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Coordination Compounds
Question
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[Cu(CN)4]2+ is more stable complex than [Cu(NH3)4]+. Why?

Answer

The oxidation state in the complex [Cu(CN)4]2+ is +2 and oxidation state in the [Cu(NH3)4]+ complex is +1.  Stability depends on the hydration energy (enthalpy) of the ions when they bond to the water molecules. The Cu2+ ion has a greater charge density than Cu+ ion and thus forms much stronger bonds releasing more energy. The extra energy needed for the second ionization of the copper is more than compensated for by the hydration, so much so that the Cu+ ion loses an electron to become Cu2+ which can then release this hydration energy.
In aqueous solution Cu+ disproportionate to Cu2+ and Cu
2Cu+------>Cu2+ +Cu.

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Some More Questions From Coordination Compounds Chapter

Write the formula for the following coordination compound:
Iron(III) hexacyanidoferrate(II)

Write the IUPAC names of the following coordination compounds:
(i) [Co(NH3)6]Cl3
(ii) [Co(NH3)5Cl]Cl2
(iii) K3[Fe(CN)6]
(iv) K3[Fe(C2O4)3]
(v) K2[PdCl4]
(vi) [Pt(NH3)2Cl(NH2CH3)]Cl.

Indicate the type of isomerism exhibited by the following complexes and draw structures for these isomers:
(i)    K[Cr(H2O)2(C2O4)2],                      (ii) [Co(en)3Cl3,
(iii) [Co(NH3)5(NO2)]|NO3]2,                 (iv) [Pt(NH3)(H2O)Cl2]

Explain on the basis of valence bond theory that [Ni(CN)4]2–  ion with square planar is diamagnetic and the [NiCl4]2– ion with tetrahedral geometry is paramagnetic.

Predict the number of unpaired electrons in the square planar [Pt(CN)4,]2– ion.

The hexaquo manganese(II) ion contains five unpaired electrons, while the hexacynoion contains only one unpaired electron. Explain using crystal field theory.