Structural Characterization and Bonding Analysis of [Hg{Fe(CO)₅}₂]²⁺ [SbF₆]^-₂

Area of Science:

• Organometallic Chemistry
• Inorganic Chemistry
• Coordination Chemistry

Background:

• Non-classical carbonyl complexes offer unique bonding insights.
• Mercury-iron interactions are of significant chemical interest.
• Understanding electronic structures aids in predicting reactivity.

Purpose of the Study:

• To synthesize and characterize the novel non-classical carbonyl complex [Hg{Fe(CO)5}2]2+.
• To investigate and compare the bonding in related mercury-iron dication and dianion species.
• To elucidate the dominant orbital interactions governing the mercury-iron bond.

Main Methods:

• Single-crystal X-ray diffraction for structural determination.
• Energy Decomposition Analysis with Natural Orbitals for Chemical Valence (EDA-NOCV) for bonding analysis.
• Synthesis via reaction of Hg(SbF6)2 and Fe(CO)5 in anhydrous HF.

Main Results:

• The linear Fe-Hg-Fe moiety and eclipsed CO conformation were confirmed by X-ray crystallography.
• Hg-Fe bond lengths in the dication are comparable to those in known dianions.
• EDA-NOCV analysis revealed dominant Hg to iron carbonyl fragment sigma back-donation in both species.
• Both dication and dianion species are best described as Hg(0) compounds.

Conclusions:

• The synthesis and structural characterization of [Hg{Fe(CO)5}2]2+ expand the known family of mercury-iron carbonyl complexes.
• Similar Hg-Fe bond characteristics and dominant sigma back-donation exist in both the dication and dianion species.
• The electron deficiency of the iron-based fragments enhances their sigma-acceptor capabilities, influencing the overall bonding.