Isolation and Catalytic Reactivity of Mononuclear Palladium(I) Complexes

Abstract

<p>Palladium complexes are among the most commonly used transition metal catalysts for different organic transformations with wide applications in the chemical synthesis. Currently, catalytic transformations involving Pd(0)/Pd(II) catalytic cycles are very well-known, and processes involving Pd(II)/Pd(III)/Pd(IV) intermediates are also gaining interest in recent years due to the increasing relevance of high-valent Pd species. By contrast, isolated low-valent Pd(I) complexes, especially mononuclear Pd(I) species, are very rare. Herein, we report the isolation of two heteroleptic Pd(I) complexes stabilized by dithiapyridinophane ligands that were fully characterized by single-crystal X-ray diffraction, EPR, IR, and UV-Vis spectroscopies, and computational studies. Excitingly, these Pd(I) complexes are shown to be superior catalysts for the C<i>sp<sup>2</sup></i>-C<i>sp<sup>3</sup> </i>Kumada cross-coupling reaction vs. their Pd(0) or Pd(II) analogs.</p>