An alternative route to Pd OACs without reduction to Pd(0) then oxidative addition could instead occur simply by coordination of an ancillary ligand of choice to an existing organopalladium(II) precursor. Along these lines, Buchwald has demonstrated that (tBuXPhos)Pd(Ar)X complexes synthesized from Pd(COD)(CH2SiMe3)2 or [Pd2(PR3)2(µ-COD)] can subsequently undergo displacement of tBuXPhos by a variety of exogenous monophosphines to generate new OACs within 1 h at 60 °C. We were similarly motivated to develop alternative synthetic approaches to a T-shaped OAC 1 (Figure , a) useful for weak base C-C and C-N coupling, 9b,22 which to date formed with unpredictable batch to batch yields when prepared by an oxidative addition route. It was subsequently discovered 1 can instead be formed in high solution yield at room temperature upon combining PAd3 with a known arylpalladate salt. We show in this work that the crystalline, air-and moisture-stable salt [Pd(4-C6H4F)(Br)µ-Br]2•2[NPr4] (2) 23 serves as a modular source of Pd OACs upon dissolution with a mono-or bidentate ancillary ligand (Figure ). This "on-demand" approach can function as a drop-in replacement for isolated OACs and other state-of-art Pd precatalysts as demonstrated in a selection of contemporary coupling reactions (vide infra).