Multimetallic complexes featuring a bridging N-heterocyclic phosphido/phosphenium ligand: Synthesis, structure, and theoretical investigation

Abstract

By incorporating an N-heterocyclic phosphenium/phosphide (NHP) ligand into a chelating pincer ligand framework (PPP+/PPP-), we have elucidated several different and unprecedented binding modes of NHP ligands in homobimetallic, heterobimetallic, and trimetallic metal complexes. One-electron reduction of the previously reported (PPP)-/MII complexes (PPP)M-Cl (M = Pd (1), Pt (2)) results in clean formation of the symmetric homobimetallic MI/MI complexes [(μ-PPP)Pd]2 (5) and [(μ-PPP)Pt]2 (6). The tridentate NHP ligand has also been utilized as a bridging linker in the M/Co heterobimetallic compounds (OC) 3Co(u-PPP)M(CO) (M = Pd (7), Pt (8)), synthesized via salt elimination from mixtures of 1 and 2 and Na[Co(CO)4]. Furthermore, an NHP-bridged trimetallic complex (PPP)2Pd3Cl2 (9) can be synthesized in a manner similar to precursor 1 (Pd(PPh 3)4 + (PPP)Cl) via careful adjustment of reaction stoichiometry. Examination of the interatomic distances and angles in complexes 5-9, in tandem with density functional theory calculations have been used to evaluate and characterize the bonding interactions in these complexes. © 2013 American Chemical Society.