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UPSC Civil Services (Mains)

Chemistry optional

  • 2 papers
  • 250 marks each
  • 3 h per paper
  • 5 of 8 questions, Q1 and Q5 compulsory

Paper I covers physical and inorganic chemistry.

UPSC Civil Services (Mains), Chemistry optional · 2021 · Paper I

Q8(c). Linear and bent nitrosyl in [Ru(PPh₃)₂Cl(NO)₂]⁺

Question

In the coordination compound [Ru(PPh₃)₂Cl(NO)₂]⁺, one NO ligand bonds linearly while the other is bent. Explain the different modes of bonding of NO ligands in this molecule and expected M—N bond orders.

Answer in brief

Linear NO is NO⁺, a σ donor and strong π acceptor, with Ru–N bond order about 2; bent NO is NO⁻, sp² N with a lone pair, σ bond only, with Ru–N bond order about 1.

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Topic notes: metal carbonyls, nitrosyls, the 18-electron and EAN rules, metal–metal bonds and clusters, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coversnitrosyl complexeslinear and bent NOmetal–nitrogen bond order18-electron ruleback-bonding

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