title: Probing the steric and electronic characteristics of a new bis-pyrrolide pincer ligand.
abstract: A new pincer ligand is synthesized to be dianionic, with the potential to be redox active. It has pyrrrole rings attached to both ortho sites of a pyridine, as the linking element. This H2L can be doubly deprotonated and then used to replace two chloride ligands in MCl2(NCPh)2, to form LM(NCPh) for M = Pd, Pt. The acid form H2L reacts with ZnEt2 with elimination of only 1 mol of ethane to yield (HL)ZnEt, a three-coordinate species with one pendant pyrrole NH functionality. This molecule binds the Lewis base p-dimethylaminopyridine (DMAP) to give first a simple 1:1 adduct that eliminates ethane on heating to form four-coordinate LZn(DMAP), which has an unusual structure due to the strong preference of the pincer ligand to bind in a mer (planar) geometry. A molecule with two HL(-) ligands each bonded in a bidentate manner to FeCl2 is synthesized and shown to contain four-coordinate iron with a flattened-tetrahedral structure. The electrochemistry of LM(NCPh) and (L)Zn(DMAP) shows three oxidation processes, which is interpreted to involve at least two oxidations of the pyrrolide arms.
authors.affiliation: Department of Chemistry, Indiana University , 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Komine
authors.forename: René W
authors.initials: RW
authors.lastname: Buell
authors.forename: Chun-Hsing
authors.initials: CH
authors.lastname: Chen
authors.forename: Alice K
authors.initials: AK
authors.lastname: Hui
authors.forename: Maren
authors.initials: M
authors.lastname: Pink
authors.forename: Kenneth G
authors.initials: KG
authors.lastname: Caulton