How many unpaired electrons are there in Ir(Br)₆⁴^-? (Br^- is a weak-field ligand.)

Question

Quizplus · Accepted Answer

First, we need to determine the electron configuration of Ir in this complex, which is [Xe]4f14 5d7 6s2. 
Then, we need to see how the ligands affect the electron configuration. 
BrS1U1P1-S1S1P0 is a weak-field ligand, so it will not cause any pairing of electrons in the d orbitals. 
Therefore, we count the number of electrons in the d orbitals that are unpaired: 
d7: 1 2 3 4 5 6 7 [unpaired] 
So there are 7 unpaired electrons initially. 
However, we also need to consider the two S1U1B0 ligands, which are strong-field ligands that cause pairing of electrons. 
Each S1U1B0 ligand causes pairing of one electron, so we need to subtract two electrons from the total: 
d7: 1 2 3 4 [unpaired] 
Therefore, the answer is 4 unpaired electrons.

How Many Unpaired Electrons Are There in Ir(Br)64-? (Br- Is

How Many Unpaired Electrons Are There in Ir(Br)₆⁴^-? (Br^- Is