Question: Write the name, stereochemistry and magnetic behaviour of the following:
(At. nos. Mn = 25, Co = 27, Ni = 28)
(i) K4[Mn(CN)6]
(ii) [Co(NH3)5Cl]Cl2
(iii) K2[Ni(CN)4]
(To remember:
Oxidation state of K is +1
Oxidation state of CN is -1
Oxidation state of NH3 is 0
Oxidation state of Cl is -1)
Solution:
(i) Oxidation state of Mn in the given complex is:
4(+1) + x + 6(-1) = 0
x = +2
IUPAC Name: Potassium hexacyanomanganate (II)
Mn2+: [Ar]3d5
CN– is a strong field ligand, so electron pairing occurs.
Hybridisation: d2sp3
Geometry: Octahedral or Square bipyrmidal
Magnetic behaviour: Paramagnetic because 1 electron is unpaired.
(ii) Oxidation state of Co in the given complex is:
x + 5(0) + (-1) + 2(-1) = 0
x = +3
IUPAC Name: Pentaamminechloridecobalt (III) chloride
Co3+: [Ar]3d6
NH3 is a strong field ligand, so electron pairing occurs.
Hybridisation: d2sp3
Geometry: Octahedral or Square bipyrmidal
Magnetic behaviour: Diamagnetic because no electron is unpaired.
(iii) Oxidation state of Ni in the given complex is:
2(+1) + x + 4(-1) = 0
x = +2
IUPAC Name: Potassium tetracyanonickelate (II)
Ni2+: [Ar]3d8
CN– is a strong field ligand, so electron pairing occurs.
Hybridisation: dsp2
Geometry: Square Planar
Magnetic behaviour: Diamagnetic because no electron is unpaired.
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