The aliphatic, phosphine-based pincer complex [(C₁₀H₁₃-1,3-(CH₂P(Cy₂)₂)Pd(Cl)] (1) is a highly active Negishi catalyst, enable to quantitatively couple various electronically activated, non-activated, deactivated, sterically hindered and functionalized aryl bromides with various diarylzinc reagents within short reaction times and low catalyst loadings. Experimental observations strongly indicate that a molecular mechanism is operative with initial chloride dissociation of 1 and formation of the cationic T-shaped 14e⁻ complex [(C₁₀H₁₃-1,3-(CH₂P(C₆H₁₁)₂)₂)Pd]⁺ (B), which undergoes oxidative addition of an aryl bromide (Ar′Br) to yield the cationic, penta-coordinated aryl bromide pincer complexes of type [(C₁₀H₁₃-1,3-(CH₂P(Cy₂)₂)Pd(Br)(aryl′)]⁺ (C) with the metal center in the oxidation state of +IV and the aryl unit in cis position relative to the aliphatic pincer core. Subsequent transmetalation with Zn(aryl)₂ result in the cationic diaryl pincer complexes of type [(C₁₀H₁₃-1,3-(CH₂P(Cy₂)₂)Pd(aryl)(aryl′)]⁺ (D), which reductively eliminate the coupling products, thereby regenerating the catalyst. The neutral square planar aryl pincer complex – a possible key intermediate in the catalytic cycle – was found to be reversibly formed in the reaction mixture but is not involved in the catalytic mechanism. Similarly, palladium nanoparticles as the catalytically active form of 1 could have been excluded.