Die Kristallstruktur von Trikobalt(II)‐dihydroxidsulfat‐dihydrat, Co 3 (OH) 2 (SO 4 ) 2 · 2 H 2 O

Tricobalt (II)‐dihydroxidesulfate‐dihydrate, Co 3 (OH) 2 (SO 4 ) 2 · 2H 2 O, is orthorhombic: a = 7.21, b = 9.77, c = 12.86 Å, V = 905.9 Å 3 , space group D   11 2 h ‐ Pbcm with four formula units per cell. The atomic positions have been determined by threedimensional Patterson and Fourier synthesis and full‐matrix least‐squares refinement of single crystal X ‐ray diffraction data. The structure shows infinite chains [001] of CoO octahedra sharing one edge with each other. These chains are linked together by alternating SO 4 tetrahedra and additional CoO octahedra, thus giving rise to a three‐dimensional network of polyhedra. There is no similarity to the well known layer structures of most hydroxide salts of divalent metals. The SO 4 tetrahedra are regular while the CoO octahedra show considerable distortion. The water molecule is coordinated to one Co atom and bonded to sulfate oxygen by two weak hydrogen bridges.