摘要
Relativistic quantum chemistry investigations are carried out to tackle the puzzling oxidation state problem in a series of MO3 trioxide anions of all d- and f-block elements with five valence electrons. We have shown here that while the oxidation states of V, Nb, Ta, Db, Pa are, as usual, all ＋V with divalent oxygen O（-II） in MO3- anions, the lanthanide elements Pr and Gd cannot adopt such high ＋V oxidation state in similar trioxide anions. Instead, lanthanide element Gd retains its usual ＋III oxi- dation state, while Pr retains a ＋IV oxidation state, thus forcing oxygen into a non-innocent ligand with an uncommon mono- valent radical （O＇） of oxidation state -I. A unique Pr＂- ＂（0）3 biradical with highly delocalized unpairing electron density on Pr（IV） and three O atoms is found to be responsible for stabilizing the monovalent-oxygen species in PRO3- ion, while GdO3 ion is in fact an OGd＋（O22-） complex with Gd（III）. These results show that a naive assignment of oxidation state of a chemical element without electronic structure analysis can lead to erroneous conclusions.
Relativistic quantum chemistry investigations are carried out to tackle the puzzling oxidation state problem in a series of MO_3^- trioxide anions of all d- and f-block elements with five valence electrons. We have shown here that while the oxidation states of V, Nb, Ta, Db, Pa are, as usual, all +V with divalent oxygen O(-II) in MO_3^- anions, the lanthanide elements Pr and Gd cannot adopt such high +V oxidation state in similar trioxide anions. Instead, lanthanide element Gd retains its usual +III oxidation state, while Pr retains a +IV oxidation state, thus forcing oxygen into a non-innocent ligand with an uncommon monovalent radical(O~·) of oxidation state -I. A unique Pr·- ·(O)_3 biradical with highly delocalized unpairing electron density on Pr(IV) and three O atoms is found to be responsible for stabilizing the monovalent-oxygen species in PrO_3^- ion, while GdO_3^- ion is in fact an OGd^+(O_2^(2-)) complex with Gd(III). These results show that a na?ve assignment of oxidation state of a chemical element without electronic structure analysis can lead to erroneous conclusions.
基金
supported by the National Basic Research Program of China(2013CB834603)
the National Natural Science Foundation of China(21173053,21433005,91426302,21221062,21201106)
