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GATE 2022 CY – Question 48

Inorganic Chemistry · Transition Metals: Coordination chemistry – structure and isomerism, theories of bonding (VBT, CFT, and MOT). Metal-metal multiple bonds. Energy level diagrams in various crystal fields, CFSE, applications of CFT, Jahn-Teller distortion. Electronic spectra of transition metal complexes: spectroscopic term symbols, selection rules, Orgel and Tanabe-Sugano diagrams, nephelauxetic effect and Racah parameter, charge-transfer spectra. Magnetic properties of transition metal complexes. Ray-Dutt and Bailar twists, Reaction mechanisms: kinetic and thermodynamic stability, associative, dissociative substitution and redox reactions. · 2 marks · Multiple choice

An octahedral Ni(II) complex has four d–d bands. Match each band with its transition.

Bands: P 1000 nm (ε=50); Q 770 nm (8); R 630 nm (55); S 375 nm (110). ε is in M$^{-1}$ cm$^{-1}$.

Transitions: I $^3A_{2g}(F)\to{}^3T_{1g}(P)$; II $^3A_{2g}(F)\to{}^3T_{1g}(F)$; III $^3A_{2g}(F)\to{}^3T_{2g}(F)$; IV $^3A_{2g}(F)\to{}^1E_g(D)$.

  1. P–IV, Q–III, R–II, S–I
  2. P–III, Q–IV, R–II, S–I
  3. P–II, Q–IV, R–I, S–III
  4. P–I, Q–IV, R–II, S–III

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Correct answer: (B) P–III, Q–IV, R–II, S–I

Explanation

Ni(II)d8 has 3A2g(F) ground state. The lowest allowed transition3T2g(F) isP at 1000nm; the next3T1g(F) isR at 630nm; the highest3T1g(P) isS at 375nm. WeakQ at 770nm is spin-forbidden1Eg(D).

Hence **P–III, Q–IV, R–II, S–I, B**.