Geometries, interaction energies and bonding in [Po(H₂O)_n]⁴⁺ and [PoCl_n]⁴⁻ⁿ complexes

Abstract

Polonium (Z = 84) is one of the rarest elements on Earth. More than a century after its discovery, its chemistry remains poorly known and even basic questions are not...

Excited states of polonium(iv): electron correlation and spin–orbit coupling in the Po4+ free ion and in the bare and solvated [PoCl5]− and [PoCl6]2− complexes

“…This intermediate step will allow us to derive methodological conclusions that are free of solvation model issues and in particular see if the conclusions that were drawn from the free-ion study are readily transferable to the Po IV complexes or if additional subtleties or simplifications apply. As already reported elsewhere, 9,11 the structures of the bare [PoCl 5 ] − and [PoCl 6 ] 2− complexes in the gas phase belong to D 3h and O h symmetry point groups (SPGs), respectively. As a consequence, excitations to the 6p x , y , z levels generate two many-electron spin–orbit free states per spin multiplicity in the [PoCl 5 ] − complex (of E′ and symmetries), and only one in the [PoCl 6 ] 2− one (T 1u ).…”

“…Though we have not performed actual bonding analyses for these levels, we note that this is somehow consistent with the significant delocalisation indices that we have previously reported for the ground state (0.5, which would be indicative of “half-bonds”). 11…”

“…Following this work, we applied the MP2/def2-TZVP level of theory to determine all the molecular geometries that are used in this work. Furthermore, we retained the same freezing scheme in the correlated calculations as in this previous work 11 ( i.e. the 5s and 5p orbitals of Po are frozen).…”

Unravelling the 6sp ← 6s absorption spectra of Bi(iii) complexes

“…Indeed, square pyramidal coordination was predicted by computational studies performed on the isoelectronic [PoCl 5 ] − . 33,34 Furthermore, the 6s 2 lone pair in [BiCl 5 ] 2− is polarised by a small but significant p character (2.0% according to natural bond orbital analysis), while in [BiCl 6 ] 3− , the lone pair has 100% 6s character, according to natural bond orbital (NBO) analysis. Studies performed on the Po(IV) analogue evidenced that a better match of the absorption spectral data was found with a model where the complex holds a water molecule ([PoCl 5 (H 2 O)] − ).…”

“…Studies performed on the Po(IV) analogue evidenced that a better match of the absorption spectral data was found with a model where the complex holds a water molecule ([PoCl 5 (H 2 O)] − ). 34 However, calculations performed on the [BiCl 5 (H 2 O)] 2− system (using an implicit PCM solvation model) resulted in the expulsion of the water molecule from the innercoordination sphere, with a calculated Bi⋯O distance of 2.754 Å. Thus, the lower oxidation state of the metal ion in the Bi(III) complex results in a weak interaction with the water ligand.…”