Manganese carbonyl fluorides: are they viable molecules?

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Computational Chemistry

Background:

• Manganese carbonyl halides (Mn(CO)(5)X and Mn(2)(CO)(8)(μ-X)(2)) are well-characterized for X = Cl, Br, I.
• The synthesis and characterization of analogous manganese carbonyl fluorides (X = F) remain elusive.
• Understanding the stability and structure of these fluorinated compounds is crucial for advancing manganese carbonyl chemistry.

Purpose of the Study:

• To investigate the structures and thermochemistry of mononuclear and binuclear manganese carbonyl fluorides.
• To explore the decarbonylation pathways and products of these novel manganese fluoride complexes.
• To determine the energetic favorability of singlet versus triplet spin states for these compounds.

Main Methods:

• Density functional theory (DFT) calculations were employed to model the structures and energetics.
• Geometries were optimized, and vibrational frequencies were calculated to confirm stable minima.
• Thermodynamic stabilities were assessed through calculated enthalpies and reaction pathways.

Main Results:

• Singlet electronic states were found to be energetically favored over triplet states for all investigated manganese carbonyl fluorides.
• The predicted structure for mononuclear manganese carbonyl fluoride is octahedral (Mn(CO)(5)F).
• Decarbonylation pathways lead to trigonal bipyramidal Mn(CO)(4)F and tetrahedral Mn(CO)(3)F, with bridging fluorine atoms in binuclear Mn(2)(CO)(n)F(2) structures.

Conclusions:

• Manganese carbonyl fluorides are predicted to be thermodynamically viable species.
• The lack of experimental synthesis is likely due to limitations in synthetic methodology, not inherent instability.
• These findings provide a theoretical foundation for future experimental efforts to synthesize manganese carbonyl fluorides.