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Preparation of Silver-Palladium Alloyed Nanoparticles for Plasmonic Catalysis under Visible-Light Illumination
Published on: August 18, 2020
Crown-ether coordination compounds of zirconium, hafnium and scandium using metal nanoparticles
Lara-Pauline Faden1, Lkhamsuren Bayarjargal2, Victor Milman3
1Institute for Inorganic Chemistry, Karlsruhe Institute of Technology (KIT), Engesserstrasse 15, D-76131 Karlsruhe, Germany. claus.feldmann@kit.edu.
Abstract:
Crown-ether coordination compounds of zirconium, hafnium and scandium were rarely reported in the past. Conventional syntheses via Lewis-acid-base reactions or metathesis reactions suffer from the high Lewis acidity and high oxophilicity of Zr4+, Hf4+ and Sc3+. Therefore, a redox approach using nanoparticles of zerovalent zirconium, hafnium, and scandium is suggested here. Zr(0), Hf(0), Sc(0) nanoparticles, 2-8 nm in size, are prepared by reduction of ZrCl4, HfCl4 and ScCl3 with sodium naphthalenide in a liquid-phase synthesis. The as-prepared Zr(0), Hf(0), Sc(0) nanoparticles are reacted in ionic liquids with 12-crown-4 (12c4), 15-crown-5 (15c5) and 18-crown-6 (18c6) exhibiting ring-opening diameters of 140 to 300 pm. As a result, four new crown-ether coordination complexes are obtained and characterized by single-crystal structure X-ray analysis. The structural variety ranges from the layered structure [AlCl2(12c4)][NaAl2Cl8] (1) over the chiral chain-type compounds [ZrCl2(15c5)][Na2Al4Cl16] (2) and [HfCl2(15c5)][Na2Al4Cl16] (3) to [ScCl2(18c6)][AlCl4] (4) with isolated ions. All compounds crystallize in space groups without inversion symmetry. Exemplarily, this was confirmed via second-harmonic generation (SHG) measurements of [ZrCl2(15c5)][Na2Al4Cl16] and [ScCl2(18c6)][AlCl4], whereof the latter shows a strong SHG signal (comparable to KH2PO4/KDP) and appears to be phase matchable.
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