Chemistry

Coordination Chemistry

325 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 chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

Which of the following statement(s) is/are true?

  1. In metal carbonyl complexes $d _{C-O}$ increases compared to that in CO molecule
  2. The pair of compounds $[Cr(H _2O) _6]Cl _3$ and $[CrCl _3(H _2O) _3]\cdot 3H _2O$ show hydrate isomerism.
  3. $d _{z^2}$ orbital of central metal atom/ion is used in $dsp^2$ hybridisation.
  4. Facid and Meridional isomers associated with $[Ma _3b _3]^{n\pm}$ type complex compound, both are optically inactive.
Reveal answer Fill a bubble to check yourself
A,D Correct answer
Explanation

(A) Metal carbonyls involve synergic bonding $(M\underset {\sigma}{\overset {\pi}\rightleftharpoons } L)$. Filled metal d orbital overlaps with antibonding pi orbital of CO. Thus the bond order and bond length in CO decreases.
Thus option A is correct.
(B) $[CrCl _3(H _2O) _3]\cdot 3H _2O$ is not a hydrate isomer of $[Cr(H _2O) _6]Cl _3$.
Thus option B is incorrect.
(C) The d-orbitals involved in s$sp^3d^2  and\  d^2sp^3$  hybridisation of the central metal ion are $d _{x^2-y^2}$  and  $d _{z^2}$ respectively.
Thus option C is incorrect.
(D) Both fac and mer isomers of $[Ma _3b _3]^{n\pm}$ are optically inactive as they contain plane of symmetry.
Thus option D is correct.

Multiple choice chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

The pi acceptor ligand are those which possess vacant $\pi$-orbitals in addition to the lone pairs of $e^-$,which of the following complex/ion has highest M-C bond order?

  1. $[V(CO) _6]^{-}$
  2. $Fe(CO) _5$
  3. $Ni(CO) _4$
  4. $[Mn(CO) _6]^+$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The M-C bond order is highest when there is the most back-bonding. This occurs in the anionic complex [V(CO)6]-, which has the highest electron density on the metal to donate into the CO pi-star orbitals.

Multiple choice chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

Which of the following complex/ion has lowest C-O bond order ?

  1. $[V(CO) _6]^-$
  2. $Fe(CO) _5$
  3. $Ni(CO) _4$
  4. $[Mn(CO) _6]^+$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

There are vacant orbitals in central atom in $[V(CO) _6]-$ which results in synergic bonding. Due to synergic bonding between V and CO the bond length between C and O increases and Bond order is inversely proportional to bond length.

Multiple choice chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

The pi acceptor ligand are those which possess vacant $\pi$-orbitals in addition to the lone pairs of $e^-$which of the following complex/ion has lowest M-C bond length ?

  1. $[V(CO) _6]^-$
  2. $Fe(CO) _5$
  3. $Ni(CO) _4$
  4. $[Mn(CO) _6]^+$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Stronger M-C bonds (higher bond order from more back-bonding) result in shorter bond lengths. [V(CO)6]- has the strongest back-bonding (most electron-rich metal), so it has the shortest M-C bond length. Option D is an error.

Multiple choice chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

Among the following complexes, the C-O bond order is lowest in :

  1. [Mn(CO)$ _6$]$^+$
  2. [Fe(CO)$ _5$]
  3. [Cr(CO)$ _6$]
  4. [V(CO)$ _6$]$^-$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The C-O bond order decreases as the extent of metal-to-ligand pi-backbonding increases. This backbonding is enhanced by a higher negative charge on the metal complex, which increases electron density on the metal center.

Multiple choice chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

Match the column :

Column-I Column-II
(a) $[Fe(CO) _4]^{2-}$ (p) Complex having lowest bond length of CO ligand
(b) $[V(CO) _6]^{-}$ (q) Follow Sidgwick's rule of E.A.N.
(c) $K[PtCl _3(C _2H _4)]$ (r) Synergic bonding is involved in complex/ion
(d) $[Fe(H _2O) _5NO]SO _4$ (s) Complex having highest bond length of CO ligand
(t) Oragnometallic compound

  1. (a) q,r,s,t; (b) p,q,r,t; (c) r,t; (d) r

  2. (a)s,t; (b) p,q,r,t; (c) r; (d) r

  3. (a) q,s,t; (b) q,r,t; (c) r,t; (d) r

  4. (a) q,r,t; (b) q,r,t; (c) r;
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
(a) The complex $[Fe(CO) _4]^{2-}$
(q) Follow Sidgwick's rule of E.A.N.
(r) Synergic bonding is involved in complex/ion
(s) Complex having highest bond length of CO ligand
(t) Oragnometalic compound
(b) The complex  $[V(CO) _6]^{\Theta}$
(p) Complex having lowest bond length of CO ligand
(q) Follow Sidgwick's rule of E.A.N.
(r) Synergic bonding is involved in complex/ion
(t) Oragnometalic compound
(c) The complex  $K[PtCl _3(C _2H _4)]$
(r) Synergic bonding is involved in complex/ion
(t) Oragnometalic compound

(d) The complex  $[Fe(H _2O) _5NO]SO _4$
(r) Synergic bonding is involved in complex/ion


Effective atomic number (EAN) is number that represents the total number of electrons surrounding the nucleus of a metal atom in a metal complex. 
It is composed of the metal atom’s electrons and the bonding electrons from the surrounding electron-donating atoms and molecules.
In Synergic bonding, the ligand donates its electron density to metal and the metal in turn backdonates its electron density to ligand.
The back donation reinforce the sigma bond, and vice versa. This type of bonding has been called the synergic bonding 
Organometallic compounds have bonds between metal atom and C atom.
Multiple choice chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

$[Ni(CO) _{4}]>[Co(CO) _{4}]^{-}>[Fe(CO) _{4}]^{2-}$ is the correct order with respect to M-C $\pi$ bond. Where M=Ni, Fe, and Co

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
In carbonylate anion, the metal has a greater electron density to
be dispersed, with the result that M-C, $\pi $ bonding is enhanced in
strength. Hence the correct order is$[Ni(CO) _{4}]<[Co(CO) _{4}]^{-}<[Fe(CO) _{4}]^{2-}$. for strength of M - C$\pi $ bond.
Multiple choice chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

Among the metal carbonyls $[Mn(CO) _6]^+, [Ti(CO) _6], [Cr(CO) _6]$ and $[V(CO) _6]^-$ the $C-O$ bond order would be lowest in :

  1. $[Mn(CO) _6]^+$
  2. $[Ti(CO) _6]^{2-}$
  3. $[Cr(CO) _6]$
  4. $[V(CO) _6]^-$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The $C-O$ bond order would be lowest at $[Mn(CO) _6]^+$. 


The metal bears a positive charge which makes the back donation process favourable. 

The electrons from the metal fill the $\pi -$ antibonding orbital of CO, they weaken the carbon-oxygen bond.

Hence, the correct option is A.

Multiple choice chemistry ionic equilibrium introduction to ionic equilibria in solution ionic equilibrium in solution ionisation of weak acids and weak bases

The number of ions given by one molecule of $K {4}Fe(CN) _{6}$ after complete dissociation is___________.

  1. $5$
  2. $11$
  3. $2$
  4. $10$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$K _4Fe(CN) _6\longrightarrow 4K^++[Fe(CN) _6]^{-4}$

Total number of ions on complete dissociation= $5$
As ions in co-ordination sphere will not dissociate so $Fe^{2+}$ and $CN^-$ ions will not dissociate into their respective ions.

Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

Following triads have approximately equal size

  1. ${ Na }^{ + },\quad { Mg }^{ 2+ },\quad { Al }^{ 3+ }$
  2. ${ F }^{ - },\quad Ne,\quad { O }^{ 2- }$
  3. $Fe,\quad Co,\quad Ni$
  4. ${ Mn }^{ + },\quad { Fe }^{ 2+ },\quad Cr$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Fe, Co, and Ni are transition metals located in the same period (Period 4) and have very similar atomic radii, making them a triad of approximately equal size.

Multiple choice chemistry d and f block elements coloured complexes magnetic nature of transition metals general characteristics of first transition series

Choose the correct answer from the alternative given.
Amongst $TiF _6^{2-}$, $CoF$,   $Cu _2$ $Cl _2$ and $NiCl$, which are the colourless species? (atomic number of Ti = 22, Co = 27, Cu = 29, Ni = 28)

  1. $CoF _6^{3-}$and $NiCl _4^{2-}$
  2. $TiF _6^{2-}$and $Cu _2Cl _2$
  3. $Cu _2Cl _2$ and $NiCl _4^{2-}$
  4. $TiF _6^{2-}$ and $CoF _6^{ 3-}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

TiF$ _6^{2-}$ -

The oxidation state of Ti is +4.
Electronic configuration of Ti$^{4+}$ is [Ar] 3d$^0 4s^0$.
So, unpaired e$^-$ s is present in d-orbitals so it is colourless.
Cu$ _2Cl _2$-
The oxidation state of Cu is +1.
Electronic configuration of Cu$^+$ is [Ar] 3d$^{10} 4s^0$.
So, no unpaired d e$^-$ s are present . Hence, the given compound is colourless.