Beiträge zur Kristallchemie und zum thermischen Verhalten von wasserfreien Phosphaten. XXXXII Die ersten Iridiumphosphate

The First Iridiumphosphates Two polymorphs of iridium(III)‐metaphosphate Ir(PO 3 ) 3 and an iridium(IV)‐silicophosphate (Ir 1−x Si x ) 3 [Si 2 O(PO 4 ) 6 ] (x ∼ 0.5) were synthesized and their crystal structures determined from single‐crystal x‐ray data. Pale pink needles of triclinic Ir(PO 3 ) 3 (Ru(PO 3 ) 3 structure type, $P{\bar 1}$ (No. 2), Z = 2, a = 6.9574(6) Å, b = 10.3628(9) Å, c = 5.0288(4) Å, α = 92.28(1)°, β = 92.80(1)°, γ = 98.60(1)°, 1574 independent reflections, 122 parameters, R 1 = 0.028, wR 2 = 0.061) were grown from a metaphosphoric acid melt. Pale pink prisms of C ‐type Ir(PO 3 ) 3 ( C ‐Al(PO 3 ) 3 structure type, C c (No. 14), Z = 12, a = 13.103(2) Å, b = 19.183(1) Å, c = 9.354(1) Å, β = 127.19(1)°, 4254 independent reflections, 354 parameter, R 1 = 0.024, wR 2 = 0.062) were obtained by chemical vapour transport (900 °C → 800 °C, addition of IrCl 3 · x H 2 O). Both metaphosphates are built of [Ir III O 6 ] octahedra and infinite $^{1}_{\infty}\rm (PO^{-}_{3})$ chains. The latter have a translation period of three phosphate tetrahedra in the triclinic modification and six in the monoclinic. 1D and double‐quantum filtered 2D 31 P‐MAS‐NMR spectra of C ‐type Ir(PO 3 ) 3 confirm the chain structure and reveal a chemical shift range between −4,8 and −30,9 ppm for the 9 crystallographically independent, however chemically similar phosphate groups. Pale orange crystals of (Ir 1−x Si x ) 3 [Si 2 O(PO 4 ) 6 ] (Si 3 [Si 2 O(PO 4 ) 6 ] structure type, $R{\bar 3}$ (No. 148), Z = 3, a = 7.8819(8) Å, c = 24.476(4) Å, 1086 independent reflections, 56 parameters, R 1 = 0.061, wR 2 = 0.190) occurred in chemical vapour transport experiments aiming at the crystallization of C ‐Ir(PO 3 ) 3 . The crystal structure of the silicophosphate consists of isolated [Ir IV O 6 ] octahedra and [Si 2 O(PO 4 ) 6 ] 12− heteropolyanions.