Copper(I) Complexes with Terphenyl-Substituted NPN Ligands Bearing Pyridyl Groups: Synthesis, Characterization, and Catalytic Studies in the S-Arylation of Thiols

TL;DR

This paper describes the synthesis and use of new copper(I) complexes with NPN ligands for efficiently forming C–S bonds in thiols.

Contribution

The study introduces novel terphenyl-substituted NPN ligands and demonstrates their effectiveness in catalyzing S-arylation reactions.

Findings

Six mononuclear Cu(I) complexes were synthesized and characterized with distorted tetrahedral geometries.

Complexes 2a and 2b showed excellent catalytic activity for S-arylation with broad substrate tolerance.

The methodology tolerated reactive functional groups and worked with aliphatic thiols.

Abstract

In this study, three new terphenyl-substituted NPN ligands bearing pyridyl groups, two phosphonites and one diaminophosphine, were synthesized and fully characterized. Their coordination chemistry with copper(I) was investigated using CuBr and [Cu(NCMe)4]PF6 as metal precursors, affording six mononuclear Cu(I) complexes, which were characterized using NMR spectroscopy and, in selected cases, single-crystal X-ray diffraction (SCXRD) analysis. The NPN ligands adopt a κ3-coordination mode, stabilizing the copper centers in distorted tetrahedral geometries. The catalytic performance of these complexes in the S-arylation of thiols with aryl iodides was evaluated. Under optimized conditions, complexes 2a and 2b exhibited excellent activity and broad substrate scope, tolerating both electron-donating and electron-withdrawing groups, as well as sterically hindered and heteroaryl substrates. The methodology also proved effective for aliphatic thiols and demonstrated high chemoselectivity in the presence of potentially reactive functional groups. In contrast, aryl bromides and chlorides were poorly reactive under the same conditions. These findings highlight the potential of well-defined Cu(I)–NPN complexes as efficient and versatile precatalysts for C–S bond formation.

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