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

Abstract

Overall two-electron oxidative addition of the aryldiazonium cation para-methoxybenzenediazonium (pmbd⁺) to [(Tp*)Pd^IIMe₂]⁻ (Tp*⁻ = hydridotris-(3,5-dimethylpyrazolyl)borate) produces the first characterized palladium(IV) aryldiazenido complex, [(Tp*)Pd^IVMe₂(pmbd)] (pmbd⁻ = para-methoxybenzenediazenido). Thermolysis in benzene forms a mixture of products that contains [(Tp*)Pd^IVMe₃] and the C–C coupled product, 4,4′-dimethoxybiphenyl. The use of acetone as the thermolysis solvent changes the product distribution towards the formation of anisole. While some involvement of two-electron pathways in the decomposition cannot be ruled out, radicals, through one-electron steps, are involved in the major pathways for decomposition. The involvement of radicals is confirmed by the solvent dependent nature of the product distribution and by observing that the added N-tert-butyl-α-phenylnitrone efficiently traps aryl radicals.