Exploring the Limits of Transition‐Metal Fluorination at High Pressures

Abstract

Fluorination is aproven method for challenging the limits of chemistry,b oth structurally and electronically.H ere we explore computationally howp ressures below3 00 GPa affect the fluorination of several transition metals.Aplethora of new structural phases are predicted along with the possibility for synthesizing four unobserved compounds:T cF 7 ,C dF 3 , OsF 8 ,and IrF 8 .The Ir and Os octaflourides are both predicted to be stable as quasi-molecular phases with an unusual cubic ligand coordination, and both compounds formally correspond to ah igh oxidation state of + 8. Electronic-structure analysis reveals that otherwise unoccupied 6p levels are brought down in energy by the combined effects of pressure and as trong ligand field. The valence expansion of Os and Ir enables ligand-to-metal F2p!M6pc harge transfer that strengthens M À Fb onds and decreases the overall bond polarity.T he lower stability of IrF 8 ,a nd the instability of PtF 8 and several other compounds below3 00 GPa, is explained by the occupation of MÀFa ntibonding orbitals in octafluorides with ametal-valence-electron count exceeding 8.

Relating atomic energy, radius and electronegativity through compression

“…Detailed analyses and consideration of electronic structure will always be necessary for quantitative evaluations of, e.g., bond strength and polarity. 66,67…”

High Valent Mercury Fluoride Ions

“…The electronic factor is used to achieve electronic stability of the high‐symmetry structure while the mechanical factor is used for the right size of the central atom to fit into the cavity of a monocyclic ring. In the 5d metal fluoride series, ReF 8 is found to be a stable compound with CN of 8 [82,83] while OsF 8 and IrF 8 are predicted to be unstable for MF 6 and F 2 dissociation channels at ambient conditions [74] but are predicted to be stable under high pressure [84–86] . Similarly PtF 8 is also predicted to be exothermic for most possible dissociation reactions at different levels of quantum chemical calculations, [87] and no quantum chemical calculation is found for AuF 8 and HgF 8 to push the OS further in these molecules.…”