The Oxidation of Heterogeneous Tl/Ni/P‐Alloys — Preparation and Crystal Structures of the Thallium Nickel Phosphates TlNi 4 (PO 4 ) 3 , Tl 4 Ni 7 (PO 4 ) 6 , and Tl 2 Ni 4 (P 2 O 7 )(PO 4 ) 2

Single crystals of the first anhydrous thallium nickel phosphates were prepared by reaction of heterogeneous Tl/Ni/P alloys with oxygen. TlNi 4 (PO 4 ) 3 (pale‐yellow, orthorhombic, space group Cmc2 1 , a = 6.441(2)Å, b = 16.410(4)Å, c = 9.624(2)Å, Z = 4) crystallizes with a structure closely related to that of NaNi 4 (PO 4 ) 3 . Tl 4 Ni 7 (PO 4 ) 6 (yellow‐brown, monoclinic, space group Cm, a = 10.711(1)Å, b = 14.275(2)Å, c = 6.688(2)Å, β = 103.50(2)°, Z = 8) is isotypic with Na 4 Ni 7 (PO 4 ) 6 , and Tl 2 Ni 4 (P 2 O 7 )(PO 4 ) 2 (brown, monoclinic, space group C2/c, a = 10.389(2)Å, b = 13.888(16)Å, c = 18.198(3)Å, β = 103.1(2)°, Z = 8) adopts the K 2 Ni 4 (P 2 O 7 )(PO 4 ) 2 structure. Tl 2 Ni 4 (P 2 O 7 )(PO 4 ) 2 could also be prepared in nearly single phase form by reaction of Tl 2 CO 3 , NiO, and (NH 4 ) 2 HPO 4 .