Exercise 7 | The Chemistry of the Transition Metals

Write the d-orbital electron configuration for the following octahedral complex ions and indicate if they are diamagnetic or paramagnetic:

Ni (II) complex

low-spin Fe (III) complex

Mn (II) complex with Δo < electron-pairing energy

Au(I) complex

Ni (II) complex: [Ar] 3d8 ⇒ 8 d-electrons ⇒ t2g6 eg2

2 unpaired electrons ⇒ paramagnetic

Fe (III) complex: [Ar] 3d5 ⇒ 5 d-electrons

low spin: electrons will first fill the t2g orbitals before occupying the higher-energy eg orbitals ⇒ t2g5 eg0

1 unpaired electron ⇒ paramagnetic

Mn (II) complex: [Ar] 3d5 ⇒ 5 d-electrons

Δo < electron-pairing energy ⇒ high-spin ⇒ d electrons occupy the eg orbitals before they pair up in the t2g orbitals ⇒ t2g3 eg2

5 unpaired electrons ⇒ paramagnetic

Au(I) complex: [Xe] 5d10 ⇒ 10 d-electrons ⇒ t2g6 eg4

no unpaired electron ⇒ diamagnetic