Cyclic Disilylated and Digermylated Germylenes

Area of Science:

• Organometallic Chemistry
• Silicon and Germanium Chemistry
• Synthetic Inorganic Chemistry

Background:

• Cyclic germylenes are less explored than their silicon analogs.
• Understanding the reactivity of low-valent silicon and germanium compounds is crucial for developing new materials and catalysts.

Purpose of the Study:

• To synthesize novel cyclic germylenes with silyl substituents.
• To investigate the reactivity of these germylenes, including silyl migration and dimerization.
• To compare the reactivity of germylenes with analogous stannylenes and plumbylenes using theoretical methods.

Main Methods:

• Reaction of a tetrasilane precursor with germanium dibromide and triethylphosphine.
• Phosphine abstraction using B(C6F5)3 to generate base-free germylenes.
• Spectroscopic characterization and theoretical calculations (DFT) to elucidate reaction mechanisms and electronic structures.

Main Results:

• Successful preparation of triethylphosphine adducts of cyclic disilylated/digermylated germylenes.
• Formation of base-free germylenes via phosphine abstraction.
• Observation of 1,2-trimethylsilyl shifts leading to silagermenes or digermenes.
• Dimerization of these intermediates via [2+2] cycloaddition to form tricyclic compounds.
• Theoretical study explaining the distinct reactivity compared to stannylenes and plumbylenes.

Conclusions:

• Novel cyclic germylenes with unique reactivity patterns were synthesized.
• The observed reactivity, including silyl shifts and cycloadditions, is attributed to electronic and steric factors.
• Theoretical insights provide a fundamental understanding of the differences between group 14 element compounds.