Making an inverted Keggin ion lacunary

Area of Science:

• Inorganic Chemistry
• Materials Science
• Catalysis

Background:

• The inverted Keggin ion, a century-old polyoxomolybdate (POMo) structure, has remained largely unmodifiable.
• Previous attempts to alter its metal-oxo scaffold were unsuccessful, limiting its potential in structural engineering and functional development.

Purpose of the Study:

• To overcome the structural inertness of the inverted Keggin-type POMo.
• To develop new building blocks for polyoxomolybdate assembly.
• To investigate the catalytic potential of modified POMo structures.

Main Methods:

• Employed a binary heterogroup-templated approach to modify the inverted Keggin-type POMo.
• Isolated two lacunary species with adjustable local structure and charge distribution.
• Assembled a cerium(III)-incorporated derivative using the lacunary species as building blocks.

Main Results:

• Successfully altered the structurally inert inverted Keggin-type POMo for the first time.
• Isolated two lacunary species with tunable structural and electronic properties.
• Demonstrated that the resulting defect-containing polyanions exhibit significant Lewis acid-base catalytic activity.
• Achieved high efficiency in pyrazole production using these novel polyanions.

Conclusions:

• The binary heterogroup-templated approach provides a viable method to functionalize the inverted Keggin-type POMo.
• The lacunary species derived from this approach are versatile building blocks for constructing new POMo architectures.
• The modified POMo structures show promise as efficient catalysts, particularly in Lewis acid-base catalysis for pyrazole synthesis.