Structural Changes in the Carbon Sphere of a Dirhodium Complex Induced by Redox or Deprotonation Reactions

TL;DR

A carbon-rich ligand binds to a dirhodium complex, and its structure changes through redox or deprotonation reactions, offering insights into metal-carbon interactions.

Contribution

The study reveals how redox and deprotonation reactions induce structural changes in a carbon-rich ligand framework bound to a dirhodium complex.

Findings

The carbon skeleton undergoes C─C bond rearrangements, including ring expansion and alkyne to allenyl isomerization.

Redox and deprotonation reactions alter the electronic structure of the carbon framework near metal sites.

XRD, NMR, EPR, and electrochemical methods confirm structural and electronic changes in the complex.

Abstract

A carbon‐rich molecule is synthesized, which mainly contains conjugated sp2 and sp hybridized carbon centers. Alkenyl and alkynyl binding sites are arranged such that this compound serves as ligand to a binuclear metal unit with a RhI─RhI bond. Furthermore, CH units are placed in proximity to the metal centers. The dicationic complex [Rh2(bipy)2{Ph2Ptrop(C≡CCy)2}]2+(OTf−)2 allows to study possible responses of the carbon‐framework to redox reactions as well as deprotonation reactions. All products are, whenever possible, characterized by X‐ray diffraction (XRD) methods, NMR and EPR spectroscopy as well as electrochemical methods. It is shown that the carbon skeleton of the ligand framework undergoes C─C bond rearrangement reactions of remarkable diversity. In combination with DFT (density functional theory) studies, these results allow to gain insight into the electronic structure changes caused by metal sites in a carbon‐rich environment, which may be of relevance for the properties of metal particles on carbon support materials when they are exposed to hydrogen, electrons, or protons.

A carbon rich ligand is synthesized, which binds to a dinuclear rhodiumI unit with a metal‐metal bond. The charge of the dicationic dirhodium complex is reduced by either adding electrons or removing protons. The carbon skeleton of the ligand framework undergoes C─C bond rearrangement reactions. Ring expansion is observed as well as alkyne to allenyl isomerization.

Figures