A Spatially Separated Germylene-Carbene Compound for Site-Selective Small-Molecule Activation

Area of Science:

• Organometallic Chemistry
• Main Group Chemistry
• Carbene and Germylene Chemistry

Background:

• N-heterocyclic carbenes (NHCs) are versatile ligands and reactive species.
• Germylenes, silicon analogs of carbenes, exhibit unique reactivity.
• Compounds featuring both germylene and carbene moieties are rare, limiting studies on their combined reactivity.

Purpose of the Study:

• To synthesize and characterize a spatially separated germylene-carbene compound.
• To investigate the site-selective reactivity of this bifunctional molecule.
• To explore its potential in small-molecule activation.

Main Methods:

• Salt elimination reaction between an (amidinato)chlorogermylene and a deprotonated N-heterocyclic carbene.
• Characterization using spectroscopic techniques and X-ray diffraction.
• Reactions with various small molecules (isocyanates, isothiocyanates, BH3·SMe2, GeCl2·dioxane, S8, mesitylazide).
• Density Functional Theory (DFT) calculations and Natural Population Analysis (NPA).

Main Results:

• Successful synthesis and characterization of the germylene-carbene compound (1).
• Demonstrated site-selective small-molecule activation: carbene center reacts with isocyanates, isothiocyanates, BH3·SMe2, and GeCl2·dioxane.
• Germylene center selectively reacts with mesitylazide, forming imidogermane.
• Two-fold addition products observed with S8 and BH3·SMe2 on both centers.
• DFT calculations revealed electronic properties influencing reactivity: HOMO on carbene carbon, HOMO-2 on Ge lone pairs, LUMO on Ge 4p orbital.

Conclusions:

• The synthesized germylene-carbene compound exhibits tunable, site-selective reactivity.
• The electronic structure dictates preferential activation at either the carbene or germylene center.
• This work expands the scope of bifunctional main group compounds and their applications in small-molecule activation.