Chemistry · Ch 4 — Transition and Inner Transition Elements
Structure of Permanganate Ion
Structure of Permanganate Ion
The permanganate ion, MnO₄⁻, adopts a regular TETRAHEDRAL geometry, directly analogous to the tetrahedral geometry already established for the chromate ion (section 4.4.2.3). In this ion, the central manganese atom -- present in the very high +7 oxidation state, i.e. as a formal Mn⁷⁺ centre -- is described as d³s hybridised, meaning three d orbitals and one s orbital combine to generate the four equivalent hybrid orbitals used to bond symmetrically to the four surrounding oxygen atoms positioned at the corners of the tetrahedron.
As with chromate, all four Mn-O bonds within the permanganate ion are equivalent to one another by symmetry and by resonance delocalisation of the ion's single negative charge across all four oxygen positions, rather than that charge being localised onto any particular oxygen atom or pair of oxygen atoms. This structural parallel between chromate (central Cr⁶⁺, tetrahedral, four equivalent Cr-O bonds) and permanganate (central Mn⁷⁺, tetrahedral, four equivalent Mn-O bonds) reflects the close similarity in bonding behaviour shown by the highest, most oxidised oxoanion forms of neighbouring 3d transition metals -- though it is worth noting that manganese here reaches an even higher formal …
What this figure shows. The permanganate ion, MnO₄⁻, drawn as a regular tetrahedron with the central manganese atom (Mn⁷⁺, d³s hybridised) bonded symmetrically to four equivalent terminal oxygen atoms, plus a matching ball-and-stick 3-D model (a grey-violet central Mn sphere surrounded by four red O spheres in tetrahedral arrangement). All four Mn-O bonds are equivalent by resonance/symmetry, analogous to the chromate ion's tetrahedral geometry but with manga …