Trinuclear magnesium imidazolate borohydride complex

Reberc, Maja (author), Mazaj, Matjaž (author), Stare, Jernej (author), Počkaj, Marta (author), Mali, Gregor (author), Li, Xiao (author), Filinchuk, Yaroslav (author), Černý, Radovan (author), Meden, Anton (author)

A new type of hybrid compound, combining properties of MOFs and borohydrides, was synthesized solvothermally using Mg(BH$_4$)$_2$ and imidazole as precursors. Material in the form of acetonitrile solvate with formula [Mg$_3${(Im)BH$_2$(Im)}$_6$(ImH)$_6$]·CH$_3$CN crystallizes in the space group R$\overline{3}$, having the unit cell parameters a = 15.1942(2) Å and c = 28.3157(3) Å as determined by single crystal X-ray diffraction. The structure was further investigated by solid-state NMR and DFT quantum chemical calculations. The main feature of the structure, reported here for the first time, is a linear trinuclear complex, where octahedrally nitrogen-coordinated Mg$^{2+}$ ions are bridged with {(Im)BH$_2$(Im)}$^−$ units, forming inside voids of 4.6 Å in diameter between the magnesium ions. Polar intermolecular interactions hold the molecules in a dense rhombohedral stacking, where a disordered acetonitrile molecule plays a cohesive role. The compound is stable in air and upon heating to about 160 °C. Using an alternative synthesis method from an imidazole melt, an imidazole solvate with the formula [Mg$_3${(Im)BH$_2$(Im)}$_6$(ImH)$_6$]·ImH and a very similar crystal structure to acetonitrile solvate was prepared. It is stable up to 220 °C. Upon further heating, it transformed into a layered structure with the formula Mg(Im$_3$BH)$_2$, space group P$\overline{3}$1c, and unit cell parameters a = 8.7338(9) Å and c = 17.621(2) Å determined by synchrotron powder diffraction. Besides its structural novelty, two types of potentially reactive hydrogens, bonded to boron and nitrogen in the same molecule, make the material highly interesting for future investigations in the fields of energy storage applications.

• Language: English
• Keywords: crystal structure, imidazoles, ligands, molecules, solvates
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Publication status: Published
• Publication version: Version of Record
• Year: 2022
• Number of pages: Str. 12708-12718
• Numbering: Vol. 61, iss. 32
• PID: 20.500.12556/RUL-138805
• UDC: 547.8.022
• ISSN on article: 0020-1669
• DOI: 10.1021/acs.inorgchem.2c01319
• COBISS.SI-ID: 117494019
• Publication date in RUL: 19.08.2022

Record is a part of a journal

• Title: Inorganic chemistry
• Shortened title: Inorg. chem.
• Publisher: American Chemical Society
• ISSN: 0020-1669
• COBISS.SI-ID: 25620480

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: kristalna struktura, imidazoli, ligandi, molekule, solvati