Scandium Phosphonioketene: Synthesis, Bonding and Reactivity

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Materials Science

Background:

• Scandium complexes are valuable in catalysis and materials science.
• Phosphonioketenes are reactive intermediates with limited exploration in organometallic chemistry.
• Understanding metal-ligand bonding is crucial for designing new functional materials.

Purpose of the Study:

• To synthesize and characterize the first scandium phosphonioketene complex.
• To investigate the structural and electronic properties of the scandium-carbon bond.
• To explore the reactivity of the scandium phosphonioketene with unsaturated substrates.

Main Methods:

• Synthesis of scandium phosphonioketene via reaction with carbon monoxide.
• X-ray diffraction analysis for structural determination.
• Density Functional Theory (DFT) calculations for electronic structure and reaction mechanism elucidation.

Main Results:

• The first scandium phosphonioketene complex (1) was successfully synthesized.
• X-ray diffraction revealed an unusually short Sc-C bond (2.138(2) Å).
• DFT calculations attributed the short bond to ionic interactions and η²-O,C coordination.
• Complex 1 demonstrated high reactivity with CO₂, ketones, imines, nitriles, and isocyanides.
• Reaction with tert-butyl isocyanide showed insertion and C-H activation, proceeding via nucleophilic attack and deprotonation.

Conclusions:

• The novel scandium phosphonioketene is a thermally stable yet highly reactive organometallic complex.
• The unique Sc-C bond characteristics enable diverse chemical transformations.
• The study provides insights into the nucleophilic reactivity and C-H activation mechanisms of scandium phosphonioketenes.