Coordination compounds with XeF 2, AsF 3 and HF as ligands to metal ions: a review of reaction systematics, Raman spectra and metal, fluoro-ligand polyhedra

Abstract

Listen

Translate article

The reactions between Ln(AsF 6) 3 (Ln: lanthanide) and excess of XeF 2 in anhydrous HF (aHF) as a solvent yield coordination compounds [Ln(XeF 2) 3](AsF 6) 3 or LnF 3 together with Xe 2F 3AsF 6 or mixtures of all mentioned products depending on the fluorobasicity of XeF 2 and LnF 3 along the series. XeF 2 in a basic aHF is able to oxidize Pr 3+ to Pr 4+ besides Ce 3+ to Ce 4+ and Tb 3+ to Tb 4+. The tetrafluorides obtained are weaker fluorobases as XeF 2 and are immediately exchanged with XeF 2 yielding Xe 2F 3AsF 6 and LnF 4. The analogous reaction between Ln(BiF 6) 3 and XeF 2 in aHF yields [Ln(XeF 2) 3](BiF 6) 3, Ln: La, Nd. Raman spectra of the compounds [Ln(XeF 2) n ](AF 6) 3 (A: As, Bi) show that no XeF + salts are formed. The interaction of XeF 2 with metal ion is covalent over the fluorine bridge. Analogous reactions of Ln(AsF 6) 3 with AsF 3 in aHF yield [Ln(AsF 3) 3](AsF 6) 3 which are stable in a dynamic vacuum at temperatures lower than 233 K. In reactions between M(AF 6) 2 (M: alkaline earth metal and Pb, A: As, Sb) and XeF 2 in aHF as a solvent, compounds of the type [M(XeF 2) n ](AF 6) 2 were synthesized. Analogous reactions with AsF 3 yield coordination compounds of the type [M(AsF 3) n ](AsF 6) 2. During the preparation of M x (AsF 6) x (M: metal in oxidation state x+) by the reaction between metal fluoride and excess of AsF 5 in aHF it was found that HF could also act as a ligand to the metal ions (e.g. Ca(HF)(AsF 6) 2).