High-Valent Fluorides and Fluoro-Oxidizers

Metal tetraoxygen molecules (MO4, M = Fe, Ru, Os, Hs, Sm, Pu) of all metal atoms M with eight valence electrons are theoretically studied using density functional and correlated wave function approaches. The heavier d-block elements Ru, Os, Hs are confirmed to form stable tetraoxides of Td symmetry in (1)A1 electronic states with empty metal d(0) valence shell and closed-shell O(2-) ligands, while the 3d-, 4f-, and 5f-elements Fe, Sm, and Pu prefer partial occupation of their valence shells and peroxide or superoxide ligands at lower symmetry structures with various spin couplings. The different geometric and electronic structures and chemical bonding types of the six iso-stoichiometric species are explained in terms of atomic orbital energies and orbital radii. The variations found here contribute to our general understanding of the periodic trends of oxidation states across the periodic table.

Section: Resultsmentioning

confidence: 99%

On the Highest Oxidation States of Metal Elements in MO₄ Molecules (M = Fe, Ru, Os, Hs, Sm, and Pu)

Huang

Schwarz

et al. 2016

“…The discovery of new and unusual OS for chemical elements has been of great interest in chemistry and materials science. The highest OS in neutral compounds is +VIII, only occurring in a few MO 4 (M = Ru, Os, Ir, Xe) oxides. − The only known compound with +IX OS is the gaseous IrO 4 + cation, as recently verified both theoretically and experimentally. , Subsequently, Yu and Truhlar suggested a rare Pt(X) species in PtO 4 2+ using single-reference calculations with density functional theory (DFT) . However, more extensive calculations with open-shell singlet DFT and multireference ab initio wavefunction theory have proved very recently that the Pt(X) species is extremely high in energy and the PtO 4 2+ cation is unlikely to be stable in ambient conditions …”

Section: Introductionmentioning

confidence: 98%

Lanthanides with Unusually Low Oxidation States in the PrB₃^– and PrB₄^– Boride Clusters

Chen

et al. 2018

Lanthanide elements typically exhibit a +III oxidation state (OS) in chemical compounds with a few in +IV or even +V OS. Although lanthanides with +II OS have been observed recently in organometallic compounds, +I OS is extremely rare. Using a joint photoelectron spectroscopy and quantum theoretical study, we have found two low OS lanthanides in doped boron clusters, PrB3 – and PrB4 –. These two clusters are shown to have planar structures, in which the Pr atom is bonded to the aromatic boron clusters via two Pr–B σ bonds. Chemical bonding and electronic structure analyses reveal that the Pr atom is in a very low OS in the two boride clusters: +II in PrB3 – and +I in PrB4 –. The current finding suggests that there should exist a whole class of boride complexes featuring rather low-valent lanthanides and expands the frontier of lanthanide chemistry.

“…This situation changed after 1950, when the concept of 5f-elements, as suggested by Bohr in 1922 , and again by Seaborg in 1945, was gradually introduced into the chemical textbooks. , In general, the highest OS of an element is limited by the number of valence electrons outside the closed, chemically inert core shells. Among neutral compounds the highest overall OS known so far is VIII, namely, for p-block element Xe (group 18), for d-block elements Ru and Os (group 8), and for some others. − …”

Section: Introductionmentioning

confidence: 99%

Oxidation States, Geometries, and Electronic Structures of Plutonium Tetroxide PuO₄ Isomers: Is Octavalent Pu Viable?

Huang

et al. 2013

In neutral chemical compounds, the highest known oxidation state of all elements in the Periodic Table is +VIII. While PuO4 is viewed as an exotic Pu(+VIII) complex, we have shown here that no stable electronic homologue of octavalent RuO4 and OsO4 exists for PuO4, even though Pu has the same number of eight valence electrons as Ru and Os. Using quantum chemical approaches at the levels of quasi-relativistic DFT, MP2, CCSD(T), and CASPT2, we find the ground state of PuO4 as a quintet (5)C2v-(PuO2)(+)(O2)(-) complex with the leading valence configuration of an (f(3))plutonyl(V) unit, loosely coupled to a superoxido (π*(3))O2(-) ligand. This stable isomer is likely detectable as a transient species, while the previously suggested planar (1)D4h-Pu(VIII)O4 isomer is only metastable. Through electronic structure analyses, the bonding and the oxidation states are explained and rationalized. We have predicted the characteristics of the electronic and vibrational spectra to assist future experimental identification of (PuO2)(+)(O2)(-) by IR, UV-vis, and ionization spectroscopy.