The first palladium(iv) aryldiazenido complex: relevance for C-C coupling

Area of Science:

• Organometallic Chemistry
• Catalysis
• Reaction Mechanisms

Background:

• Palladium complexes are crucial in organic synthesis.
• Understanding the reactivity of high-valent palladium species is essential for developing new catalytic transformations.
• Aryldiazonium cations offer unique synthetic utility.

Purpose of the Study:

• To synthesize and characterize the first palladium(IV) aryldiazenido complex.
• To investigate the decomposition pathways of this novel palladium(IV) complex.
• To elucidate the role of radical intermediates in the thermolysis of palladium complexes.

Main Methods:

• Synthesis of a novel palladium(IV) complex via oxidative addition.
• Thermolysis experiments in different solvents (benzene, acetone).
• Product analysis using spectroscopic and chromatographic techniques.
• Radical trapping experiments with N-tert-butyl-α-phenylnitrone.

Main Results:

• The first characterized palladium(IV) aryldiazenido complex, [(Tp*)PdIVMe2(pmbd)], was successfully synthesized.
• Thermolysis in benzene yielded palladium(IV) trimethyl species and a C-C coupled product.
• Thermolysis in acetone shifted product distribution towards anisole formation.
• Evidence strongly supports the involvement of radical intermediates in the decomposition pathways, confirmed by solvent dependence and radical trapping.

Conclusions:

• The synthesis of the palladium(IV) aryldiazenido complex expands the known organometallic chemistry of palladium.
• The decomposition of this complex proceeds primarily through radical pathways, not exclusively two-electron processes.
• Solvent effects significantly influence the product distribution, highlighting the importance of reaction environment in radical reactions.