Which of the following d orbitals has highest energy in square planer complexes ?

Options

A. `d_(xy)`
B. `d_(xy)`
C. `d_(x^(2)-y^(2))`
D. `d_(yz)`

Answer

C

Explanation

The crystal field splitting energy `Delta` is small in tetrahedral complexes but much larger in square planar complexes. Square palner complexes look loke octahedral ones except that the two trans ligands along the z axis are missing. In square planer complexes, the `d_(x^(2)-y^(2))` is highest in energy because it points directly at all four ligands, which lie along the x and y axes. The splitting pattern is more complicated here than for the octahedral and tetrahedral case, but the main point to remember is that a larger energy gap exists between the `d_(x^(2)-y^(2))` orbital and the four lower-energy orbitals. Square planar geomertry is mopst common for metal ions with electron configuration `d^(8)` because this configuration favours low spin complexes in which alll four lower energy orbitals are filled and the higher energy `d_(x^(2)-y^(2))` orbital is vacant. Common examples are `[Ni(CN)_(4)]^(2-)` , `[PdC1_(4)]^(2-)` `[PrC1_(4)]^(2-)` and `[Pt(NH_(3))_(2)C1_(2)]`.