Coordination Compounds

According to crystal field theory, the correct order of ligands with respect to their decreasing order of field strength is

NEET 2026

1CO > NH₃ > H₂O > Cl⁻

2CO > H₂O > NH₃ > Cl⁻

3Cl⁻ > H₂O > NH₃ > CO

4Cl⁻ > NH₃ > H₂O > CO

NTA Answer: Option 1(final)

Report an error · Every fix is public: corrections log

Among the species given below, the spin-only magnetic moment is highest for (Given : Atomic number of Ti = 22, Mn = 25, Fe = 26 and Co = 27)

NEET 2026

1[Mn(CN)₆]³⁻

2[Fe(CN)₆]³⁻

3[Co(NH₃)₆]³⁺

4[Ti(H₂O)₆]³⁺

NTA Answer: Option 1(final)

Report an error · Every fix is public: corrections log

Lesson: IUPAC Nomenclature Coordination

NEET 2026

The formula of tetraammineaquachloridocobalt(III) chloride is

1[Co(NH₃)₄Cl₂] × H₂O

2[Co(NH₃)₄]Cl₃ × H₂O

3[Co(NH₃)₄(H₂O)Cl]Cl

4[Co(NH₃)₄(H₂O)Cl]Cl₂

NTA Answer: Option 4(final)

Report an error · Every fix is public: corrections log

Lesson: Isomerism Coordination

NEET 2026

The complex which has facial and meridional isomers is (Given : py = pyridine and en = H₂N–CH₂–CH₂–NH₂)

1[Cr(py)₃(Cl)₃]

2[Cr(H₂O)₆]³⁺

3[Co(NH₃)₄(H₂O)₂]³⁺

4[Ni(en)₂(H₂O)₂]²⁺

NTA Answer: Option 1(final)

Report an error · Every fix is public: corrections log

Lesson: Werner Theory

NEET 2026

A 1:3 electrolyte in an aqueous solution is

1[CoCl₂(NH₃)₄]Cl

2[CoCl(NH₃)₅]Cl₂

3[Co(NH₃)₆]Cl₃

4[Co(NH₃)₃(NO₂)₃]

NTA Answer: Option 3(final)

Report an error · Every fix is public: corrections log

The correct order of the wavelength of light absorbed by the following complexes is, A. [Co(NH3)6] 3+ B. [Co(CN)6] 3– C. [Cu(H2O)4] 2+ D. [Ti(H2O)6] 3+ Choose the correct answer from the options given below:

NEET 2025

1C < A < D < B

2B < D < A < C

3B < A < D < C

4C < D < A < B

NTA Answer: Option 3(final)

Report an error · Every fix is public: corrections log

NEET 2025

Out of the following complex compounds, which of the compound will be having the minimum conductance in solution?

1[Co(NH3)5Cl]Cl

2[Co(NH3)3Cl3]

3[Co(NH3)4Cl2]

4[Co(NH3)6]Cl3

NTA Answer: Option multi:2,3(final)

Report an error · Every fix is public: corrections log

Lesson: Valence Bond Coordination

NEET 2025

Which of the following are paramagnetic? A. [NiCl4] 2– B. Ni(CO)4 C. [Ni(CN)4] 2– D. [Ni(H2O)6] 2+ E. Ni(PPh3)4 Choose the correct answer from the options given below :

1A, D and E only

2A and C only

3B and E only

4A and D only

NTA Answer: Option 4(final)

Report an error · Every fix is public: corrections log

Given below are two statements : Statement I: Both [Co(NH ) ]3+ and [CoF ]3– complexes are octahedral but differ in their magnetic behaviour. 3 6 6 Statement II: [Co(NH ) ]3+ is diamagnetic whereas [CoF ]3– is paramagnetic. 3 6 6 In the light of the above statements, choose the correct answer from the options given below:

NEET 2024Revised key

1Both Statement I and Statement II are true

2Both Statement I and Statement II are false

3Statement I is true but Statement II is false

4Statement I is false but Statement II is true

NTA Answer: Option 1(revised_final)

Report an error · Every fix is public: corrections log

Given below are two statements : Statement I : [Co(NH₃)₆]³⁺ is a homoleptic complex whereas [Co(NH₃)₄Cl₂]⁺ is a heteroleptic complex. Statement II : Complex [Co(NH₃)₆]³⁺ has only one kind of ligands but [Co(NH₃)₄Cl₂]⁺ has more than one kind of ligands. In the light of the above statements, choose the correct answer from the options given below.

NEET 2024Revised key

1Both Statement I and Statement II are true

2Both Statement I and Statement II are false

3Statement I is true but Statement II is false

4Statement I is false but Statement II is true

NTA Answer: Option 1(revised_final)

Report an error · Every fix is public: corrections log

Homoleptic complex from the following complexes is

NEET 2023

1Diamminechloridonitrito-N-platinum (II)

2Pentaamminecarbonatocobalt (III) chloride

3Triamminetriaquachromium (III) chloride

4Potassium trioxalatoaluminate (III)

NTA Answer: Option 4(final)

Report an error · Every fix is public: corrections log

Lesson: Chelation

NEET 2023

Which complex compound is most stable?

1[Co(NH₃)₃(NO₃)₃]

2[CoCl₂(en)₂]NO₃

3[Co(NH₃)₆]₂(SO₄)₃

4[Co(NH₃)₄(H₂O)Br](NO₃)₂

NTA Answer: Option 2(final)

Report an error · Every fix is public: corrections log

Lesson: IUPAC Nomenclature Coordination

NEET 2022

The IUPAC name of the complex- [Ag(H2O)2][Ag(CN)2] is:

1diaquasilver(I) dicyanidoargentate(I)

2dicyanidosilver(II) diaquaargentate(II)

3diaquasilver(II) dicyanidoargentate(II)

4dicyanidosilver(I) diaquaargentate(I)

NTA Answer: Option 1(final)

Report an error · Every fix is public: corrections log

The order of energy absorbed which is responsible for the color of complexes (A) [Ni(H2O)2(en)2] 2+ (B) [Ni(H2O)4(en)]2+ and (C) [Ni(en)3] 2+ is

NEET 2022

1(B) > (A) > (C)

2(A) > (B) > (C)

3(C) > (B) > (A)

4(C) > (A) > (B)

NTA Answer: Option 4(final)

Report an error · Every fix is public: corrections log

Ethylene diaminetetraacetate (EDTA) ion is :

NEET 2021

1Tridentate ligand with three "N" donor atoms

2Hexadentate ligand with four "O" and two "N" donor atoms

3Unidentate ligand

4Bidentate ligand with two "N" donor atoms

NTA Answer: Option 2(final)

Report an error · Every fix is public: corrections log

Match List-I with List-II. List-I List-II (a) [Fe(CN)6] 3– (i) 5.92 BM (b) [Fe(H2O)6] 3+ (ii) 0 BM (c) [Fe(CN)6] 4– (iii) 4.90 BM (d) [Fe(H2O)6] 2+ (iv) 1.73 BM Choose the correct answer from the options given below.

NEET 2021

1(a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)

2(a)-(iv), (b)-(ii), (c)-(i), (d)-(iii)

3(a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)

4(a)-(i), (b)-(iii), (c)-(iv), (d)-(ii)

NTA Answer: Option 1(final)

Report an error · Every fix is public: corrections log

Which of the following is the correct order of increasing field strength of ligands to form coordination compounds ?

NEET 2020

1CN⁻ < C₂O₄²⁻ < SCN⁻ < F⁻

2SCN⁻ < F⁻ < C₂O₄²⁻ < CN⁻

3SCN⁻ < F⁻ < CN⁻ < C₂O₄²⁻

4F⁻ < SCN⁻ < C₂O₄²⁻ < CN⁻

NTA Answer: Option 2(final)

Report an error · Every fix is public: corrections log

Exam traps and common mistakes in this unit

Trap

High-spin vs low-spin from ligand field

Category: Similar Terms

Student defaults to one spin state. Strong-field ligand (CN⁻, CO, NH₃ for some) → low-spin (Δ > P, electrons pair). Weak-field (F⁻, H₂O, Cl⁻) → high-spin.

When it triggers

Coordination compound with given ligand asking for magnetic moment, color, or spin state.

How to avoid

Memorise spectrochemical series: I⁻ < Br⁻ < Cl⁻ < F⁻ < OH⁻ < H₂O < NH₃ < en < CN⁻ < CO. NH₃, CN⁻, CO usually strong-field. F⁻, H₂O, Cl⁻ usually weak-field.

Mistake

Defaults to high-spin (or low-spin) without checking ligand field strength.

Root cause: concept gap

Correction

Strong-field ligand (CN⁻, CO, NH₃ when applicable): Δ > P → low-spin. Weak-field (F⁻, Cl⁻, H₂O): Δ < P → high-spin. Use spectrochemical series.

Formulas in this unit

Magnetic moment of coordination complex

μ = n (n + 2) BM

Same spin-only formula but n depends on high-spin/low-spin from CFT.

Symbol	Quantity	SI Unit
n	unpaired electrons	-

Valid when

High vs low spin determined by Δ_o vs P
Octahedral (or tetrahedral with Δ_t)

Crystal field splitting (octahedral vs tetrahedral)

Δ_{t} \approx \frac{4}{9} Δ_{o}

Tetrahedral splitting is smaller than octahedral due to fewer/farther ligands.

Symbol	Quantity	SI Unit
Delta_o	octahedral splitting	J or eV
Delta_t	tetrahedral splitting	J or eV

Valid when

Same metal and same ligand
Mostly high-spin tetrahedral due to small Δ_t

NEET question patterns in this unit

Determine high-spin or low-spin from ligand field strength. Strong-field (CN, CO): low-spin. Weak-field (F, H2O): high-spin.

InterpretationMedium

Common distractors

forgets weak vs strong ligand

Default low-spin always

Lesson: IUPAC Nomenclature Coordination

Apply IUPAC rules: ligands alphabetical, prefixes for multiplicity, oxidation state of metal.

RecallMedium

Common distractors

wrong order ligands

Uses non-alphabetical order