The Groves-Spiro Dioxomanganese(V) Story

摘要

The introduction in the seminal 1962 Ballhausen-Gray paper that provided the first molecular orbital description of metal-oxygen multiple bonds (Figure 1) concluded with the following statement:"It also might be hoped that an understanding of the principal features of the bonding in VO~(2+) will be a helpful guide in attempts to develop a general theory of the electronic structures of MO~(n+) and MO_2~(n+) complexes.The last sentences in that paper (published in the first issue of Inorg.Chem.) read as follows:"Indeed,it is clear that any complete discussion of the electronic structures of the oxy-cations of the transition and actinium series must allow for substantial oxygen to metal pi-bonding.Furthermore,it can be qualitatively understood why ions of this type in the first transition series usually have the formula MO~(n+) (TiO~(2+),VO~(2+) CrO~(3+)),while similar ions in the actinium series are invariably MO_2~(n+) (UO_2~(2+),NpO_2~(2+)).The two 2p_(pi) orbitals on oxygen can satisfy the pi-bonding capacities of the two 3d_(pi) orbitals of a first transition series metal ion,but it takes at least two oxygens to satisfy the combined pi-bonding capacities offered by the 5f and 6d orbitals of the metal ions in the actinium series."