Solid-phase synthesis of protonated nitrogen-containing heterocyclic compounds with the boron cluster anions starting from [Eu(H2O)9]2[B10Cl10]3: Synthesis, structure, and thermal properties of (НL)2[B10Cl10] (L = 7-amino-4-methylcoumarin or 1-ethyl-2-(4-methoxyphenyl) azobenzimidazole)

Abstract The paper proposes a new method for the synthesis of salts of a perchlorinated derivative of the decahydro-closo-decaborate anion with neutral N-containing organic bases L1 and L2 starting from previously prepared europium precursor [Eu(H2O)9]2[B10Cl10]3. Compound [Eu(H2O)9]2[B10Cl10]3 was first synthesized and characterized by elemental analysis, X-ray powder diffraction, IR spectroscopy and its thermal properties were studied by TGA. The protonation of organic bases L was carried out in the solid phase in the presence of precursor [Eu(H2O)9]2[B10Cl10]3. For comparison, the reaction was carried out in solution: in the CH3CN/CF3COOH system and in an aqueous solution of (H3O)2[B10Cl10] with pronounced acidic properties. The influence of reaction conditions on the composition and structure of the final products was analyzed. Salts of the composition (НL)2[B10Cl10] (L is 1-ethyl-2-(4-methoxyphenyl)azobenzimidazole (L1) and 7-amino-4-methylcoumarin (L2)) and (HL2)(H9O4) [B10Cl10] were synthesized and characterized by X-ray diffraction. The thermal properties of the obtained salts and ligand L1 (C16H16N4O) were studied in air in the temperature range 20–600°С.