Exam Master Review Sheet - Coordination Compounds

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EXAM MASTER REVIEW SHEET

Coordination Compounds

Strategic Summary for JEE Main, Advanced & NEET

1. Werner's Theory & EAN

Primary Valency

• Corresponds to Oxidation State.
• Ionizable & Non-directional.

Secondary Valency

• Corresponds to Coordination Number.
• Non-ionizable & Directional (Geometry).

Effective Atomic Number (EAN):

\[ \text{EAN} = Z - \text{O.S.} + 2(\text{C.N.}) \]

If EAN = Atomic no. of next noble gas, the complex is generally more stable.

2. Isomerism in Complexes

Structural Isomerism

• Ionization: Exchange of ions inside/outside sphere.
• Linkage: Ambidentate ligands (\(SCN^-\) vs \(NCS^-\)).
• Hydrate: Difference in water molecules as ligands.
• Coordination: Exchange of ligands between cation/anion spheres.

Stereoisomerism

• Geometrical (Cis-Trans): \(MA_2B_4, MA_3B_3\) (Facial-Meridional).
• Optical: Shown by complexes lacking a plane of symmetry. (Common in chelating complexes like \([Co(en)_3]^{3+}\)).

3. Valence Bond Theory (VBT)

C.N.	Hybridization	Geometry	Example
4	\(sp^3\)	Tetrahedral	\([Ni(CO)_4]\)
4	\(dsp^2\)	Square Planar	\([Ni(CN)_4]^{2-}\)
6	\(sp^3d^2\)	Outer Orbital Octahedral	\([CoF_6]^{3-}\)
6	\(d^2sp^3\)	Inner Orbital Octahedral	\([Co(NH_3)_6]^{3+}\)

4. Crystal Field Theory (CFT)

Octahedral Splitting (\(\Delta_o\)):

Splitting pattern: \(t_{2g}\) (Lower), \(e_g\) (Higher)

\[ \text{CFSE} = [-0.4n_{t_{2g}} + 0.6n_{e_g}]\Delta_o + mP \]

\(P\) = Pairing Energy

Tetrahedral Splitting (\(\Delta_t\)):

Splitting pattern: \(e\) (Lower), \(t_2\) (Higher)

\[ \Delta_t = \frac{4}{9} \Delta_o \]

Pairing rarely occurs in tetrahedral complexes.

Spectrochemical Series:

\(I^- < Br^- < SCN^- < Cl^- < S^{2-} < F^- < OH^- < C_2O_4^{2-} < H_2O < NCS^- < EDTA^{4-} < NH_3 < en < CN^- < CO\)

Strong field ligands (\(CN^-, CO\)) cause pairing (\(\Delta_o > P\)).

5. Stability & Synergic Bonding

Stepwise Stability

\[ M + 4L \rightleftharpoons ML_4 \] \[ \beta_4 = K_1 \cdot K_2 \cdot K_3 \cdot K_4 \]

Higher \(\beta\) value indicates higher stability.

Synergic Bonding (Carbonyls)

Metal to Ligand \(\pi\)-backbonding.
• Strengthens \(M-C\) bond.
• Weakens \(C-O\) bond (increases bond length).

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