Electronic and steric effects of substituents in 1,3-diphenylprop-2-yn-1-one during its reaction with Ru₃(CO)₁₂

Abstract

Thermal reaction of Ru₃(CO)₁₂ with alkynyl ketones PhC≡CC(O)R (R=Ph (1); 2-Cl-Ph (2); 4-NO₂-Ph (3); 2-NH₂-Ph (4); and 2-CH₃COO-Ph (5)) proceeds in toluene with the formation of Ru₃(CO)₉(μ-CO)(η⁴-triruthenium) derivatives (1a–5a), Ru(CO)₃(η⁴-ruthenole) derivatives (1b–4b, 1c–5c and 4d) and cyclotrimerization products (1e–2e and 1f–3f). Compounds 1a–5a were isolated from the reaction of Ru₃(CO)₁₂ with one equivalent of 1–5, respectively. Ruthenoles 1b–3b and 1c–3c were collected by adding 1–3 to the corresponding 1a–3a in a molar ratio of 1 : 1. Cyclotrimerization products 1e–2e and 1f–3f were obtained when 1–3 were added to their corresponding 1b–2b and 1c–3c, respectively. 4b, 4c and 4d were afforded during the reaction of 4 with 4a, but only 5c was collected during the reaction of 5 with 5a. All compounds were characterized by NMR, FT-IR, and MS-ESI and most of them were structurally confirmed by single crystal X-ray diffraction. The results suggest that electronic and steric effects of the substituents in the phenyl ring of 1,3-diphenylprop-2-yn-1-one play important roles in regulating the reaction pathways. An electron-withdrawing group is beneficial to the formation of b, c and further formation of e and f; an electron-donating group favors the production of ruthenoles b, c and d, but disfavors the formation of e and f; a substituent with large steric-hindrance prefers only the formation of c.

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Introduction

Ru₃(CO)₁₂ has attracted the great interest of researchers in inorganic, organic and catalytic chemistry due to its abundant reactivity and unique catalytic activity.¹ It has been highly effective in the activation and conversion of chemical bonds in the construction of diverse C–X (X = C, N, O, Si, etc.) bonds,² and widely used in reactions such as hydroamination,³ hydroesterification,⁴ silylation,⁵ cycloaddition,⁶ transfer hydrogenation,⁷ carbonylation⁸ and hydrohydroxyalkylation.⁹ In order to understand the mechanisms of Ru₃(CO)₁₂ activated C–C and C–H bonds, reactions of Ru₃(CO)₁₂ with NHCs, arenes, alkenes and alkynes were extensively investigated.¹⁰ Some carbonyl ruthenium compounds formed via Ru₃(CO)₁₂ and unsaturated hydrocarbons have been used in catalytic systems.¹¹ In these reactions, coordination atoms play a very important role in the activation of neighboring chemical bonds and construction of compound skeletons,¹² such as the interaction between oxygen atoms and ruthenium atoms in the activation of open-cage fullerenes with ruthenium carbonyl clusters.¹³ These conclusions provide more possibilities for Ru₃(CO)₁₂ to become a potential catalyst for the conversion of alkyne compounds.

The reactions of Ru₃(CO)₁₂ with alkynes have been studied for many years. A variety of coordination modes were reported.¹⁴ There are usually relevant to many catalytic processes involving polynuclear species and unsaturated organic molecules.¹⁵ In 2005, compound (μ-H)₂Ru₃(CO)₉{μ₃-η²[H₂C=C(H)C≡CC(=O)OCH₃]} was isolated by the activation of methanol and CO in the reaction of 1,4-dichloro-but-2-yne (DCB) and Ru₃(CO)₁₂.¹⁶ Then, two types of complexes Ru₃(CO)₉(μ-CO){μ₃-η²-(‖)-HC≡CR} and Ru₃(CO)₉(μ-CO){μ₃-η²-(⊥)-HC≡CR}(R=C₆H₄-4-CH₃, C₆H₃-2,5-(CH₃)₂, etc.) were collected by M. Hernandez-Sandoval in the reaction of activated cluster [Ru₃(CO)₁₀(NCMe₃)₂] with terminal alkynes.¹⁷ Recently, P. Mathur demonstrated that one C≡C bond of FcC₂C₂Ph (Fc = ferrocenyl) was activated by Ru₃(CO)₁₂, and a series of novel mixed Ru/Pt clusters were isolated.¹⁸ In general, the reaction of Ru₃(CO)₁₂ with functionalized acetylenes can afford a variety of unexpected products,¹⁹ that means alkyne ligands always experienced sophisticated transformations, these properties limited our understanding on activation of C≡C bonds.

Alkynyl ketones are important structural units with unsaturated functional groups. They are often employed as key templates in modern chemical synthesis.²⁰ The C≡C bonds of ynones are good π-acceptors,²¹ whilst the adjacent carbonyl groups can coordinate as 2e σ donors.²² For understanding the reactive activity of 1,3-ynones with Ru₃(CO)₁₂, thermolytic reaction of Ru₃(CO)₁₂ with 1-(4-methoxyphenyl)-3-phenylprop-2-yn-1-one have been investigated systematically in our group, and a series of Ru₂–Ru₄ framework clusters including a triruthenium and a tetraruthenium intermediates and three ruthenoles were isolated.²³ After a detailed analysis of the results, we proposed that the electron-donating methoxy group in the phenyl ring of the 1-(4-methoxyphenyl)-2-propyn-1-one may play an important role in the transformation reaction. As a continuing work in the chemistry of Ru₃(CO)₁₂ with alkynyl ketones, we investigated the electronic and steric effects of the substituents in the phenyl ring of 1,3-diphenylprop-2-yn-1-one on the structures of the intermediates and final products during its thermolytic reactions with Ru₃(CO)₁₂.

In this paper, we examined in detail the reaction process of Ru₃(CO)₁₂ with 1,3-diphenylprop-2-yn-1-one derivatives (1–5) containing in its phenyl ring, for example, no substituent (1), electron-withdrawing groups (2–3), an electron-donating group (4) and a sterically hindered group (5). The coordination and coupling of the alkynyl ketone molecules formed a series of intermediate ruthenium clusters and cyclotrimerization products. Through a detailed examination of the reaction processes, we revealed that substituents in the phenyl rings of the acetylenic ketones are vital for the reaction process and that the formation of products has been affected comprehensively by the steric hindrance and/or electronic properties of the substituents.

Results and discussion

Syntheses and characterization

Reactions of Ru₃(CO)₁₂ and the 1,3-ynones were performed in toluene at 90 °C under nitrogen atmosphere and monitored consistently by TLC technique. It was found that color of each reaction solution gradually changed from orange to red-brown and the non-reacted Ru₃(CO)₁₂ precipitated after cooling. All isolated compounds were completely characterized by FT-IR, NMR, ESI mass spectrometry and most of them were additionally characterized by single crystal X-ray diffraction. The reaction process is illustrated in Scheme 1 according to the experimental results and TLC technique as well as the structural characterization analyses.

Scheme 1 The reaction process of Ru₃(CO)₁₂ with 1,3-ynones (1–5). R=Ph (1); 2-Cl-Ph (2); 4-NO₂-Ph (3); 2-NH₂-Ph (4); 2-CH₃COO-Ph (5).

Synthesis of Ru₃(CO)₉(μ-CO)(η⁴-triruthenium) derivatives 1a–5a

When a toluene solution of an 1,3-ynone (1–5) (0.03 mmol) and Ru₃(CO)₁₂ (0.01 mmol) was stirred at 90 °C for 30 min under nitrogen atmosphere, Ru₃(CO)₉(μ-CO)(η⁴-triruthenium) derivatives (1a–5a) were formed due to binding of the C≡C bonds of 1–5 and the Ru metal skeletons. Each of the new clusters has a similar structural framework according to the characterization results and the crystal structure of 5a is shown in Fig. 1 was taken as an example. The IR spectrum of 5a was similar to those observed in the compounds M₃(CO)₉(μ-CO)L (M = Ru, Os).^23,24 The absorption bands peaked in the range of 2017–2104 cm⁻¹ and at 1878 cm⁻¹ were assigned to the terminal and bridging CO groups, respectively. The dramatic red shift of the stretch vibration of the C≡C bond in 5a from 2191 cm⁻¹ to ca. 1446 cm⁻¹ reveals further that the coordination interaction between the carbon atoms of the C≡C bond and the Ru central metals is very strong. The chemical shifts of the C≡C bond moved downwards to 150.8 and 148.2 ppm, confirming again the strong interaction between the C≡C bond and the Ru atoms. The chemical shifts of the carbonyl carbon atoms directly with Ru atoms cannot be distinguished, indicating that in solution there are fluxional for the terminal and bridging CO on the ¹³C{1H} NMR time scale.

Fig. 1 ORTEP view of cluster 5a showing 50% ellipsoids. Selected bond lengths (Å) and bond angles (°): Ru1–Ru2 = 2.845(2); Ru2–Ru3 = 2.712(2); Ru1–Ru3 = 2.749(2); Ru1–C19 = 1.939(3); Ru1–C21 = 2.029(2); Ru1–C10 = 2.126(2); Ru2–C11 = 2.091(2); Ru2–C21 = 2.337(2); Ru3–C11 = 2.317(2); Ru3–C10 = 2.211(2); Ru3–C19 = 2.873(2); C10–C11 = 1.396(3); C9–C10 = 1.498(3); C9–O3 = 1.219(2); C19–O5 = 1.337(3); C21–O7 = 1.149(3); Ru1–C19–Ru3 = 66.4(1); Ru1–C21–Ru2 = 81.0(1).

The compound 5a consists of a triangular arrangement of the ruthenium atoms, in which the Ru–Ru bond distances are in the range of 2.712(2)–2.845(2) Å. The coordination of the alkynyl ketone (5) with Ru3 is in a η² mode, but with Ru1 and Ru2 is in a η¹ mode. The C10–C11 bond length is 1.396(3) Å, located between the typical C–C single bond and double bond, indicative again of the strong coordination strength of the Ru–C bonds.²⁵ The distances of Ru1–C19 and Ru3–C19 are 1.939(3) and 2.873(2) Å, respectively. The angle of Ru1–C19–O5 is 169.2(2)°. In addition, there is a carbonyl exists between Ru1 and Ru3 atoms.

Synthesis of Ru(CO)₃(η⁴-ruthenole) derivatives 1b–4b, 1c–5c and 4d

When the reaction time of the above reaction was prolonged from 0.5 h to 1 h, Ru(CO)₃(η⁴-ruthenole) derivatives b (1b–4b), c (1c–5c) and d (4d) were separated by flash chromatography. The structural characterizations showed that structures of the new ruthenoles are of diverse coupling combinations of the C≡C units in the 1,3-ynones, such as modes b (head to tail coupling), c (head to head coupling) and d (tail to tail coupling).²³ Each ruthenole contains a metallacyclopentadienyl framework, which is alike in structure to the carbonyl complexes [M(CO)(η⁴-metallole)] (M = Fe, Ru, Os) formed by combination of alkynes with group 8 metals.^23,26 The molecular structure of 1b, as an example, was depicted in Fig. 2. The structure of 1b showed an eclipsed conformation of the carbonyls on the two ruthenium centers, with the dihedral angle of R1–Ru2–C35_plane and R1–Ru2–C32_plane being 2.1(1)°. The special arrangement geometrically prevents an apical carbonyl to be close enough to the ring metal Ru1 for a CO bridging conformation. Hence, all carbonyls are terminal with almost parallel Ru–C–O angle.

Fig. 2 ORTEP view of cluster 1b showing 50% ellipsoids. Selected bond lengths (Å) and bond angles (°): Ru1–Ru2 = 2.734(2), Ru1–C8 = 2.254(2), Ru1–C9 = 2.316(2), Ru1–C24 = 2.243(2), Ru1–C23 = 2.252(2), Ru2–C9 = 2.098(2), Ru2–C23 = 2.068(2), C7–C8 = 1.515(3), C7–O1 = 1.214(2), C8–C9 = 1.411(3), C8–C24 = 1.458(3), C23–C24 = 1.420(3), C22–C23 = 1.491(3), C22–O2 = 1.217(2), C9–Ru2–C23 = 77.6(1), Ru1–C32–O4 = 177.0(2), Ru2–C35–O7 = 179.6(2).

Compared the structures of b and c, each of the crystal structures of ruthenoles c (taking 2c·1/2C₆H₁₄ shown in Fig. 3 as an example) appeared a routine staggered conformation of the carbonyls. The dihedral angles between Ru1–Ru2–C35_plane and Ru1–Ru2–C31_plane, Ru1–Ru2–C32_plane are 58.4(2)° and 41.0(2)°, respectively. The distances of Ru1–C35 is 2.742(5) Å. The staggered orientation in 2c·1/2C₆H₁₄ allows the C35 close to the Ru1 metal for a weak interaction, which formed a semi-bridging carbonyl across the Ru–Ru bond. The IR absorption at 1944 cm⁻¹ also confirms its presence.

Fig. 3 ORTEP view of cluster 2c·1/2C₆H₁₄ showing 50% ellipsoids (solvent molecules have been omitted for clarity). Selected bond lengths (Å) and bond angles (°): Ru1–Ru2 = 2.712(1), Ru1–C8 = 2.097(4), Ru1–C23 = 2.096(5), Ru1–C35 = 2.742(5), Ru2–C8 = 2.223(4), Ru2–C9 = 2.300(5), Ru2–C23 = 2.232(5), Ru2–C24 = 2.310(5), Ru2–C35 = 1.908(5), C7–C8 = 1.496(7), C7–O1 = 1.213(7), C8–C9 = 1.436(6), C9–C24 = 1.435(7), C23–C24 = 1.440(5), C22–C23 = 1.495(7), C22–O2 = 1.215(5), C8–Ru1–C23 = 53.2(1), Ru2–C35–O7 = 169.7(4), Ru2–C35–Ru1 = 68.7(1).

The crystal structure of 4d·3/4CH₂Cl₂ (Fig. 4) also showed an eclipsed conformation of carbonyls on the two ruthenium centers, the dihedral angle of R1–Ru2–C35_plane and R1–Ru2–C33_plane is 1.0(1)° between the equatorial Ru2–CO and Ru1–CO bonds, indicating that the Ru1, Ru2, C33 and C35 atoms are almost coplanar. All carbonyls are terminal with almost linear Ru–C–O angle, similar to those in compounds 1b–4b.

Fig. 4 ORTEP view of cluster 4d·3/4CH₂Cl₂ showing 50% ellipsoids (solvent molecules have been omitted for clarity). Selected bond lengths (Å) and bond angles (°): Ru1–Ru2 = 2.704(4), Ru1–C9 = 2.085(3), Ru1–C24 = 2.083(3), Ru2–C9 = 2.319(4), Ru2–C8 = 2.224(3), Ru2–C23 = 2.234(2), Ru2–C24 = 2.339(3), C7–C8 = 1.518(5), C7–O1 = 1.227(5), C8–C9 = 1.417(5), C8–C23 = 1.460(5), C23–C24 = 1.412(5), C22–C23 = 1.523(5), C22–O2 = 1.233(5), C9–Ru1–C24 = 79.2(1), Ru1–C33–O5 = 176.9(3), Ru2–C35–O7 = 174.8(4).

Synthesis of the cyclotrimerization products e (1e–2e) and f (1f–3f)

When Ru₃(CO)₁₂ (0.1 mmol) reacted with 3 equivalent of an 1,3-ynone (1–3) (0.3 mmol) in toluene (90 °C) for 2 h under nitrogen atmosphere, two types of cyclotrimerization products e (1e–2e) and f (1f–3f) were formed. The structures of 1e and 3f·CH₂Cl₂ are illustrated in Fig. 5, taking as examples. The reaction of Ru₃(CO)₁₂ with 4 or 5 afforded, however, no cyclotrimerization products in the same reaction conditions and even extended the reaction time. M. Kawatsura also isolated the alkyne cyclotrimerization products using Ru₃(CO)₁₂ as catalyst.^11c

Fig. 5 ORTEP view of cluster 1e (left) and 3f·CH₂Cl₂ (right) showing 50% ellipsoids (solvent molecules have been omitted for clarity). Selected bond lengths (Å) and bond angles (°): 1e (the left): C1–C2 = 1.403(3), C2–C3 = 1.405(2), C3–C4 = 1.400(2), C4–C5 = 1.409(3), C5–C6 = 1.403(3), C1–C6 = 1.398(2), C1–C7 = 1.519(3), C3–C20 = 1.516(3), C6–C39 = 1.513(3), C7–O1 = 1.220(2), C20–O2 = 1.222(3), C39–O3 = 1.222(3). 3f·CH₂Cl₂ (the right): C1–C2 = 1.399(5), C2–C3 = 1.399(6), C3–C4 = 1.397(4), C4–C5 = 1.398(5), C5–C6 = 1.402(6), C1–C6 = 1.399(4), C1–C7 = 1.507(6), C3–C20 = 1.512(6), C5–C33 = 1.505(4), C7–O1 = 1.217(5), C20–O4 = 1.208(5), C33–O = 1.215(4).

Step-wise conversion from ynones to final products

To clarify the formation process of the products at each step, the reaction of Ru₃(CO)₁₂ with ynones 1–5 were studied in detail and monitored by TLC technique. It was observed that the triruthenium clusters 1a–5a are unstable, decomposing slowly in toluene. The mixing of 1a–5a with Ru₃(CO)₁₂ in toluene did not give any new ruthenium clusters. By adding the corresponding 1,3-ynones 1–3 in the clusters 1a–3a in toluene at 90 °C, ruthenoles b (1b–3b) and c (1c–3c) were detected. If 4 was added in 4a in toluene, three ruthenoles 4b, 4c and 4d were found. However, the addition of 5 in 5a in toluene only 5c was monitored. Compared with our previous work,²³ no corresponding tetraruthenium clusters were detected in the reaction, however. It is possible that the corresponding tetraruthenium clusters is extremely unstable in the reaction system and cannot be found. The formation of the diverse ruthenoles through reaction of the triruthenium clusters a with the corresponding 1,3-ynones justify that the triruthenium cluster a is the key intermediates in the generation of ruthenoles.

Then reactions of the ruthenoles with the corresponding ynones were studied to explore how the cyclotrimerization products e and f were formed. It was found that e (1e–2e) was detected when ruthenoles 1c and 2c were mixed with 1 and 2, respectively, in toluene at 90 °C. The cyclotrimerization products 1f–3f were found in the reaction of ruthenoles 1b–3b with the corresponding 1–3, respectively. Therefore, we believed that ruthenoles are intermediates during the formation of the cyclotrimerization products.

The electronic effect of substituents on the acetylene cyclotrimerization has been reported by T. Takahashi.²⁷ He found that acetylenes with electron-withdrawing groups (CN, CONMe₂ or COPh) could be used for cycloaddition reaction, and unactivated alkynes such as 4-octyne did not give the desired benzene derivatives even at higher temperature.²⁷ According to the explanation of T. Takahashi, 1,3-diphenylprop-2-yn-1-one is an electron-withdrawing group activated alkyne, so it is feasible that the reaction of 1 with the corresponding ruthenole can afford the cyclotrimerization products 1e and 1f. Therefore, it is easier that 2e, 2f and 3f can be produced in the similar reactions. Compound 4 is a derivative of 1 with a strong electron-donating group in the phenyl ring, which weakens the reactivity of 4 in the cyclotrimerization reaction. However, an electron-donating group in the phenyl ring of 1 favors the formation of ruthenole d, which can explain the formation of 4d and a similar compound we reported previously.²³ An ortho-acetyl group in the phenyl ring of 5 has certain electron-withdrawing ability, but its larger steric hindrance results in the forming of 5c as the unique ruthenole in the reaction of 5a with 5, and this strong steric effect further prevents the formation of cyclotrimerization products.

Experimental

Materials and equipment

All reactions and manipulations were performed using standard Schlenk line techniques under dry nitrogen. Ru₃(CO)₁₂ and the 1,3-ynones were synthesized according to the literature procedure.²⁸ Solvents were purified, dried and distilled under nitrogen atmosphere prior to use. FT-IR spectra were recorded on a Bruker Tensor 27 Fourier-transform spectrometer. ¹H and ¹³C{1H} NMR spectra were performed on a Bruker Avance 400 MHz spectrometer unless indicated. ESI was recorded on a Thermo DecaMax (LC-MS) mass spectrometer with an ion-trap mass detector. While high-resolution mass spectra were recorded in ESI mode on a Waters UPLC-Q-TOF mass spectrometer. The structural measurements of single crystals were carried out with a Bruker SMART APEX-II CCD detector.

Synthesis

1,3-diphenylprop-2-yn-1-one (1), 1-(2-chloro-phenyl)-3-phenylprop-2-yn-1-one (2), 1-(4-nitro-phenyl)-3-phenylprop-2-yn-1-one (3), 1-(2-amino-phenyl)-3-phenylprop-2-yn-1-one (4) and 2-(3-phenylpropioloyl)phenylacetate (5) were used to react with Ru₃(CO)₁₂. Since the reaction processes are similar, the reaction procedure of 1 with Ru₃(CO)₁₂ was taken as an example. Both 1 (0.1856 g, 0.9 mmol) and Ru₃(CO)₁₂ (0.1918 g, 0.3 mmol) were added in 15 mL toluene and heated at 90 °C for 0.5 h, during which the color of the reaction solution gradually changed from orange to red-brown. The solvent was removed and the residue was chromatographed (the chromatographic column is of 305 mm length and 32 mm internal diameter) on silica gel with dichloromethane and petroleum ether, five main products were eluted in the sequence of 1a, 1b, 1c, 1e and 1f, with the eluent dichloromethane/petroleum ether being (v/v) 1 : 5, 3 : 5, 1 : 1, 5 : 3 and 3 : 1, respectively. And then the products were recrystallized by dichloromethane and hexane.

[Ru₃(CO)₉(μ-CO)₂{μ₃-η¹:η²:η¹-(Ph)C(O)CC(Ph)}] (1a). Yield: 12%. FT-IR (KBr, cm⁻¹): 2923 vs, 2854 s, 2104 s, 2057 vs, 2002 s, 1882 m, 1461 w. ¹H NMR (400 MHz, CDCl₃) δ 7.62–7.64 (t, 2H, C₆H₅), 7.29–7.33 (m, 1H, C₆H₅), 7.20–7.24 (t, 2H, C₆H₅), 6.89–6.99 (m, 3H, C₆H₅), 6.82–6.84 (m, 2H, C₆H₅). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 195.8, 176.4 (CO), 162.6, 148.4 (C≡C), 132.8, 132.3, 129.9, 128.6, 128.3, 128.2, 127.7 (C₆H₅). MS (m/z, ESI−) 790.737 (M−). Anal. calcd for C₂₅H₁₀O₁₁Ru₃: 790.738.

[Ru(CO)₃{μ₄-η¹:η²:η¹:η¹-(PhC(O))CC(Ph)C(PhC(O))C(Ph)Ru (CO)₃}] (1b). Yield: 18%. FT-IR (KBr, cm⁻¹): 3074 m, 3028 m, 2958 w, 2927 w, 2858 w, 2090 vs, 2059 vs, 2023 vs, 1994 vs, 1488 vs. ¹H NMR (400 MHz, CDCl₃) δ 7.75–7.79 (t, 3H, C₆H₅), 7.27–7.49 (m, 6H, C₆H₅), 7.11–7.15 (m, 1H, C₆H₅), 6.90–7.01 (m, 10H, C₆H₅). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 196.5, 196.1, 195.8, 194.9, 193.8, 193.4, 192.4, 191.9 (CO), 181.9, 181.2, 145.9, 145.7 (C≡C), 135.5, 134.4, 134.1, 133.9, 133.6, 133.3, 132.8, 132.6, 130.2, 129.8, 129.7, 129.6, 129.1, 128.6, 128.4, 128.0, 127.9, 127.7, 127.6, 123.5 (C₆H₅). MS (m/z, ESI−) 783.926 (M−). Anal. calcd for C₃₆H₂₀O₈Ru₂: 783.925.

[Ru(CO)₃{μ₄-η¹:η²:η¹:η¹-(PhC(O))CC(Ph)C(Ph)C(PhC(O))Ru (CO)₃}μ-CO] (1c). Yield: 10%. FT-IR (KBr, cm⁻¹): 3026 w, 2923 vs, 2854 s, 2090 vs, 2061 vs, 2029 vs, 2000 vs, 1982 vs, 1448 m. ¹H NMR (400 MHz, CDCl₃) δ 7.83–7.85 (d, 3H, C₆H₅), 7.35–7.37 (d, 3H, C₆H₅), 7.26–7.30 (t, 4H, C₆H₅), 7.10–7.12 (d, 4H, C₆H₅), 6.86–6.93 (m, 6H, C₆H₅). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 197.2, 195.2, 195.0, 193.3 (CO), 169.9 (C≡C), 135.2, 134.2, 132.7, 131.5, 130.9, 130.0, 129.6, 129.4, 129.1, 128.8, 128.7, 128.3, 128.1, 127.8, 123.9, 121.3 (C₆H₅). MS (m/z, ESI−) 780.923 (M−). Anal. calcd for C₃₆H₂₀O₈Ru₂: 780.926.

1,3,4-Triphenyl-2,5,6-tribenzoylbenzene (1e). Yield: 27%. FT-IR (KBr, cm⁻¹): 3058 m, 3026 w, 1668 vs, 1446 m, 1213 vs. ¹H NMR (400 MHz, CDCl₃) δ 7.52–7.58 (m, 6H, C₆H₅), 7.26–7.35 (m, 3H, C₆H₅), 7.13–7.21 (m, 9H, C₆H₅), 6.73–7.05 (m, 12H, C₆H₅). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 198.0, 197.9, 197.3 (CO), 141.3, 140.8, 140.4, 139.2, 139.1, 137.7 (C₆), 137.6, 137.1, 136.9, 136.8, 136.2 (6× C₆C̲), 133.0, 132.8, 132.7, 131.0, 130.0, 129.6, 129.5, 129.4, 128.0, 127.8, 127.7, 127.6, 127.3, 127.1, 126.9 (C₆H₅). MS (m/z, ESI−) 618.219 (M−). Anal. calcd for C₄₅H₃₀O₃: 618.219.

1,3,5-Triphenyl-2,4,6-tribenzoylbenzene (1f·CH₂Cl₂). Yield: 30%. FT-IR (KBr, cm⁻¹): 3080 m, 3055 m, 3026 m, 1666 vs, 1446 s, 1238 vs. ¹H NMR (400 MHz, CDCl₃) δ 7.51 (s, 6H), 7.33 (s, 6H), 7.19 (s, 9H), 6.94 (s, 9H). ¹³C{1H} NMR (101 MHz, CDCl₃): δ 197.0 (CO), 139.9 (C₆), 137.8, 136.0 (2× C₆C̲), 132.9, 130.7, 129.3, 128.0, 127.7, 127.4 (C₆H₅). MS (m/z, ESI−) 618.219 (M−). Anal. calcd for C₄₅H₃₀O₃: 618.219.

[Ru₃(CO)₉(μ-CO)₂{μ₃-η¹:η²:η¹-(2-Cl-PhC(O))CC(Ph)}] (2a). Yield: 5%. FT-IR (KBr, cm⁻¹): 3064 w, 2958 w, 2923 m, 2852 w, 2102 vs, 2071 vs, 2025 vs, 1895 vs, 1645 vs. ¹H NMR (400 MHz, CDCl₃) δ 7.32–7.34 (d, 1H, C₆H₄), 6.97–7.18 (m, 6H, C₆H₄, C₆H₅), 6.85–6.87 (d, 2H, C₆H₅). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 195.7, 177.9 (CO), 162.2, 148.6 (C≡C), 135.1, 133.0, 132.0, 131.1, 131.0, 128.1 (C₆H₄), 127.9, 127.86, 126.4 (C₆H₅). MS (m/z, ESI−) 824.628 (M−). Anal. calcd for C₂₅H₉ClO₁₁Ru₃: 824.699.

[Ru(CO)₃{μ₄-η¹:η²:η¹:η¹-(2-ClPhC(O))CC(Ph)C(2-Cl-PhC(O))C(Ph)Ru(CO)₃}] (2b). Yield: 20%. FT-IR (KBr, cm⁻¹): 3060 w, 3028 w, 2954 m, 2925 m, 2852 m, 2123 m, 2092 vs, 2061 vs, 2025 vs, 1975 vs, 1664 s. ¹H NMR (400 MHz, CDCl₃) δ 7.69–7.70 (d, 1H, C₆H₄), 7.42–7.43 (d, 1H, C₆H₄), 6.97–7.16 (m, 8H, C₆H₄, C₆H₅), 6.66–6.92 (m, 8H, C₆H₄, C₆H₅). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 196.6, 196.4, 195.7, 194.6, 193.5, 190.7, 179.1, 178.6 (CO), 153.5, 146.0 (C≡C), 140.9, 135.0, 134.8, 134.6, 133.4, 133.2, 133.1, 133.0, 132.8, 132.2, 132.2, 131.4 (C₆H₄), 130.8, 130.6, 128.2, 128.1, 127.7, 127.5, 126.8, 125.7, 124.1, 123.9 (C₆H₄). MS (m/z, ESI−) 851.862 (M−). Anal. calcd for C₃₆H₁₈Cl₂O₈Ru₂: 851.847.

[Ru(CO)₃{μ₄-η¹:η²:η¹:η¹-(2-Cl-PhC(O))CC(Ph)C(Ph)C(2-Cl-Ph-C(O))Ru(CO)₃}μ-CO]·1/2C₆H₁₄ (2c·1/2C₆H₁₄). Yield: 11%. FT-IR (KBr, cm⁻¹): 3060 w, 2956 w, 2923 m, 2854 w, 2090 vs, 2063 vs, 2030 vs, 2000 vs, 1944 vs, 1656 s. ¹H NMR (400 MHz, CDCl₃) δ 7.71–7.73 (d, 2H, C₆H₄), 7.15–7.21 (m, 6H, C₆H₄), 7.03–7.15 (d, 4H, C₆H₅), 6.89–6.95 (m, 6H, C₆H₅). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 197.2, 195.0, 194.4, 193.1 (CO), 168.4 (C≡C), 135.5, 134.0, 133.4, 132.2, 131.6, 131.5 (C₆H₄), 130.2, 128.1, 127.7, 125.8 (C₆H₅). MS (m/z, ESI−) 851.845 (M−). Anal. calcd for C₃₆H₁₈Cl₂O₈Ru₂: 851.847.

1,3,4-Triphenyl-2,5,6-tris(2-chlorobenzoyl)benzene (2e). Yield: 7%. FT-IR (KBr, cm⁻¹): 3057 m, 3026 w, 2956 w, 2925 w, 2852 w, 1666 vs. ¹H NMR (400 MHz, CDCl₃) δ 7.46–7.49 (t, 2H, C₆H₄), 7.26–7.28 (d, 1H, C₆H₄), 6.93–7.08 (m, 12H, C₆H₄, C₆H₅), 6.79–6.85 (d, 12H, C₆H₄, C₆H₅). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 196.6, 196.5, 194.9 (CO), 142.6, 141.2, 141.0, 140.6, 139.4 (C₆), 137.7, 136.8, 136.5, 136.4, 136.1 (6× C₆C̲), 133.3, 133.1, 133.0, 132.8, 132.4, 132.3, 132.2, 131.6, 130.8, 130.4 (C₆H₄), 130.1, 129.5, 127.9, 127.7, 127.6, 127.4, 127.1, 127.0, 126.3, 126.0 (C₆H₅). MS (m/z, ESI−) 722.099 (M−). Anal. calcd for C₄₅H₂₇Cl₃O₃: 722.100.

1,3,5-Triphenyl-2,4,6-tris(2-chlorobenzoyl)benzene (2f). Yield: 24%. FT-IR (KBr, cm⁻¹): 3060 m, 2966 w, 2854 w, 1668 vs, 1224 vs. ¹H NMR (400 MHz, CDCl₃) δ 7.28–7.30 (d, 3H, C₆H₄), 6.93–7.19 (m, 24H, C₆H₄, C₆H₅). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 194.5 (CO), 140.8, 139.4, 136.6 (2× C₆C̲), 136.3, 133.0, 132.6, 132.0, 130.7 (C₆H₄), 129.9, 127.8, 127.7, 126.9, 126.3 (C₆H₅). MS (m/z, ESI−) 722.100 (M−). Anal. calcd for C₄₅H₂₇Cl₃O₃: 722.100.

[Ru₃(CO)₉(μ-CO)₂{μ₃-η¹:η²:η¹-(Ph)CC(4-NO₂-PhC(O))}] (3a). Yield: 7%. FT-IR (KBr, cm⁻¹): 2923 vs, 2854 s, 2059 m, 2017 m, 1460 m. ¹H NMR (400 MHz, CDCl₃) δ 8.05–8.10 (m, 2H, C₆H₄), 7.75–7.77 (d, 2H, C₆H₄), 6.93–6.99 (m, 4H, C₆H₅), 6.78–6.80 (d, 1H, C₆H₅). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 192.9, 176.2 (CO), 158.6, 148.9 (C≡C), 147.3, 136.6, 130.0, 129.5, 127.8 (C₆H₄), 127.4, 126.8, 126.5, 122.7, 122.1 (C₆H₅), 122.0 (C₆H₄). MS (m/z, ESI−) 835.724 (M−). Anal. calcd for C₂₅H₉NO₁₃Ru₃: 835.723.

[Ru(CO)₃{μ₄-η¹:η²:η¹:η¹-(4-NO₂PhC(O))CC(Ph)C(4-NO₂-PhC(O))C(Ph)Ru(CO)₃}]·C₆H₁₄ (3b·C₆H₁₄). Yield: 22%. FT-IR (KBr, cm⁻¹): 3105 w, 3076 w, 3055 w, 2098 vs, 2067 vs, 2027 vs, 1975 vs, 1529 vs, 1344 vs. ¹H NMR (400 MHz, CDCl₃) δ 8.12–8.21 (m, 8H, C₆H₄), 6.88–7.01 (m, 10H, C₆H₅). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 196.0, 195.2, 194.7, 194.4, 192.5, 191.2, 179.5, 177.7 (CO), 150.3, 149.9 (C≡C), 145.3, 139.4, 139.0, 133.5, 130.4, 130.2, 129.7, 129.6, 129.1, 128.7 (C₆H₄), 128.5, 128.1, 123.9, 123.5 (C₆H₅), 123.4 (C₆H₄). MS (m/z, ESI−) 872.910 (M−). Anal. calcd for C₃₆H₁₈N₂O₁₂Ru₂: 872.896.

[Ru(CO)₃{μ⁴-η¹:η²:η¹:η¹-(4-NO₂-PhC(O))CC(Ph)C(Ph)C(4-NO₂Ph-C(O))Ru(CO)₃}μ-CO] (3c). Yield: 19%. FT-IR (KBr, cm⁻¹): 3053 w, 2958 w, 2925 w, 2854 w, 2096 vs, 2063 vs, 2021 vs, 1523 s, 1334 s. ¹H NMR (400 MHz, CDCl₃) δ 8.35–8.37 (d, 2H, C₆H₄), 8.22–8.24 (d, 2H, C₆H₄), 8.14–8.19 (t, 2H, C₆H₄), 8.04–8.10 (m, 2H, C₆H₄), 7.84–7.94 (m, 1H, C₆H₅), 7.61–7.72 (m, 2H, C₆H₅), 7.45–7.51 (t, 3H, C₆H₅), 7.14–7.16 (d, 1H, C₆H₅), 6.94–7.09 (m, 3H). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 195.4, 194.9, 193.8, 192.8, 189.1 (CO), 167.7, 150.1 (C≡C), 149.9, 146.9, 143.1, 139.7, 134.3, 133.5, 131.3, 131.2, 130.7, 130.3 (C₆H₄), 129.4, 129.1, 128.9, 128.7, 128.6, 128.2, 123.9 (C₆H₅), 123.5, 123.4, 121.3 (C₆H₄). MS (m/z, ESI−) 872.893 (M−). Anal. calcd for C₃₆H₁₈N₂O₁₂Ru₂: 872.896.

1,3,5-Triphenyl-2,4,6-tris(4-nitrobenzoyl)benzene·CH₂Cl₂ (3f·CH₂Cl₂). Yield: 16%. FT-IR (KBr, cm⁻¹): 3105 w, 3060 w, 2925 w, 2856 w, 1683 s, 1525 vs, 1346 s. ¹H NMR (400 MHz, CDCl₃) δ 8.04–8.08 (t, 6H, C₆H₄), 7.63–7.71 (m, 6H, C₆H₄), 6.91–7.03 (d, 15H, C₆H₅). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 197.0, 196.8, 194.8 (CO), 150.0, 149.9, 149.8 (C₆H₄), 142.1, 142.0, 141.5, 141.2, 141.0, 139.3 (C₆), 139.2, 135.7, 135.2 (2× C₆C̲), 134.9, 130.9, 130.0, 129.9 (C₆H₄), 128.7, 128.1, 127.9, 123.4, 123.2, 123.1 (C₆H₅). MS (m/z, ESI−) 753.175 (M−). Anal. calcd for C₄₅H₂₇N₃O₉: 753.175.

[Ru₃(CO)₉(μ-CO)₂{μ₃-η¹:η²:η¹-(Ph)CC(2-NH₂-PhC(O))}] (4a). Yield: 7%. FT-IR (KBr, cm⁻¹): 2952 vs, 2923 vs, 2854 s, 2073 m, 2046 m, 2011 m, 1460 m. ¹H NMR (400 MHz, CDCl₃) δ 7.52–7.54 (d, 2H, C₆H₄), 6.97–7.03 (m, 5H, C₆H₅), 6.84–6.89 (t, 2H, C₆H₄), 6.45–6.47 (d, 2H, NH₂). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 194.5, 175.9 (CO), 164.5 (C₆H₄), 150.8, 148.5 (C≡C), 132.5, 128.1 (C₆H₄), 128.0, 127.7 (C₆H₅), 113.9 (C₆H₄). MS (m/z, ESI−) 805.673 (M−). Anal. calcd for C₂₅H₁₁NO₁₁Ru₃: 805.749.

[Ru(CO)₃{μ₄-η¹:η²:η¹:η¹-(2-NH₂PhC(O))CC(Ph)C(2-NH₂-PhC(O))C(Ph)Ru(CO)₃}] (4b). Yield: 29%. FT-IR (KBr, cm⁻¹): 3483 m, 3340 m, 3057 w, 2923 s, 2854 m, 2088 vs, 2059 vs, 2021 vs, 2000 vs, 1973 vs, 1581 s. ¹H NMR (400 MHz, CDCl₃) δ 7.54–7.62 (dd, 2H, C₆H₄), 6.88–7.06 (m, 12H, C₆H₄, C₆H₅), 6.51–6.55 (t, 1H, C₆H₄), 6.32–6.41 (m, 3H, C₆H₄), 5.94–5.97 (d, 4H, NH₂). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 199.3, 196.6, 196.2, 195.4, 194.1, 193.5, 184.5, 175.1 (CO), 150.5, 150.4 (C₆H₄), 146.3, 135.4 (C≡C), 134.8, 134.4, 134.3, 133.9, 133.8, 130.1, 128.7, 128.1 (C₆H₄), 127.8, 127.4, 127.3, 123.2, 117.4, 117.0, 115.9 (C₆H₅), 114.8 (C₆H₄). MS (m/z, ESI−) 812.948 (M−). Anal. calcd for C₃₆H₂₂N₂O₈Ru₂: 812.948.

[Ru(CO)₃{μ₄-η¹:η²:η¹:η¹-(2-NH₂-PhC(O))CC(Ph)C(Ph)C(2-NH₂Ph-C(O))Ru(CO)₃}μ-CO] (4c). Yield: 15%. FT-IR (KBr, cm⁻¹): 2954 s, 2923 vs, 2854 s, 2057 s, 2003 s, 1961 m, 1593 m. ¹H NMR (400 MHz, CDCl₃) δ 7.75–7.89 (dd, 2H, C₆H₄), 7.28–7.57 (m, 12H, C₆H₄, C₆H₅), 6.96–7.12 (m, 4H, C₆H₄), 6.70–6.91 (m, 4H, NH₂). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 186.5 (CO), 153.2 (C₆H₄), 136.1, 135.4 (C≡C), 134.8, 128.5, 125.1, 120.7 (C₆H₄), 118.5, 115.9, 112.0 (C₆H₅), 111.5 (C₆H₄). MS (m/z, ESI−) 812.948 (M−). Anal. calcd for C₃₆H₂₂N₂O₈Ru₂: 812.948.

[Ru(CO)₃{μ₄-η¹:η²:η¹:η¹-(Ph)CC(2-NH₂PhC(O))C(2-NH₂PhC(O))C(Ph)Ru(CO)₃}]·3/4CH₂Cl₂ (4d·3/4CH₂Cl₂). Yield: 23%. FT-IR (KBr, cm⁻¹): 3475 w, 3348 w, 2952 s, 2923 vs, 2854 s, 2088 vs, 2057 vs, 2019 vs, 1969 vs, 1639 m. ¹H NMR (400 MHz, CDCl₃) δ 7.60–7.87 (m, 3H, C₆H₄), 7.21–7.41 (m, 5H, C₆H₄, C₆H₅), 6.94–7.12 (m, 8H, C₆H₄, C₆H₅), 6.83–6.86 (t, 1H, C₆H₄), 6.68–6.71 (t, 1H, C₆H₄), 6.01–6.32 (m, 4H, NH₂). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 197.8, 196.4, 194.4, 193.8, 192.7, 191.7, 180.6 (CO), 151.0, 150.4 (C₆H₄), 146.1, 143.0 (C≡C), 135.3, 134.6, 134.5, 134.3, 133.2, 131.4, 131.0, 130.1 (C₆H₄), 129.0, 128.9, 128.3, 127.6, 127.3, 123.2, 117.3, 116.3 (C₆H₅), 115.9, 115.3 (C₆H₄). MS (m/z, ESI−) 815.947 (M−). Anal. calcd for C₃₆H₂₂N₂O₈Ru₂: 815.947.

[Ru₃(CO)₉(μ-CO)₂{μ₃-η¹:η²:η¹-(2-CH₃COO-PhC(O))CC(Ph)}] (5a). Yield: 10%. FT-IR (KBr, cm⁻¹): 3058 w, 3030 w, 2925 w, 2854 w, 2104 m, 2071 vs, 2056 vs, 2017 vs, 1878 m, 1760 m. ¹H NMR (400 MHz, CDCl₃) δ 7.27–7.30 (m, 2H, C₆H₄), 7.00–7.05 (m, 3H, C₆H₄, C₆H₅), 6.87–6.96 (m, 4H, C₆H₅), 2.23 (s, 3H, CH₃). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 194.8, 174.7, 169.6 (CO), 166.5 (C₆H₄), 150.8, 148.2 (C≡C), 133.5, 131.7, 128.3, 127.9 (C₆H₄), 127.7, 125.9, 125.6 (C₆H₅), 124.4 (C₆H₄), 21.0 (CH₃). MS (m/z, ESI−) 846.728 (M−). Anal. calcd for C₂₇H₁₂O₁₃Ru₃: 846.742.

[Ru(CO)₃{μ₄-η¹:η²:η¹:η¹-(2-CH₃COO-PhC(O))CC(Ph)C(Ph)C(2-CH₃COOPh-C(O))Ru(CO)₃}μ-CO]·CH₂Cl₂ (5c·CH₂Cl₂). Yield: 29%. FT-IR (KBr, cm⁻¹): 3060 w, 3030 w, 2927 w, 2854 w, 2092 vs, 2063 vs, 2025 vs, 1975 vs, 1770 s, 1118 vs. ¹H NMR (400 MHz, CDCl₃) δ 7.63–7.85 (m, 3H, C₆H₄), 7.33–7.44 (m, 3H, C₆H₄), 7.10–7.24 (m, 2H, C₆H₄), 6.85–7.04 (m, 10H, C₆H₅), 2.21–2.29 (t, 6H, CH₃). ¹³C{1H} NMR (101 MHz, CDCl₃) δ 196.3, 195.8, 195.7, 195.0, 194.8, 194.3, 193.4, 189.9, 180.4 (CO), 169.6, 169.1 (C₆H₄), 149.8, 149.8, 145.8, 134.2 (C≡C), 134.1, 133.9, 133.3, 133.1, 132.7, 132.5, 132.2, 131.9 (C₆H₄), 131.4, 130.0, 128.6, 128.4, 128.2, 128.1, 127.8, 127.6, 127.4, 125.7, 125.0, 124.9 (C₆H₅), 124.5, 123.9 (C₆H₄), 20.9 (CH₃). MS (m/z, ESI−) 899.931 (M−). Anal. calcd for C₄₀H₂₄O₁₂Ru₂: 899.935.

Crystallography

X-ray structural measurements were carried out with a Bruker SMART APEX-II CCD detector using graphite monochromated MoKα radiation (λ = 0.71073). The data were collected by the ω–2θ scan mode, and absorption correction was applied by using Multi-Scan. The structure was solved by direct methods (SHELXS-97) and refined by full-matrix least squares against F2 using SHELXL-97 software.²⁹ Non-hydrogen atoms were refined with anisotropic thermal parameters. All hydrogen atoms were geometrically fixed and refined using a riding model.

The single crystals of compounds 1a, 1b, 1e, 1f, 2a, 2c, 3b, 3f, 4b, 4d, 5a and 5c suitable for single crystal X-ray diffraction were successfully grown up from slow evaporation of their dichloromethane/hexane solutions at 4 °C. Relevant crystallographic data were given in Table S1 in the ESI.† Crystallographic data for the structural analysis have been deposited with the Cambridge Crystallographic Data Centre: 1553521 (1a), 1553523 (1b), 1553526 (1e), 1553527 (1f), 1553511 (2a), 1553512 (2c), 1545197 (3b), 1545199 (3f), 1553513 (4b), 1553516 (4d), 1553504 (5a) and 1553509 (5c).†

Conclusions

We isolated a series of new ruthenium clusters and cyclotrimerization products by investigating reactions of five 1,3-diphenylprop-2-yn-1-one derivatives with Ru₃(CO)₁₂. The activation of the 1,3-ynones and the transformation of the cluster skeletons demonstrated that the triruthenium clusters and ruthenoles are important intermediates during the formation of the final products. More importantly, the substituents in the phenyl ring of 1,3-diphenylprop-2-yn-1-one exerted great effects on the reaction pathways during the transformation reactions. We revealed that the product distribution is dependent strongly on both the electronic and steric effects of the substituents on the acetylenic ketones. This discovery allows us to control the direction of the reaction by adjusting the substituents in the phenyl ring of 1,3-diphenylprop-2-yn-1-one. Moreover, further reactions between ruthenoles and the corresponding alkyne ketones proceed if a group can activate the carbon–carbon triple bond of an alkyne ketone, it brings us a new idea about applications of ruthenoles in the field of organic synthesis.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

This work is supported by the National Natural Science Foundation of China (21401124, 21171112).

Notes and references

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Footnote

† Electronic supplementary information (ESI) available: Crystal structures of 1a, 1f, 2a, 3b, 4b, 5c, 2f, 3c and 1c, CIF; checkcif, ¹H NMR spectra, ¹³C{1H} NMR spectra, FT-IR spectra and other electronic format. CCDC 1553521, 1553523, 1553526, 1553527, 1553511, 1553512, 1545197, 1545199, 1553513, 1553516, 1553504 and 1553509. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7ra13626a

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