At this point, the alignment of several observations culminated in a significant advance. The Pd(II) complex [Pd(π-C4H7)(IPr)Cl] is known to form the Pd(I) dimer Pd2(μ-allyl)(μ-Cl)(IPr)2 in the presence of base and ethanol, which are reducing conditions. Iodide is known to stabilize Pd(I) dimers of the type [Pd(X)(P t Bu3)]2 (X = Br vs I, 12 kcal/mol), and exogenous iodide is required in the present reductive cross-couplings. Finally, as tri-tert-butylphosphine was identified by HTE as a superior ligand for the coupling of 1a with 2a, the commercially available Pd(I) complex [Pd(I)(P t Bu3)]2 (2.5 mol%) was evaluated as catalyst at 100 ⁰C. To our delight, the product of reductive cross-coupling 3a was formed in 88% yield. When the reaction was run in an open atmosphere, 3a was formed in a nearly identical 86% yield, and at lower loadings of [Pd(I)(P t Bu3)]2 (1 mol%) 3a was isolated in 80% yield.