CPC Inorganic Chemistry & Coordination Compounds 2 — Questions and Answers
Question 1: Cisplatin is an effective anticancer drug while transplatin is not, primarily because cisplatin can:
- Cross the cell membrane more rapidly due to higher lipophilicity
- Form intrastrand crosslinks between two adjacent guanine bases on DNA (Correct answer)
- Be reduced to Pt(0) inside the nucleus to alkylate DNA
- Directly inhibit RNA polymerase through square planar geometry
Correct answer: Form intrastrand crosslinks between two adjacent guanine bases on DNA
Cisplatin's cis geometry allows it to bridge two adjacent guanine residues on the same DNA strand, blocking replication; transplatin's geometry prevents this intrastrand coordination.
Question 2: Crystal Field Theory (CFT) accounts for the spectrochemical series by:
- Calculating covalent orbital overlap between ligands and the metal center
- Treating ligands as point charges and ranking their ability to split d-orbital energies (Δ) (Correct answer)
- Including π-backbonding contributions from the metal to empty ligand orbitals
- Applying molecular orbital theory to determine metal–ligand bond order
Correct answer: Treating ligands as point charges and ranking their ability to split d-orbital energies (Δ)
CFT uses a purely electrostatic model, treating ligands as point charges and ordering them by the magnitude of d-orbital splitting they produce.
Question 3: What is the Crystal Field Stabilization Energy (CFSE) for a strong-field (low-spin) d6 octahedral complex?
- −2.4 Δo (Correct answer)
- −0.4 Δo
- −2.0 Δo
- −0.6 Δo
Correct answer: −2.4 Δo
A low-spin d6 complex fills all six electrons into the t2g set (each at −0.4 Δo), giving a total CFSE of 6 × (−0.4 Δo) = −2.4 Δo.
Question 4: Which of the following complexes exhibits optical isomerism?
- [Co(NH3)4Cl2]+
- [Co(en)3]3+ (Correct answer)
- [Pt(NH3)2Cl2]
- [CoCl4]2−
Correct answer: [Co(en)3]3+
[Co(en)3]3+ is a tris-bidentate complex with D3 symmetry possessing non-superimposable mirror images (Δ and Λ enantiomers).
Question 5: The Jahn-Teller distortion is most pronounced for which d-electron configuration in an octahedral complex?
- d6 low-spin
- d8
- d9 (Correct answer)
- d3
Correct answer: d9
A d9 configuration places electrons unevenly in the eg set (one orbital doubly occupied, one singly occupied), producing the largest Jahn-Teller distortion.
Question 6: What is the hybridization of the central nickel atom in [Ni(CN)4]2−?
- sp3
- sp3d
- dsp2 (Correct answer)
- d2sp3
Correct answer: dsp2
CN− is a strong-field ligand; Ni2+ (d8) undergoes dsp2 hybridization, placing all electrons in four orbitals and giving a square planar geometry.
Question 7: Which of the following is classified as a π-acceptor (pi-acceptor) ligand?
- F−
- H2O
- CO (Correct answer)
- NH3
Correct answer: CO
CO donates electrons to the metal via σ-bonding but accepts electron density back from the metal into its π* antibonding orbitals (synergic backbonding).
CPC Inorganic Chemistry & Coordination Compounds 2
Cisplatin is an effective anticancer drug while transplatin is not, primarily because cisplatin can: