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GATE 2020 CY – Question 44

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 aqueous $[Ni(NH_3)_6]^{2+}$ absorption spectrum has a very weak band between $^3A_{2g}\to{}^3T_{2g}$ and $^3A_{2g}\to{}^3T_{1g}(F)$. Which transition causes it? Ni atomic number is 28.

  1. $^3A_{2g}\to{}^1T_{1g}$
  2. $^3A_{2g}\to{}^1T_{2g}$
  3. $^3A_{2g}\to{}^1E_g$
  4. $^3A_{2g}\to{}^1A_{2g}$

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Correct answer: (C) $^3A_{2g}\to{}^1E_g$

Explanation

Octahedral Ni(II) is d⁸ with a triplet ³A₂g ground state. The intense reference bands are spin-allowed triplet-to-triplet transitions. The intervening weak band is the spin-forbidden transition to ¹Eg, which acquires weak intensity through coupling mechanisms. Thus C. The energy ordering as well as the change in spin identifies the particular singlet state.

More 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. questions

All 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. questions →