1 research outputs found
Synthesis and Characterization of [(OH)TeNb<sub>5</sub>O<sub>18</sub>]<sup>6–</sup> in Water Solution, Comparison with [Nb<sub>6</sub>O<sub>19</sub>]<sup>8–</sup>
Reaction
of [Nb<sub>6</sub>O<sub>19</sub>]<sup>8–</sup> with
H<sub>6</sub>TeO<sub>6</sub> in water gives telluropentaniobate [(OH)ÂTeÂNb<sub>5</sub>O<sub>18</sub>]<sup>6–</sup> (<b>1</b>) as single
product, which was isolated as Na<sup>+</sup> and mixed Na<sup>+</sup>/K<sup>+</sup> salts. Crystal structures were determined for Na<sub>6</sub>[(OH)ÂTeNb<sub>5</sub>O<sub>18</sub>]·15H<sub>2</sub>O (<b>Na</b><sub><b>6</b></sub><b>-1</b>) and K<sub>6</sub>NaÂ[Nb<sub>5.5</sub>Â{TeÂ(OH)}<sub>0.5</sub>O<sub>18.5</sub>]·26H<sub>2</sub>O (<b>K</b><sub><b>6</b></sub><b>Na-1</b>). Formation of <b>1</b> was monitored with electrospray
ionization mass spectrometry (ESI-MS) and <sup>125</sup>Te NMR techniques.
Capillary electrophoresis was used to calculate electrophoretic mobilities
and radii of the anionic species in solutions of [(OH)ÂTeÂNb<sub>5</sub>O<sub>18</sub>]<sup>6–</sup> and [Nb<sub>6</sub>O<sub>19</sub>]<sup>8–</sup> in borate buffer. No condensation or
degradation products were detected. Reactions of <b>1</b> with
{Cp*Rh}<sup>2+</sup> sources gives 1:1 and 2:1 hybrid polyoxometalate,
which are present in solution as a mixture of isomers, as detected
by <sup>125</sup>Te NMR. The isomerism is related to various possibilities
of coordination of {Cp*Rh}<sup>2+</sup> to different {M<sub>3</sub>O<sub>3</sub>} faces, relative to the unique Te atom. According to
ESI-MS experiments in water and methanol, rapid redistribution of
the organometallic fragments between the 1:1 and 2:1 complexes takes
place. The 1:1 complexes are more stable in water, while 2:1 complexes
dominate in methanol. X-ray structural analysis of the crystals isolated
from 2:1 reaction mixture allowed identification of Na<sub>3</sub>[{Cp*Rh}<sub>2</sub>ÂTeNb<sub>5</sub>O<sub>19</sub>]·24H<sub>2</sub>O (<b>Cp*</b><sub><b>2</b></sub><b>Rh</b><sub><b>2</b></sub><b>-1</b>) with two {Cp*Rh}<sup>2+</sup> fragments capping the opposing faces of the Lindqvist anion