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Article

Confined Catalysis Involving a Palladium Complex and a Self-Assembled Capsule for the Dimerization of Vinyl Arenes and the Formation of Indane and Tribenzo–Pentaphene Derivatives

by
Maxime Steinmetz
and
David Sémeril
*
Synthèse Organométallique et Catalyse, UMR-CNRS 7177 Institut de Chimie de Strasbourg, Strasbourg University, 67008 Strasbourg, France
*
Author to whom correspondence should be addressed.
Catalysts 2025, 15(6), 585; https://doi.org/10.3390/catal15060585
Submission received: 16 May 2025 / Revised: 3 June 2025 / Accepted: 6 June 2025 / Published: 12 June 2025
(This article belongs to the Special Issue Sustainable Catalysis for Green Chemistry and Energy Transition)
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Abstract

:
The [PdCl2(cod)] complex was encapsulated inside a self-assembled hexameric capsule obtained via a reaction of 2,8,14,20-tetra-undecyl-resorcin[4]arene and water. The formation of an inclusion complex was deduced from a combination of spectral measurements (UV-visible, 1H NMR and DOSY spectroscopies). The latter proved effective in the dimerization of styrene derivatives under mild conditions, with a catalyst loading of 0.5 mol% at 60 °C. Electronically enriched vinyl arenes underwent cyclization of the catalytic products, leading to the quasi-quantitative formation of indanes from 4-tert-butylstyrene and 9-vinylanthracene. In the instance of 9-vinylanthracene, the rearrangement product is tribenzo–pentaphene, which is formed in 50% of conversions.

Graphical Abstract

1. Introduction

The dimerization reaction of vinyl arenes is catalyzed either by acids, particularly in confined spaces such as zeolites [1,2,3], or by various organometallic complexes based on iron [4], nickel [5], ruthenium [6,7], yttrium [8] and, mainly, palladium [9,10,11,12,13,14,15,16,17,18,19]. However, the presence of a co-catalyst is generally required. The addition of a Lewis acid, such as BF3 [9], [In(OTf)3] [10,11] and [Cu(OTf)2] [12,13], or a Brönsted acid [14] is essential to make commercially available palladium complexes (e.g., [PdCl2] or [Pd(OAc)2]) catalytically active. As example, Lim and co-workers catalyzed the dimerization of styrene using [PdCl(η3-C3H5)]2 (0.5 mol%) with triphenylphosphine (PPh3) and silver triflate (AgOTf) as co-catalysts (1.1 mol% each). After 12 h at room temperature in CH2Cl2, the dimeric product was isolated in a 93% yield. The formed product contained approximately 3–5% of trimers [18]. Concurrent with this, a particularly high-performance catalytic system was reported by Myagmarsuren and co-workers. The catalyst, which is generated in situ, is composed of [Pd(OAc)2] combined with PPh3 and BF3•OEt2 in proportions of 2 and 7 equivalents per palladium atom, respectively. The authors demonstrated that, under optimal conditions, employing a catalyst loading as low as 9.5 × 10−4 mol% results in the conversion of 71% of styrene after 7 h at a temperature of 70 °C, with the absence of a solvent. The analysis of the formed products revealed the formation of 93% of dimer and 7% of trimers and polymers [9].
Another activation method is the use of cationic palladium complexes [15,16,17,18,19]. Generally, palladium complexes result in the selective formation of the “head-to-tail” dimerization product corresponding to (E)-but-1-ene-1,3-diyldibenzene (3a) when styrene (1a) is used as the substrate (Scheme 1).
We have recently demonstrated that a neutral organometallic complex [20] can be encapsulated inside a self-assembled capsule generated by six 2,8,14,20-tetra-undecyl-resorcin(4)arene unit 5 and eight water molecules [21] (Scheme 2). It is clear that the interior of this capsule shows an affinity for halogens, particularly chlorine [22,23,24,25,26]. Interactions between hydrogen bond acceptor ligands and 56 have also been demonstrated [27]. These interactions will lead to chloride abstraction by the capsule, forming a cationic complex. This should facilitate the formation of inclusion complexes.
In this context, we report the encapsulation of the commercially available [PdCl2(cod)] complex (6; cod = 1,5-cyclooctadiene) in the hexameric capsule 56. We evaluated the formed inclusion complex 6⊂56 in the dimerization of vinyl arenes for the formation of indane (7) and tribenzo–pentaphene (8) derivatives.

2. Results and Discussion

2.1. Formation of Inclusion Complex

First, we studied the encapsulation of the [PdCl2(cod)] complex (6) in the hexameric capsule 56. The small volume of the palladium complex, 232 Å3 [28], corresponds to an occupancy volume of 17% inside the capsule, which is lower than the ideal value defined by Rebek (55% ± 9) [29]. This allows the diffusion of organic molecules into the capsule. The two chlorine atoms of complex 6 are not sterically hindered, which should allow interaction with the inner walls of capsule 56 and thus facilitate the formation of the inclusion complex 6⊂56.
The NMR study of the inclusion complex was carried out with complex 6 in the presence of 56 ([5] = 26 mM and [6] = 4 mM) in H2O-saturated CDCl3 (Figure 1). The 1H NMR spectrum shows that after adding 56, the signals of complex 6 disappeared. The small volume of the palladium complex means it moves quickly within the large inner capsular space, where a multitude of possible conformations of the complex 6 in 56 can be assumed. A modification of the phenol signals of 56 is also evident, demonstrating their potential interactions with guest 6 (Figure 1b). The addition of five equivalents of NEt4Cl, a competitor to the encapsulation of 6, induces the regeneration of the original signals of complex 6. This clearly shows that the phenomenon is reversible and that the organometallic species 6 is not modified during encapsulation (Figure 1c). We can note that complex 6 is co-encapsulated with molecules of chloroform (CHCl3⊂56, visible at δ = 4.8–5.1 ppm [30]) and probably molecules of water [31,32].
The DOSY NMR spectrum generated from a mixture of complex 6 (diffusion coefficient 1120 μm2s−1; hydrodynamic volume 150 Å3; Figure S1) and 1.1 equivalent of resorcinarenyl capsule 56 (diffusion coefficient 225 μm2s−1; hydrodynamic volume 18,800 Å3) shows the formation of an inclusion complex 6⊂56 (diffusion coefficient 222 μm2s−1; hydrodynamic volume 19,600 Å3; Figure 2). A slight deformation of the supramolecular assembly is observed during the encapsulation process; this deformation results in a small increase in capsule volume (4% variation) compared to the hexameric capsule 56 alone.
The UV-visible spectroscopy study shows a shift in the absorbance maximum (Figure 3). However, the broad band formed, which centered at around 340 nm for 6⊂56, did not allow us to assign an absorbance maximum and therefore a shift value to this signal. This broadening is explained by the rapid movement of the palladium complex and various interactions between 6 and the inner walls of the capsule. These interactions induce the formation of several species with slightly different but close maximum absorbance. The addition of NEt4Cl reliably regenerates the original spectrum observed for free complex 6 (λ = 347 nm).

2.2. Catalytic Study

Styrene 1a dimerizes in the presence of palladium(II) 6 complex and the hexameric capsule 56 (Scheme 3). The reaction was first studied with 1 mol% of 6 and 1.1 mol% of 56 at 60 °C. Reaction kinetics were carried out and can be seen in Figure 4.
A selective “head-to-tail” dimerization forming product (E)-but-1-ene-1,3-diyldibenzene 3a was observed; the formation of products 2a (“tail-to-tail”) and 4a (“head-to-head”) was not formed. Optimum formation of 3a under these conditions was achieved in 27% yield after 24 h at conversion of styrene of 72%. It has been demonstrated that an increase in reaction time does not result in a higher amount of formed 3a. As the conversion approaches 100%, it has been observed that the amount of 3a decreases. Concurrently, the quantity of generated oligomers increases. The degradation of 3a can be explained by the confinement of the active species. It is reasonable to hypothesize that the process of dimer 3a ejection necessitates a temporal interval during which a new molecule of styrene or dimer 3a can diffuse into the capsule. This diffusion results in the formation of oligomers and the consumption of 3a. This observation is also applicable to the other tested vinyl arenes (vide infra).
The linearity of the conversion indicates that the reaction rate is equivalent to a reaction of order 0. This well-known kinetics is frequently observed for enzymes and is described by the Michaelis–Menten kinetics model, as depicted in Equation (1) [33,34,35,36]. This equation is valid for enzymes or related catalysts. The reaction involves only one reactant, and the substrate concentration is higher than the Michaelis constant (KM) of the catalyst. This constant corresponds to the substrate concentration for which the reaction rate is half the maximum reaction rate (vmax) [37]. It is related to the dissociation constant of the enzyme/substrate complex. A low KM value indicates a high association constant between catalyst and substrate, leading to increased catalytic activity.
v0 = (vmax [S])/(KM + [S])
with v0 = initial velocity (M·min−1); vmax = maximum initial velocity (M·min−1); [S] = initial substrate concentration (M); KM = Michaelis constant.
The obtained results, combined with the Hanes–Woolf representation [36,38] (Figure 5), determined the value of the KM constant for our system. This value is 3.4 × 10−2 M (vmax = 2.65 × 10−4 M/min), indicating a low affinity of styrene for the interior of the 56-cavity. The catalytic constant kcat was also determined, with a calculated value of 1.0 × 10−3 s−1 (Equation (2)). The latter value is used to determine the catalytic efficiency of the catalytic system 6⊂56, corresponding to the ratio kcat/KM. The obtained constant was 3.2 × 10−2 M−1·s−1. This is indicative of a low active catalytic system.
kcat = vmax/[6⊂56]. (with kcat in min−1 and [6⊂56] in M)
Control reactions were conducted to assess the impact of the complex 6 and the hexameric capsule 56 on styrene 1a dimerization (Table 1). It is clear that no reactivity was observed in the absence of 6 or 56 (Table 1, entries 2–4). As the introduction mentions, activation of the palladium complex and/or vinyl arene is necessary to make this reaction active. In capsule 56, its acidity [22,39] means it activates the alkene and complex 6 by polarizing the Pd-Cl bond. Substitution of capsule 56 with acetic acid (pKa = 4.76, similar to the pKa of the capsule) fails to activate complex 6 (Table 1, entry 5). The addition of DMSO to the 6⊂56 inclusion complex breaks the hydrogen bonding network of the supramolecular assembly [30]. Under these conditions (6 + 56 + DMSO (10% v/v)), no conversion is observed (Table 1, entry 6). The addition of five equivalents of NEt4Cl, a competitor for the encapsulation of the organometallic complex 6, also renders the system inactive (Table 1, entry 7). These experiments show that the reaction takes place within the inner capsular space of 56. A final control experiment was carried out with D2O instead of H2O. The objective was to ascertain whether the mechanism involves lattice water molecules. The 1H NMR spectra of the dimerization products 3a, formed under these two conditions, show no deuterium incorporation, ruling out addition or protonation of styrene by water molecules (see Figure S21) (Table 1, entry 8).
The influence of the catalyst loading 6⊂56 was thoroughly studied (Table 2). As expected, a higher catalytic loading (2 mol% of 6⊂56 instead of 1 mol%) results in higher styrene conversion (Table 2, entries 1–3). This increase in activity also induces lower proportions of dimerization product 3a. The maximum yield was obtained after 16 h, yielding 93% styrene conversion and 25% dimer 3a (Table 2, entry 2). This decrease is explained by the higher activity of the catalyst, which induces greater oligomerization of 3a.
Conversely, lower catalyst loading (Table 2, entries 5–8) results in lower conversion but higher proportions of product 3a. The optimum time is 40 h for a 3a formation of 42% (87% styrene conversion and 48% dimer 3a; Table 2, entry 7). A longer time leads to a significant drop in 3a dimer formation (Table 2, entry 8). This demonstrates the importance of reaction time in this dimerization.
Eight additional styrene derivatives 1b–i were studied for this reaction (Table 3). The optimal catalytic conditions found when styrene 1a was employed (0.5 mol%, 6⊂56, 60 °C, 40 h) were not ideal in the case of substituted vinyl arenes. The substrate reactivities were decisive. The yields of formed products were low. This was due to a lack of reactivity or subsequent reaction of dimerization products leading to the degradation of the latter compounds, with mainly the formation of oligomers.
For substrates with electron deficient vinyl functions, 4-chlorostyrene (1b) and 4-fluorostyrene (1c), low reactivities were observed, with conversions of 13% and 17% for 3b and 3c, respectively, after 40 h of reaction (Table 3, entries 1 and 3). For these substrates, a clear distribution in favor of dimerization products 3b and 3c was observed. Longer reaction times increase the conversions of 1b and 1c, without increasing the amounts of dimeric products (Table 3, entries 2 and 4).
For 4-methylstyrene (1d), the reactivity was similar to that of styrene (1a), the (E)-4,4′-(but-1-ene-1,3-diyl)bis(methylbenzene) (3d) was obtained in a 21% yield over a 32 h reaction time. (Table 3, entry 6). However, the dimerization product was more reactive. The electronic enrichment should make the olefin coordinate more easily with the metal center. This should increase the propagation step, leading to a higher proportion of oligomerization products. This is supported by the observation that 4-methoxystyrene exclusively formed oligomeric products.
Sterically hindered alkenes with electronically enriched vinyl functions, 4-tert-butylstyrene (1e), α-methylstyrene (1f) and 9-vinylanthracene (1g), low amount of dimeric products was observed and rearrangement of the latter dimers was isolated. In fact, the formation of 5-(tert-butyl)-3-(4-(tert-butyl)phenyl)-1-methyl-2,3-dihydro-1H-indene (7e) from the dimerization and cyclization of 1e was achieved in a 39% yield after 72 h of reaction (cis/trans ratio = 60/40) (Scheme 4a; Table 3, entry 8). The greater steric hindrance and electronic enrichment of the aromatic ring of 1e favor the formation of this product. It is noteworthy that the formation of cyclization product 7d is only observed in trace amounts for vinyl arene 1d.
In the course of testing α-methylstyrene (1f) as a reagent, the formation of two dimerization products, corresponding to (4-methylpent-1-ene-2,4-diyl)dibenzene 9 and its regioisomer (E)-(4-methylpent-2-ene-2,4-diyl)dibenzene 10, was observed in addition to the rearrangement product 1,1,3-trimethyl-3-phenylindane (7f) (Scheme 4b; Table 3, entry 9 and Figure S20) [40]. The latter indane derivative is quantitatively obtained after 40 h of reaction (Table 3, entry 10). The quantitative formation of the indane 7f can be explained by the presence of sterically hindered methylenic groups, which inhibit the formation of larger oligomers, and by the formation of a tetrasubstituted carbon, which favors cyclization of the dimerization product by the Thorpe-Ingold effect [41,42].
In the case of 9-vinylanthracene (1g), a majority of product was observed that did not correspond to the expected dimerization product. Following a purification process and the employment of advanced characterization techniques, including mass and NMR spectroscopies (1H, 13C, DEPT, COSY, NOESY, and HSQC), the structure of the rearrangement product 8 was unequivocally confirmed through a X-ray diffraction study (see Supplementary Materials; Scheme 5). For a reaction time of 40 h, the tribenzo–pentaphene derivative 8 was obtained in a 50% yield (Table 3, entry 11). To the best of our knowledge, no prior observations in the relevant literature have documented the formation of rearrangement product 8.
The substantial formation of indanes 7e and 7f and tribenzo–pentaphene 8, catalyzed by the inclusion complex 6⊂56, can be explained by the augmented steric hindrance of dimeric intermediates, which limits the concomitant diffusion of vinyl arene into the capsule and, consequently, oligomerization reactions. Furthermore, rearrangement products exhibit increased compactness, thereby facilitating easier accommodation within the intracavity space. Finally, these products have been shown to lack a reactive carbon–carbon double bond, a property that hinders their degradation once formed.
As anticipated, the bulky alkene 1h did not undergo conversion (Table 3, entry 12). The capsule cavity is not capable of accommodating two alkenes due to spatial limitations. Furthermore, it hinders the adoption of the transition state necessary for the formation of dimerization products. trans-Stilbene (1i) was also subjected to this reaction, but no conversion was observed (Table 3, entry 13). The absence of reactivity is should be attributable to the functionalization of the vinyl group. The use of the aliphatic alkene corresponding to 1-hexene does not result in the formation of dimerization products; however, isomerization of the double bond is observed, with the predominant formation of 3-hexene (Table 3, entry 14).

2.3. Mecanistic Considerations

Control experiments (Table 1) demonstrate that the dimerization reaction requires the simultaneous presence of the palladium complex 6 and the supramolecular capsule 56, and takes place inside its cavity. Furthermore, experiments carried out in the presence of D2O demonstrate an absence of deuterium incorporation into the dimeric products, thereby ruling out the possibility of protonation by structural water molecules of the hexameric structure. Inspired by the relevant literature and these results, the following mechanism is proposed (Scheme 6).
Initially, the [PdCl2(cod)] complex is activated by a water molecule within the capsule structure. The formation of hydrogen bond between the chlorine atom of the complex and the structural water molecule, in particular through the hydrogen atom pointing towards the interior of the cavity as highlighted by the groups of Neri [22,24], Gaeta [25], and Colasson [27], activates the Pd-Cl bond (intermediate I). Subsequent to the coordination of styrene (intermediate II), the vinyl function of the substrate is inserted into the activated Pd-Cl bond (intermediate III). A β-hydride elimination subsequently generates the active palladium hydride species (intermediate IV) with the elimination of (2-chlorovinyl)benzene. This species permits the insertion of the vinyl function of the substrate into the Pd-H bond, thereby forming intermediate V. The subsequent insertion of a vinyl function from a second substrate molecule into the Pd-C bond (intermediate VI) following by β-hydride elimination, results in the formation of dimeric product 1a and the regeneration of the active palladium–hydride species (intermediate IV).
To ascertain the involvement of water molecules of the supramolecular structure in the formation of cyclization products, reactions were carried out in the presence of D2O instead of H2O for substrates 1e–g. For the three vinyl arenes, no deuterium incorporation into the cyclization products could be observed (Figures S22–S24). Conversions and product distributions close to those of H2O were observed in these experiments (Table 4). These results demonstrate that the water molecules within the capsule do not play a role in the reaction mechanism.
Regarding the formation of indane (7e and 7f) and tribenzo–pentaphene (8) derivatives, the initially “head-to-tail” dimerization of vinyl aryls substrates should be considered, as observed at shorter reaction time in the case of α-methylstyrene (1f) (Table 3, entry 9). Subsequently, one (in the case of indanes) or two (in the case of tribenzo-pentaphene) successive insertions of aromatic double bonds in the Pd-C bond, followed by a β-hydride elimination with aromatization of the six-membered ring. This process resulted in the formation of cyclic compounds 7e, 7f and 8 with the regeneration of the palladium hydride active species (Scheme 7).

3. Materials and Methods

3.1. General Remarks

All manipulations were carried out under dry argon. Routine 1H, 19F{1H}, 13C{1H} and DOSY spectra were recorded with Bruker FT instruments (AC 300, 500 and 600). CDCl3 was degassed, passed down a 5 cm thick basic alumina column and stored under argon. 1H and 13C{1H} NMR spectra were referenced to residual protonated solvents (δ = 7.26 and 77.16 ppm, respectively). 19F{1H} spectroscopic data were provided relative to external CCl3F. Chemical shifts and coupling constants were reported in ppm and Hz, respectively. UV-visible spectra were performed on an Agilent Technologies Cary 60 UV-Vis spectrometer from Agilent Technologies (Santa Clara, CA, USA). Mass spectra were recorded on a Bruker MicroTOF spectrometer (ESI-TOF) from Bruker Daltonics (Billerica, MA, USA). Tetraethylammonium chloride, styrene, 4-methylstyrene, 4-tert-butylstyrene, 4-chlorostyrene, 4-fluorostyrene, trans-stilbene, 1-hexene and α-methylstyrene are commercially available products (Alfa Aesar, Sigma-Aldrich, Honeywell or Abcr) and were used as received, without any further purification. 2,8,14,20-Tetra-undecyl-resorcin[4]arene (5) [26], [PdCl2(cod)] (6) [43] and 9-vinylanthracene (1g) [44] were prepared according to the procedures from the literature.

3.2. Catalytic Reactions

Under argon, the [PdCl2(cod)] complex (6) (1.1 mg, 0.5 mol%) was dissolved in CHCl3 saturated with H2O (1.0 mL). The resorcinarene (5) (28.7 mg, 3.2 mol%) was added and the resulting solution was stirred at room temperature for 0.5 h. Then, the vinyl arene (0.8 mmol) was added, and the reaction mixture was heated at 60 °C. After cooling to room temperature, CH2Br2 (14 μL, 0.2 mmol) was added as an internal standard and an aliquot of the solution was analyzed by 1H NMR. The products were unambiguously identified by 1H and 13C{1H} NMR after their isolation via flash chromatography on silica gel (eluent: pentane/CH2Cl2: 98/2 v/v). Their NMR spectra were compared to those reported in the literature.

3.2.1. Dimeric Products

(E)-But-1-ene-1,3-diyldibenzene (3a) [45] (Rf: 0.42 pentane/CH2Cl2: 98/2 v/v): 1H NMR (300 MHz, CDCl3): δ = 7.39–7.36 (m, 2H, arom CH of C6H5), 7.34–7.27 (m, 6H, arom CH of C6H5), 7.25–7.18 (m, 2H, arom CH of C6H5), 6.47–6.35 (m, 2H, CH(CH3)CH=CH), 3.70–3.62 (m, 1H, CH(CH3)CH=CH), 1.48 (d, 3H, CH(CH3)CH=CH, 3JHH = 6.9 Hz); 13C{1H} NMR (126 MHz, CDCl3): δ = 145.77 (s, arom Cquat of C6H5), 137.71 (s, arom Cquat of C6H5), 135.38 (s, CH(CH3)CH=CH), 128.66 (s, CH(CH3)CH=CH), 128.63 (s, arom CH of C6H5), 127.45 (s, arom CH of C6H5), 127.18 (s, arom CH of C6H5), 126.36 (s, arom CH of C6H5), 126.29 (s, arom CH of C6H5), 42.71 (s, CH(CH3)CH=CH), 21.36 (s, CH(CH3)CH=CH) ppm.
(E)-4,4′-(But-1-ene-1,3-diyl)bis(chlorobenzene) (3b) [46] (Rf: 0.40 pentane/CH2Cl2: 98/2 v/v): 1H NMR (500 MHz, CDCl3): δ = 7.30–7.27 (m, 2H, arom CH of C6H4Cl), 7.27–7.25 (m, 4H, arom CH of C6H4Cl), 7.20–7.17 (m, 2H, arom CH of C6H4Cl), 6.36–6.28 (m, 2H, CH(CH3)CH=CH), 3.64–3.58 (m, 1H, CH(CH3)CH=CH), 1.44 (d, 3H, CH(CH3)CH=CH, 3JHH = 7.0 Hz); 13C{1H} NMR (126 MHz, CDCl3): δ = 143.91 (s, arom Cquat of C6H4Cl), 135.98 (s, arom Cquat of C6H4Cl), 135.47 (s, CH(CH3)CH=CH), 132.93 (s, arom Cquat of C6H4Cl), 132.16 (s, arom Cquat of C6H4Cl), 128.81 (s, arom CH of C6H4Cl), 128.80 (s, arom CH of C6H4Cl), 128.78 (s, arom CH of C6H4Cl), 127.91 (s, CH(CH3)CH=CH), 127.51 (s, arom CH of C6H4Cl), 42.10 (s, CH(CH3)CH=CH), 21.22 (s, CH(CH3)CH=CH) ppm.
(E)-4,4′-(But-1-ene-1,3-diyl)bis(fluorobenzene) (3c) [14] (Rf: 0.36 pentane/CH2Cl2: 98/2 v/v): 1H NMR (500 MHz, CDCl3): δ = 7.33–7.28 (m, 2H, arom CH of C6H4F), 7.23–7.19 (m, 2H, arom CH of C6H4F), 7.02–6.99 (m, 2H, arom CH of C6H4F), 6.99–6.95 (m, 2H, arom CH of C6H4F), 6.34 (d, 1H, CH(CH3)CH=CH, 3JHH = 16.0 Hz), 6.25 (dd, 1H, CH(CH3)CH=CH, 3JHH = 16.0 Hz, 3JHH = 6.5 Hz), 3.66–3.59 (m, 1H, CH(CH3)CH=CH), 1.44 (d, 1H, CH(CH3)CH=CH, 3JHH = 7.0 Hz); 13C{1H} NMR (126 MHz, CDCl3): δ = 162.07 (d, arom Cquat of C6H4F, 1JCF = 246.7 Hz), 161.43 (d, arom Cquat of C6H4F, 1JCF = 244.4 Hz), 141.11 (d, arom Cquat of C6H4F, 4JCF = 3.2 Hz), 134.78 (d, CH(CH3)CH=CH, 5JCF = 2.0 Hz), 133.56 (d, arom Cquat of C6H4F, 4JCF = 3.3 Hz), 128.65 (d, arom CH of C6H4F, 3JCF = 7.8 Hz), 127.58 (d, arom CH of C6H4F, 3JCF = 7.9 Hz), 127.52 (s, CH(CH3)CH=CH), 115.39 (d, arom CH of C6H4F, 2JCF = 19.2 Hz), 115.22 (d, arom CH of C6H4F, 2JCF = 18.8 Hz), 41.78 (s, CH(CH3)CH=CH), 21.31 (s, CH(CH3)CH=CH); 19F{1H} NMR (282 MHz, CDCl3): δ = −115.28 (s, C6H4F), −117.15 (s, C6H4F) ppm.
(E)-4,4′-(But-1-ene-1,3-diyl)bis(methylbenzene) (3d) [14] (Rf: 0.37 pentane/CH2Cl2: 98/2 v/v): 1H NMR (500 MHz, CDCl3): δ = 7.25–7.24 (m, 2H, arom CH of C6H4CH3), 7.17–7.16 (m, 2H, arom CH of C6H4CH3), 7.13–7.12 (m, 2H, arom CH of C6H4CH3), 7.10–7.08 (m, 2H, arom CH of C6H4CH3), 6.39–6.29 (m, 2H, CH(CH3)CH=CH), 3.62–3.57 (m, 1H, CH(CH3)CH=CH), 2.33 (s, 3H, C6H4CH3), 2.32 (s, 3H, C6H4CH3), 1.44 (d, 3H CH(CH3)CH=CH, 3JHH = 7.0 Hz); 13C{1H} NMR (126 MHz, CDCl3): δ = 142.95 (s, arom Cquat of C6H4CH3), 136.84 (s, arom Cquat of C6H4CH3), 135.80 (s, arom Cquat of C6H4CH3), 135.00 (s, arom Cquat of C6H4CH3), 134.59 (s, CH(CH3)CH=CH), 129.31 (s, arom CH of C6H4CH3), 129.29 (s, arom CH of C6H4CH3), 128.30 (s, CH(CH3)CH=CH), 127.33 (s, arom CH of C6H4CH3), 126.17 (s, arom CH of C6H4CH3), 42.27 (s, CH(CH3)CH=CH), 21.48 (s, CH(CH3)CH=CH), 21.29 (s, C6H4CH3), 21.15 (s, C6H4CH3) ppm.

3.2.2. Indane Derivatives

trans-5-(tert-Butyl)-3-(4-(tert-butyl)phenyl)-1-methyl-2,3-dihydro-1H-indene (trans-7e; major isomer 60% after purification; Rf: 0.39 pentane/CH2Cl2: 98/2 v/v): 1H NMR (500 MHz, CDCl3): δ = 7.30–7.28 (m, 3H, arom CH), 7.19–7.17 (m, 2H, arom CH), 7.11–7.11 (m, 1H, arom CH), 7.08–7.06 (m, 1H, arom CH), 4.41 (dd, 1H, CH(CH3)CH2CH, 3JHH = 8.5 Hz, 3JHH = 5.5 Hz), 3.35–3.28 (m, 1H, CH(CH3)CH2CH), 2.30–2.25 (m, 1H, CH(CH3)CH2CH), 2.18–2.13 (m, 1H, CH(CH3)CH2CH), 1.31 (s, 9H, C(CH3)3), 1.28 (d, 3H, CH(CH3)CH2CH, 3JHH = 6.5 Hz), 1.27 (s, 9H, C(CH3)3); 13C{1H} NMR (126 MHz, CDCl3): δ = 149.58 (s, arom Cquat), 148.68 (s, arom Cquat), 146.24 (s, arom Cquat), 145.59 (s, arom Cquat), 142.74 (s, arom Cquat), 127.93 (s, arom CH), 127.37 (s, arom CH), 125.29 (s, arom CH), 125.22 (s, arom CH), 122.09 (s, arom CH), 49.14 (s, CH(CH3)CH2CH), 45.29 (s, CH(CH3)CH2CH), 37.44 (s, CH(CH3)CH2CH), 34.62 (s, C(CH3)3), 34.37 (s, C(CH3)3), 31.60 (s, C(CH3)3), 31.42 (s, C(CH3)3), 20.16 (s, CH(CH3)CH2CH) ppm.
cis-5-(tert-Butyl)-3-(4-(tert-butyl)phenyl)-1-methyl-2,3-dihydro-1H-indene (cis-7e; minor isomer 40% after purification; Rf: 0.39 pentane/CH2Cl2: 98/2 v/v): 1H NMR (500 MHz, CDCl3): δ = 7.35–7.33 (m, 2H, arom CH), 7.17–7.16 (m, 1H, arom CH), 7.06–7.03 (m, 2H, arom CH), 6.99–6.99 (m, 1H, arom CH), 6.88–6.85 (m, 1H, arom CH), 4.21 (dd, 1H, CH(CH3)CH2CH, 3JHH = 11.0 Hz, 3JHH = 7.5 Hz), 3.32–3.11 (m, 1H, CH(CH3)CH2CH), 2.71–2.66 (m, 1H, CH(CH3)CH2CH), 1.61–1.55 (m, 1H, CH(CH3)CH2CH), 1.36 (d, 3H, CH(CH3)CH2CH, 3JHH = 6.5 Hz), 1.34 (s, 9H, C(CH3)3), 1.26 (s, 9H, C(CH3)3); 13C{1H} NMR (126 MHz, CDCl3): δ = 149.45 (s, arom Cquat), 148.95 (s, arom Cquat), 146.47 (s, arom Cquat), 146.08 (s, arom Cquat), 141.86 (s, arom Cquat), 128.79 (s, arom CH), 124.19 (s, arom CH), 123.85 (s, arom CH), 123.46 (s, arom CH), 122.73 (s, arom CH), 122.22 (s, arom CH), 121.77 (s, arom CH), 50.28 (s, CH(CH3)CH2CH), 47.34 (s, CH(CH3)CH2CH), 37.89 (s, CH(CH3)CH2CH), 34.43 (s, C(CH3)3), 34.34 (s, C(CH3)3), 31.44 (s, C(CH3)3), 31.29 (s, C(CH3)3), 19.17 (s, CH(CH3)CH2CH) ppm.
1,1,3-Trimethyl-3-phenyl-2,3-dihydro-1H-indene (7f) [40] (Rf: 0.47 pentane/CH2Cl2: 98/2 v/v): 1H NMR (500 MHz, CDCl3): δ = 7.32–7.27 (m, 2H, arom CH), 7.26–7.21 (m, 3H, arom CH), 7.21–7.18 (m, 2H, arom CH), 7.17–7.13 (m, 2H, arom CH), 2.44 and 2.22 (AB spin system, 2H, C(CH3)2CH2C(CH3), 2JHH = 13.0 Hz), 1.71 (s, 3H, C(CH3)2CH2C(CH3)), 1.37 (s, 3H, C(CH3)2CH2C(CH3)), 1.06 (s, 3H, C(CH3)2CH2C(CH3)); 13C{1H} NMR (126 MHz, CDCl3): δ = 152. 34 (s, arom Cquat of C6H4), 151.15 (s, arom Cquat of C6H4), 148.86 (s, arom Cquat of C6H5), 128.11 (s, arom CH of C6H5), 127.33 (s, arom CH of C6H4), 126.83 (s, arom CH of C6H5), 126.76 (s, arom CH of C6H5), 125.61 (s, arom CH of C6H4), 125.15 (s, arom CH of C6H4), 122.70 (s, arom CH of C6H4), 59.37 (s, C(CH3)2CH2C(CH3)), 50.95 (s, C(CH3)2CH2C(CH3)), 43.02 (s, C(CH3)2CH2C(CH3)), 31.03 (s, C(CH3)2CH2C(CH3)), 30.82 (s, C(CH3)2CH2C(CH3)), 30.52 (s, C(CH3)2CH2C(CH3)) ppm.

3.2.3. Tribenzo–Pentaphene Derivative

Rf: 0.10 pentane/CH2Cl2: 98/2 v/v; 1H NMR (500 MHz, CDCl3): δ = 8.44 (d, 1H, arom CH, CHo, 3JHH = 12.0 Hz), 8.18 (s, 1H, arom CH, CHs), 8.02 (d, 1H, arom CH, CHr, 3JHH = 11.5 Hz), 7.71 (d, 1H, arom CH, CHn, 3JHH = 7.5 Hz), 7.70 (d, 1H, arom CH, CHk, 3JHH = 7.5 Hz), 7.68–7.65 (m, 1H, arom CH, CHt), 7.59–7.55 (m, 1H, arom CH, CHp), 7.51–7.48 (m, 1H, arom CH, CHq), 7.43 (s, 1H, arom CH, CHj), 7.32–7.29 (m, 1H, arom CH, CHl), 7.29–7.26 (m, 1H, arom CH, CHm), 7.21–7.19 (m, 1H, arom CH, CHv), 7.19–7.17 (m, 1H, arom CH, CHu), 7.02 (d, 1H, arom CH, CHi, 3JHH = 10.0 Hz), 6.68 (dd, 1H, arom CH, CHh, 3JHH = 9.5 Hz, 3JHH = 6.0 Hz), 4.97–4.92 (m, 1H, CHe), 4.22 (dd, 1H, CHf, 3JHH = 8.0 Hz, 3JHH = 8.0 Hz), 3.88 (dd, 1H, CHg, 3JHH = 6.7 Hz, 3JHH = 6.7 Hz), 3.26–3.19 (m, 1H, CHa), 2.32 (ddd, 1H, CHc, 2JHH = 14.5 Hz, 3JHH = 6.0 Hz, 3JHH = 5.5 Hz), 2.06 (ddd, 1H, CHd, 2JHH = 14.5 Hz, 3JHH = 9.0 Hz, 3JHH = 4.5 Hz), 1.40 (d, 3H, CHb)3, 3JHH = 7.0 Hz); 13C{1H} NMR (126 MHz, CDCl3): δ = 138.25, 136.94, 134.24, 132.68, 132.28, 132.27, 131.08, 130.91, 130.41, 129.18 and 128.79 (11s, arom Cquat), 130.55 (s, CHh=CHi), 130.01 (s, CHh=Chi), 129.44, 128.43, 126.22, 125.15, 125.11, 125.04, 124.96, 124.81, 124.53, 124.49, 124.08, 123.93 and 121.47 (13s, arom CH), 40.20 (s, C(Hc)(Hd)), 37.91 (s, CHg), 37.41 (s, CHf), 32.49 (CHe), 28.01 (s, CHa), 20.73 (s, C(Hb)3) ppm. MS (ESI-TOF): m/z = 408.19 [M]+ (expected isotopic profiles) as shown in Figure 6.

4. Conclusions

The commercially available neutral complex [PdCl2(cod)] was found to be encapsulated within a self-assembled capsule formed from 2,8,14,20-tetra-undecyl-resorcin[4]arene and water. The inclusion complex catalyzed the dimerization of styrene derivatives with a low catalyst loading under mild conditions. This catalytic system necessitates the combination of the palladium complex and the supramolecular capsule, which was able to activate the organometallic precursor with the structural water molecules.
The dimerization reaction of vinyl arenes is acutely sensitive to the steric hindrance of the substrate and the electronic density of the double bond. In the case of electron-rich olefins, a rearrangement of the dimerization products into the formation of indane or tribenzo–pentaphene derivatives is observed.
The reactivity of the inclusion complex could be further exploited in olefin isomerization, a reactivity observed in the case of aliphatic alkenes, to enable, for example, internal olefins to form aldehydes via a Claisen rearrangement [47].

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/catal15060585/s1, Figure S1. DOSY NMR of palladium complex 6; characterizing data of (E)-but-1-ene-1,3-diyldibenzene (3a) with Figure S2. 1H NMR spectrum and Figure S3. 13C{1H} NMR spectrum; characterizing data of (E)-4,4′-(but-1-ene-1,3-diyl)bis(chlorobenzene) (3b) with Figure S4. 1H NMR spectrum and Figure S5. 13C{1H} NMR spectrum; characterizing data of (E)-4,4′-(but-1-ene-1,3-diyl)bis(fluorobenzene) (3c) with Figure S6. 1H NMR spectrum, Figure S7. 13C{1H} NMR spectrum and with Figure S8. 19F{1H} NMR spectrum; characterizing data of (E)-4,4′-(but-1-ene-1,3-diyl)bis(methylbenzene) (3d) with Figure S9. 1H NMR spectrum and Figure S10. 13C{1H} NMR spectrum; characterizing data of 5-(tert-butyl)-3-(4-(tert-butyl)phenyl)-1-methyl-2,3-dihydro-1H-indene (7e) with Figure S11. 1H NMR spectrum and Figure S12. 13C{1H} NMR spectrum; characterizing data of 1,1,3-trimethyl-3-phenyl-2,3-dihydro-1H-indene (7f) with Figure S13. 1H NMR spectrum and Figure S14. 13C{1H} NMR spectrum; characterizing data of 11-methyl-3b,3b1,12,12a-tetrahydro-11I-tribenzo[a,de,rst]pentaphene (8) with Figure S15. 1H NMR spectrum, Figure S16. 13C{1H} NMR spectrum, Figure S17. Mass spectrum (ESI-TOF), Figure S18. Mass spectrum (ESI-TOF) and X-Ray Crystal Structure Analysis of 8 with Figure S19. ORTEP, Table S1. Crystal data and structure refinement parameters [48,49], Table S2. Lengths (Å) and Table S3. Angles (°); Catalyzed formation of indane with Figure S20. 1H NMR spectrum (CDCl3) of a mixture of compounds 7f, 9 and 10 [40,50]; Experiments with D2O instead of H2O with Figure S21. Selected zone of 1H NMR spectrum of dimerization of styrene carried out with H2O (top) and D2O (bottom), Figure S22. Selected zone of 1H NMR spectrum of the formation of 5-(tert-butyl)-3-(4-(tert-butyl)phenyl)-1-methyl-2,3-dihydro-1H-indene (7e) carried out with H2O (top) and D2O (bottom), Figure S23. Selected zone of 1H NMR spectrum of the formation of 1,1,3-trimethyl-3-phenyl-2,3-dihydro-1H-indene (7f) carried out with H2O (top) and D2O (bottom) and Figure S24. Selected zone of 1H NMR spectrum of the formation of 11-methyl-3b,3b1,12,12a-tetrahydro-11H-tribenzo[a,de,rst]pentaphene (8) carried out with H2O (top) and D2O (bottom); Synthesis of 4,4′,4″-((4-vinylphenyl)methanetriyl)tris(bromobenzene) (1h) with Figure S25. 1H NMR spectrum and Figure S26. 13C{1H} NMR spectrum.

Author Contributions

Conceptualization, M.S. and D.S.; methodology, M.S. and D.S.; validation, D.S.; formal analysis, M.S.; investigation, M.S.; resources, D.S.; data curation, M.S. and D.S.; writing—original draft preparation, M.S.; writing—review and editing, D.S.; supervision, D.S. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The data presented in this study are available upon request from the corresponding authors.

Acknowledgments

M.S. thanks M.R.T. for the research fellowship. This work was supported by the Agence Nationale de la Recherche (HEXCAPS Programme, ANR-24-CE07-1738).

Conflicts of Interest

The authors declare no conflicts of interest.

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Catalysts 15 00585 sch001
Scheme 1. Vinyl arenes dimerization.
Scheme 1. Vinyl arenes dimerization.
Catalysts 15 00585 sch001
Catalysts 15 00585 sch002
Scheme 2. Dynamic self-assembled resorcinarenyl capsule 56.
Scheme 2. Dynamic self-assembled resorcinarenyl capsule 56.
Catalysts 15 00585 sch002
Catalysts 15 00585 g001
Figure 1. 1H NMR study of: (a) 6; (b) 6⊂56 and (c) after addition of NEt4Cl (signals from 6 labeled x) to 6⊂56.
Figure 1. 1H NMR study of: (a) 6; (b) 6⊂56 and (c) after addition of NEt4Cl (signals from 6 labeled x) to 6⊂56.
Catalysts 15 00585 g001
Catalysts 15 00585 g002
Figure 2. DOSY spectrum of the inclusion complex 6⊂56.
Figure 2. DOSY spectrum of the inclusion complex 6⊂56.
Catalysts 15 00585 g002
Catalysts 15 00585 g003
Figure 3. UV-visible absorption spectra of free complex 6 ([6] = 0.3 mM) (green); inclusion complex 6⊂56 ([5] = 2.0 mM) (blue); and after addition of NEt4Cl ([NEt4Cl] = 1.5 mM) (red).
Figure 3. UV-visible absorption spectra of free complex 6 ([6] = 0.3 mM) (green); inclusion complex 6⊂56 ([5] = 2.0 mM) (blue); and after addition of NEt4Cl ([NEt4Cl] = 1.5 mM) (red).
Catalysts 15 00585 g003
Catalysts 15 00585 sch003
Scheme 3. Dimerization of vinyl arenes catalyzed by the inclusion complex 6⊂56.
Scheme 3. Dimerization of vinyl arenes catalyzed by the inclusion complex 6⊂56.
Catalysts 15 00585 sch003
Catalysts 15 00585 g004
Figure 4. Dimerization kinetics of styrene (1a): conversion of 1a in red and formation of dimerization product 3a in green. Conditions: [PdCl2(cod)] (1.1 mg, 1 mol%), capsule 56 (28.7 mg, 1.1 mol%), styrene 1a (46 μL, 0.4 mmol), CHCl3 saturated with H2O (1 mL), 60 °C. Determined by 1H NMR after addition of CH2Br2 (7 μL, 0.1 mmol) as internal standard.
Figure 4. Dimerization kinetics of styrene (1a): conversion of 1a in red and formation of dimerization product 3a in green. Conditions: [PdCl2(cod)] (1.1 mg, 1 mol%), capsule 56 (28.7 mg, 1.1 mol%), styrene 1a (46 μL, 0.4 mmol), CHCl3 saturated with H2O (1 mL), 60 °C. Determined by 1H NMR after addition of CH2Br2 (7 μL, 0.1 mmol) as internal standard.
Catalysts 15 00585 g004
Catalysts 15 00585 g005
Figure 5. Hanes–Wolf plot.
Figure 5. Hanes–Wolf plot.
Catalysts 15 00585 g005
Catalysts 15 00585 sch004
Scheme 4. Formation of indanes (a) 7e and (b) 7f.
Scheme 4. Formation of indanes (a) 7e and (b) 7f.
Catalysts 15 00585 sch004
Catalysts 15 00585 sch005
Scheme 5. Formation of tribenzo–pentaphene 8.
Scheme 5. Formation of tribenzo–pentaphene 8.
Catalysts 15 00585 sch005
Catalysts 15 00585 sch006
Scheme 6. Postulated reaction mechanism for the dimerization of vinyl arenes.
Scheme 6. Postulated reaction mechanism for the dimerization of vinyl arenes.
Catalysts 15 00585 sch006
Catalysts 15 00585 sch007
Scheme 7. Proposed mechanism for the formation of indanes (a) (7e and 7f) and (b) tribenzo–pentaphene (8).
Scheme 7. Proposed mechanism for the formation of indanes (a) (7e and 7f) and (b) tribenzo–pentaphene (8).
Catalysts 15 00585 sch007
Catalysts 15 00585 g006
Figure 6. 11-Methyl-3b,3b1,12,12a-tetrahydro-11H-tribenzo[a,de,rst]pentaphene (8).
Figure 6. 11-Methyl-3b,3b1,12,12a-tetrahydro-11H-tribenzo[a,de,rst]pentaphene (8).
Catalysts 15 00585 g006
Table 1. Control experiments 1.
Table 1. Control experiments 1.
EntryComplex 6Capsule 56AdditiveConversion (%) 2Products Distribution (%) 2
3aOligomers
1yesyesno723862
2nonono0//
3noyesno0//
4yesnono0//
5yesnoAcOH 3traces//
6yesyesDMSO 40//
7yesyesNEt4Cl 50//
8yesyesD2O 6803565
1 Conditions: styrene 1a (46 μL, 0.4 mmol), [PdCl2(cod)] (6; 1.1 mg, 1 mol%), capsule 56 (28.7 mg, 1.1 mol%), CHCl3 saturated with H2O (1 mL), 24 h, 60 °C. 2 Determined by 1H NMR after addition of CH2Br2 (7 μL, 0.1 mmol) as internal reference. 3 Solution of AcOH (4 μM, 1 mol%) in CHCl3 saturated with H2O as solvent. 4 DMSO (100 μL, 10% v/v). 5 NEt4Cl (2 mg, 5 mol%). 6 CHCl3 saturated with D2O as solvent (1 mL).
Table 2. Influence of the catalyst loading 6⊂56 1.
Table 2. Influence of the catalyst loading 6⊂56 1.
EntryLoading of 6⊂56 (Mol%)Time (h)Conversion (%) 2Products Distribution (%) 2
3aOligomers
12 312882080
216932575
324952080
41 424723862
50.5 524604852
636824852
740874852
844902476
1 Conditions: [PdCl2(cod)] (6; 1.1 mg, 1 mol%), capsule 56 (28.7 mg, 1.1 mol%), CHCl3 saturated with H2O (1 mL), 60 °C; 2 determined by 1H NMR after addition of CH2Br2 (7 μL, 0.1 mmol) as internal reference; 3 styrene 1a (23 μL, 0.2 mmol); 4 styrene 1a (46 μL, 0.4 mmol); 5 styrene 1a (92 μL, 0.8 mmol).
Table 3. Vinyl arenes studied 1.
Table 3. Vinyl arenes studied 1.
EntryVinyl Arene (1)Time (h)Conversion (%) 2Products Distribution 2
Formed ProductsDegradation
1Catalysts 15 00585 i001(1b)40133b: 62%38%
272413b: 20%80%
3Catalysts 15 00585 i002(1c)40173c: 59%41%
472253c: 8%92%
5Catalysts 15 00585 i003(1d)24443d: 34% and 7d: traces66%
632753d: 28% and 7d: traces72%
7Catalysts 15 00585 i004(1e)40353e: traces and 7e: 91%9%
872573e: traces and 7e: 68%32%
9Catalysts 15 00585 i005(1f)24989: 7%, 10: 7% and 7f: 86%/
10401007f: 100%/
11Catalysts 15 00585 i006(1g)40955g: traces and 8: 50%50%
12Catalysts 15 00585 i007(1h)400//
13Catalysts 15 00585 i008(1i)400//
141-hexene 7290Isomers /
1 Conditions: [PdCl2(cod)] (6; 1.1 mg, 0.5 mol%), capsule 56 (28.7 mg, 0.54 mol%), substrate 1 (0.8 mmol), CHCl3 saturated with H2O (1 mL), 60 °C. 2 Determined by 1H NMR after addition of CH2Br2 (14 μL, 0.2 mmol) as internal reference.
Table 4. H2O versus D2O 1.
Table 4. H2O versus D2O 1.
EntryVinyl Arene (1)WaterConversion (%) 2Deuterium
Incorporation		Products Distribution 2
Formed ProductsDegradation
1Catalysts 15 00585 i009(1e)H2O35/7e: 91% (cis/trans: 60/40)9%
2D2O27No7e: 89% (cis/trans: 60/40)11%
3Catalysts 15 00585 i010(1f)H2O100/7f: 100%/
4D2O98No7f: 100%/
5Catalysts 15 00585 i011(1g)H2O95/5g: traces and 8: 50%50%
6D2O98No5g: traces and 8: 54%46%
1 Conditions: [PdCl2(cod)] (6; 1.1 mg, 0.5 mol%), capsule 56 (28.7 mg, 0.54 mol%), substrate 1 (0.8 mmol), CHCl3 saturated with H2O or D2O (1 mL), 60 °C. 2 Determined by 1H NMR after addition of CH2Br2 (14 μL, 0.2 mmol) as internal reference.
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Steinmetz, M.; Sémeril, D. Confined Catalysis Involving a Palladium Complex and a Self-Assembled Capsule for the Dimerization of Vinyl Arenes and the Formation of Indane and Tribenzo–Pentaphene Derivatives. Catalysts 2025, 15, 585. https://doi.org/10.3390/catal15060585

AMA Style

Steinmetz M, Sémeril D. Confined Catalysis Involving a Palladium Complex and a Self-Assembled Capsule for the Dimerization of Vinyl Arenes and the Formation of Indane and Tribenzo–Pentaphene Derivatives. Catalysts. 2025; 15(6):585. https://doi.org/10.3390/catal15060585

Chicago/Turabian Style

Steinmetz, Maxime, and David Sémeril. 2025. "Confined Catalysis Involving a Palladium Complex and a Self-Assembled Capsule for the Dimerization of Vinyl Arenes and the Formation of Indane and Tribenzo–Pentaphene Derivatives" Catalysts 15, no. 6: 585. https://doi.org/10.3390/catal15060585

APA Style

Steinmetz, M., & Sémeril, D. (2025). Confined Catalysis Involving a Palladium Complex and a Self-Assembled Capsule for the Dimerization of Vinyl Arenes and the Formation of Indane and Tribenzo–Pentaphene Derivatives. Catalysts, 15(6), 585. https://doi.org/10.3390/catal15060585

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