title: Promoting Difficult Carbon-Carbon Couplings: Which Ligand Does Best?
abstract: A Pd complex, cis-[Pd(C6F5)2(THF)2] (1), is proposed as a useful touchstone for direct and simple experimental measurement of the relative ability of ancillary ligands to induce C-C coupling. Interestingly, 1 is also a good alternative to other precatalysts used to produce Pd0L. Complex 1 ranks the coupling ability of some popular ligands in the order PtBu3>o-TolPEWO-F≈tBuXPhos>P(C6F5)3≈PhPEWO-F>P(o-Tol)3≈THF≈tBuBrettPhos≫Xantphos≈PhPEWO-H≫PPh3according to their initial coupling rates, whereas their efficiency, depending on competitive hydrolysis, is ranked tBuXPhos≈PtBu3≈o-TolPEWO-F>PhPEWO-F>P(C6F5)3≫tBuBrettPhos>THF≈P(o-Tol)3>Xantphos>PhPEWO-H≫PPh3. This "meter" also detects some other possible virtues or complications of ligands such as tBuXPhos or tBuBrettPhos.
authors.affiliation: IU CINQUIMA/Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, Paseo de Belén, 7, ES47071, Spain.
authors.forename: Estefanía
authors.identifier: 0000-0003-4366-7983
authors.initials: E
authors.lastname: Gioria
authors.affiliation: IU CINQUIMA/Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, Paseo de Belén, 7, ES47071, Spain.
authors.forename: Juan
authors.identifier: 0000-0003-4366-7983
authors.initials: J
authors.lastname: Del Pozo
authors.affiliation: IU CINQUIMA/Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, Paseo de Belén, 7, ES47071, Spain.
authors.forename: Jesús M
authors.identifier: 0000-0003-4561-1131
authors.initials: JM
authors.lastname: Martínez-Ilarduya
authors.affiliation: IU CINQUIMA/Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, Paseo de Belén, 7, ES47071, Spain. espinet@qi.uva.es.
authors.forename: Pablo
authors.identifier: 0000-0001-8649-239X
authors.initials: P
authors.lastname: Espinet
keywords: cross-coupling mechanisms; homogeneous catalysis; palladium catalysis; phosphines; reductive elimination