2 research outputs found
Fluoridonitrosyl Complexes of Technetium(I) and Technetium(II). Synthesis, Characterization, Reactions, and DFT Calculations
A mixture of [TcÂ(NO)ÂF<sub>5</sub>]<sup>2â</sup> and [TcÂ(NO)Â(NH<sub>3</sub>)<sub>4</sub>F]<sup>+</sup> is formed during the reaction
of pertechnetate with acetohydroxamic acid (Haha) in aqueous HF. The
blue pentafluoridonitrosyltechnetateÂ(II) has been isolated in crystalline
form as potassium and rubidium salts, while the orange-red ammine
complex crystallizes as bifluoride or PF<sub>6</sub><sup>â</sup> salts. Reactions of [TcÂ(NO)ÂF<sub>5</sub>]<sup>2â</sup> salts
with HCl give the corresponding [TcÂ(NO)ÂCl<sub>4/5</sub>]<sup>â/2â</sup> complexes, while reflux in neat pyridine (py) results in the formation
of the technetiumÂ(I) cation [TcÂ(NO)Â(py)<sub>4</sub>F]<sup>+</sup>,
which can be crystallized as hexafluoridophosphate. The same compound
can be synthesized directly from pertechnetate, Haha, HF, and py or
by a ligand-exchange procedure starting from [TcÂ(NO)Â(NH<sub>3</sub>)<sub>4</sub>F]Â(HF<sub>2</sub>). The technetiumÂ(I) cation
[TcÂ(NO)Â(NH<sub>3</sub>)<sub>4</sub>F]<sup>+</sup> can be oxidized
electrochemically or by the reaction with CeÂ(SO<sub>4</sub>)<sub>2</sub> to give the corresponding TcÂ(II) compound [TcÂ(NO)Â(NH<sub>3</sub>)<sub>4</sub>F]<sup>2+</sup>. The fluorido ligand in [TcÂ(NO)Â(NH<sub>3</sub>)<sub>4</sub>F]<sup>+</sup> can be replaced by CF<sub>3</sub>COO<sup>â</sup>, leaving the â[TcÂ(NO)Â(NH<sub>3</sub>)<sub>4</sub>]<sup>2+</sup> coreâ untouched. The experimental
results are confirmed by density functional theory calculations on
[TcÂ(NO)ÂF<sub>5</sub>]<sup>2â</sup>, [TcÂ(NO)Â(py)<sub>4</sub>F]<sup>+</sup>, [TcÂ(NO)Â(NH<sub>3</sub>)<sub>4</sub>F]<sup>+</sup>, and [TcÂ(NO)Â(NH<sub>3</sub>)<sub>4</sub>F]<sup>2+</sup>
Single-Site VO<sub><i>x</i></sub> Moieties Generated on Silica by Surface Organometallic Chemistry: A Way To Enhance the Catalytic Activity in the Oxidative Dehydrogenation of Propane
We
report here an accurate surface organometallic chemistry (SOMC)
approach to propane oxidative dehydrogenation (ODH) using a Ό<sup>2</sup>-oxo-bridged, bimetallic [V<sub>2</sub>O<sub>4</sub>(<i>acac</i>)<sub>2</sub>] (<b>1</b>) (<i>acac</i> = acetylacetonate anion) complex as a precursor. The identity and
the nuclearity of the product of grafting and of the subsequent oxidative
treatment have been systematically studied by means of FT-IR, Raman,
solid-state (SS) NMR, UVâvis DRS, EPR and EXAFS spectroscopies.
We show that the grafting of <b>1</b> on the silica surface
under a rigorous SOMC protocol and the subsequent oxidative thermal
treatment lead exclusively to well-defined and isolated monovanadate
species. The resulting material has been tested for the oxidative
dehydrogenation of propane in a moderate temperature range (400â525
°C) and compared with that of silica-supported vanadium catalysts
prepared by the standard impregnation technique. The experimental
results show that the catalytic activity in propane ODH is strongly
upgraded by the degree of isolation of the VO<sub><i>x</i></sub> species that can be achieved by employing the SOMC protocol