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Why are different colours observed in octahedral and tetrahedral complexes for the same metal and same ligands?

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प्रश्न

Why are different colours observed in octahedral and tetrahedral complexes for the same metal and same ligands?

दीर्घउत्तर
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उत्तर

Lower wavelength is absorbed in octahedral complex than tetrahedral complex for the same metal and ligand. In tetrahedral coordination entity, formation of the d-orbital splitting is inverted and is smaller as compared to the octahedral field splitting. For the same metal-ligand complexes, it can be shown that

`Δ_t = (4/9)Δ_0`.

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अध्याय 9: Coordination Compounds - Exercises [पृष्ठ १२७]

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एनसीईआरटी एक्झांप्लर Chemistry Exemplar [English] Class 12
अध्याय 9 Coordination Compounds
Exercises | Q VI. 50. | पृष्ठ १२७

संबंधित प्रश्न

On the basis of crystal field theory, write the electronic configuration for d4 ion if ∆0 < P.


Draw figure to show the splitting of d orbitals in an octahedral crystal field.


How does the magnitude of Δo decide the actual configuration of d orbitals in a coordination entity?


Why are low spin tetrahedral complexes not formed?


Give the electronic configuration of the following complexes on the basis of Crystal Field Splitting theory.

\[\ce{[CoF6]^{3-}, [Fe(CN)6]^{4-} and [Cu(NH3)6]^{2+}}\].


\[\ce{CuSO4 . 5H2O}\] is blue in colour while \[\ce{CuSO4}\] is colourless. Why?


Using crystal field theory, draw energy level diagram, write electronic configuration of the central metal atom/ion and determine the magnetic moment value in the following:

\[\ce{[CoF6]^{3-}, [Co(H2O)6]^{2+}, [Co(Cn)6]^{3-}}\]


The CFSE for octahedral [CoCl6]−4 is 18,000 cm−1. What will be the CFSE for tetrahedral [CoCl3]−2?


Considering crystal field theory, strong-field ligands such as CN:


Crystal field stabilising energy for high spind4 octahedral complex is:-


Using crystal field theory, write the electronic configuration of d5 ion, if Δ0 > P.


What is crystal field splitting energy?


Consider that d6 metal ion (M2+) forms a complex with aqua ligands and the spin only magnetic moment of the complex is 4.90 BM. The geometry and the crystal field stabilization energy of the complex are ______.


The complex that has highest crystal field splitting energy (Δ) is ______.


On the basis of Crystal Field theory, write the electronic configuration for the d5 ion with a strong field ligand for which Δ0 > P.


Read the passage carefully and answer the questions that follow.

Crystal field splitting by various ligands

Metal complexes show different colours due to d-d transitions. The complex absorbs light of specific wavelength to promote the electron from t2g to eg level. The colour of the complex is due to the transmitted light, which is complementary of the colour absorbed.

The wave number of light absorbed by different complexes of Cr ion are given below:

Complex Wavenumber of light absorbed (cm-1) Energy of light absorbed (kJ/mol)
[CrA6]3- 13,640 163
[CrB6]3+ 17,830 213
[CrC6]3+ 21,680 259
[CrD6]3- 26,280 314

Answer the following questions:

(a) Out of ligands "A", "B", "C" and "D", which ligand causes maximum crystal field splitting? Why?

OR

Which of the two, “A” or “D” will be a weak field ligand? Why?

(b) Which of the complexes will be violet in colour? [CrA6]3- or [CrB6]3+ and why?
(Given: If 560 - 570 nm of light is absorbed, the colour of the complex observed is violet.)

(c) If the ligands attached to Cr3+ ion in the complexes given in the table above are water, cyanide ion, chloride ion, and ammonia (not in this order).

Identify the ligand, write the formula and IUPAC name of the following:

  1. [CrA6]3-
  2. [CrC6]3+

The value of the spin only magnetic moment for one of the following configurations is 2.84 BM. The correct one is:


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