The Pincer Platform Beyond Classical Coordination Patterns

Abstract

The pincer platform provides increased stability and often a rigid coordination mode in transition metal complexes that allows for the incorporation of reactive functional groups in the coordination sphere of a metal. Classical coordination patterns in pincer‐type complexes were established over the past decades, involving a preferred set of binding sites. In the current review, we discuss pincer‐type ligands with remarkable bonding situations and reactivity patterns, which are beyond the privileged ligand systems frequently used in homogeneous catalysis and bond activation reactions. This includes ligands with ligating atoms based on metalloid elements, π‐systems as well as different kinds of metallo‐ligands. We categorize the discussed pincer‐type ligands herein according to the covalent bond classification and distinguish between metallo‐ligands and ligands, which are based on nonmetal and metalloid elements.

Nickel and Palladium Complexes of a PP(O)P Pincer Ligand Based upon a peri-Substituted Acenaphthyl Scaffold and a Secondary Phosphine Oxide

“…Pincer ligands endow their metal complexes with high thermal stability by tridentate chelation and usually enforce a meridional geometry at the transition metal. They are of paramount importance for the development of homogeneous catalysts, and consequently, the design of new pincer ligands is a worthwhile task . In this regard, the incorporation of SPOs into the pincer ligand design is a promising strategy. − As previously shown by Bourissou et al, the reaction of (2- i Pr 2 PC 6 H 4 ) 2 P­(O)H ( Ia ) with [(COE) 2 IrCl] 2 (COE = cyclooctene) and (P t Bu 3 ) 2 Pd, respectively, proceeded via oxidative addition and provided the PP­(O)P pincer metal hydride complexes (2- i Pr 2 PC 6 H 4 ) 2 P­(O)­Ir­(Cl)H ( II ) and (2- i Pr 2 PC 6 H 4 ) 2 P­(O)­PdH ( III ) (Scheme ).…”

Spin-state crossover in photo-catalyzed nitrile dihydroboration via Mn-thiolate cooperation

“…The metal-pincer complex decorated with CO ligands is a widely used catalyst platform. 28 Currently, many of these complexes use phosphine-based pincers and rely on elevated temperatures to kinetically access their respective reaction pathways. Despite the rich history of catalysis using photoinduced CO dissociation, 29 use of UV irradiation in systems which use an MLC platform is rare.…”

Configurational Flexibility of a Triaryl-Supported SBS Ligand with Rh and Ir: Structural Investigations and Olefin Isomerization Catalysis

“…Pincer ligands are highly prized because of their exceptional thermal stability, high modularity, and unprecedented small-molecule binding, activation, and catalysis when combined with transition metals . Studies demonstrating the remarkable reactivity of canonical PCP and PNP pincer complexes (especially alkane dehydrogenation) have led to a bourgeoning interest in new pincer ligand platforms with diverse donor–atom combinations and structures to further enhance reactivity.…”