Ruthenium Nitrosyl Complexes with N-Heterocyclic Ligands

Area of Science:

• Inorganic Chemistry
• Coordination Chemistry
• Ruthenium Complexes

Background:

• Nitrosyl complexes are important in coordination chemistry.
• Understanding the electronic properties and reactivity of nitrosyl ligands is crucial.

Purpose of the Study:

• To synthesize and characterize a series of trans nitrosyl ruthenium complexes.
• To investigate the influence of different ligands (L) on the properties and reactivity of these complexes.
• To explore the relationship between electronic structure and reactivity.

Main Methods:

• Synthesis of trans-[Ru(NH(3))(4)L(NO)](BF(4))(3) complexes.
• Characterization using elemental analysis, spectroscopy (UV-Vis, IR, NMR, EPR), and electrochemistry.
• Kinetic and equilibrium studies of reactions with hydroxide ions.
• X-ray crystallography for structural determination.

Main Results:

• Successful preparation of four trans nitrosyl ruthenium complexes with imidazole, L-histidine, pyridine, and nicotinamide ligands.
• High nu(NO) stretching frequencies indicate a significant positive charge on the nitrosyl group.
• Variable reactivity with hydroxide ions, with equilibrium constants ranging from 2.2 x 10^5 to 4.6 x 10^13 L^2 mol^-2.
• A single redox process observed, attributed to the Ru(II)-NO+ moiety.
• Linear correlations between nu(NO), redox potentials, and ligand electronic properties (summation operatorE(L)).
• Crystal structure confirms the linear Ru-N-O arrangement, characteristic of Ru(II)-NO+.

Conclusions:

• The electronic properties and reactivity of the nitrosyl ligand are significantly modulated by the auxiliary ligand (L).
• The oxidizing strength of the coordinated NO group correlates with the pi-acidity of the ligand.
• The Ru(II)-NO+ moiety is confirmed in these complexes.