Harnessing low-valent metal centers through non-bonding orbital interactions

Area of Science:

• Organometallic Chemistry
• Inorganic Synthesis
• Computational Chemistry

Background:

• Low-valent indium complexes are of interest due to their unique electronic properties and potential applications.
• Bis(imino)pyridine ligands offer versatile coordination environments for metal centers.
• Understanding ligand-metal interactions is crucial for designing stable and functional organometallic compounds.

Purpose of the Study:

• To synthesize and characterize a series of low-valent indium(I) complexes featuring a bis(imino)pyridine scaffold.
• To investigate the effect of varying steric bulk on the indium(I) center and ligand coordination.
• To computationally analyze the electronic structure and bonding interactions within these complexes.

Main Methods:

• Stepwise synthesis of indium(I) complexes with varying aryl substituents on the bis(imino)pyridine ligand.
• Spectroscopic (NMR, IR) and crystallographic analyses to characterize the synthesized compounds.
• Computational methods including orbital population, bond order, and energy decomposition analysis.

Main Results:

• Synthesis of indium(I) complexes [ {Ar'N=CPh}(2)(NC(5)H(3)) ]In(+)(OTf)(-) (1-3) with weak or no coordination observed.
• Formation of an indium(III) complex [ {2,6-Me(2)C(6)H(3)N=CPh}(2)(NC(5)H(3)) ]In(OTf)(2)Cl (4) under specific conditions.
• Computational analysis revealed minimal covalent interactions and limited ligand-to-metal donation from the bis(imino)pyridine ligand.

Conclusions:

• The stability of indium(I) complexes correlates with the reduced contribution of the In(I) 5s lone pair to the HOMO.
• Steric crowding around the metal center enhances this effect due to non-bonding orbital interactions.
• These findings provide a basis for designing novel low-valent metal complexes with tailored electronic properties.