Issue 20, 2024

A redox-active ligand combines a PCP pincer site with a bidentate N–N donor in opposition

Abstract

A binucleating ligand (2) combining a monoanionic PCP pincer cleft with a monoanionic N–N cleft has been prepared on the basis of bis(imidazolyl)methane (1). Installation of divalent Pd or Pt into the PCP cleft proceeded smoothly, with the formation of square planar (PCP)MCl complexes (M = Pd or Pt). The “C” in the PCP is the central carbon of the β-diketiminate-like N–N cleft. The N–N cleft in these complexes was obtained in three levels of protonation. In 4-Pd and 4-Pt, the N–N cleft carries one proton and is neutral; in 3-Pd or 3-Pt, it is additionally protonated by HCl, and in 6-Pd or 6-Pt, the proton has been removed by the (Me3Si)2NLi base and replaced by Li. The chloride in 4-Pd/Pt was replaced with an iodide to make 6-Pd/Pt in a metathesis with Me3SiI. Compounds 4-Pd/Pt and 6-Pd/Pt exhibited tautomerism reminiscent of acetylacetone and β-diketimines, possessing either an NH or a CH bond. Compounds 6-Pd/Pt possess a lithiated N–N cleft and serve as convenient transmetallation agents. Their reactions with BF3(OEt2), ½ZnCl2, or TaCl5 produced new compounds 7-Pd/Pt, 8-Pd/Pt, and 9-Pd/Pt that carry a BF2, ½Zn, or TaCl4 units in the N–N cleft. Compounds 8-Pd/Pt are trimetallic with a central Zn coordinated by two N–N clefts each of which carries a (PCP)MCl on the opposite side. Structures of 3-Pd, 7-Pt, 8-Pd, and 9-Pd in the solid state were established by X-ray diffractometry. They demonstrate the remarkable planarity of the extended conjugated organic π-system into which the N–N and the PCP binding sites are incorporated. Electrochemical studies on 7–9 established that each of these extended π-systems can be oxidized twice quasi-reversibly. Compounds 9-Pd/Pt could be additionally reduced quasi-reversibly by a single electron, which was ascribed to the reduction of the TaV center to TaIV. They also differed from 7 and 8 in possessing apparent lower-energy LMCT bands responsible for the blue or purple colors.

Graphical abstract: A redox-active ligand combines a PCP pincer site with a bidentate N–N donor in opposition

Supplementary files

Article information

Article type
Research Article
Submitted
21 Jun 2024
Accepted
22 Aug 2024
First published
28 Aug 2024
This article is Open Access
Creative Commons BY-NC license

Inorg. Chem. Front., 2024,11, 7040-7048

A redox-active ligand combines a PCP pincer site with a bidentate N–N donor in opposition

D. W. Leong, Y. Shao, N. Bhuvanesh and O. V. Ozerov, Inorg. Chem. Front., 2024, 11, 7040 DOI: 10.1039/D4QI01563K

This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. You can use material from this article in other publications, without requesting further permission from the RSC, provided that the correct acknowledgement is given and it is not used for commercial purposes.

To request permission to reproduce material from this article in a commercial publication, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party commercial publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements