Chapter 4 - Jacobs University

Chapter 5
Organoruthenium POM
tungsten site is of interest as it exhibits four equatorial, terminal ligands (Figure 5.3–5.5). To our
knowledge, this motif has never been observed before in polyoxometalate chemistry. We believe
that we are looking at a cis-WO 2 (H 2 O) 2 group, rather than a tungsten center with four terminal
hydroxo ligands. This is supported by the bond lengths around the unique tungsten atom: two of
them are short, presumably oxo bonds (W25–O25A, 1.67(3) Å; W25–O25D, 1.839(13) Å) and
two are long bonds, presumably to water (W25–O25C, 2.27(3) Å; W25–O25B, 2.22(3) Å).
Additional tungstate has also been observed in the lanthanide complexes
{Ln 4 (H 2 O) 28 [KÌP 8 W 48 O 184 (H 4 W 4 O 12 ) 2 Ln 2 (H 2 O) 10 ] 13- } x (Ln = La, Ce, Pr, Nd) and probably it also
resulted from in situ decomposition of P 8 W 48 . 18f However, in those structures the additional
tungstate was attached to individual “P 2 W 12 ” units (rather than bridging them, as here) and the
cyclic P 8 W 48 assembly was not distorted.
Figure 5.5 Side-view of 3 showing that the four organoruthenium units are grafted near the rim of the
central cavity, with the hydrophobic p-cymene groups protruding away from the hydrophilic polyanion.
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