Elsevier

Solid State Sciences

Volume 6, Issue 6, June 2004, Pages 509-517
Solid State Sciences

The structures of X2[(Mo6Cl8)Cl6nH2O, X=NH4, K, Rb, Cs

https://doi.org/10.1016/j.solidstatesciences.2004.03.005Get rights and content

Abstract

The title compounds were synthesized from MoCl2 and the appropriate commercial chlorides and their structures were solved by a combination of single crystal X-ray diffraction analysis and theoretical methods. The NH4, K and Rb compounds are essentially isostructural, and crystallize in space group Ia (No. 9) with the cell parameters (in Å) a=9.173(1), b=14.986(2), c=17.505(3), β=92.94(2)° (NH4); a=9.140(4), b=14.852(5), c=17.445(11), β=93.48(6)° (K); a=9.215(1), b=14.941(3), c=17.532(2), β=92.70(1)° (Rb); while the Cs compound crystallizes in space group P21/n (No. 14) with the cell dimensions a=9.771(3), b=12.984(4), c=21.535(4), β=90.81(3)°.

Introduction

This study is part of an ongoing project that deals with supramolecular compounds based on the Mo6Cl142− cluster and derivatives thereof. The Mo6Cl142− entity shows remarkable stability, and may be handled as a building block for extended molecular assemblies from solution as well as in solid state reaction. Together with cations containing hydrogen it has a propensity for remarkably strong and rigid hydrogen bonded networks [1], [2]. The similarities in the hydrogen bonding motif are remarkable even when structures containing counterions of different size are used.

Section snippets

Synthesis

MoCl2 was synthesized from MoCl5 and Mo metal [3]. (NH4)2[(Mo6Cl8)Cl6]·H2O was synthesized from a mixture (1:1 vol) of a hot saturated solution of (H3O)2[(Mo6Cl8)Cl6]·7H2O and NH4Cl in 2M HCl. Yellow tabular crystals precipitated after slow cooling to room temperature. K2[(Mo6Cl6]·H2O was synthesized by dissolving (H3O)2[(Mo6Cl8)Cl6]·7H2O and KCl in hot 1M HCl. Slow cooling to room temperature yielded yellow needle-shaped crystals. Rb2[(Mo6Cl8)Cl6]·H2O and Cs2[(Mo6Cl8)Cl6]·3H2O were synthesized

Results and discussion

Fractional atomic coordinates for the four compounds are given in Table 2a, Table 2b, Table 2c, Table 2d. Since hydrogen positions are calculated, ESD's are not applicable. Isotropic displacement parameters for the calculated positions where determined, and for these ESD's are given. As in all known compounds containing the Mo6Cl142− unit, this entity is highly regular with MoMo distances close to 2.6 Å and MoCl distances around 2.5 Å. The Mo6Cl142− cluster has a coordination from H2O

References (9)

There are more references available in the full text version of this article.
View full text