Cooperative Aliphatic PNP Amido Pincer Ligands – Versatile Building Blocks for Coordination Chemistry and Catalysis

Cooperative Aliphatic PNP Amido Pincer Ligands – Versatile Building Blocks for Coordination Chemistry and Catalysis:

Abstract

In this review, the coordination chemistry of electron-rich metal complexes with the simple aliphatic, anionic diphosphanylamido ligand {N(CH₂CH₂PR₂)₂}^– is covered and compared with other commonly used, anionic PEP (E = C, N) pincer ligands. The strong π-basicity of this ligand enables both the stabilization of electronically and coordinatively highly unsaturated complexes and their use as cooperating ligands in bifunctional stoichiometric bond activation reactions and catalysis. Versatile ligand backbone dehydrogenation gives access to related enamido and dienamido ligands {(R₂PCHCH)N(CH₂CH₂PR₂)}^– and {N(CHCHPR₂)₂}^–, respectively. This oxidative functionalization enables fine-tuning of the ligand donor properties and thereby of the structural features, electronic structure, and reactivity of the respective complexes, which is discussed for several examples.

Aliphatic PNP pincer ligands, HN(CH₂CH₂PR₂)₂, and ligands derived from them by backbone functionalization, are versatile chelating ligands for metal–ligand cooperative small molecule activation and catalysis. This microreview covers the recent work with these ligands and provides a comprehensive comparison with related pincer systems.