Carboranyl diphosphenes: synthesis, structure and reactivity.

Area of Science:

• Organometallic Chemistry
• Boron Chemistry
• Phosphorus Chemistry

Background:

• Carboranes are cage compounds containing boron and carbon atoms.
• Diphosphenes are compounds containing a P=P double bond, which are often reactive.
• Iminophosphines are precursors to various phosphorus-containing compounds.

Purpose of the Study:

• To synthesize and characterize novel carboranyl-diphosphenes.
• To investigate the structural differences between related diphosphene compounds.
• To explore the coordination chemistry and reactivity of these carboranyl-diphosphenes.

Main Methods:

• Synthesis of iminocarboranyldichlorophosphines.
• Reduction using potassium graphite (KC8) in tetrahydrofuran (THF).
• Structural characterization using single-crystal X-ray analysis and 31P NMR spectroscopy.
• Coordination studies with tungsten pentacarbonyl tetrahydrofuran complex.
• Reactivity studies with oxidizing agents.

Main Results:

• Carboranyl-diphosphenes [1-P-2-[C(tBu)=N(Ar)]-1,2-C2B10H10]2 (Ar = Dmp or Ph) were prepared in good yields.
• Compounds exhibit similar dimeric structures in the solid state but different solution structures due to steric effects of the aryl groups.
• Diphosphenes show differential coordination behavior towards W(CO)5(THF) but similar reactivity with oxidizing agents.
• Evidence suggests dissociation into carboranyl phosphinidene intermediates in THF.

Conclusions:

• The steric bulk of aryl substituents significantly influences the solution structure and coordination chemistry of carboranyl-diphosphenes.
• These diphosphenes serve as versatile precursors for various phosphorus(III) compounds.
• The formation of carboranyl phosphinidene intermediates is a key aspect of their reactivity.