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

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

  1. Metal carbonyls are the examples of only $\sigma$-bonded organometallic complexes.
  2. Metal carbonyls are the examples of only $\pi$-bonded organometallic complexes.
  3. Metal carbonyls are the examples of organometallic complexes which involve both $\sigma$- and $\pi$-bonds between metal and carbon of the carbonyl group.
  4. Metal carbonyls involve both $\sigma$- and $\pi$-bonds between metal and oxygen of the carbonyl group.
Reveal answer Fill a bubble to check yourself
A,B,D Correct answer
Explanation

Metal carbonyls involve synergistic bonding where the metal donates electrons into the CO pi-antibonding orbital (pi-backbonding) and CO donates electrons into the metal d-orbitals (sigma-bonding). Therefore, they are not examples of only sigma or only pi bonded complexes, making statements A, B, and D incorrect.

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

If the bond length of the C - O bond in CO is 1.128$\overset{o}{A}$ what is the value of the bond length in [Fe(CO)$ _5$] ?

  1. $1.15$ $\overset{o}{A}$
  2. $1.128$ $\overset{o}{A}$
  3. $1.72$ $\overset{o}{A}$
  4. $1.118$ $\overset{o}{A}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In metal carbonyl complexes like Fe(CO)5, back-bonding from the metal d-orbitals to the pi* antibonding orbitals of CO weakens the C-O bond and increases its bond length compared to free carbon monoxide.

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

If the bond length of $CO$ bond in carbon monoxide is 1.128 $\overset{o}A$, then what is the value of $CO$ bond length in $Fe$$(\mathrm{C}\mathrm{O}) _{5}$? 

  1. 1.15 $\overset{o}A$
  2. 1.128 $\overset{o}A$
  3. 1.72 $\overset{o}A$
  4. 1.178 $\overset{o}A$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The metal (Fe) makes the back bonding to CO. The metal to ligand bonding creates a synergic effect which strengthens the bond between CO and the metal (Fe).Which results in the contraction of CO bond length.

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 coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

If in the mixed carbonyl, the other ligand is also pi acceptor, it would compete with the ligand CO for gaining the metal $d _\pi$ electron charge. The higher is the extent of back donation in CO, the lesser will be the stretching vibration frequency for C-O bond. If $PF _3$ is better $\pi$-acceptor than CO, then answer the following.


Select the correct order of stretching vibration frequency C-O bond in the following molecules :

  1. $[Ni(CO) _4] > [Ni(PF _3)(CO) _3]$
  2. $[Ni(CO) _4] < [Ni(CO) _3 (PF _3)]$
  3. $[Ni(CO) _4] = [Ni(PF _3)(CO) _3]$

  4. Can not predicted
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

If $PF _3$ is a better $\pi$-acceptor ligand than CO, then
extent of back donation from $M \overset{\pi}{\rightarrow} C \equiv O$ decreases, and hence bond order of CO will less decrease.
Stretching frequency of C - O bond $\propto$ bond order of C $\equiv$ O.
Therefore, stretching frequency of $[Ni(PF _3)(CO) _3] >  [Ni(CO) _4]$.

Multiple choice chemistry substances in daily use polyester and acrylic rayon and nylon synthetic fibres
Nylon has high elasticity and tensile strength.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Nylon is a synthetic thermoplastic linear polyamide-based polymer. 


It is used for a variety of applications to include clothing, reinforcement in rubber material like car tires, for use as a rope or thread, and for a number of injection molded parts for vehicles and mechanical equipment. 


It is exceptionally strong, relatively resistant to abrasions and moisture absorptivity, long-lasting, resistant to chemicals, elastic and easy to wash. 

It is the plastic of choice for components in the engine compartment of vehicles because of its high tensile strength, temperature resilience, and chemical compatibility.

Therefore, option A is correct.