Conversion of Pd(i) off-cycle species into highly efficient cross-coupling catalysts

We report on the facile conversion of [Pd-2(mu-Cl)(mu-eta(3)-R-allyl)(NHC)(2)] complexes, which are commonly considered undesirable off-cycle species in cross-coupling reactions, into active [PdCl(mu-Cl)(NHC)](2) pre-catalysts. All reactions proceed under mild conditions (40 degrees C, 1-2 hours in acetone) using inexpensive HCl as both an oxidant and chloride source. DFT calculations were performed to explore the possible mechanism of this transformation, which appears to involve a combination of two different pathways. Moreover this study provides insights into factors favoring and hindering Pd(i) dimer formation undesirable in catalysis.

Automated summary

This study demonstrates an easy conversion of [Pd-2(mu-Cl)(mu-eta(3)-R-allyl)(NHC)(2)] complexes into active [PdCl(mu-Cl)(NHC)](2) pre-catalysts using inexpensive HCl as both an oxidant and chloride source under mild conditions. DFT calculations reveal a mechanism involving a combination of two different pathways, providing insights into factors favoring and hindering Pd(I) dimer formation in catalysis.