Chemistry

Coordination Chemistry

319 Questions

Coordination chemistry focuses on coordination compounds, their structures, and their magnetic properties. The questions cover primary and secondary valencies, ligand types, and geometries of complexes. This topic is heavily tested in chemistry competitive exams and requires a good grasp of molecular structures.

primary and secondary valencycomplex geometriesligand field theorymagnetic properties of complexesisomerism in complexes

Coordination Chemistry Questions

Multiple choice

Which of the following sets represents weak field ligands only?

  1. S2-, SCN-, NO3-

  2. NO2-, CN-, PPh3

  3. Cl-, N3-, NO2-

  4. NO3-, NO2-, I-

  5. PPh3, S2-, SCN-
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

On the basis of ligand field theory, the spectrochemical series is an empirically-derived list of ligands ordered by the size of the splitting CFSE that they produce. It can be seen that the low-field ligands are all pi-donors, the high field ligands are pi-acceptors, and ligands such as H2O and NH3, which are are in the middle. The spectrochemical series is give as: I− < Br− < S2− < SCN− < Cl− < NO3− < N3− < F− < OH− < C2O42− < H2O < NCS− < CH3CN < py (pyridine) < NH3 < en (ethylenediamine) < bipy (2,2'-bipyridine) < phen (1,10-phenanthroline) < NO2− < PPh3 < CN− < CO. Hence, S2-, SCN- and NO3- all are weak field ligands.

Multiple choice

Which of the following pairs represents high spin complexes?

  1. [FeF6]3-, [Mn(H2O)6]3+

  2. [Cr(NH3)6]3+, [Mn(CN)6]3-

  3. [CoF6]3-, [Cr(NH3)6]3+

  4. [Co(NH3)6]3+, [Mn(CN)6]3-

  5. [Mn(CN)6]3-, [Mn(H2O)6]3+
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

[FeF6]3- and [Mn(H2O)6]3+ both have sp3d2 hybridisation, and hence  are outer orbital or high spin complexes.

Multiple choice

Match the coordination complexes in Column-I with corresponding coordination numbers and select the correct opinion given below.

 
Column-I Column-II
P. [Mn(H2O)6]2+ 1. 7
Q. [(Ph4As)2Mn(NO3)4] 2. 8
R. [Mn(EDTA)(H2O)]2- 3. 5
S. [Mn(S2C6H3Me)2]- 4. 4
5. 6

  1. P - 3, Q - 5, R - 1, S - 2

  2. P - 4, Q - 2, R - 3, S - 5

  3. P - 5, Q - 2, R - 1, S - 4

  4. P - 3, Q - 2, R - 4, S - 1

  5. P - 2, Q - 5, R - 1, S - 3
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The coordination complexes [Mn(H2O)6]2+, [(Ph4As)2Mn(NO3)4], [Mn(EDTA)(H2O)]2- and [Mn(S2C6H3Me)2]- have the coordination numbers of 6, 8, 7 and 4 respectively. Hence, the representation of the codes P-5, Q-2, R-1, S-4 is the correct answer.

Multiple choice

CO is isoelectronic with

  1. O2+

  2. CN-

  3. CH3-

  4. N2+
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

CO : 14 electrons CN- : 14 electrons CO and  CN-  are  isoelectronic.

Multiple choice

Which metal ion represents zero value of CFSE if it associated with weak field ligand?

  1. Fe3+

  2. Fe2+

  3. Cr2+

  4. Mn+

  5. Mn3+
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In weak field ligand, the filling of electrons are in accordance with Hund’s rule. The CFSE is given by the formula: CFSE = value of t2g (n) + value of eg (n) Dq, Fe3+ corresponds to the d5 configuration. Now, CFSE for Fe3+ (d5) = -4 (3) + 6 (2) = -12 + 12 = 0 Dq CFSE for Fe2+ (d6) = -4 (4) + 6 (2) = -16 + 12 = -4 Dq CFSE for Cr2+ (d4) = -4 (3) + 6 (1) = -12 + 6 = -6 Dq CFSE for Mn+ (d6) = -4 (4) + 6 (2) = -16 + 12 = -4 Dq CFSE for Mn3+ (d4) = -4 (3) + 6 (1) = -12 + 6 = -6 Dq Hence, the metal ion with zero CFSE is Fe3+ when it associated with weak field ligand.

Multiple choice

Which of the following d-electronic configurations in an octahedral complex will give the maximum CFSE?

  1. Low spin-d4

  2. High spin-d4

  3. Low spin-d5

  4. High spin-d5

  5. High spin-d7
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In octahedral complexes, CFSE is given by the formula:  CFSE = value of t2g (n) + value of eg (n) Dq Now, CFSE for low spin d4 = -4 (4) + 6 (0) = -16 + 0 = -16 Dq CFSE for high spin d4 = -4 (3) + 6 (1) = -12 + 6 = -6 Dq CFSE for low spin d5 = -4 (5) + 6 (0) = -20 + 0 = -20 Dq CFSE for high spin d5 = -4 (3) + 6 (2) = -12 + 12 = 0 Dq CFSE for low spin d7 = -4 (5) + 6 (2) = -20 + 12 = -8 Dq Hence, low spin d5 will give the maximum CFSE in an octahedral complex.

Multiple choice

Which of the following is a pair of square planar complexes?

  1. [PtCl4]2- and [ZnCl4]2-

  2. [Ni(CN)4]2- and [CoCl4]2-

  3. [ZnCl4]2- and [Ni(CN)4]2-

  4. [CoCl4]2- and [PtCl4]2-

  5. [PtCl4]2- and [Ni(CN)4]2-
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

d8 ions form square planar complexes with strong field ligands. For example, [Ni(CN)4]2-
All the complexes of Pt(II) and Au(II) are square planar. For example, [PtCl4]2-

Multiple choice

Among the following complexes, the largest crystal field splitting occurs in

  1. [CrCl6]3-

  2. [Cr(H2O)6]3+

  3. [Cr(NH3)6]3+

  4. [Cr(CN)6]3-

  5. [Cr(en)3]3+
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The oxidation state and the strength of the ligands determine the extent of crystal field splitting. The higher the oxidation state or the stronger the ligand, the larger will be the splitting. Ligands are classified as strong or weak based on the spectrochemical series: I- < Br- < Cl- < SCN- < F- < OH- < ox2-< ONO- < H2O < SCN- < EDTA4- < NH3 < en < NO2- < CN- CN-  is among one of the strongest field ligands. Crystal field splitting will be the highest in [Cr(CN)6]3-.

Multiple choice

Which of the following complexes is not correctly named?

  1. Na3[Ag(S2O3)2]: Sodium bis(thiosulphato)argentite(I)

  3. [Pt(py)4][PtCl4]: Tetrapyridineplatinum(II)tetrachloroplatinate

  4. Li[AlH4]: Lithium tetrahydridoaluminate(III)

  5. [Zn(NCS)]2+: Tetrathiocyanato-N-zinc(II) cation
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Correct IUPAC name of [Fe(C5H5)2] is bis(cyclopentadienyl)iron(II).