Lanthanoid Pseudo-Grignard Reagents: A Major Untapped Resource.

Area of Science:

• Organometallic Chemistry
• Lanthanide Chemistry
• Synthetic Inorganic Chemistry

Background:

• Pseudo-Grignard reagents, specifically phenyl ytterbium iodide (PhLnI) and phenyl europium iodide (PhEuI), offer a novel synthetic route.
• These reagents are prepared via oxidative addition of iodobenzene to ytterbium or europium metal at low temperatures.
• Bulky N,N'-bis(aryl)formamidines serve as versatile ligands in coordination chemistry.

Purpose of the Study:

• To explore the reactivity of phenyl lanthanide iodides (PhLnI) with bulky N,N'-bis(aryl)formamidines.
• To synthesize and characterize a range of new lanthanide (Ln) complexes.
• To investigate the structural diversity and coordination behavior of the resulting organometallic compounds.

Main Methods:

• Preparation of pseudo-Grignard reagents PhLnI (Ln=Yb, Eu) in THF or DME at -78°C.
• Reaction of PhLnI with various N,N'-bis(aryl)formamidines (e.g., DippForm, XylForm, MesForm).
• Characterization of the synthesized lanthanide complexes using techniques such as X-ray crystallography.

Main Results:

• Formation of an extensive series of divalent (LnII) and trivalent (LnIII) lanthanide complexes.
• Structural diversity observed, including monomers, polymers, and bridged dimers, with varying coordination numbers.
• Identification of a characteristic structural feature: cisoid orientation of iodide ligands relative to the formamidinate ligand.

Conclusions:

• Pseudo-Grignard reagents PhLnI are effective in synthesizing a wide array of lanthanide complexes with bulky formamidinate ligands.
• The synthetic scope extends to other ligand types, such as pyrazolates and amides, demonstrating the reagents' utility.
• The study highlights the rich coordination chemistry and structural variability of ytterbium and europium complexes.