Sequential Double Dearomatization of the Pyrazolate-Based “Two-in-One” Pincer Ligand in a Dinuclear Rhodium(I) Complex

Abstract

A binucleating pyrazolate‐based ligand providing two tridentate PNN compartments is shown to form a dinuclear rhodium(I) complex [L{Rh(CO)}2](PF6) (1) that can be deprotonated at both side arm methylene groups between pyridine and phosphino donors to give K[L {Rh(CO)}2] (3). Sequential twofold deprotonation has been monitored by NMR and UV/Vis spectroscopy and proceeds via the neutral intermediate L {Rh(CO)}2 (2). X‐ray crystallographic characterization of 1 and the K[2,2,2]+ salt 3′ ([2,2,2] is a cryptand) evidences pyridine dearomatization upon deprotonation, and all spectroscopic and structural signatures are in good agreement with those of related mononuclear rhodium complexes based on a common PNN pincer ligand, which corroborates that pyrazolate‐bridged L– is best described as a scaffold with two pincer‐type subunits.

A dirhodium(I) complex of a pyrazolate‐bridged ligand that provides two pincer‐type PNN compartments can be sequentially deprotonated at both subunits, which is accompanied by double dearomatization. This mirrors the dearomatization that forms the basis of metal‐ligand cooperative reactivity in mononuclear analogues. image John Wiley \u0026 Sons, Ltd.