Binuclear Cobalt Paddlewheel-Type Complexes: Relating Metal-Metal Bond Lengths to Formal Bond Orders

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Materials Science

Background:

• Paddlewheel-type binuclear cobalt complexes are well-established structures.
• These complexes feature diverse ligands and coordination geometries around the bimetallic core.

Purpose of the Study:

• To model paddlewheel-type binuclear cobalt complexes using density functional theory (DFT).
• To investigate the effects of metal oxidation states and spin multiplicities on complex properties.
• To correlate computed bond orders with experimental bond lengths.

Main Methods:

• Density functional theory (DFT) calculations were employed.
• Unsubstituted ligands were used for modeling.
• A revised electron bookkeeping method was applied to determine formal bond orders (fBO).

Main Results:

• DFT results for bond lengths and spin multiplicities closely align with experimental data for substituted complexes.
• Trends in metal oxidation state and spin multiplicity effects were consistent across different ligand series.
• Computed cobalt-cobalt bond lengths correlate with formal bond order values, ranging from 0.5 to 2.

Conclusions:

• DFT provides accurate predictions for the structural and electronic properties of paddlewheel cobalt complexes.
• Inherent electronic structure significantly influences the geometry of trigonal complexes.
• Formal bond order calculations offer a quantitative measure of the cobalt-cobalt interaction strength.