Potassium chlorido-tris-(hypersil-oxy)aluminate dimer

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Materials Science

Background:

• The tris-(tri-methyl-silylsiloxide) ligand, or hypersiloxide, is exceptionally bulky.
• Steric hindrance in bulky ligands presents challenges in synthesizing monomeric metal complexes.
• Understanding the coordination behavior of bulky ligands is crucial for developing new materials.

Purpose of the Study:

• To synthesize the monomeric aluminium tris(hypersilyloxide), Al(OSi(SiMe3)3)3.
• To characterize the structure and coordination of the product formed from aluminium chloride and potassium hypersiloxide.

Main Methods:

• Reaction of aluminium chloride (AlCl3) with three equivalents of potassium hypersiloxide.
• Isolation and characterization of the crystalline product using X-ray crystallography.

Main Results:

• A 40% yield of a crystalline KCl adduct of aluminium tris(hypersilyloxide) was obtained.
• The product, [Al2K2Cl2(C19H27OSi4)6], features a dimeric structure with a planar K2Cl2 ring.
• Structural analysis revealed specific K-Cl distances and ring angles, with the ring located on an inversion center.

Conclusions:

• The bulky hypersiloxide ligand leads to dimerization of the aluminium complex.
• The formation of a K2Cl2 ring highlights unusual coordination modes for this sterically demanding system.
• No supra-molecular coordination was observed, indicating the steric bulk limits further aggregation.