Mixed-Ligand Precursors for the Preparation of MgF2 Films: Effect of the Fluorinated Substitute on the Structure and Thermal Properties

New magnesium complexes [Mg(H<sub>2</sub>O)<sub>2</sub>(ofhac)<sub>2</sub>] <b>1</b> and [Mg(tmeda)(ofhac)<sub>2</sub>] <b>2</b> (ofhac = <span class="mathjax-tex">\(\text{C}{{\text{F}}_{\text{3}}}\text{C(O)}\)</span><span class="mathjax-tex">\(\text{CHC(O)}{{\text{C}}_{\text{2}}}\text{F}_{5}^{-}\)</span>, tmeda = N,N,N′,N′-tetramethylethylenediamine) with a 1,1,1,2,2,6,6,6-octafluorohexane-3,5-dionate ligand are prepared. The composition of these compounds is confirmed by elemental analysis and IR spectroscopy, the structure is determined by XRD. The coordination environment of magnesium is distorted octahedral in both complexes. The ofhac ligands are coordinated in the bidentate-cyclic mode; the lengths of Mg–O bonds are similar and vary within 2.033(14)-2.063(18) Å. The aqua ligands in <b>1</b> occupy <i>cis</i> positions (<i>d</i>(Mg–O) = 2.0511(18) Å, θ(O–Mg–O) = 85.0(1)°) and participate in the system of O–H…O and O–H…F hydrogen bonds forming a chain packing. The tmeda ligand in <b>2</b> performs a chelating function (<i>d</i>(Mg–N) = 2.212(4) Å, θ(N–Mg–N) = 81.0(6)°). The dependence of the structure and the thermal properties of the complexes on the size of the fluorinated substituent (C<sub>2</sub>F<sub>5</sub> instead of CF<sub>3</sub>) is estimated by comparing the complex with its analogues bearing 1,1,1,5,5,5-hexafluoro-2,4-pentadionate ligands. The crystal structures of [Mg(H<sub>2</sub>O)<sub>2</sub>(L)<sub>2</sub>] are homeotypic; the analogues of [Mg(tmeda)(L)<sub>2</sub>] crystallize in different space groups. The absence of <i>trans</i> isomers in [Mg(H<sub>2</sub>O)<sub>2</sub>(L)<sub>2</sub>] is confirmed by powder XRD. The thermogravimetry experiments in flowing helium and sublimation tests in vacuum showed that complexes with the ofhac ligand are more volatile. Introducing a C<sub>2</sub>F<sub>5</sub> groups into the ligand also decreases the melting point of the compounds, more significantly for aqua complexes.</p><div class="c-article-section__figure" data-test="figure" data-container-section="figure"><figure><div class="c-article-section__figure-content"><div class="c-article-section__figure-item"><picture><source type="image/webp" srcset="//media.springernature.com/lw685/springer-static/image/art%3A10.1134%2FS0022476623070090/MediaObjects/10947_2023_2617_Figa_HTML.png?as=webp"><img src="//media.springernature.com/lw685/springer-static/image/art%3A10.1134%2FS0022476623070090/MediaObjects/10947_2023_2617_Figa_HTML.png" alt="" loading="lazy" width="550" height="422"></picture></div></div></figure></div>

Authors
Rikhter E.A. 1, 2 , Lee X. 3 , Vikulova E.S. 1 , Kochelakov D.V. 1 , Korolkov I.V. 1 , Khrustalev V.N. 4, 5 , Gao E. 3 , Morozova N.B. 1
Journal
Journal of Structural Chemistry
Issue number
7
Language
English
Pages
1250-1260
State
Published
Volume
64
Year
2023
Organizations
  • 1 Nikolaev Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences
  • 2 Novosibirsk State University
  • 3 School of Chemical Engineering, University of Science and Technology Liaoning, Anshan
  • 4 RUDN University
  • 5 Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences
Keywords
magnesium; β-diketonate; fluorinated precursor; volatility; x-ray diffraction analysis; thermal analysis.; inorganic chemistry; physical chemistry; atomic; molecular; Optical and Plasma Physics; Atomic/Molecular Structure and Spectra; solid state physics
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