Hetero- and Homoleptic Magnesium Triazenides

A Blueprint for the Stabilization of Sub-Valent Alkaline Earth Complexes

The study of sub-valent Group 2 chemistry is a relatively new research field, being established in 2007 with the report of the first Mg(I) dimers. These species are stabilized by the formation of a Mg-Mg covalent bond; however, the extension of this chemistry to heavier alkaline earth (AE) metals has been frustrated by significant synthetic challenges, primarily associated with the instability of heavy AE-AE interactions. Here we present a new blueprint for the stabilization of heavy AE(I) complexes, based upon the reduction of AE(II) precursors with planar coordination geometries. We report the synthesis and structural characterisation of homoleptic trigonal planar AE(II) complexes of the monodentate amides {N(SiMe3 )2 }- and {N(Mes)(SiMe3 )}- . DFT calculations showed that the LUMOs of these complexes all show some d-character for AE = Ca-Ba. DFT analysis of the square planar Sr(II) complex [Sr{N(SiMe3 )2 }(dioxane)2 ]∞ revealed analogous frontier orbital d-character. AE(I) complexes that could be accessed by reduction of these AE(II) precursors were modelled computationally, revealing exergonic formation in all cases. Crucially, NBO calculations show that some d-character is preserved in the SOMO of theoretical AE(I) products upon reduction, showing that d-orbitals could play a crucial role in achieving stable heavy AE(I) complexes.

Obtaining and characteristic of the magnesium organic forms on the basis of products of bifidobacteria processing and their metabolites

The possibility of obtaining bioavailable mixed ligand chelate complexes of Magnesium has been considered. As bioligands, it is proposed to use the metabolites and products of enzymatic hydrolysis of the peptidoglycans of the cell walls of Bifidobacterium bifidum AC-1670. As ligands, fragments of peptidoglycans of cell walls of bifidobacteria, which have their own immunotropic effects, were used. Destruction of bacterial cells was done by ultrasound treatment with subsequent enzymatic hydrolysis with papain. It was found that the highest content of potential ligands for chelation was obtained by ultrasound treatment at a frequency of 35 kg for 600 seconds with subsequent enzymatic hydrolisys, which lasted for 180 minutes at a ratio of the enzyme: substrate 1:1. In this case, the accumulation of amino acids in the hydrolyzate was 11.35 mg/cm3, low molecular weight peptides - 7.54 mg/cm3. The liquid phase of the product of the disintegration of the bacterial mass is investigated for the presence of metabolites that can participate in the formation of chelating magnesium complexes. Qualitative composition and quantitative content of organic acids are determined. It is established that in the product of disinfection of bifidobacteria the following acids are present: acetic (445.5 mg/dm3), lactic (284.6 mg/dm3), benzoic (1.3 mg/dm3). It has been established that the obtained mixed ligand systems are effective chelating agents and bind magnesium in an amount of 14 mg/cm3. The method of IR spectroscopy has proved that this system is formed with the participation of polydentant ligands. Determination of the pH stability of the complex showed that in the range of pH values 4–7, the chelate system is stable, at pH 2 only 10% of the complex is stored, at a pH of 9 – 60%. The thermostability of the complex was investigated by the method of differential scanning calorimetry. It was established that the complex is stable in the temperature range of 20-122 ° С, and therefore can be used as a physiologically functional ingredient in the health foods, the technology of which involves high-temperature processing.