Question

For `"pentamminechlorochromium(III+) nitrate"`...can you...?

`"a. Give the d-electron count at the transition metal centre."`
`"b. Predict the spin state of the d-electrons."`
`"c. Identify the outer sphere ions?"`
`"d. Predict whether the complex is paramagnetic,"`
`"e. Give a possible coordination sphere isomer."`

Answer 1

We start with a `Cr^(3+)` metal ion, that is surrounded by (coordinated to) 6 ligands in an octahedral array, to give `[Cr(NH_3)_5Cl]^(2+)(NO_3^-)_2`

Explanation:

a. The transition metal ion `Cr^(3+)` has a `d^3` electron count at the metal centre.
b. These `d^3` electrons are all unpaired.
c. The outer sphere ligands are reasonably the nitrate counter ions; as written the nitrates are not coordinated to the metal.
d. The complex is certainly a paramagnet. How do I know this?
e. For a coordination sphere isomer, simply replace one of the octahedrally coordinate ligands (ammine or chloro) with the counter ion, nitrato: i.e. `[Cr(NH_3)_5(NO_3)]^(2+)`.