Organometallic Compounds MCQ Quiz in বাংলা - Objective Question with Answer for Organometallic Compounds - বিনামূল্যে ডাউনলোড করুন [PDF]

CONCEPT:

Metal Carbonyls and Their Properties

• Metal carbonyls are complexes composed of a metal center bonded to carbon monoxide ligands.
• Carbon monoxide (CO) acts as a ligand and can donate electron density to the metal (acting as a Lewis base) and can accept electron density from the metal (acting as a Lewis acid).
• pπ-pπ back bonding (also known as π-back bonding) occurs when the metal donates electron density back into the π* anti-bonding orbitals of the CO ligand, strengthening the metal-CO bond.

EXPLANATION:

• In the context of metal carbonyls, CO can act as both a Lewis base and a Lewis acid, due to its ability to donate and accept electron density.
• The metal center in the carbonyl complex primarily acts as a Lewis acid, accepting electron density from the CO ligand's lone pair.
• pπ-pπ back bonding enhances the stability of the metal-carbon monoxide bond by allowing electron density transfer from the metal to the CO ligand.
• 
• Considering these properties:
  • CO acts as a Lewis base and Lewis acid - This is true.
  •  Metal acts as Lewis base and Lewis acid - This is false. The metal primarily acts as a Lewis acid.
  • pπ-pπ back bonding takes place - This is true.
• Therefore, the false statement about metal carbonyls is Option 2.

Therefore, the correct answer is Option 2: Metal acts as Lewis base and Lewis acid.

CONCEPT:

Bonding in Metal Carbonyls (M-CO Bonding)

• Metal carbonyl complexes are compounds where carbon monoxide (CO) acts as a ligand to a metal center, usually a transition metal.
• In these complexes, bonding between the metal and CO involves both σ-bonding and π-backbonding:
  • σ-bonding: The carbon atom in CO donates its lone pair of electrons to the metal. This donation happens through the σ orbital of CO, forming a σ bond between the carbon atom and the metal.
  • π-backbonding (π-bonding): The metal, in turn, donates electron density from its d-orbitals into the π (anti-bonding) orbital of CO, which creates a π bond. This back-donation strengthens the metal-CO interaction by stabilizing the bond.
• Because of this back-donation, the CO bond within the carbonyl complex weakens slightly, and the C≡O bond length increases compared to free CO.

EXPLANATION:

• CO has two key orbitals:
  • σ orbital: This is a bonding orbital between the carbon and oxygen. It can donate electron density (from the lone pair on carbon) to the metal, forming a σ bond.
  • π* orbital: This is the anti-bonding π orbital of CO. It can accept electron density from the metal’s d-orbitals through back-donation, leading to the formation of a π bond.
• In metal carbonyl complexes:
  • The carbon in CO forms a σ bond by donating its lone pair to the metal.
  • The metal’s d-orbitals participate in π-backbonding, donating electrons into the π orbital of CO, which results in a π bond between the metal and CO.

CONCLUSION:

• The correct option is: Option 3: It is π bond between d-orbital of metal and π* orbital of CO

CONCEPT:

18-Electron Rule (Effective Atomic Number Rule)

• The 18-electron rule is a guideline used primarily for transition metal complexes to predict the stability of the metal complex.
• According to this rule, a stable metal complex should have a total of 18 valence electrons (including the metal’s own electrons and those donated by ligands).
• This is because, for many transition metals, having 18 valence electrons provides a closed-shell electron configuration similar to that of noble gases, making the complex stable.
• To check whether a complex follows the 18-electron rule, you need to count the valence electrons contributed by:
  • The metal center (based on its group in the periodic table).
  • The ligands (each ligand typically donates a certain number of electrons).

EXPLANATION:

• Let’s evaluate each complex to see whether it obeys the 18-electron rule:
• Ni(CO)₄ (Nickel tetracarbonyl)
  • Nickel is in the 10th group of the periodic table, so it has 10 valence electrons.
  • Each CO ligand donates 2 electrons, and there are 4 CO ligands, contributing a total of 8 electrons.
  • Total electron count = 10 (from Ni) + 8 (from 4 CO ligands) = 18 electrons.
  • Conclusion: Ni(CO)₄ obeys the 18-electron rule.
• [Cr(NH₃)₆]³⁺ (Hexaamminechromium(III))
  • Chromium is in the 6th group of the periodic table, so it has 6 valence electrons.
  • Each NH₃ ligand donates 2 electrons, and there are 6 NH₃ ligands, contributing a total of 12 electrons.
  • Since the complex has a 3+ charge, we subtract 3 electrons from the total.
  • Total electron count = 6 (from Cr) + 12 (from NH₃) − 3 (due to charge) = 15 electrons.
  • Conclusion: [Cr(NH₃)₆]³⁺ does not obey the 18-electron rule.
• [Fe(CN)₆]⁴⁻ (Hexacyanoferrate(II))
  • Iron in this complex is in the +2 oxidation state (Fe²⁺), so it has 6 valence electrons (8 − 2 = 6).
  • Each CN⁻ ligand donates 2 electrons, and there are 6 CN ligands, contributing a total of 12 electrons.
  • Total electron count = 6 (from Fe) + 12 (from CN ligands) = 18 electrons.
  • Conclusion: [Fe(CN)₆]⁴⁻ obeys the 18-electron rule.
• [Co(NH₃)₆]³⁺ (Hexaamminecobalt(III))
  • Cobalt in this complex is in the +3 oxidation state (Co³⁺), so it has 6 valence electrons (9 − 3 = 6).
  • Each NH₃ ligand donates 2 electrons, and there are 6 NH₃ ligands, contributing a total of 12 electrons.
  • Total electron count = 6 (from Co) + 12 (from NH₃) = 18 electrons.
  • Conclusion: [Co(NH₃)₆]³⁺ obeys the 18-electron rule.

CONCLUSION:

The complex that does not obey the 18-electron rule is Option 2: [Cr(NH₃)₆]³⁺.

CONCEPT:

Structure of Metal Carbonyl Complexes

• Metal carbonyl complexes are coordination compounds consisting of a metal center bonded to carbon monoxide (CO) ligands.
• The nature of the bonding in metal carbonyls can include metal-metal linkages, terminal CO groups, and bridging CO groups, depending on the structure of the complex.
• The oxidation state of the metal in these complexes is important for understanding their reactivity and stability.
• In certain metal carbonyls, the metal may exist in a zero oxidation state, as seen in the case of complexes like [Mn₂(CO)₁₀] and [Co₂(CO)₈].

EXPLANATION:

• The given structures [Mn₂(CO)₁₀] and [Co₂(CO)₈] are metal carbonyl complexes, where both Mn and Co are in zero oxidation states.
• In these complexes, the metal-metal linkage is present, which is a characteristic feature in such compounds, indicating the presence of metal-metal bonds between the metal centers.
• Terminal CO groups are present in the structure, as these CO ligands are directly bonded to the metal centers.
• In [Mn₂(CO)₁₀], there are no bridging CO groups; all CO ligands are terminally bound to the metal centers.
• The metal in both complexes is in the zero oxidation state, as shown by the nature of the bonding and charge balance of the entire molecule.

Hence, the correct answer is the option: Only A, B, D.

CONCEPT:

Isoelectric Species

• Isoelectric species are ions or molecules that have the same number of electrons.
• To determine if species are isoelectric, count the total number of electrons in each species and compare them.

CALCULATION:

• Atomic Numbers:
  • Sn (Tin): 50
  • Se (Selenium): 34
  • Bi (Bismuth): 83
  • Al (Aluminum): 13
• Calculate the number of electrons in each ion:
  • Option 1: Sn^4- and Se₉⁵⁺
    • Sn^4-: 4 + 4 = 8 electrons
    • Se₉⁵⁺: 6 x 9- 5 = 49 electrons (not isoelectronic)
  • Option 2: Se₉⁵⁺ and Bi₉⁵⁺
    • Se₉⁵⁺:  6 x 9- 5 = 49 electrons
    • Bi₉⁵⁺: 5 x 9 - 5 = 40 electrons (not isoelectronic)
  • Option 3: Se₉^4- and Al₉^4-
    • Se₉^4-: 6 x 9- 5 = 50 electrons
    • Al₉^4-: 3 x 9 + 4 = 31  electrons
  • Option 4: Se₉^4- and Bi₉⁵⁺
    • Se₉^4-:  6 x 9- 5 = 50 electrons
    • Bi₉^5-:  5 x 9 +5 = 50 electrons ( isoelectronic)

So, Option 4 Se94-, Bi95- are  isoelectronic

The Correct Answer is b > c > a.

Concept:-

Metallocene: Metallocenes are a class of organometallic compounds where a transition metal is sandwiched between two cyclopentadienyl (Cp) ligands. These compounds have a unique structure and exhibit interesting properties. The Molecular Orbital Theory (MOT) can be used to describe the electronic structure of metallocenes.

Explanation:-

\(e_{1g}^*\)(dxz, dyz) orbital of metallocene are analogous to e_g orbital of octahedral complexes. Thus, greater the number of electron in \(e_{1g}^*\)orbital longer will be the bond length. 

(a). [Fe(η⁵ -Cp)₂]: \(e_{2g}^4\ a_{1g}^2\)

(b).  [Ni(η⁵ -Cp)₂]: \(e_{2g}^4\ a_{1g}^2\ e_{1g}^{*2}\)

(c). [Co(η⁵ -Cp)₂]: \(e_{2g}^4\ a_{1g}^2\ e_{1g}^{*1}\)

• Order of number of electron in \(e_{1g}^{*}\) is b > c >  a.
• Order of Bond Order: a > c > b.
• Order of M-C bond length: b > c >  a.

Conclusion:-

Correct order of M-C bond length of metallocenes (a-c) is b > c > a.

The correct answer is cis-Platin

Concept:-

• Coordination Chemistry: cis-Platin is a coordination complex, and its activity is linked to its coordination to DNA.
• DNA Interaction: The interaction of cis-Platin with DNA is crucial for its anticancer activity.
• Cell Cycle Regulation: cis-Platin affects the cell cycle, leading to cell growth inhibition and apoptosis.

Explanation:-

• cis-Platin is a coordination complex with the chemical formula [PtCl₂​(NH_3​)₂​].
• The central platinum atom is coordinated to two chloride ions and two ammonia molecules in a square planar arrangement.
• 
• cis-Platin is known for its ability to bind to DNA.
• It forms covalent bonds with the purine bases (adenine and guanine) in DNA through a process known as cross-linking.
• cis-Platin induces intrastrand and interstrand cross-links in the DNA molecule.
• In intrastrand cross-linking, adjacent purine bases on the same DNA strand are linked together by covalent bonds.
• In interstrand cross-linking, purine bases on opposite DNA strands are linked.
• Inhibition of DNA Replication and Transcription: The formation of these cross-links interferes with the normal functioning of DNA, inhibiting processes such as replication and transcription.
• The distorted DNA structure hinders the separation of DNA strands and prevents enzymes involved in DNA replication and transcription from functioning properly.
• By interfering with DNA processes, cis-Platin inhibits the growth of rapidly dividing cells, including cancer cells.
• It induces cell cycle arrest and apoptosis in cancer cells.

Conclusion:-

cis-Platin is an important anticancer drug that functions by disrupting DNA structure and processes in rapidly dividing cells, ultimately inhibiting cell growth.

The correct answer is 4

Concept:-

• Cluster Compounds: These are assemblies of metal atoms bonded together.
• Metal-Metal Bonds: Direct bonds between transition metals in a cluster or compound.
• Carbonyl Complexes: Metal complexes containing metal-to-carbon monoxide (CO) bonds.
• Three-center-two-electron bonding: A concept in bonding theory that describes a scenario where two electrons are spread over three atomic centers.

Explanation:-

• To determine the number of Os-Os bonds in the given complex [H2Os3(CO)10], we should understand that the complex is a cluster compound where the metal atoms are directly linked to each other by metal-metal bonds, creating a metal core (in this case, an Os₃ core).
• H₂Os₃(CO)₁₀ is known as the tri-osmium cluster. This is a complex metal carbonyl, and the structure is a triangle of three osmium (Os) atoms.
• To find metal-metal bond
• 2 + 8x3 + 10x2 +2x = 18x3
• 46 + 2x= 54
• 2x= 54-46
• x = 8/2
• x = 4

Conclusion:-

So , The number of M-M bond in [H2Os3(CO)10] is 4

The correct answer is 2 > 4 > 3 >1

Concept:-

The factor affecting the metal-carbon bond :

• Nature of the Metal: The bond strength depends on the nature of the metal utilized in the metal carbonyl complex. Transition metals with a higher oxidation state or a greater number of d-electrons can form stronger and more numerous bonds with carbon monoxide due to better overlap and greater back-donation capabilities. For example, metals like Ni, Fe, and Co in lower oxidation state form more stable carbonyls.
• Electronic Configuration of Metal: The capacity of the metal atom to donate electrons from its d orbitals to the pi* antibonding orbitals of CO plays a key role in bond strength. The more effectively this electron donation occurs, the more stable is the carbonyl complex. For example, metals that achieve 18-electron stability upon bonding to CO tend to form very stable carbonyl complexes.
• Nature of the Ligand (CO in this case): Polarizability and the basic nature of the ligand can play a role in metal-carbon monoxide bond strength. Carbon monoxide is a strong field ligand and possesses a vacant pi* antibonding molecular orbital which accept electron cloud from the metal atom. So, the extent of this electron acceptance from CO will determine the bond strength.
• Synergic Back Bonding: The metal-to-ligand back donation of electrons can greatly stabilize these structures. In the case of a metal carbonyl complex, this is sometimes called synergic back bonding. This refers to the interaction where the metal donates electron density to the CO ligand's pi* antibonding orbital, and in return, the filled sigma MO of CO donates electron density back to the metal d-orbitals. The stronger the back bonding, the more stable the metal carbonyl, and the stronger the metal-CO bond.

Explanation:-

Ligands having empty orbitals that can interact with metal d-orbitals for the formation of π-bond are called π-acceptor ligands. These ligands possesses vacant C which can be vacant π*- anti-bonding molecular orbitals or empty d- orbitals of metals alongwith filled σ-orbitals. On bonding metal d-orbital donate its electron density to empty π-orbital of these ligands and this type of bonding is called π-back bonding

L_n-M-C\(\overline=\)O

If the ligand is π-acceptor ligand there will be no back bonding such that V_co increase

v_{co(π-acceptor)}  > vco(sigma-donar)  > vco(π-doner)

The extent of π-acceptor ligand power:

NO⁺ > CO > PF₃ > PCl₃  > P(OAr)₃  > PPh₃  > P(OR)₃  > PEt₃ > PCy₃

such that The answer is 2 > 4 > 3 >1

Conclusion:-

So, the correct answer is 2 > 4 > 3 >1

The correct answer is 4.99

Concept:-

• Stoichiometry: It involves calculating the quantities of reactants or products in a chemical reaction. Here we are using it to calculate the moles and mol%.
• Mole concept: It is used to calculate the moles from the given mass and molar mass.
• Metathesis reactions: They also called exchange reactions, are a type of chemical reactions where two compounds exchange ions or bonds to form different compounds.
• Molar mass: The mass of one mole of a substance. It is used in stoichiometric calculations.

Explanation:-

C₁₅H₁₇0                     
My 15x12+17x1+16
= 180 +17 +16
=180+33=213
RuP₂Cl₂C₄₃H₇₂
Molar mass =101+ 35.5x2+43x12+72x1+31x2
Molar mass =101+71+62 + 43 x 12+72x1= 822

Number of moles of X
=(4.32) / (213)
= 0.021

Number of moles of Y = (822 x 10^-3)/(822)
  =0.001 mol
Mol % of Y= (0.001) / (0.001+0.021) x 100
=100/21
=4.99
Conclusion:-
So, The mol% of the catalyst Y used in this reaction is 4.99