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

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 pi-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.