Extending the Row of Lanthanide Tetrafluorides: A Combined Matrix-Isolation and Quantum-Chemical Study

Only the neutral tetrafluorides of Ce, Pr, and Tb as well as the [LnF(7)](3-) anions of Dy and Nd, with the metal in the +IV oxidation state, have been previously reported. We report our attempts to extend the row of neutral lanthanide tetrafluorides through the reaction of laser-ablated metal atoms with fluorine and their stabilization and characterization by matrix-isolation IR spectroscopy. In addition to the above three tetrafluorides, we found two new tetrafluorides, (NdF4)-Nd-3 and (DyF4)-Dy-7, both of which are in the +IV oxidation state, which extends this lanthanide oxidation state to two new metals. Our experimental results are supported by quantum-chemical calculations and the role of the lanthanide oxidation state is discussed for both the LnF(4) and [LnF(4)](-) species. Most of the LnF(4) species are predicted to be in the +IV oxidation state and all of the [LnF(4)](-) anions are predicted to be in the +III oxidation state. The LnF(4) species are predicted to be strong oxidizing agents and the LnF(3) species are predicted to be moderate to strong Lewis acids.