End-On Bridging Dinitrogen Complex of Scandium

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Rare-Earth Chemistry

Background:

• Over 40 rare-earth metal dinitrogen complexes with side-on bridges have been characterized.
• The structural diversity and reactivity of these complexes are not fully understood.

Purpose of the Study:

• To synthesize and characterize a rare-earth metal complex with an end-on dinitrogen bridge.
• To investigate the structural and electronic properties of this novel complex.
• To explore the reactivity and photochemistry of the end-on dinitrogen complex.

Main Methods:

• Reduction of Sc(NR2)3 under dinitrogen at -35 °C.
• X-ray crystallography for structural determination.
• Raman spectroscopy to analyze the N-N bond.
• Evans method and DFT calculations to study magnetic properties and electronic structure.

Main Results:

• The first end-on dinitrogen bridge in a rare-earth metal complex, {K(crypt)}2{[(R2N)3Sc]2[μ-η1:η1-N2]}, was successfully synthesized and characterized.
• The N-N bond distance (1.221(3) Å) and Raman stretch (1644 cm-1) confirm the (N═N)2- character.
• DFT calculations and magnetic measurements indicate a triplet ground state for the Sc2N2 core.
• Photolysis under UV-light resulted in the formation of a monomeric Sc2+ complex, demonstrating light-induced reactivity.

Conclusions:

• The synthesis of the end-on dinitrogen complex represents a significant structural departure from previously known side-on complexes.
• The alkali metal chelating agent plays a crucial role in the reversibility of dinitrogen binding, as evidenced by comparisons between crypt and crown ether systems.
• This work opens new avenues for exploring the fundamental chemistry of dinitrogen activation and transformation by rare-earth metals.