Inverting the Electronic Structure of Diylidylgermylenes by Backbone Modification

Area of Science:

• Organometallic Chemistry
• Main Group Chemistry
• Carbene Analogues

Background:

• Diylidyltetrylenes are typically nucleophilic due to electron-donating ylide substituents.
• Tuning electronic properties of these species is crucial for controlling their reactivity.

Purpose of the Study:

• To investigate the tunability of diylidylgermylene electronic properties.
• To explore the impact of cyano substituents on germylene nucleophilicity/electrophilicity.

Main Methods:

• Density functional theory (DFT) calculations.
• Synthesis of cyano-substituted germylenes and related species.
• X-ray diffraction (XRD) analysis.

Main Results:

• Cyano groups significantly lower the LUMO energy of diylidylgermylenes, inducing electrophilic character.
• Attempts to synthesize the target germylene yielded a germanide, supporting its electrophilic nature.
• XRD revealed a monomeric germylene with long Ge-ylide bonds, indicating minimal pi-stabilization.

Conclusions:

• Electronic properties of diylidylgermylenes are highly tunable via substituent modification.
• Cyano-substituted diylidylgermylenes exhibit electrophilic behavior, contrasting with typical nucleophilic analogues.
• The observed reactivity and structural features are consistent with a weak Ge-C bond and electrophilic germylene intermediate.