K3CeCN6 what is the oxidation state of Cr

Question

K3CeCN6

what is the oxidation state of Cr

what's the electron configuration

the complex ion has numerous linkage isomers, draw 2 examples

the complex ion is a low spin, how would i draw the orbital occupation diagram for the d electrons of Cr

Answer 1

K3CeCN6 what is the oxidation state of Cr

K3CeCN6

what is the oxidation state of Cr

what's the electron configuration

the complex ion has numerous linkage isomers, draw 2 examples

the complex ion is a low spin, how would i draw the orbital occupation diagram for the d electrons of Cr

1. First, I think the question refers to K₃CrCN₆ , that is, Chromium not Cerium.
2. The oxidation state of the chromium is +3.

Potassium is a +1 and the cyanide ion is a -1, so

3* (+1) + 6 * (-1) + 1 * Cr = 0

3 - 6 + Cr = 0

Cr = +3

1. The electron configuration of Cr is (I'm assuming they want the +3 ion)

( [Ar] 3s² 3p⁶ 3d³ )⁺³

In the neutral atom, the configuration is ... 3d⁵ 4s¹ because full and half-filled sub-orbitals are especially stable (exception to the Aufbau principle).

1. The complex ion has numerous linkage isomers, draw 2 examples.

The six-coordination complex is an octahedral geometry: Transition metal at the center, surrounded by 4 ligands in a square plane plus 1 ligand above the plane and 1 below. The bonding arrangement for the K₃CrCN₆ is three ^.CN: ligands joined to the Cr at the C end by covalent bonds using the 4s and 3d unpaired electrons of the Cr. The other three ^.CN: ligands combine with the potassium as neutral ligands KCN: that bond to the Cr at the N end. The nitrogen coordinate-covalently donates its lone pair to the empty 3d sub-orbitals of the chromium.

I can't do a decent picture here, but suffice it to say that for two arrangements:

1. a [KCN:] will be in each polar position with the third one at one corner of the square; the three [ ^.CN:] ligands fill the other planar positions.
2. three [KCN:] ligands occupy planar positions with the the three [ ^.CN:] ligands filling the 4th planar corner plus both poles.

1. The complex ion is a low spin, how would i draw the orbital occupation diagram for the d electrons of Cr

___ ___

x²-y² z²

_1_ _1_ _1_

xy xz yz

1. first half-fill the lower 3 orbitals, as shown,
2. a 4th and 5th electron occupy the upper 2 sub-orbitals in the neutral atom,
3. for the Cr+3 ion, only the lower 3 sub-orbitals are occupied (half full).