K1.10Zr2Se6, Rb0.86Zr2Se6 and CS0.8OZr2Se6. The first intercalation compounds of zirconium triselenide

Single crystals of K1.10Zr2Se6, Rb0.86Zr2Se6 and Cs0.80Zr2Se6 were obtained by reacting powdered mixtures of A(2)Se (A = K, Rb, Cs), Zr and Se at 850 degreesC. K1.10Zr2Se6 and Rb0.86Zr2Se6 crystallize in space group Immm (Z = 2), with a = 3.746(3), b = 5.354(8), c = 21.929(3) Angstrom and a = 3.756(1), b = 5.354(8), c = 22.81(1) Angstrom, respectively. Cs0.80Zr2Se6 crystallizes in space group Cmc2(1) (Z = 2), with a = 3.747(1), b = 24.102(5), c = 5.332(2) (.) Angstrom. The compounds are characterized by complex anionic layers (2)(infinity)[Zr2Se6](x-) with intercalated alkali cations. As in ZrSe3, the layers are built from columns of trigonal prisms (1)(infinity)[ZrSe3], connected by additional waist contacts, yielding an eightfold coordination for the Zr atoms. The mean Zr-Se bond lengths correspond to those found in the binary compound. The Se-Se bond lengths are significantly altered, however, indicating a reduction of the Se-Se bond order due to the electron transfer from the alkali metal.