron pair at the thallium(I) ion in Na 2 Tl(PO 2 NH) 3 · 2H 2 O. This finding is corroborated by a comparison with the analogous potassium compound, Na 2 K(PO 2 NH) 3 · 2H 2 O, which was found to be isotypic to Na 2 Tl(PO 2 NH) 3 · 2H 2 O.