Solvent-Dependent Reactivity of Fe(CO)₅ under Superacidic and Oxidative Conditions

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Solid-State Chemistry

Background:

• Iron pentacarbonyl (Fe(CO)5) is a foundational organometallic compound.
• Understanding the reactivity of metal carbonyls in different solvent environments is crucial for synthetic chemistry.
• Superacids and oxidation-stable solvents offer unique reaction media for exploring novel chemical transformations.

Purpose of the Study:

• To investigate the solvent-dependent reactivity of iron pentacarbonyl (Fe(CO)5) with arsenic pentafluoride (AsF5).
• To characterize the resulting iron complexes formed in anhydrous hydrogen fluoride (HF) and liquid sulfur dioxide (SO2).
• To explore the formation and structural characterization of novel iron carbonyl species.

Main Methods:

• Reactions were conducted in anhydrous HF and liquid SO2 solvents.
• Structural characterization of the products was achieved using X-ray diffraction.
• Spectroscopic techniques and quantum chemical calculations were employed for comprehensive analysis.

Main Results:

• In anhydrous HF, Fe(CO)5 reacts with AsF5 to form the protonated complex [FeH(CO)5]+, a highly acidic transition metal hydride.
• In liquid SO2, Fe(CO)5 undergoes oxidation and dimerization to yield the dinuclear cation [Fe2(CO)10]2+, isoelectronic with Mn2(CO)10.
• This study presents the first structural characterization of a homoleptic dinuclear transition metal carbonyl cation, [Fe2(CO)10]2+.
• An iron-centered triad (neutral Fe(CO)5, radical cation [Fe(CO)5]+•, and dication [Fe2(CO)10]2+) was structurally and spectroscopically characterized.

Conclusions:

• The choice of solvent significantly influences the reaction pathway and products of Fe(CO)5 with AsF5.
• The formation of [FeH(CO)5]+ highlights the potential for isolating highly acidic metal hydride complexes.
• The discovery of [Fe2(CO)10]2+ expands the known family of dinuclear transition metal carbonyl cations.
• Solvent effects play a critical role in the dimerization of the iron pentacarbonyl radical cation.