A second polymorph with composition Co₃(PO₄)₂·H₂O

Abstract

Single crystals of Co3(PO4)2·H2O, tricobalt(II) bis­[ortho­phosphate(V)] monohydrate, were obtained under hydro­thermal conditions. The compound is the second polymorph of this composition and is isotypic with its zinc analogue, Zn3(PO4)2·H2O. Three independent Co2+ cations are bridged by two independent orthophosphate anions. Two of the metal cations exhibit a distorted tetra­hedral coordination while the third exhibits a considerably distorted [5 + 1] octa­hedral coordination environment with one very long Co—O distance of 2.416 (3) Å. The former cations are bonded to four different phosphate anions, and the latter cation is bonded to four anions (one of which is bidentate) and one water mol­ecule, leading to a framework structure. Additional hydrogen bonds of the type O—H⋯O stabilize this arrangement.

Role of Water During Crystallization of Amorphous Cobalt Phosphate Nanoparticles

“…Besides impurities or surface active molecules, which can stabilize the amorphous phase, water is a key variable. Cobalt phosphate has been reported as octahydrate (CPO), tetrahydrate, two monohydrates, , and an anhydrous cobalt phosphate . For example, the water content of amorphous Zn 3 (PO 4 ) 2 spans a range from nominally zero to two water molecules of hydration per formula unit.…”