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Article

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

by
M. Trinidad Martín
1,*,
Ana Gálvez del Postigo
1,
Práxedes Sánchez
1,
Eleuterio Álvarez
1,
Celia Maya
1,
M. Carmen Nicasio
2 and
Riccardo Peloso
1,*
1
Instituto de Investigaciones Químicas (IIQ), Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO−CINQA), Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Sevilla, 41092 Sevilla, Spain
2
Departamento de Química Inorgánica, Universidad de Sevilla, 41071 Sevilla, Spain
*
Authors to whom correspondence should be addressed.
Molecules 2025, 30(15), 3167; https://doi.org/10.3390/molecules30153167
Submission received: 30 June 2025 / Revised: 22 July 2025 / Accepted: 23 July 2025 / Published: 29 July 2025
(This article belongs to the Special Issue Inorganic Chemistry in Europe 2025)
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Review Reports Versions Notes

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.

1. Introduction

Organic sulfur compounds constitute a broad class of naturally occurring substances with diverse biochemical and pharmacological properties, making them essential in various biological processes and medical applications [1,2,3]. In particular, thioethers are useful intermediates in the synthesis of a variety compounds that exhibit biological and pharmaceutical properties [4,5,6]. In recent decades, several non-catalytic synthetic strategies for the preparation of organic sulfides under mild conditions have been reported [7,8,9,10]. On the other hand, the development of catalytic processes for the synthesis of thioethers is generating increasing interest within the chemical community. In this regard, the metal-catalyzed coupling of organic halides with thiols is a straightforward way to obtain thioethers [11,12,13]. Although C-S coupling reactions have received less attention compared to other C-heteroatom bond formation reactions, mainly due to the fact that sulfur often causes catalyst poisoning and makes the reaction inefficient [14,15,16], considerable progress has been made in this field over the years [11,13,17,18,19,20].
Palladium-based catalysts for the S-arylation of thiols have been known since 1978 [19]. However, the high cost of this metal makes the development of processes based on more abundant and cheaper metals, such as copper, necessary. The first example of a copper-based catalytic system for C-S bond formation was reported by Palomo and coworkers in 2000 [21]. This system required a phosphazene-type base to carry out the couplings effectively. Since then, the use of copper(I) compounds as catalysts in the arylation of thiols has been actively developed, using more accessible bases and polydentate auxiliary N,O- or N,N-ligands [22,23,24,25]. Despite the advances, examples of the S-arylation of thiols catalyzed by well-defined copper species remain scarce.
In recent years, we have dedicated much effort to the synthesis of P(III) compounds functionalized with terphenyl groups, with the general objective of expanding this class of ligands and studying their coordination chemistry and catalytic properties in combination with late transition metals [26,27,28,29,30,31]. In particular, we successfully synthesized a family of dinuclear Cu(I) complexes of the general formula CuX(PR2Ar′) (X = Cl, Br, I; Ar′ = substituted m-terphenyl; R = alkyl, Scheme 1), which performed remarkably as precatalysts in copper-catalyzed azide–alkyne cycloaddition reactions on water [29].
Herein, we report on the preparation and characterization of three new tridentate NPN-donor ligands of the phosphonite and diaminophosphine types, in which the nitrogen donors pertain two pyridyl rings. Moreover, we describe a family of Cu(I) complexes stabilized by the NPN ligands and their use as precatalysts in the S-arylation of thiols.

2. Results

2.1. Synthesis and Properties of Terphenyl-Substitued NPN Ligands Bearing Pyridyl Groups

On the basis of our recently reported procedures for the preparation of terphenyl-phosphonite ligands [27], we reacted the dihalophosphines PArXyl2X2 (X = Cl, Br; ArXyl2 = 2,6-bis (2,6-dimethylphenyl) phenyl) with the pyridine derivatives 2-hydroxypyridine, 2-hydroxy-6-methylpyridine, and 2-aminopyridine at an approximately 1.9:1 molar ratio in the presence of triethylamine to selectively produce the corresponding NPN ligands NOPONXyl2, NOPONXyl2-e2, and N2PN2Xyl2, respectively, as colorless solid materials, in good yields (Scheme 2). Optimization of the reaction conditions implied the use of a slight excess of the parent dihalophosphines in order to avoid the presence of unreacted pyridines in the reaction mixture, which otherwise would require laborious work-up operations. Conversely, small amounts of residual PArXyl2X2 could easily be removed by washing the crude solid products with pentane.
The 31P{1H} NMR spectra of the three ligands in CDCl3 consiss of unique singlets in the 140–150 ppm range for the two phosphonites NOPONXyl2 and NOPONXyl2-Me2 and at a significantly lower frequency, ca. 38 ppm, for the diaminophosphine N2PN2Xyl2. As similarly observed for related terphenyl phosphonites, fast rotations around the P—C, P—O, and P—N bonds of the three molecules on the NMR time scale (Figure 1) account for the simplicity of their 1H NMR spectra, which can be rationalized by an apparent C2v symmetry. Accordingly, for the three ligands, the four methyl groups of the xylyl rings give rise to one resonance at ca. 2 ppm, and the pyridyl groups originate only one pattern of signals. For the diaminophosphine ligand N2PN2Xyl2, a diagnostic broad peak at 5.04 ppm in CDCl3 solution is generated by the two equivalent protons of the NH fragments.
The diaminophosphine N2PN2Xyl2 is indefinitely air-stable at room temperature, both as a pure solid material and dissolved in common organic solvents such as CHCl3, CH2Cl2, THF, and C6H6, even upon the addition of water. Contrarily, the phosphonites NOPONXyl2 and NOPONXyl2-Me2 have to be stored under an inert atmosphere of N2 or Ar to avoid hydrolysis yielding the corresponding phosphinic acid [27]. Thus, solid samples of pure NOPONXyl2 quantitatively converted into (O=)PH(OH)ArXyl2 (1) and 2-hydoxypyridine after 72 h of exposure to air (Scheme 3). The same reaction products formed in approximately 24 h when pure samples of NOPONXyl2 were dissolved in THF/D2O or CDCl3/D2O mixtures. The presence of a P—H (or P—D) bond in the newly formed phosphinic acid 1 in CDCl3 solution, i.e., the predominance of the P(V) tautomer (O=)PH(OH)ArXyl2 over the P(III) one, P(OH)2ArXyl2, was doubly proven by the following: (a) a doublet centered at 6.93 ppm with a 1JHP coupling constant of 575 Hz in the 1H NMR spectrum of samples of 1 produced without the addition of D2O; (b) a 1:1:1 triplet at 22.5 ppm (1JPD = 117 Hz) in the 31P{1H} NMR spectrum samples of 1 obtained by reactions with D2O.
Slow evaporation of the solvent from CDCl3 solutions of NOPONXyl2, prepared with the addition of one drop of D2O, allowed the isolation of a colorless crystalline material, which was identified by SCXRD analyses as the hydrogen-bonded adduct of the phosphinic acid 1 with 2-pyridone (Figure 2). The O–H···O interaction involves the hydroxyl hydrogen H2 of the phosphinic acid (donor, O2) and the carbonyl oxygen of the pyridone ring (acceptor, O3), with an O2···O3 (donor···acceptor) distance of 2.445(3) Å, an H2···O3 (H···acceptor) distance of 1.46(5) Å, and a corresponding angle of 169(5)°, consistent with a strong and highly directional hydrogen bond. An additional H-bond is observed between the nitrogen atom N1 of the pyridone and the phosphoryl oxygen O1 (N1···O1: 2.693(3) Å; O1···H1A: 1.81(4) Å; N1–H1A···O1: 178°). This structural arrangement is in line with similar hydrogen bond motifs observed in related phosphinic acid structures [32,33,34], all showing P(=O)OH···O = C hydrogen bonds with comparable geometrical parameters (O–H distances ≈ 0.82–0.95 Å, H···O distances ≈ 1.4–1.5 Å, and O···O distances ≈ 2.4–2.6 Å).
Presumably as a consequence of the additional steric protection provided by the two methyl groups of the 6-methylpyridyl substituents, the decomposition of NOPONXyl2-Me2 caused by water is significantly slower compared to that of NOPONXyl2. Using the same reaction conditions employed for NOPONXyl2, the hydrolysis of NOPONXyl2-Me2 took roughly twice the time.

2.2. Synthesis and Characterization of Cu(I) Complexes with NOPONXyl2, NOPONXyl2-Me2, and N2PN2Xyl2

Two commonly used copper(I) precursors, CuBr and [Cu(NCMe)4]PF6, were reacted with the three NPN ligands described in the previous section to prepare two series of Cu(I) complexes of the general formulas CuBrL (L = NOPONXyl2: 2a; NOPONXyl2-Me2: 2b; N2PN2Xyl2: 2c) and [Cu(NCMe)L]PF6 (L = NOPONXyl2: 3a; NOPONXyl2-Me2: 3b; N2PN2Xyl2: 3c), respectively (Scheme 4).
The formation of the aforementioned complexes was confirmed by their 31P{1H} NMR spectra in the CDCl3 solution, which exhibited broad singlets up-field shifted by approximately 20–30 ppm relative to the free ligands. 1H NMR spectra of complexes 2a–c do not show relevant differences compared to those of the ligands, whereas the presence of a coordinated acetonitrile molecule in complexes 3a–c is evidenced by a singlet at ca. 2.4–2.5 ppm corresponding to the CH3 group.
The slow diffusion of petroleum ether into dichloromethane solutions of complexes 2b, 2c, and 3b at approximately −20 °C yielded single crystals suitable for SCXRD analysis, enabling the determination of their molecular structures in the solid state. The corresponding ORTEP representations are shown in Figure 3, Figure 4 and Figure 5, respectively, along with the corresponding lists of selected bond distances and angles. In all three complexes, the NPN ligands adopt a κ3 coordination mode, with the metal center lying in a markedly distorted tetrahedral environment, resembling a disphenoidal or seesaw-like arrangement. The bond angles at copper range from ca. 80–85°, corresponding to the P-Cu-N angles within the cupracycles, to ca. 130–150° for the P-Cu-Br and P-Cu-NCMe angles. These angular distortions are reflected in the values of the four-coordinate geometry index, τ4 [35], which are 0.68, 0.69, and 0.67 for complexes 2b, 2c, and 3b, respectively. Notably, as observed in the right-side views shown in Figure 3, Figure 4 and Figure 5, the cupracycles in complex 2c are nearly perfectly planar, whereas those in 2b and 3b appear slightly twisted, likely due to the increased steric hindrance introduced by the methyl substituent on the pyridyl rings.
Terphenyl groups have shown the ability to stabilize unsaturated coordination compounds by means of metal–carbon secondary interactions [26,27,28,29,30,31]. Taking this into account, we reacted complex 2b with AgBF4 in dichloromethane, aiming to replace the Cu-Br bond with a weaker non-covalent interaction involving the terphenyl ring. The 31P{1H} NMR spectrum of the crude material obtained after filtration and evaporation of the volatiles revealed the formation of two new species associated with singlet resonances at 23.5 ppm and 25.5 ppm. The slow evaporation of CDCl3 from the NMR tube yielded pale yellow crystals of the dinuclear complex [Cu2Cl(N2PN2Xyl2)2]BF4, 4, in which two [Cu(N2PN2Xyl2)]+ units are bridged by a chloride anion (Figure 6). Although no mechanistic studies were performed, the formation of compound 4 can likely be attributed to the use of dichloromethane as the reaction medium together with the high reactivity of the in situ-generated [Cu(N2PN2Xyl2)]+ cation. Furthermore, the slight difference observed between the two 31P{1H} NMR signals in the initial mixture suggests that the second product is plausibly the bromine-bridged analog of 4.

2.3. Catalytic Studies of the S-Arylation of Thiols

To test the catalytic activity of complexes 2a–2c in the arylation of thiols, the reaction of thiophenol with iodobenzene was chosen as the model system. Catalytic experiments were initially performed using the conditions previously applied for copper-assisted C-S bond formation, namely, dioxane solution at 110 °C, NaOtBu as the base, and 5 mol% catalyst loading [23]. Under these conditions, nearly quantitative yields of the C-S coupling product, diphenyl sulfide, were obtained using 2a as the catalyst system (Table 1, entry 1). Since the base NaOtBu is incompatible with several functional groups, such as esters or aldehydes, other bases were tested. Notably, the weaker inorganic base K3PO4 provided full conversion to the thioether product (entry 3). Lowering the temperature to 100 °C produced a slight decrease on the reaction yield (entry 4). At this temperature, the use of other solvents did not improve the reaction outcome (entries 5 and 6).
However, reducing the catalyst loading down to 2 mol% did not produce an appreciable decrease in the catalytic efficiency of the system, although lower loadings significantly lessened the reaction yield (entries 7–9). Under the optimized reaction conditions, complex 2b performed very similarly to 2a, whereas complex 2c showed significantly lower activity, possibly due to the deprotonation of the diaminophosphine N2PN2Xyl2 ligand under basic conditions. Finally, no reaction was observed in the absence of a copper catalyst.
Encouraged by the results obtained using iodobenzene, we tested bromobenzene and chlorobenzene as electrophiles in the S-arylation of thiophenol (Table 2).
In all experiments conducted with 2a as the catalyst, very low conversions were obtained, even when increasing the catalyst loading up to 10 mol% or using different solvents and bases.
Complexes 2a and 2b were both chosen to explore the scope of C–S coupling reactions under the optimized reaction conditions. As summarized in Scheme 5, a broad range of (hetero)aryl iodides were coupled with a variety of thiophenols, affording the corresponding thioethers in good-to-excellent yields. Both electron-donating (b–g, k–o, q) and electron-withdrawing substituents (h–i) on the aryl iodides were well tolerated. Moreover, the increased steric demand due to the ortho-substitution on both coupling partners did not require any modification of the reaction conditions, including catalyst loading (e and f). Notably, aryl halides such as 1-chloro-4-iodobenzene and 1-bromo-4-iodobenzene underwent selective coupling with thiophenols exclusively at the C-I bond, while C-Cl and C-Br bonds remained unaltered (h and i). Furthermore, nitrogen-containing heteroaryl halides served as effective electrophilic coupling partners, delivering the desired products in high yields (j, q, and r).
Regarding the scope of the nucleophile, p-substituted thiophenols with both electron-withdrawing (l) or electron-donating groups (f, g, m, and n) exhibited comparable reactivity. Importantly, thiols featuring functional groups prone to arylation, such as unprotected hydroxyl or amine groups, underwent C–S coupling with complete chemoselectivity (m and n), eliminating the need for protective groups. Furthermore, the coupling with aliphatic thiols, which are typically more challenging due to their lower nucleophilicity, was also explored under the same reaction conditions. Primary (r), secondary (o and p), and tertiary alkyl thiols (q) were efficiently coupled with a variety of (hetero)aryl iodides, demonstrating the broad applicability of this catalytic protocol.

3. Materials and Methods

All synthetic procedures and manipulations were performed under an oxygen-free nitrogen atmosphere using standard Schlenk techniques. Solvents were thoroughly dried and degassed prior to use. Copper(I) bromide was obtained as a colorless solid via the aqueous reduction of CuSO4·5H2O (1 equiv) with Na2SO3 (2 equiv) in the presence of sodium bromide (approx. 4 equiv). The resulting solid was isolated by filtration, washed with acetic acid, and diethyl ether, dried under a vacuum, and stored under nitrogen. The dihalophosphines PX2ArXyl2 [36] and [Cu(MeCN)4]PF6 [37] were synthesized following procedures from the literature. All other reagents were purchased commercially and used without further purification.
Solution NMR spectra were recorded on Bruker Avance DPX-300 and DPX-400 spectrometers. Chemical shifts for 1H and 13C NMR were referenced to residual solvent peaks, while 31P NMR shifts were referenced externally to H3PO4. Elemental analyses were carried out by the Microanalysis Service at the Instituto de Investigaciones Químicas (IIQ). Single-crystal X-ray diffraction (SCXRD) studies were conducted at the Centro de Investigación, Tecnología e Innovación de la Universidad de Sevilla (CITIUS), and at the Instituto de Investigaciones Químicas, cicCartuja (Seville). Detailed synthetic procedures for all ligands and metal complexes, along with their spectroscopic data, are provided in the Supplementary Materials.

General Catalytic Procedure for the S-Arylation of Thiols with Aryl Iodides

Solid samples of 1 or 2 (0.02 mmol) were dissolved in dioxane (1 mL). The aryl iodide (1.2 mmol), the thiol (1.0 mmol), and K3PO4 (2.0 mmol) were added under a nitrogen atmosphere. After 24 h at 110 °C, the reaction mixture was allowed to cool to room temperature, diluted with ethyl acetate (10 mL), and filtered through Celite. The conversion was determined via GC analysis. Pure products were obtained after purification via flash chromatography on silica gel with petroleum ether (unless otherwise indicated) and identified using 1H NMR spectroscopy for a comparison with literature data [38,39,40,41,42,43,44,45,46,47,48,49].

4. Conclusions

Three novel terphenyl-substituted NPN ligands bearing pyridyl groups were synthesized from the parent dihalophosphines in high yields. Their coordination to copper(I) precursors CuBr and [Cu(NCMe)4]PF6 led to the formation of six mononuclear Cu(I) complexes, in which the ligands adopt a κ3-coordination mode, stabilizing the copper centers in distorted tetrahedral geometries. Complexes 2a and 2b demonstrated high catalytic activity in the S-arylation of thiols with aryl iodides, providing the efficient coupling of an ample range of (hetero)aryl iodides with both aromatic and aliphatic thiols. In addition, the catalytic protocol showed excellent chemoselectivity and functional group tolerance. These findings highlight the potential of well-defined Cu(I)–NPN complexes as efficient and versatile precatalysts for C–S bond formation, offering a promising alternative to more expensive or toxic metal-based systems.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/molecules30153167/s1: synthetic procedures and characterization data for ligands, metal complexes, NMR data and isolated yields for products a–r, crystallographic data for compounds 1, 2b, 2c, 3b, and 4. Crystallographic data [50,51] for the structures reported in this article have been deposited in the Cambridge Crystallographic Data Centre (CCDC) under the deposition numbers 2467385 (1), 2467386 (2b), 2467387 (2c), 2467388 (3b), and 2467389 (4), and can be obtained free of charge from the CCDC via https://www.ccdc.cam.ac.uk/structures/ (accessed on 22 July 2025).

Author Contributions

Conceptualization: R.P., M.C.N. and M.T.M.; experiments: M.T.M. and A.G.d.P.; SCXRD analyses: E.Á. and C.M.; writing—original draft preparation: R.P. and M.T.M.; writing—review and editing: R.P., P.S. and M.C.N.; supervision: R.P. and M.C.N. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by US/FEDER/JUNTA, UE (Grant, US126226), MCIN/AEI/10.13039/501100011033 (grant PID2020-113797RB-C22).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding authors.

Conflicts of Interest

The authors declare no conflicts of interest.

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Molecules 30 03167 sch001
Scheme 1. Terphenylphosphine complexes of Cu(I) used as precatalysts in azide–alkyne cycloaddition reactions on water (X = Cl, Br, I; R = Me, Et, iPr, c-C5H9; R′ = Me, iPr; R″ = H, Me) [29].
Scheme 1. Terphenylphosphine complexes of Cu(I) used as precatalysts in azide–alkyne cycloaddition reactions on water (X = Cl, Br, I; R = Me, Et, iPr, c-C5H9; R′ = Me, iPr; R″ = H, Me) [29].
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Scheme 2. Synthesis of terphenyl-substituted NPN ligands bearing pyridyl groups.
Scheme 2. Synthesis of terphenyl-substituted NPN ligands bearing pyridyl groups.
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Figure 1. Schematic representation of the dynamic processes that account for the apparent C2v symmetry of NOPONXyl2 evinced by its 1H NMR spectrum in CDCl3.
Figure 1. Schematic representation of the dynamic processes that account for the apparent C2v symmetry of NOPONXyl2 evinced by its 1H NMR spectrum in CDCl3.
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Scheme 3. Hydrolysis of the phosphonite ligands NOPONXyl2 and NOPONXyl2-Me2.
Scheme 3. Hydrolysis of the phosphonite ligands NOPONXyl2 and NOPONXyl2-Me2.
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Figure 2. ORTEP view of the X-ray structure of the hydrogen-bonded adduct of the phosphinic acid 1 with 2-pyridone, with ellipsoids at the 50% probability level. Selected bond distances (Å): P1-O1 1.497(2), P1-O2 1.536(2), O2·∙·O3 2.446(3), O1·∙·N1 2.693(3), C1-O3 1.278(4).
Figure 2. ORTEP view of the X-ray structure of the hydrogen-bonded adduct of the phosphinic acid 1 with 2-pyridone, with ellipsoids at the 50% probability level. Selected bond distances (Å): P1-O1 1.497(2), P1-O2 1.536(2), O2·∙·O3 2.446(3), O1·∙·N1 2.693(3), C1-O3 1.278(4).
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Scheme 4. Synthesis of Cu(I) complexes 2a–c and 3a–c.
Scheme 4. Synthesis of Cu(I) complexes 2a–c and 3a–c.
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Figure 3. ORTEP view of the X-ray structure of complex 2b in the solid state, with ellipsoids at the 50% probability level and H atoms omitted for clarity (left); capped-sticks view along the C—P bond (right). Selected bond distances (Å) and angles (deg): Cu1-P1 2.2233(6), Cu1-N1 2.087(2), Cu1-N2 2.163(1), Cu1-Br1 2.3420(3); P1-Cu1-N1 83.88(5), P1-Cu1-N2 80.37(5), P1-Cu1-Br1 136.63(2), Br1-Cu1-N1 128.01(5), Br1-Cu1-N2 114.72(5), N1-Cu1-N2 100.70(7).
Figure 3. ORTEP view of the X-ray structure of complex 2b in the solid state, with ellipsoids at the 50% probability level and H atoms omitted for clarity (left); capped-sticks view along the C—P bond (right). Selected bond distances (Å) and angles (deg): Cu1-P1 2.2233(6), Cu1-N1 2.087(2), Cu1-N2 2.163(1), Cu1-Br1 2.3420(3); P1-Cu1-N1 83.88(5), P1-Cu1-N2 80.37(5), P1-Cu1-Br1 136.63(2), Br1-Cu1-N1 128.01(5), Br1-Cu1-N2 114.72(5), N1-Cu1-N2 100.70(7).
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Figure 4. ORTEP view of the X-ray structure of complex 2c in the solid state, with ellipsoids at the 50% probability level and H atoms omitted for clarity (left); capped-sticks view along the C—P bond (right). Selected bond distances (Å) and angles (deg): Cu1-P1 2.2377(9), Cu1-N1 2.051(3), Cu1-N3 2.042(3), Cu1-Br1 2.3542(5); P1-Cu1-N1 85.78(9), P1-Cu1-N3 85.61(8), P1-Cu1-Br1 149.94(3), Br1-Cu1-N1 111.11(9), Br1-Cu1-N3 108.77(7), N1-Cu1-N3 112.3(1).
Figure 4. ORTEP view of the X-ray structure of complex 2c in the solid state, with ellipsoids at the 50% probability level and H atoms omitted for clarity (left); capped-sticks view along the C—P bond (right). Selected bond distances (Å) and angles (deg): Cu1-P1 2.2377(9), Cu1-N1 2.051(3), Cu1-N3 2.042(3), Cu1-Br1 2.3542(5); P1-Cu1-N1 85.78(9), P1-Cu1-N3 85.61(8), P1-Cu1-Br1 149.94(3), Br1-Cu1-N1 111.11(9), Br1-Cu1-N3 108.77(7), N1-Cu1-N3 112.3(1).
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Figure 5. ORTEP view of the X-ray structure of the cationic complex 3b in the solid state, with ellipsoids at the 50% probability level and H atoms omitted for clarity (left); capped-sticks view along the C–P bond (right). Selected bond distances (Å) and angles (deg): Cu1-P1 2.222(3), Cu1-N1 2.083(9) Cu1-N2 2.112(8) Cu1-N3 1.941(9); P1-Cu1-N1 85.2(3), P1-Cu1-N2 81.6(3), P1-Cu1-N3 139.1(3), N3-Cu1-N1 125.7(3) N3-Cu1-N2 109.0(3) N1-Cu1-N2 106.7(3).
Figure 5. ORTEP view of the X-ray structure of the cationic complex 3b in the solid state, with ellipsoids at the 50% probability level and H atoms omitted for clarity (left); capped-sticks view along the C–P bond (right). Selected bond distances (Å) and angles (deg): Cu1-P1 2.222(3), Cu1-N1 2.083(9) Cu1-N2 2.112(8) Cu1-N3 1.941(9); P1-Cu1-N1 85.2(3), P1-Cu1-N2 81.6(3), P1-Cu1-N3 139.1(3), N3-Cu1-N1 125.7(3) N3-Cu1-N2 109.0(3) N1-Cu1-N2 106.7(3).
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Figure 6. ORTEP view of the X-ray structure of the cationic complex 4 in the solid state, with ellipsoids at the 50% probability level and H atoms omitted for clarity. Selected bond distances (Å) and angles (deg): Cu1-P1 2.2369(7), Cu2-P2 2.2456(7), Cu1-N1 2.043(2) Cu1-N3 2.075(2), Cu2-N5 2.065(2), Cu2-N7 2.067(2), Cu1-Cl1 2.2456(7), Cu2-Cl2 2.2571(7); P1-Cu1-Cl1 146.96(3), P2-Cu2-Cl1 142.85(3), Cu1-Cl1-Cu2 119.52(3), N1-Cu1-N3 115.25(8), N5-Cu2-N7 108.85(8), Cl1-Cu1-N1 112.12(6), Cl1-Cu1-N3 110.06(6), Cl1-Cu2-N5 107.42(6), Cl1-Cu2-N7 121.42(6).
Figure 6. ORTEP view of the X-ray structure of the cationic complex 4 in the solid state, with ellipsoids at the 50% probability level and H atoms omitted for clarity. Selected bond distances (Å) and angles (deg): Cu1-P1 2.2369(7), Cu2-P2 2.2456(7), Cu1-N1 2.043(2) Cu1-N3 2.075(2), Cu2-N5 2.065(2), Cu2-N7 2.067(2), Cu1-Cl1 2.2456(7), Cu2-Cl2 2.2571(7); P1-Cu1-Cl1 146.96(3), P2-Cu2-Cl1 142.85(3), Cu1-Cl1-Cu2 119.52(3), N1-Cu1-N3 115.25(8), N5-Cu2-N7 108.85(8), Cl1-Cu1-N1 112.12(6), Cl1-Cu1-N3 110.06(6), Cl1-Cu2-N5 107.42(6), Cl1-Cu2-N7 121.42(6).
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Scheme 5. Scope of the C–S coupling of (hetero)aryl iodides with thiophenols and aliphatic thiols catalyzed by complexes 2a and 2b. Reaction conditions: aryl halide (1.2 mmol), thiophenol (1.0 mmol), K3PO4 (2.0 mmol), 2a or 2b (2 mol %), dioxane (1 mL), 110 °C, 24 h. Isolated yield of products (average of two runs).
Scheme 5. Scope of the C–S coupling of (hetero)aryl iodides with thiophenols and aliphatic thiols catalyzed by complexes 2a and 2b. Reaction conditions: aryl halide (1.2 mmol), thiophenol (1.0 mmol), K3PO4 (2.0 mmol), 2a or 2b (2 mol %), dioxane (1 mL), 110 °C, 24 h. Isolated yield of products (average of two runs).
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Table 1. Optimization of the reaction conditions for the coupling of iodobenzene and thiophenol catalyzed by complexes 2a, 2b, and 2c a.
Table 1. Optimization of the reaction conditions for the coupling of iodobenzene and thiophenol catalyzed by complexes 2a, 2b, and 2c a.
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EntryVariationYield (%) b
1None98
2LiOtBu instead of NaOtBu99
3K3PO4 instead of NaOtBu98
4K3PO4 as the base and 100 °C instead of 110 °C91
5K3PO4 as the base, 100 °C, and THF instead of dioxane75
6K3PO4 as the base, 100 °C, and toluene instead of dioxane63
7K3PO4 as the base and 2.5 mol% catalyst loading97
8K3PO4 as the base and 2 mol% catalyst loading91
9K3PO4 as the base and 1 mol% catalyst loading80
102b as the catalyst90
112c as the catalyst38
12No copper catalyst-
(a) Reaction conditions: iodobenzene (1.2 mmol), thiophenol (1.0 mmol), base (2.0 mmol), catalyst (1–5 mol%), solvent (1 mL), 110 °C, 24 h; (b) isolated yield of products (average of two runs).
Table 2. Coupling of thiophenol with bromobenzene and chlorobenzene catalyzed by 2a a.
Table 2. Coupling of thiophenol with bromobenzene and chlorobenzene catalyzed by 2a a.
EntryCatalystBaseSolventCatalyst Load (mol %)Yield (%) b
1PhBrK3PO4dioxane2-
2PhBrK3PO4dioxane52
3PhBrK3PO4dioxane105
4PhBrNaOtBudioxane107
5PhBrK3PO4DMF1011
6PhBrK3PO4NMP1012
7PhBrNaOtBuDMF1014
8PhClK3PO4dioxane10-
9PhClNaOtBudioxane10-
10PhClNaOtBuDMF104
(a) Reaction conditions: phenyl halide (1.2 mmol), thiophenol (1.0 mmol), base (2.0 mmol), catalyst 2a (2–10 mol%), solvent (1 mL), 110 °C, 24 h; (b) isolated yields.
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Martín, M.T.; del Postigo, A.G.; Sánchez, P.; Álvarez, E.; Maya, C.; Nicasio, M.C.; Peloso, R. Copper(I) Complexes with Terphenyl-Substituted NPN Ligands Bearing Pyridyl Groups: Synthesis, Characterization, and Catalytic Studies in the S-Arylation of Thiols. Molecules 2025, 30, 3167. https://doi.org/10.3390/molecules30153167

AMA Style

Martín MT, del Postigo AG, Sánchez P, Álvarez E, Maya C, Nicasio MC, Peloso R. Copper(I) Complexes with Terphenyl-Substituted NPN Ligands Bearing Pyridyl Groups: Synthesis, Characterization, and Catalytic Studies in the S-Arylation of Thiols. Molecules. 2025; 30(15):3167. https://doi.org/10.3390/molecules30153167

Chicago/Turabian Style

Martín, M. Trinidad, Ana Gálvez del Postigo, Práxedes Sánchez, Eleuterio Álvarez, Celia Maya, M. Carmen Nicasio, and Riccardo Peloso. 2025. "Copper(I) Complexes with Terphenyl-Substituted NPN Ligands Bearing Pyridyl Groups: Synthesis, Characterization, and Catalytic Studies in the S-Arylation of Thiols" Molecules 30, no. 15: 3167. https://doi.org/10.3390/molecules30153167

APA Style

Martín, M. T., del Postigo, A. G., Sánchez, P., Álvarez, E., Maya, C., Nicasio, M. C., & Peloso, R. (2025). Copper(I) Complexes with Terphenyl-Substituted NPN Ligands Bearing Pyridyl Groups: Synthesis, Characterization, and Catalytic Studies in the S-Arylation of Thiols. Molecules, 30(15), 3167. https://doi.org/10.3390/molecules30153167

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