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投稿者: Yuma Morimoto

Article

Probing the Steric and Electronic Characteristics of a New Bis-Pyrrolide Pincer Ligand

Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
Inorg. Chem., 2014, 53 (3), pp 1361–1369
DOI: 10.1021/ic402120r
Publication Date (Web): January 10, 2014
Copyright © 2014 American Chemical Society
*K.G.C.: e-mail, caulton@indiana.edu; tel, 812-855-4798.

Synopsis

A new diprotic and potentially redox active pincer ligand, H2L, with pyrrrole rings attached to both ortho sites of a pyridine, forms LM(NCPh) for M = Pd, Pt. The molecule (HL)ZnEt binds p-dimethylaminopyridine (DMAP) to give four-coordinate LZn(DMAP). Electrochemistry shows three oxidation processes, which is interpreted to involve at least two pyrrolide oxidations. (HL)2Fe is shown to contain four-coordinate iron with a flattened-tetrahedral structure.

Abstract

Abstract Image
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.
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