Air‐Stable, Phosphine‐Free Anionic Palladacyclopentadienyl Catalysts: Remarkable Halide and Pseudohalide Effects in Stille Coupling

The Stille cross‐coupling of allylic and benzyl bromides is shown to proceed efficiently using phosphine‐free dinuclear anionic palladacyclopentadienyl catalysts possessing bridging ( N , O )‐imidate ligands. The type of bridging anion influences the catalytic activity considerably. Halide anions such as chloride, bromide or iodide also influence the catalytic activity but to a far lesser extent than the pseudohalide imidate anions (from succinimide or phthalimide). A Baldwin‐type cooperative effect is seen with 7a using CuI as a co‐catalyst, in the presence of two equivalents of CsF in DMF at 40 °C. In toluene, these additives slow down substrate turnover.