Nitrosyl Ligands

Nitrosyl Ligands (NO)

Electron Contribution:

  • 2 electrons (linear, neutral ligand).
  • 1 electron (bent, neutral ligand).

Key Features:

  • Strong σ-donor.
  • Acts as a π-acceptor similar to CO.
  • Greater reactivity than CO.
  • Found in complexes like [Fe(CO)2(NO)2].

Proposed Image: A model of [Fe(CN)4(NO)2]-2 with linear and bent NO ligands labeled.

Bonding and Structure:

Linear (NO)+: Bond angle of 180º, isoelectric with CO, strong π-acceptor. 

Bent (NO)-: Bond angle of 120º-140º, resembles imido. 

Linear              Bent

Synthesis of Metal-Nitrosyl Complexes:

Direct Reaction:

  • NO Gas with Metal Complex: [Fe(CO)6] + NO → [Fe(CO)5NO] + CO

Nitrosyl Transfer Reagents:

  • NOBF4 for NO+ transfer.
  • Me3SiNO for NO- transfer.

Applications:

There are not many uses for nitrosyl complexes in organic chemistry, however they are assumed to be intermediates in catalytic converters in cars to reduce the emmision of NOx gas.

Nitrosyls are used in pharmaceutical applications for the slow release of NO.