Design of a Versatile and Improved Precatalyst Scaffold for Palladium-Catalyzed Cross-Coupling: (η3-1-tBu-indenyl)2(μ-Cl)2Pd2

We describe the development of (eta(3)-1-Bu-t-indenyl)(2)(mu-Cl)(2)Pd-2, a versatile precatalyst scaffold for Pd-catalyzed cross-coupling. Our new system is more active than commercially available (eta(3)-cinnamyl)(2)(mu-Cl)(2)Pd-2 and is compatible with a range of NHC and phosphine ligands. Precatalysts of the type (eta(3)-1-Bu-t-indenyl)Pd(Cl)(L) can either be isolated through the reaction of (eta(3)-1-Bu-t-indenyl)(2)(mu-Cl)(2)Pd-2 with the appropriate ligand or generated in situ, which offers advantages for ligand screening. We show that the (eta(3)-1-Bu-t-indenyl)(2)(mu-Cl)(2)Pd-2 scaffold generates highly active systems for a number of challenging cross-coupling reactions. The reason for the improved catalytic activity of systems generated from the (eta(3)-1-Bu-t-indenyl)(2)(mu-Cl)(2)Pd-2 scaffold compared to (eta(3)-cinnamyl)(2)(mu-Cl)(2)Pd-2 is that inactive Pd-I dimers are not formed during catalysis.