Two hydrogen ligands on tetrairidium clusters: a relativistic density functional study

Area of Science:

• Computational Chemistry
• Inorganic Chemistry
• Materials Science

Background:

• Understanding the structural and energetic properties of transition metal-ligand complexes is crucial for catalysis and materials science.
• Previous studies on iridium-4 clusters (Ir(4)H) indicated a preference for terminal hydrogen coordination.

Purpose of the Study:

• To determine the structural and energetic characteristics of iridium-4 clusters with two hydrogen ligands (Ir(4)H(2)).
• To compare the properties of Ir(4)H(2) with those of Ir(4)H.
• To investigate the binding energies and stability of various Ir(4)H(2) isomers.

Main Methods:

• Relativistic density functional theory (DFT) was employed to model the electronic structure and energetics.
• Calculations focused on identifying stable isomers and determining hydrogen binding energies.

Main Results:

• Terminal coordination of hydrogen ligands is preferred for Ir(4)H(2), similar to Ir(4)H.
• Square-planar Ir(4) isomers are the most stable, with high hydrogen binding energies (up to 318 kJ mol(-1) per atom).
• Tetrahedral and butterfly isomers also show significant hydrogen binding energies (up to ~300 kJ mol(-1)).
• A large number of stable minima were found for all isomer types.
• The structural and energetic properties of Ir(4)H(2) are unexpectedly similar to Ir(4)H.
• The reaction of H(2) with Ir(4) to form H(2)Ir(4) is exothermic (up to 170 kJ mol(-1)).

Conclusions:

• The binding of a second hydrogen ligand to Ir(4) has a minimal effect on the cluster's properties.
• Ir(4)H(2) complexes exhibit high stability, particularly in square-planar configurations.
• The findings provide insights into the behavior of hydrogen on transition metal clusters, relevant for catalysis.