Functional polyoxometalates from solvothermal reactions of VOSO4 with tripodal alkoxides – a study on the reactivity of different “tris” derivatives

We report a study on the structure directing effects of functional groups and counterions. The aim was to find a facile and high yielding synthetic procedure to obtain polyoxometalate (POM) building blocks for post- functionalisation. Therefore, solvothermal reactions of VOSO4 with various tris(hydroxymethyl)methane derivatives in alkaline methanolic solutions were investigated. In doing so, new POM fragments were isolated and characterised. The binding modes of the functionalised tripodal alkoxides turned out to be surprisingly different

Hexafluoridotechnetate(IV) Revisited

Novel synthetic routes to hexafluoridotechnetate(IV) are reported, and for the first time the single-crystal X-ray structures of several M2[TcF6] salts (M = Na, K, Rb, Cs, NH4, and NMe4) were determined. The ammonium and the alkaline metal salts crystallize in the trigonal space group P3m, while the NMe4(+) salt belongs to the space group R3. [TcF6](2-) salts are widely stable in aqueous solution. In alkaline media, however, a slow hydrolysis is observed, and the first hydrolysis product, the dimeric, oxido-bridged complex [F5Tc-O-TcF5](4-), could be studied structurally

IR studies of H/D exchange of water, hydroxyl, and carboxylic groups reveal slowly diffusing lattice defects in sub-nanometer pores

We have studied the properties of a series of solid hydrated organic porous networks with pore diameters ranging from approximately 0.4 to 0.9 nm using the attenuated total reflection infrared (ATR-IR) technique. These subnanometer organic pores are composed of water and of organic racemic bicyclic monomers containing carboxylic, alcoholic, ether functions and different appendices. In particular, the doubly hydrated hydroxyl acids 1 2H2O and 2 2H 2O form cylindrical pores in which half of the water molecules are part of the walls and the other half are located inside the pores. In a first step, by a comparison of the spectra of a family of related compounds, the COOH, COH as well as the wall and pore water stretches were assigned. The COOH bands are broad and red-shifted as compared to carboxylic acid dimers, and exhibit a substructure assigned to Fermi resonances. The OH stretches fulfill well Novak's correlation with the corresponding crystallographic O...O distances. In a second step, we have followed the deuteration of the different functional groups of solid 2 2H2O by ATR-IR by heavy water vapor. Surprisingly, we observe that the rates of deuteration are the same for all functional groups although exhibiting biexponential time dependence, in contrast to the liquid state where COOH groups exchange protons with water much faster than with alcohols. This result is rationalized in terms of slowly diffusing lattice defects resembling a local liquid or glass in the subnano scale in which the different exchange reactions take place. The nonexponential deuteration is explained in terms of a faster deuteration of crystal surface layers. © 2011 American Chemical Society.The financial support from the Spanish Ministry of Science and Technology (MST/FEDER, project CTQ2007-61024/BQU), of the Deutsche Forschungsgemeinschaft, Bonn, Germany and of the Fonds der Chemischen Industrie, Frankfurt, is gratefully acknowledged . N.P.H. thanks the Ramón Areces Foundation for a postdoctoral grant.Peer Reviewe

[Fe19] “Super-Lindqvist” Aggregate and Large 3D Interpenetrating Coordination Polymer from Solvothermal Reactions of [Fe2(OtBu)6]with Ethanol

International audienceThe syntheses, crystal structures, and physical properties of [HFe19O14(OEt)30] and {Fe11(OEt)24}1 are reported. [HFe19O14(OEt)30] has an octahedral shape. Its core with a central Fe metal ion surrounded by six m6-oxo ligands is arranged in the rock salt structure. {Fe11(OEt)24}1 is a mixedvalencecoordination polymer in which FeIII metal ions form three 3D interpenetrating (10,3)-b nets. The arrangement of the FeIII ions can also be compared to that of Si ions in a-ThSi2. Thus, the described structures are at the interface between molecular and solid-state chemistry

Fluoridonitrosyl Complexes of Technetium(I) and Technetium(II). Synthesis, Characterization, Reactions, and DFT Calculations

A mixture of [Tc­(NO)­F₅]^2– and [Tc­(NO)­(NH₃)₄F]⁺ is formed during the reaction of pertechnetate with acetohydroxamic acid (Haha) in aqueous HF. The blue pentafluoridonitrosyltechnetate­(II) has been isolated in crystalline form as potassium and rubidium salts, while the orange-red ammine complex crystallizes as bifluoride or PF₆^– salts. Reactions of [Tc­(NO)­F₅]^2– salts with HCl give the corresponding [Tc­(NO)­Cl_4/5]^−/2– complexes, while reflux in neat pyridine (py) results in the formation of the technetium­(I) cation [Tc­(NO)­(py)₄F]⁺, 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 [Tc­(NO)­(NH₃)₄F]­(HF₂). The technetium­(I) cation [Tc­(NO)­(NH₃)₄F]⁺ can be oxidized electrochemically or by the reaction with Ce­(SO₄)₂ to give the corresponding Tc­(II) compound [Tc­(NO)­(NH₃)₄F]²⁺. The fluorido ligand in [Tc­(NO)­(NH₃)₄F]⁺ can be replaced by CF₃COO^–, leaving the “[Tc­(NO)­(NH₃)₄]²⁺ core” untouched. The experimental results are confirmed by density functional theory calculations on [Tc­(NO)­F₅]^2–, [Tc­(NO)­(py)₄F]⁺, [Tc­(NO)­(NH₃)₄F]⁺, and [Tc­(NO)­(NH₃)₄F]²⁺