Ag(I) and Tl(I) Precursors as Transfer Agents of a Pyrrole-Based Pincer Ligand to Late Transition Metals

A PNP ligand, (PNP)-P-pyr (((PNP)-P-pyr)H = 2,5-bis((di-iso-propylphosphino)methyl)pyrrole), which employs a pyrrole unit as a central anionic nitrogen donor, was designed. The corresponding group 10 metal chlorides as well as iridium and ruthenium compounds were isolated. In order to conduct this work, [((PNP)-P-pyr)Tl] and [((PNP)-P-pyr)Ag](2) were synthesized and characterized. The thallium and silver species were paramount in the formation of the iridium and ruthenium complexes, which could not be isolated using ((PNP)-P-pyr)H or the corresponding lithium pyrrolide salt. Interestingly, the solid state molecular structure of [((PNP)-P-pyr)Tl] indicates that the metal center engages in an eta(2) intermolecular interaction with the backbone of a neighboring pyrrole molecule instead of the expected bonding to the phosphine arms.