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?

  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 neither of the two, 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- are all weak field ligands.

Multiple choice

Which of the following pairs represents high spin complexes?

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

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

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

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

  5. [Mn(CN)6]3- and [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 answer.

 
Column-I
Column-II
P. [Mn(NH3)6]2+ 1. 7
Q. [(Ph4As)2Mn(NO2)4] 2. 8
R. [Mn(EDTA)(NH3)]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(NH3)6]2+, [(Ph4As)2Mn(NO2)4], [Mn(EDTA)(NH3)]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

Paramagnetic materials have a small and positive susceptibility to magnetic fields. Which among the following is a paramagnetic salt?

  1. Cobalt (II) bromide

  2. Cobalt (II) chloride

  3. Cobalt (II) carbonate

  4. Cobalt (II) sulfate
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cobalt (II) carbonate is the inorganic compound with the formula CoCO3. This reddish paramagnetic solid is an intermediate in the hydrometallurgical purification of cobalt from its ores, as an inorganic pigment and as a precursor to catalysts.

Multiple choice

A hexadentate ligand has 6 lone pairs of electrons which can form co ordinate bonds with the same metal ion.--------------------- behaves as a hexadentate ligand .

  1. Ethylenediaminetetraacetic acid

  2. Icosane

  3. Endosulfan

  4. Endrin
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Ethylenediaminetetraacetic acid, widely abbreviated as EDTA is a polyamino carboxylic acid and a colourless, water-soluble solid. It is widely used to dissolve limescale. Its usefulness arises because of its role as a hexadentate ligand and chelating agent, i.e., its ability to sequester metal ions such as Ca2+ and Fe3+.

Multiple choice

Among the following ---------------------- is paramagnetic in nature.

  1. perchloryl fluoride

  2. platinum hexafluoride

  3. selenium tetrafluoride

  4. silver(II) fluoride
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Platinum hexafluoride is the chemical compound. It is a dark-red volatile solid that forms a red gas. The compound is a unique example of platinum in the +6 oxidation state. With only four d-electrons, it is paramagnetic with a triplet ground state.

Multiple choice

Which of the following is the diamagnetic subustance?

  1. O2

  2. NaCl

  3. Fe

  4. Ni and CO
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This option is correct as diamagnetic behaviour is shown by those subustances which contain fully filled orbitals. No unpaired electron is present, and this condition is fulfilled by the NaCl. This subustance is weakly repelled by external magnetic field.

Multiple choice

A ligand is an ion, a molecule or a molecular group that binds to another chemical entity to form a larger complex. Among the following which one is characterised by a divalent organic ligand?

  1. Cyclopentadienyl complex

  2. Metallocene

  3. Sandwich compound

  4. Transition metal carbene
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A transition metal carbene complex is a organometallic compound featuring a divalent organic ligand. The divalent organic ligand coordinated to the metal center is called a carbene. Carbene complexes for almost all transition metals have been reported.

Multiple choice

A carbene is a divalent organic ligand coordinated to the metal center. A carbene which can be likened to ketones is

  1. Difluorocarbene

  2. Fischer carbenes

  3. Schrock carbenes

  4. N-heterocyclic carbenes
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Fischer carbenes can be likened to ketones, with the carbene carbon being electrophilic, much like the carbonyl carbon of a ketone. Like ketones, Fischer carbene species can undergo Aldol-like reactions. The hydrogen atoms attached to the carbon α to the carbene carbon are acidic, and can be deprotonated by a base such as n-butyllithium, to give a nucleophile which can undergo further reaction.