Tag: chemistry

Questions Related to chemistry

Which of the following does not have a metal-carbon bond:

chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

  1. $C _{2}H _{5}MgBr$

  2. $K\left [ Pt \left ( C _{2}H _{4} \right ) Cl _{3}\right ]$

  3. $Ni\left ( CO \right ) _{4}$

  4. $Al\left ( OC _{2}H _{5} \right ) _{3}$

Show answer
Correct Option: D
Explanation:

Chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal.

$C _2H _5MgBr$ is a $\sigma$-bonded complexes.
$K[Pt(C _2H _4)Cl _3]$ contains a bond between carbon and potassium which is a metal.
$Ni(CO) _4$ also contains metal-carbon bond as it is itself a metal carbonyl.

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

chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

  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.

Show answer
Correct Option: A,D
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.

Select the correct order of C-O bond order in mixed phosphine carbonyl complex :

chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

  1. $[(Ph _3P) _3Mo(CO) _3] > [(Ph _2PCl) _3Mo(CO) _3] > (PhPCl _2) _3 Mo (CO) _3]$

  2. $[(Ph _3P) _3Mo(CO) _3] > [(Ph _2PCl) _3Mo(CO) _3] < (PhPCl _2) _3 Mo (CO) _3]$

  3. $[(Ph _3P) _3Mo(CO) _3] = [(Ph _2PCl) _3Mo(CO) _3] > (PhPCl _2) _3 Mo (CO) _3]$

  4. $[(Ph _3P) _3Mo(CO) _3] < [(Ph _2PCl) _3Mo(CO) _3] > (PhPCl _2) _3 Mo (CO) _3]$

Show answer
Correct Option: B
Explanation:

As phenyl group increases, resonance increases and bond length increases so order is
$[(Ph _3P) _3Mo(CO) _3] > [(Ph _2PCl) _3Mo(CO) _3] < (PhPCl _2) _3 Mo (CO) _3]$

The π acid ligands donate their lone pairs to the metal to form a normal σ bond with the latter in addition to it, the vacant orbitals accept e− from the filled metal orbitals to form a type of π−bond which supplements the σ bond.

Which of the following has lowest C-O bond length ?
chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

  1. $[Ni(CO) _4]$

  2. $[Co(CO) _4]^{-}$

  3. $[Fe(CO) _4]^{2-}$

  4. $[Mn(CO) _6]^+$

Show answer
Correct Option: D
Explanation:

This type of bonding where a metal is bonded with the carbon of a carbonyl compound is known as synergic bonding. In a metal carbonyl, the M-C bond has both σ and π character. The ligand donates eΘ pair to the central metal atom, and simultaneously accepts eΘ pair from central metal atom through synergic bonding. Here, all the options are examples of organometallic compounds. Due to synergic bonding, the metal carbon bond strength increases and bond length decreases due to the partial double bond character. Thus, the C-O bond strength decreases and bond length increases and bond order of CO decreases as the number of antibonding electrons increase. Out of the four options, the option D has Mn+, implying that the electron donating nature among the options is minimum. Therefore, tendency of synergic bonding is minimum, and thus M-C bond length is maximum implying that C-O bond strength is maximum and C-O bond length is minimum.

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?

chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

  1. $[V(CO) _6]^{-}$

  2. $Fe(CO) _5$

  3. $Ni(CO) _4$

  4. $[Mn(CO) _6]^+$

Show answer
Correct Option: A

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

chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

  1. $[V(CO) _6]^-$

  2. $Fe(CO) _5$

  3. $Ni(CO) _4$

  4. $[Mn(CO) _6]^+$

Show answer
Correct Option: A
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.

Which of the following complex/ion has highest C-O bond length ?

chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

  1. $[V(CO) _6]^-$

  2. $Fe(CO) _5$

  3. $Ni(CO) _4$

  4. $[Mn(CO) _6]^+$

Show answer
Correct Option: A
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.

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 ?

chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

  1. $[V(CO) _6]^-$

  2. $Fe(CO) _5$

  3. $Ni(CO) _4$

  4. $[Mn(CO) _6]^+$

Show answer
Correct Option: A

In which of the following cases, the synergic bonding takes place at the n-orbital of the ligand ? 

chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

  1. [PtCl$ _3$(C$ _2$H$ _4$)]$^-$

  2. [Ni(PF$ _3$)$ _4$]

  3. [Cr(C$ _6$H$ _6$)$ _2$]

  4. [Fe($\pi$-C$ _5$H$ _5$)$ _2$]

Show answer
Correct Option: A,C,D

Which of the following is/are example( s) of $\sigma$-bonded organometallic compound ? 

chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

  1. Al$ _2$(CH$ _3$)$ _6$

  2. Pb(CH$ _3$)$ _4$

  3. Zn(C$ _2$H$ _5$)$ _2$

  4. Ferrocene

Show answer
Correct Option: A,B,C
Explanation:

Option (A),(B),(C) are correct.Ferrocene is example of organometallic compound but is not $\sigma$-bonded. Its formula is $Fe(C _5H _5) _2$. It is the prototypical metallocene, a type of organometallic chemical compound consisting of two cyclopentadienyl rings bound on opposite sides of a central metal atom. Such organometallic compounds are also known as sandwich compounds. Each cyclopentadienyl (Cp) ring is then allocated a single negative charge, bringing the number of -electrons on each ring to six, and thus making them aromatic. These twelve electrons (six from each ring) are then shared with the metal via covalent bonding.