[Be(OH2)4]Cl2– Herstellung, IR‐Spektrum und Kristallstruktur

The dubious origin of beryllium toxicity

Four mechanisms have been proposed in the literature to explain beryllium toxicity; they can be divided in two groups of two mechanisms: (i) replacement type: models 1 and 2; (ii) addition type: models 3 and 4. At this moment is not possible to select the best model not even to establish if one of these models will be the ultimate mechanism of beryllium toxicity. However, it is important to know the still open discussion about something so important associated with one of the simplest elements of the periodic table.

Beryllium triflates: synthesis and structure of BeL2(OTf)2 (L=H2O, THF, n Bu2O)

Beryllium and BeCl2 were treated with trifluoromethanesulfonic acid and trimethylsilyltriflate, respectively to form beryllium triflates BeL2(OTf)2 (L=H2O, THF, n Bu2O). The Be–O atomic distances (1.605–1.635 Å) between Be2+ and the triflate anions in solid state are the shortest known distances of this kind in a metal triflate yet. Attempts to remove the solvate molecules led to the decomposition of the obtained compounds.

Ab Initio Molecular Dynamics Investigation of Beryllium Complexes

Structures of aqueous [Be(H₂O)₄]²⁺, its outer-sphere and inner-sphere complexes with F^-, Cl^-, and SO₄^2-, and dinuclear complexes with a [Be₂(κ-OH)(κ-SO₄)]⁺ core have been studied through Car-Parrinello molecular dynamics (CPMD) simulations with the BLYP functional. According to constrained CPMD/BLYP simulations and pointwise thermodynamic integration, the free energy of deprotonation of [Be(H₂O)₄]²⁺ and its binding free energy with F^- are 9.6 and -6.2 kcal/mol, respectively, in good accord with available experimental data. The computed activation barriers for replacing a water ligand in [Be(H₂O)₄]²⁺ with F^- and SO₄^2-, 10.9 and 13.6 kcal/mol, respectively, are also in good qualitative agreement with available experimental data. These ligand-substitution reactions are indicated to follow associative interchange mechanisms with backside (S_N2-like) attack of the anion relative to the aquo ligand it is displacing. Outperforming static density functional theory computations of the salient kinetic and thermodynamic quantities involving simple polarizable continuum solvent models, CPMD simulations are validated as a promising tool for studying the structures and speciation of beryllium complexes in aqueous solution.

Solution Behavior of Beryllium Halides in Dimethylformamide

The reactivity of beryllium compounds in N,N-dimethylformamide (DMF) is fairly uncharted. However, as a versatile O-donor solvent, DMF enables reaction conditions that are inaccessible in solvents more commonly applied in beryllium chemistry. Here we present a comprehensive study on the interaction of beryllium halides BeX₂ (X = F, Cl, Br, I) with DMF. Through NMR and IR spectroscopy as well as single-crystal X-ray diffraction, we were able to characterize several Be(DMF)_1-4X₂ species and distinguish the competitiveness of the investigated halides against DMF. On the basis of titration experiments, [BeCl(DMF)₃]⁺ was identified as the dominant compound when BeCl₂ was dissolved in DMF. The unpredicted high beryllium-halide bond strength in chloro complexes as well as the instability of iodo compounds is discussed. The latter showed a distinctively different coordination chemistry compared to the other beryllium halides. In addition to that, the first example of a compound with the hexaiodidodiberyllate anion ([Be₂I₆]^2-) was characterized. On the basis of our results, BeBr₂ is a superior starting material compared to the other beryllium halides for the synthesis of coordination chemistry compounds.

The Oxygen-Rich Beryllium Oxides BeO4 and BeO6

Two novel isomers of BeO4 with the structures OBeOOO and OBe(O3 ) in the electronic triplet state have been prepared as well as the known disuperoxide complex Be(O2 )2 in solid noble-gas matrices. We also report the synthesis of the oxygen-rich bis(ozonide) complex Be(O3 )2 in the triplet state which has a D2d equilibrium geometry. The molecular structures were identified by infrared absorption spectroscopy with isotopic substitutions as well as quantum chemical calculations.