From [2Mn2S] Diamond Cores to Butterfly Rhombs: Transformations That Highlight Alternating Peptide Binding Sites.

Area of Science:

• Organometallic Chemistry
• Bioinorganic Chemistry

Background:

• Thiocarboxamide chelates form [2Mn2S] diamond core complexes with Mn(I) centers.
• These complexes exhibit syn- and anti-isomers, interconverting through monomeric intermediates.

Purpose of the Study:

• To investigate the reductive transformation of [2Mn2S] diamond core complexes.
• To understand the role of ligand protonation state and structure in the reduction process.
• To explore implications for peptide fragment binding and low-valent metal carbonyl uptake.

Main Methods:

• Chemical reduction of manganese-thiocarboxamide complexes.
• Structural and chemical analyses (e.g., X-ray crystallography, spectroscopy).
• Ligand modification and comparison with tethered systems.

Main Results:

• Reduction leads to loss of a thiocarboxamide ligand and formation of a dianionic butterfly rhomb with a short Mn(0)-Mn(0) bond (2.52 Å).
• Reduction is dependent on the amide protonation state; complete deprotonation prevents core reduction.
• Tertiary amide ligands lacking amide-H preserve the diamond core during reduction.
• Dimer dissociation is necessary for the reductive transformation.

Conclusions:

• Organomanganese carbonyl chemistry provides models for peptide fragment binding.
• The study elucidates pathways for low-valent metal carbonyl uptake relevant to biocatalysts.
• Ligand design is crucial for controlling reductive transformations in manganese complexes.