Cation Distribution in Mixed Formates. II. The Structure of the Mixed Crystal Cu0.5Zn0.5(HCOO)2·2H2O

The structure of the 1 : 1 mixed crystal between Cu(HCOO)2·2H2O and Zn(HCOO)2·2H2O has been determined on the basis of 878 visual intensity data. The space group is P21/c, with a=8.77, b=7.25, c=9.17 Å, β=98.0°, and Z=4. The structure is similar to that of Cu(HCOO)2·2H2O, except that the two metal ions are distributed over two metal ion sites, the Cu2+ ions being mostly localized in the [Cu(HCOO)2] sheet, and except that the longest axis of the coordination octahedron around the Cu2+ ion in this sheet is nearly perpendicular to it. It is suggested that the type of sheet found in the mixed crystal as well as in Cu(HCOO)2·4H2O is more favorable than that in Cu(HCOO)2·2H2O for an independent [Cu(HCOO)2] sheet.