High-Valent Pd Coordination Compounds

Abstract

In contrast to the well-established chemistry of Pd0 and PdII, high-valent palladium complexes bearing PdIII and PdIV have only recently been explored as intermediates in various CC and CX bond formation reactions. While these compounds have been proposed as important intermediates in such reaction mechanisms, their isolation and characterization have been reported only in the past two decades. This chapter focuses on the coordination chemistry of PdIII and PdIV complexes that have been isolated and well-characterized using traditional spectroscopy techniques such as X-ray crystallography and X-ray absorption spectroscopy (XAS) methods, electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), electrospray ionization mass spectrometry (ESI-MS), and elemental analysis (EA). We assemble different types of chelating ligands that have been capable of stabilizing the Pd center at the oxidation state of +3 or +4 in either monomeric or dinuclear form. Additionally, we also include some one-dimensional molecular chains consisting of PdIII centers. The central focus of this chapter is to highlight the structural properties of those high valent Pd complexes and how the choice of the coordinating ligands could be imperative to stabilize the Pd center at its high oxidation states as well as tuning the electronic properties of such metal complexes.