Through-ring bonding in edge sharing dimers of octahedral complexes

Area of Science:

• Inorganic Chemistry
• Theoretical Chemistry
• Materials Science

Background:

• Binuclear complexes with M2X2 rings are crucial in various chemical applications.
• Understanding their structural preferences is key to designing new materials.
• Previous studies have explored bonding in these systems with varying success.

Purpose of the Study:

• To investigate preferred structural motifs in M2X2 rings of binuclear complexes.
• To develop a simplified electron counting scheme for predicting these structures.
• To provide a general description of structure and bonding in M2X2 diamond frameworks.

Main Methods:

• Qualitative orbital arguments.
• Extended Hückel calculations on chromium (Cr) compounds.
• Density Functional Theory (DFT) calculations on Cr and manganese (Mn) compounds.
• Structural database analysis.

Main Results:

• A simplified electron counting scheme for M2X2 frameworks was deduced.
• Complexes with four or six framework electrons are predicted to have short M-M or X-X distances.
• Complexes with eight framework electrons are predicted to have no short through-ring distance.
• Metal-metal bonding prediction is possible for XR2-bridged complexes using t2g-like orbitals.

Conclusions:

• The framework electron counting scheme successfully predicts structural preferences in M2X2 diamond frameworks.
• The scheme is consistent with existing electron rules for related compounds.
• The electron counting method is independent of formal oxidation states, offering broad applicability.