Issue 33, 2019

Structural and chemical properties of half-sandwich rhodium complexes supported by the bis(2-pyridyl)methane ligand

Abstract

[Cp*Rh] complexes (Cp* = pentamethylcyclopentadienyl) supported by bidentate chelating ligands are a useful class of compounds for studies of redox chemistry and catalysis. Here, we show that the bis(2-pyridyl)methane ligand, also known as dipyridylmethane or dpma, can support [Cp*Rh] complexes in the formally +III and +II rhodium oxidation states. Specifically, two new rhodium complexes ([Cp*Rh(dpma)(L)]n+, L = Cl−, CH3CN) have been isolated and structurally characterized, and the properties of the complexes have been compared with those of [Cp*Rh] complexes bearing the related dimethyldipyridylmethane (Me2dpma) ligand. Complex [Cp*Rh(dpma)(NCCH3)]2+ displays a quasireversible rhodium(III/II) reduction by cyclic voltammetry; related electron paramagnetic resonance (EPR) spectroscopic studies confirm access to the unusual rhodium(II) oxidation state. Further reduction to the formally rhodium(I) oxidation state, however, is followed by deprotonation of dpma, as observed in electrochemical studies and chemical reduction experiments. This reactivity can be understood to occur as a consequence of the presence of doubly benzylic protons in the dpma ligand, since use of the analogous Me2dpma enables reduction to rhodium(I) without involvement of ligand deprotonation. These findings highlight the important role of the ligand backbone substitution pattern in influencing the stability of highly-reduced complexes, a key class of metal species for study of electron and proton management in catalysis.

Graphical abstract: Structural and chemical properties of half-sandwich rhodium complexes supported by the bis(2-pyridyl)methane ligand

Supplementary files

Article information

Article type
Paper
Submitted
30 Apr 2019
Accepted
27 May 2019
First published
28 May 2019

Dalton Trans., 2019,48, 12396-12406

Author version available

Structural and chemical properties of half-sandwich rhodium complexes supported by the bis(2-pyridyl)methane ligand

D. Lionetti, V. W. Day and J. D. Blakemore, Dalton Trans., 2019, 48, 12396 DOI: 10.1039/C9DT01821B

To request permission to reproduce material from this article, 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 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