Photon Factory Activity Report 2005 #23 Part B (2006)
Crystallography

NW2/2005G153

Molecular growth and intermolecular condensation of {Mo154-x}
Tomoji OZEKI*, Sayaka SHISHIDO
Department of Chemistry and Materials Science, Tokyo Institute of Technology,O-okayama, Meguro-ku, Tokyo 152-8551, Japan
Introduction
During the past decade, chemistry of molybdenumoxide giant clusters with nano-sized ring shape, where theMo atoms are in the +5/+6 mixed valence state, has
exploded to give numerous kinds of compounds of thisfamily [1]. These compounds show extraordinarily highnuclearity (typically more than 100 metal atoms withmore than 400 oxygen atoms) that depends on thepreparative conditions, which then influence to theirstructures.
However, almost all the preparative
procedures vary from sample to sample and thus acomprehensive survey of the formation conditions ofthese compounds is still lacking. Here we have prepareda series of {Mo154-x} compounds from precisely controlled
preparative procedures.
Single crystal synchrotron
radiation X-ray diffraction of these samples revealed thepH dependence of the molecular growth and intermolecular condensation reactions of the Mo nano-rings.
Results and Discussions
From an survey on the pH dependence of the synthetic
conditions, we have obtained three kinds of compounds, 1,2 and 3, which were obtained from solutions carefully
controlled to pH at 2.2, 1.7 and 1.4, respectively.
Compound 1 crystallized in monoclinic C2/m with a =42.0599(7) Å, b = 40.0450(5) Å, c = 22.5450(3) Å, and β= 94.587(1)º at 123K. A total of 219,779 reflections weremeasured, of which 47,374 were unique with Rint = 0.0636.
The current agreement factor is: R1 = 0.0593 for 37,460
reflections with I>2σ(I) and wR2 = 0.0709 for allreflections. Compound 2 crystallized in monoclinic C2/c
with a = 59.1887(5) Å, b = 47.1521(5) Å, c =31.8640(3)Å, and β = 109.695(1)º at 123K. A total of 369,563
reflections were measured, of which 103,302 were uniquewith Rint = 0.0800. The current agreement factor is: R1 =0.0903 for 50,188 reflections with I>2σ(I) and wR2 =0.1552 for all reflections. Compound 3 crystallized inmonoclinic C2/m with a = 33.4487(5)Å, b = 53.5509(10)Å, c =26.6748(10) Å, and β = 107.175(1)º at 123K. A
total of 374,815 reflections were measured, of which
73,161 were unique with Rint = 0. 0754. The current
agreement factor is: R1 = 0. 1026 for 44,475 reflections
with I>2σ(I) and wR2 = 0.1444 for all reflections.
Synchrotron X-ray diffraction of these samples
revealed that compounds 1, 2 and 3 contains giant
clusters formulated as {Mo142O490}, {Mo148O499O12/2} and{Mo150O514O4/2}, respectively. While {Mo142O490} in 1 isisolated from its neighboring anions, {Mo148O499O12/2} in 2
is connected to six neighboring anions through 12 linker
O atoms (12/2 means that each of these 12 atoms areshared by an adjacent anion). {Mo150O514O4/2} in 3 isconnected to two neighboring anions into a chain
structure. These results indicate that the nuclearity ofthese anions can be directly controlled by the acidity ofthe mother liquor while the mechanism of intermolecularcondensation involves other factors, such as the structuresof the constituent nano-clusters.

Figure 1. Structures of the {Mo142} anion in 1 (left) and{Mo150} anion in 3 (right). Increase in the nuclearity
results in the thickness of the nano-ring, while the radii
are kept almost constant.

Figure 2. Packing diagram of compound 2 showing aslice of its three-dimensional network structure.

Figure 3. Packing diagram of 3 showing the onedimensional chain structure.
References[1] See, for example, A. Müller, R. Maiti, M.
Schmidtmann, H. Bögge, S. K. Das and W. Zhang, Chem.
Commun., 2126-2127 (2001).
* tozeki@cms.titech.ac.jp

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