Hyperconjugative aromaticity and protodeauration reactivity of polyaurated indoliums

Area of Science:

• * Organic Chemistry
• * Quantum Chemistry

Background:

• * Aromaticity is typically associated with sp²-hybridized atoms in cyclic structures, conferring stability and unique reactivity.
• * Introducing sp³-hybridized atoms often disrupts electron conjugation and damages aromaticity.
• * Polymetalated organic compounds present unique electronic and structural properties.

Purpose of the Study:

• * To investigate the occurrence and impact of extended hyperconjugative aromaticity (EHA) in metalated indole systems.
• * To explore the role of sp³-hybridized carbon atoms in influencing aromaticity.
• * To compare the reactivity of polyaurated indolium species with varying degrees of metalation.

Main Methods:

• * Computational modeling to analyze electronic structure and aromaticity.
• * Synthesis and characterization of penta-aurated and tetra-aurated indolium compounds.
• * Investigation of reaction mechanisms, specifically protodeauration.

Main Results:

• * Demonstrated EHA in a metalated indole ring containing two gem-diaurated tetrahedral carbon atoms.
• * Observed extended electron conjugation in penta-aurated indolium due to dual hyperconjugation.
• * Found that EHA facilitates a facile protodeauration reaction at the Au-N bond.
• * Contrasted this with tetra-aurated indolium, which showed poor bond averaging and inertness.

Conclusions:

• * Metalation significantly impacts the aromaticity of polymetalated species.
• * EHA in polyaurated indolium systems arises from dual hyperconjugation and influences reactivity.
• * The degree of metalation and the presence of sp³-hybridized centers are critical for determining aromaticity and reaction pathways.