A new nanomagnetic Pd-Co bimetallic alloy as catalyst in the Mizoroki–Heck and Buchwald–Hartwig amination reactions in aqueous media

A Pd-Co bimetallic alloy encapsulated in melamine-based dendrimer supported on magnetic nanoparticles denoted as γ-Fe2O3@MBD/Pd-Co was synthesized by a facile co-complexation-reduction method and characterized sufficiently. The catalytic evaluation of γ-Fe2O3@MBD/Pd-Co showed promising results in the Mizoroki–Heck and Buchwald–Hartwig amination reactions of various iodo-, bromo- and challenging chloroarenes in aqueous media. The synergetic cooperative effect of both Pd and Co and dispersion of the catalyst in water due to the encapsulation of γ-Fe2O3 by melamine-based dendrimer lead to high catalytic performance compared with the monometallic counterparts. The dispersion of the magnetic catalyst also facilitates the recovery and reuse of the catalyst by ten consecutive extraction and final magnetic isolation with no loss of catalytic activity, keeping its structure unaltered.


Synthesis of γ-Fe 2 O 3 -MBD.
The synthesized γ-Fe 2 O 3 -melamine from the previous step (1 g) and Et 3 N (10 mL) was sonicated about 30 min at room temperature. ECH (1 mL) was added to this stirring mixture drop wise. The mixture was heated to a temperature of 60 °C and kept for 24 h. Then, melamine (5 mmol, 0.63 g) was added and further stirred for 48 h at the same temperature. The resulting solid was isolated by an external magnet and washed several times with distilled H 2 O (3 × 20 mL) and EtOH (3 × 20 mL). It was dried in a vacuum oven at 50 °C. Elemental analysis of γ-Fe 2 O 3 -MBD for nitrogen (17.5%) showed that in total, 2 mmol of melamine was loaded on 1 g of γ-Fe 2 O 3 -MBD. General procedure for the Mizoroki-Heck cross-coupling reaction catalyzed by γ-Fe 2 O 3 -MBD/ Pd-Co. γ-Fe 2 O 3 -MBD/Pd-Co (0.05 mol% based on Pd) was added to a stirred suspension of haloarene (1 mmol), Et 3 N (2 mmol), alkene (1.3 mmol) in water (1 mL). The resulting mixture was heated at 60 °C. The reaction was monitored by TLC and, after the times shown in Table 3, the reaction was cooled down to room temperature. The organic compound was extracted twice with EtOAc (2 × 5 mL). The final organic layer was dried over MgSO 4 and filtered. Organic solvent evaporated under vacuum to give the crude product, which was purified by column chromatography (silica gel) using 50:1 volume ratio of n-hexane:EtOAc as eluent. The aqueous phase, containing the bimetallic catalyst, was again used for a new identical process. The resulting suspension was heated at 50 °C and the reaction was monitored by TLC. After the times depicted in Table 6, the reaction mixture was cooled down. The organic product was extracted three times with EtOAc (3 × 5 mL). The combined organic layers were dried over MgSO 4 and the solvent evaporated under vacuum to give the crude product, which was purified by column chromatography (silica gel) using 10:1 volume ratio of n-hexane:EtOAc as eluent. The aqueous phase, containing the bimetallic catalyst, was again used for a new identical process.

Synthesis of γ-Fe
General procedure for the Buchwald-Hartwig amination reaction of aryl chlorides and bromides with arylamines catalyzed by γ-Fe 2 O 3 -MBD/Pd-Co. γ-Fe 2 O 3 -MBD/Pd-Co (0.07 mol% based on Pd) was added to a stirred suspension of chloroarenes or bromoarenes (1 mmol), t-BuONa (2 mmol), and arylamines (1.2 mmol) in H 2 O (1 mL). The resulting mixture was heated at 70 °C. The reaction was monitored by TLC and, after the times shown in Table 6, the reaction was cooled down to room temperature. The organic product was extracted three times with EtOAc (5 mL). The combined organic layers were dried over MgSO 4 and the solvent was evaporated under vacuum to give the crude product, which was purified by column chromatography (silica gel) using 10:1 volume ratio of n-hexane:EtOAc as eluent. The aqueous phase, containing the bimetallic catalyst, was again used for a new identical process.

Results and discussion
In Scheme 1, the approach which we have used for the preparation of Pd/Co bimetallic catalyst (γ-Fe 2 O 3 @MBD/ Pd-Co) is illustrated. In the first step, γ-Fe 2 O 3 was functionalized by the reaction with 3-chloro-trimethoxypropylsilane and subsequent treatment with melamine to produce γ-Fe 2 O 3 -melamine (Scheme 1, G0.5). The nucleophilic reaction of γ-Fe 2 O 3 -melamine with epichlorohydrin (ECH), as a bifunctional molecule for growing of dendritic branches afforded γ-Fe 2 O 3 -melamine-ECH (Scheme 1, G1). Ring opening reaction of terminal epoxides in γ-Fe 2 O 3 -melamine-ECH by melamine produced 1.5 generation of dendrimer-magnetite incorporation (γ-Fe 2 O 3 @MBD, G1.5). The last step involves the intercalating of metal complexes into the interior cavity of γ-Fe 2 O 3 @MBD followed by reduction with NaBH 4 as a reducing agent. The metal content of γ-Fe 2 O 3 @MBD/Pd-Co was calculated and quantified employing ICP analysis revealing 0.75 and 3.15 mmol of Pd and Co, respectively, (molar ratio Pd:Co = 1:4.2) per 1 g of the catalyst. Elemental analysis of γ-Fe 2 O 3 -melamine and γ-Fe 2 O 3 @MBD showed that the loadings of melamine on the catalyst were 9.88 and 17.50%, respectively, based on the nitrogen content.
As shown in Fig 10 . The XRD pattern of the sample showed two diffraction signals were placed around 2θ = 44.8 and 47.5° due to the Co species (JCPD-15-0806) 30 . However, those peaks mentioned above slightly shift to larger angles compared with the single metal counterpart 30,31 . The shift could be related to the bimetallic alloy formation. Figure 3 depicts the thermogravimetric analysis of γ-Fe 2 O 3 @MBD. In this plot the first weight loss of 1.18% (< 171 °C), corresponded with the loss of physically adsorbed water. The second weight elimination of 11.61% (171-446 °C) occurred as a consequence of degradation and decomposition of the organic material. These data justified that the melamine-based dendrimers are conveniently grafted on the magnetic nanoparticles. Magnetic properties of γ-Fe 2 O 3 @MBD/Pd-Co and γ-Fe 2 O 3 were surveyed employing a vibrating sample magnetometer (VSM) at room temperature (Fig. 4). Figure 4 revealed that the saturation magnetization value correspondieng to γ-Fe 2 O 3 @MBD/Pd-Co is approximately 59.07 emu g −1 . The drop of the saturation magnetization of γ-Fe 2 O 3 @ MBD/Pd-Co compared with γ-Fe 2 O 3 (76.48 emu g −1 ) was related to the coating of γ-Fe 2 O 3 by melamine-based dendrimer. The magnetization curves did not show a hysteresis loop, which justifiyed the superparamagnetic nature of the resulting NPs. High magnetic properties of NPs were appropriate for their further recovery from the reaction media by the simple magnetic separation using a conventional magnet. www.nature.com/scientificreports/ A deep XPS analysis was done to characterize the chemical composition of γ-Fe 2 O 3 @MBD/Pd-Co surface (Fig. 5). The peaks associated to carbon, nitrogen, oxygen, silicon, iron, palladium and cobalt are evidently detected in the XPS plot (Fig. 5a). The C1s spectrum (Fig. 5b) showed binding energies at 284.5 (C sp2 -N and C-C), 286.0 (C-O and C=N), and 288.1 (C-N) eV 32,33 . Deconvolution of N 1s region showed two peaks at 398.0 and 399.5 eV corresponding to C-N=C and N-H, respectively (Fig. 5c) 34 . In Fig. 5d, the peaks at 335.1 (3d 5/2 ) and 340.4 eV (3d 3/2 ), corresponded to Pd in the zero oxidation state. The peaks at 336.6 (3d 5/2 ) and 341.8 eV (3d 3/2 ) indicated that a small amount of Pd presents in (II) oxidation state 35,36 . The typical peaks located at 780.6 (2p 3/2 ) and 796.4 eV (2p 1/2 ) revealed the presence of cobalt (0) in the catalyst (Fig. 5e). It was also detected the presence of both weaker peaks at 782.6 (2p 3/2 ) and 798.4 eV (2p 1/2 ) corresponding to cobalt (II) species. Different weak satellite peaks at 785.8, 788.6, 801.3 and 803.0 eV 30 , showed the existence of Co 3 O 4 on the catalyst surface 37 . The displacement of the 2p 3/2 signal of cobalt to a lower energy and a positive shift in the 3d 5/2 peak of Pd indicated the alloying of Co with Pd 38 . Moreover, the atomic distribution of palladium versus cobalt in the surface of γ-Fe 2 O 3 @ MBD/Pd-Co is 1:8.45, which is notably higher than the stoichiometric value (1:4.2) calculated by ICP analysis. This larger value demonstrates that the bimetallic Pd-Co nanoparticles generates a core-shell structure with a cobalt-rich shell and a palladium-rich core 39,40 , and consequently, a larger cobalt surface is exposed.
The morphology of the surface and size of the particles of the freshly prepared new catalyst were analyzed by transmission electron microscopy (TEM) (Fig. 6). In Fig. 6a a spherical morphology of γ-Fe 2 O 3 magnetic nanoparticles was shown. Comparing TEM image of γ-Fe 2 O 3 @MBD/Pd-Co ( Fig. 6b) with γ-Fe 2 O 3 showed that dendrimer-magnetite incorporation was dispersed considerably. Figure 6e shows an average diameter size of ̴ 12 nm for γ-Fe 2 O 3 @MBD/Pd-Co. Characteristic lattice fringes for 2 2 0 planes of γ-Fe 2 O 3 with a d-spacing of  www.nature.com/scientificreports/ 0.28 nm recognized in Fig. 6c. Moreover, TEM images, revealed a homogeneous spreading of the cobalt and palladium alloy nanoparticles immobilized onto the γ-Fe 2 O 3 @MBD surface (Fig. 6c). The size distribution histogram of palladium and cobalt alloy nanoparticles (Fig. 6f), illustrated a high size uniformity of the detected spherical nanoparticles with diameter of about ~ 3-5 nm. Figure 6d depicted the lattice fringe spacing ~ 3.26-3.71 Å related to the Pd-Co alloy nanoparticles [41][42][43] . The EDS elemental mapping images of the γ-Fe 2 O 3 @MBD/Pd-Co are presented in Fig. 7. The EDS images prove the presence of the Fe, Co and Pd elements on the γ-Fe 2 O 3 @MBD/Pd-Co surface. As it is observed in the Fig. 7, cobalt is denser than palladium on the surface of it.

Mizoroki-Heck cross-coupling reaction catalyzed by γ-Fe 2 O 3 @MBD/Pd-Co in water.
Mizoroki-Heck cross-coupling reactions are applied for the preparation of natural products, pharmaceuticals and biologically active molecules 3,44-46 . These reactions, involving the generation of new carbon-carbon bonds formation, have found several commercial applications for the synthesis of fine chemicals such as herbicide prosulfuron, anti-inflammatory naproxen, or anti-asthma agent Singulair in the multi-ton scale in each year 47 . Generally, the Mizoroki-Heck cross-coupling reaction is catalyzed by palladium complexes 48 . However, another transition metals such as Ni 49 , Co 50 and Cu 51 have been recently reported as catalysts for this purpose. Due to the advantageous of bimetallic catalysts such as enhanced catalytic activity which comes from the synergistic effect of the monometallic counterparts, in the past decades, some bimetallic catalysts such as Pd/Cu 52 , Pd/Pt 53 , Pd/ Co 11 , Pd/Au 54 , Pd/Ni 55 , Pd/Fe 56 and etc. have been developed for the Mizoroki-Heck cross-coupling reaction. The synthetic routes published in the literature have certain limitations due to the necessary high temperature, the large amount of catalyst loading, the introduction of additives, the employment of organic solvents and the use of an unrecyclable catalyst. In addition, most of the reported methods suffered from lack of generality for the coupling reactions employing chloroarenes. Continuing with our research on the design and the preparation of novel and attractive catalytic systems to conduct environmentally friendly cross-coupling reactions 4 , herein, we have surveyed the catalytic activity of a novel γ-Fe 2 O 3 @MBD/Pd-Co as the first magnetically recyclable Pd/Co bimetallic catalyst in the Mizoroki-Heck coupling reactions.
At first, the coupling reaction of iodobenzene with n-butyl acrylate (1:1.3 molar ratio) in water was investigated as a bench reaction to optimize the effect of the catalyst loading, type of the base and temperature on the reaction completion (Table 1). In the preliminary studies, this model reaction was envestigated in the presence of variable amounts of γ-Fe 2 O 3 @MBD/Pd-Co using Et 3 N as the base (2 equiv.) at 60 °C (Table 1, entries 1-3). The best amount of the catalyst was 0.05 mol% ( Table 1, entry 3). The reaction did not work when any amount of the catalyst was not used (Table 1, entry 4). This result proved the crucial role of the catalyst for this transformation. Several bases such as K 2 CO 3 CsCO 3 , Na 2 CO 3 , NaHCO 3 , KOH and NaOEt were examined for the model reaction using 0.05 mol% of the catalyst at 60 °C (Table 1, entries 5-10). Whitin the bases tested, Et 3 N was found to be the www.nature.com/scientificreports/ most effective base (Table 1, entry 3). When no bases was used, the corresponding product was obtained with a desirable yield (Table 1, entry 11), which showed that the intrinsic basic sites of melamine-based dendrimer may also promote the reaction in some extent. Subsequently, the reaction was attempted at lower temperatures ( Table 1, entries 12 and 13). Here, the product was produced in very low yields and using longer reaction times, especially when the reaction was carried out at room temperature. The coupling reaction of iodobenzene with n-butyl acrylate (1:1.3 molar ratio) under optimized reaction conditions was also studied in the presence of the catalyst containing different ratios of Pd:Co ( Table 2). As the ratio of Pd:Co is changed from 1:5.8 to 1:4.2, the efficiency of the catalyst is increased (entry 2). This could be Using the optimized reaction conditions, the scope of Mizoroki-Heck cross-coupling reaction catalyzed by γ-Fe 2 O 3 @MBD/Pd-Co was investigated by employing various aryl halides to react with olefins in water ( Table 3). The results of Table 3 reveal that this catalytic protocol is very efficient for running coupling reaction of tested haloarenes. It is worth to mention that any homo-coupling reaction was not occurred in all of the reactions tested. Iodoarenes were coupled with assorted alkenes such as alkyl acrylates and methyl methacrylate following the optimal reaction conditions obtaining the desired products in 95-99% yields ( Table 3, entries 1-6). Bromo-and chloroarenes, underwent satisfactory coupling reactions with n-butyl acrylate furnishing products in good to  www.nature.com/scientificreports/  Figure S1-S13). Since the recovery and recycling of the supported catalysts are very important issues from both the practical and environmental point of view, the reusability of the catalyst in the model reaction was investigated under optimized reaction conditions. Due to the nitrogen and hydroxyl groups in γ-Fe 2 O 3 @MBD/Pd-Co, the catalyst was dissolved in the aqueous layer with no affinity to the organic layer (Fig. 8). According to this feature, the product was extracted with ethyl acetate, while the catalyst remained in the aqueous layer (Fig. 8b). The aqueous layer containing the catalyst was allowed to react with a new batch of iodobenzene, n-butyl acrylate and Et 3 N. At the end, the catalyst was separated from the aqueous phase employing a magnet (Fig. 8c). The catalytic activity of the recovered catalyst was identical to the original one, and the same behavior took place after ten runs (Fig. 9). FT-IR spectrum, XPS pattern and TEM images of the catalyst recovered after the tenth reaction, indicated that the catalyst remained unchanged (Fig. 10).
The heterogeneous nature of the catalyst was checked by the hot filtration and poisoning tests. In the hot filtration test, after approximate 40% of the coupling reaction of chlorobenzene with n-butylacrylate, the solid was separated at the reaction temperature using an external magnetic field and the reaction was permitted to stir for 4 h. Any additional transformation indicated that the catalysis was heterogeneous in nature (Fig. 11). In the poisoning test, S 8 (0.07 g) was used as a scavenger for the metal. Under this condition, any considerable change in the progress of the reaction was not observed.

C-N cross-coupling reaction catalyzed by γ-Fe 2 O 3 @MBD/Pd-Co in water. Arylamines and their
derivatives possess a paramount importance as intermediates for pharmaceuticals and natural products, agrochemicals, conducting polymers (PANI), and dyes in the chemical industry [57][58][59] . Arylamines are extremely important ligand for the coordination to transition metals 60 . The Buchwald-Hartwig coupling of amines and aryl halides in the presence of Pd is a great method for the preparation of arylamines [61][62][63] . Since the discovery of Buchwald-Hartwig amination reaction 64 , research efforts have concentrated on this reaction and significant development have been achieved on the improvement of the conventional reaction conditions such as using diverse transition metals, ligands, and solvents as well as extending substrate scope 65 . The importance of bimetallic catalysts in organic synthesis has recently encouraged organic chemists to use these kinds of catalysts in coupling reactions. Along this line, Fe@Pd nanowire 66 , Pd/Ni nanoparticles 67 and Pd/Cu complexes 68 have been used as bimetallic catalysts for the C-N coupling reactions. Encouraged by the facile Mizoroki-Heck cross-coupling reaction catalyzed by γ-Fe 2 O 3 @MBD/Pd-Co, we have tried our catalyst for C-N coupling reaction as well.  www.nature.com/scientificreports/ Surprisingly, to the best of our knowledge, there is not any report on the Buchwald-Hartwig amination reaction catalyzed by Pd/Co bimetallic nanoparticles.
To investigate the catalytic activity of the γ-Fe 2 O 3 @MBD/Pd-Co toward the Buchwald-Hartwig amination reaction, the cross-coupling reaction of chlorobenzene as a poor reactive aryl donor, with aniline in aqueous media, was selected as a bench reaction. Several reaction factors such as the catalyst loading, base and temperature were screened. The results are collected in Table 4. As it is remarked in Table 4, the best yield of the product was observed when 0.07 mol% of the catalyst was used (Table 4, entry 2). Among all the tested organic and inorganic bases (Table 4, entries 6-9), t-BuONa was found to be the most effective base. When any bases was not used, the product was isolated in 54% yield after 24 h (Table 4, entry 10), which showed that the intrinsic basic sites of melamine-based dendrimer may also promote the reaction. The model reaction was studied at different temperatures (Table 4, entries [11][12][13] and the greatest yield of the desired product was produced at 80 °C (Table 4, entry 2). The assessment of the temperature and the catalyst loading was also done for iodobenzene as a highly reactive aryl donor in Table 5. The information given by all these experiments confirmed that 0.05 mol% of the catalyst and 50 °C are the most appropriate conditions to complete the reaction successfully (Table 5, entry 3).
Next, the chemical scope of this novel bimetallic catalyst was explored and the results are summarized in Table 6. Many aryl iodides were coupled with different arylamines in the presence of γ-Fe 2 O 3 @MBD/Pd-Co and t-BuONa under optimized reaction conditions (0.05 mol% of the catalyst, 50 °C) and the corresponding products were obtained in 82-93% yields ( Table 6, entries 1-6). The coupling reaction of bromo-and chloroarenes with several arylamines was fruitful using 0.07 mol% of the catalyst at 80 °C (Table 6, entries 7-15).
The Mizoroki-Heck and Buchwald-Hartwig amination reactions of chlorobenzene with n-butyl acrylate and aniline, respectively, catalyzed by monometallic counterparts including γ-Fe 2 O 3 @MBD/Pd, γ-Fe 2 O 3 @MBD/Co, Fe 2 O 3 @MBD/Pd(OAc) 2 , γ-Fe 2 O 3 @MBD/CoCl 2 , physical mixture of γ-Fe 2 O 3 @MBD/Pd and γ-Fe 2 O 3 @MBD/Co, Pd(OAc) 2 , CoCl 2 .6H 2 O, and Fe 2 O 3 @MBD/Co 3 O 4 were also investigated and the results were compared with the bimetallic catalyst (γ-Fe 2 O 3 @MBD/Pd-Co) (Fig. 12). Obviously, the bimetallic particles provided higher www.nature.com/scientificreports/ chemical yield (99%) compared with the monometallic counterparts in both reduced and nonreduced forms, physical mixture of monometallic counterparts, and non-supported metal salts and also supported cobalt oxide. The enhanced catalytic activity of these new species is probably originated by a synergistic effect of both metals. Based on the results and fully characterization of the catalyst and other previous contributions 11, 69 , we tentatively proposed a plausible mechanisms for Mizoroki-Heck and Buchwald-Hartwig amination reactions in the presence of γ-Fe 2 O 3 @MBD/Pd-Co (Scheme 2). As it is clear in Fig. 12, the Mizoroki-Heck and Buchwald-Hartwig amination reactions proceeded with higher efficiency when involved γ-Fe 2 O 3 @MBD/Pd-Co as a bimetallic catalyst than monometallic counterparts. These finding are in good agreements with a negative shift of the 2p 3/2 peak of Co and a positive shift in the 3d 5/2 peak of Pd in the XPS analysis (Fig. 5). The peak shifts indicate that the neighbouring cobalt atoms contribute to increase the electronic density of Pd centres and facilitates the oxidative addition of haloarenes to Pd (0) 11 . Evidently, this step in the coupling reactions is responsible for the higher activity of bimetallic catalysts compared with monometallic counterparts. In the proposed mechanism shown in Scheme 2, at first, the Pd-Co alloy underwent oxidative addition with haloarenes to form an organometallic intermediate I   www.nature.com/scientificreports/ Mizoroki-Heck coupling product. Finally, the base-assisted elimination of H-X from species V occurred to regenerate the catalyst. In the suggested mechanism for Buchwald − Hartwig amination reactions, the product is formed through the base-assisted elimination of H-X from intermediate III by subsequent reductive elimination. Finally, the catalytic activity of γ-Fe 2 O 3 @MBD/Pd-Co was compared with those of reported Pd bimetallic catalysts in the Mizoroki-Heck and Buchwald-Hartwig amination reactions ( Table 7). As summarized in Table 7, the most efficiency in the carbon-carbon and carbon-nitrogen coupling reactions of aryl iodides, bromides and chlorides with olefins and aryl amines was observed in the presence of γ-Fe 2 O 3 @MBD/Pd-Co. Most of the reported methods suffer from lack of generality for the coupling reactions of aryl chlorides. Notably, chlorarenes are the most widely available and inexpensive halides compared with other aromatic halides, but are the most challenging ones. Furthermore, the reported procedures have one or more of drawbacks such as requiring high temperature, large quantity of the catalyst, unrecyclable catalysts, additives and organic solvents. High catalytic performance of Fe 2 O 3 @MBD/Pd-Co is the result of the synergetic cooperative effect of both Pd and Co in γ-Fe 2 O 3 @MBD/Pd-Co and its dispersion in water, due to the encapsulation of MNPs by melamine-based dendrimer, which caused better contact between the catalyst and the reactants. Most importantly, the dispersion of the magnetic catalyst facilitates the catalyst recovery and reuse by ten consecutive extraction and at the end magnetic isolation. Among the reported methods, using water as an ecofriendly solvent, simple catalyst recovery and reuse, easy work-up and not needing any additive make our protocol more environmentally benign method for the C-C and C-N cross-coupling reactions.

Conclusion
In summary, in this work, melamine-based dendrimer supported on γ-Fe 2 O 3 magnetic nanoparticles was efficiently employed as a suitable material for the in situ preparation of palladium-cobalt nanoparticles by reduction with NaBH 4 . TEM images indicated uniform distribution of fairly small palladium and cobalt alloy nanoparticles supported on the surface of the catalyst. The catalyst was characterized by FT-IR, XRD, XPS, VSM, TGA, ICP and elemental analysis. It was used as a new water-dispersible/magnetically recyclable Pd/Co heterogeneous bimetallic catalyst (γ-Fe 2 O 3 @MBD/Pd-Co) for the efficient Mizoroki-Heck and Buchwald-Hartwig amination reactions in water. A variety of iodo-, bromo-and chloroarenes successfully reacted with acrylates, styrene and anilines to yield the corresponding products. Using this protocol, products were achieved in good to high yields in water as an ecofriendly solvent and without using any additives. The synergistic cooperative effect of both Pd and Co in the encapsulated catalyst leads to high catalytic performance in the cross-coupling reactions in aqueous media. The dispersion of the magnetic catalyst facilitates the catalyst recovery and reuse by ten consecutive extraction and at the end magnetic isolation. The experiments based on isolation of the catalyst in the hot filtration test and using S 8 in the poisoning test, showed that the observed catalysis was heterogeneous in nature. Use of water as an ecofriendly solvent, simple catalyst recovery and reuse, ease of work-up and not needing any additive make this method an environmentally benign procedure for the carbon-carbon and carbon-nitrogen cross-coupling reactions (Supplementary Information). www.nature.com/scientificreports/ www.nature.com/scientificreports/  www.nature.com/scientificreports/