Formation of a Bridging Phosphinidene Thorium Complex

Area of Science:

• Organometallic Chemistry
• Thorium Chemistry
• Phosphorus Chemistry

Background:

• Thorium organometallic compounds are of interest due to their unique electronic properties and potential applications.
• Phosphinidene complexes, featuring a trivalent phosphorus atom bonded to a metal, are reactive intermediates that are challenging to isolate and characterize.

Purpose of the Study:

• To report the synthesis and structural characterization of the first thorium phosphinidene complex.
• To elucidate the mechanism of its formation, including the role of C-H and P-H bond activation.

Main Methods:

• Reaction of bis(pentamethylcyclopentadienyl)dimethylthorium(IV) with a sterically hindered phosphine.
• Structural determination of the resulting thorium phosphinidene complex.
• Transition state calculations to investigate the reaction mechanism.

Main Results:

• The first thorium phosphinidene complex, [(C5Me5)2Th]2(μ2-P[(2,6-CH2CHCH3)2-4-(i)PrC6H2], was successfully synthesized and structurally characterized.
• Methane was produced as a byproduct, resulting from both phosphine deprotonation and C-H bond activation of isopropyl groups.
• Computational studies supported a mechanism involving sequential P-H, C-H, C-H, and P-H bond activations.

Conclusions:

• The successful synthesis of a thorium phosphinidene complex expands the known chemistry of early actinide organometallics.
• The mechanistic insights provide a deeper understanding of bond activation processes in thorium complexes.
• This work opens avenues for exploring the reactivity and applications of thorium-based phosphorus compounds.