Palladium complexes solvent extraction

Palladium(II) chloride (1.0 g, 5.6 mmole) is added to a solution of 30 mL water and 1.0 mL concentrated HC1 contained in a 100-mL, round-bottomed flask. The resulting mixture is heated under reflux until all the palladium(II) chloride dissolves. The dark reddish-brown solution is then allowed to cool to room temperature, and trenMe63 (1.65 g, 7.1 mmole) is slowly added. The resulting yellow solution is then heated at reflux for 30 minutes and allowed to cool again to room temperature. Small portions of Na2C03 are carefully added to the solution until the pH is adjusted to approximately 11.0 as measured by using a colorpHast indicator stick [the checkers report that careful addition of 25% NaOH solution works equally well.]. The solvent is removed by means of a rotoevaporator and the yellow residue is dried in vacuo at room temperature. The palladium complex is extracted from the residue by the successive use of four 25-mL portions of hot chloroform. The combined chloroform extracts are filtered to remove insoluble materials and are evaporated to near dryness on the rotoevaporator. Acetone (30 mL) is added to precipitate the product, which is collected by filtration and dried in vacuo at room temperature. The yield is 1.2 g (52%) [the checkers report a yield of 2.15 g (93%) when ether is used to precipitate the product which is somewhat soluble in acetone.]. 

Yordanov, A. T. Mague, J. T. Roundhill, D. M. Solvent extraction of divalent palladium and platinum from aqueous solutions of their chloro complexes using an N,N- dimethyldithiocarbamoylethoxy substituted calix 4 arene. Inorg. Chim. Acta 1995, 240, 441 146. 

The reaction is carried out under a dry nitrogen atmosphere. To a mixture of 7.32 g (40 mmol) of ( )-bromophenylethcnc and 0.20 mmol of the palladium complex are added 100 mL (80 mmol) of a 0.8 M solution of [a-(trimethylsilyl)benzyl]magnesium bromide in diethyl ether at —78 °C. The mixture is allowed to warm and stirred at 0 "C for 2 d and then hydrolyzed with 10% HCI at 0 C. The organic layer and ether extracts from the aqueous layer are combined, washed with aq NaHCG3 and then water, and dried over anhyd MgS04. The solvent is evaporated and the product isolated by distillation yield 10.1 g (93% ) bp 135-139 JC/0.9 Torr [a]p° —43.9 (c = 1.0, benzene) 95% op (determined by hydrogenation and direct comparison with an authentic sample prepared via asymmetric hydrosilylation and correlated with 1,3-diphenyl-t -propanol). 

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Palladium-catalyzed cross-coupling reactions often require relatively large amounts of catalysts which have to be removed from the reaction product. Fluorous palladium complexes offer a solution to this problem, since they are soluble in fluorous solvents and can be readily separated from the organic product by liquid-liquid extractions. 

Pozzi, Sinou, and co-workers prepared a fluorous chiral phosphine, (R)-2- bis[4-(1 H,1 H-perfluorooctyloxy)phenyl]phosphino -2 -(l H,1 H-perfluorooctyloxy)-l, 1 -binaphthyl (F content = 52%, partition coefficient n-perfluorooctane/toluene = 0.23, n-perfluorooctane/CHjOH = 7.42) and used for a chiral ligand of palladium complex in an asymmetric aUyHc alkylation of 1,3-diphenylprop-2-enyl acetate [8]. The reaction was carried out at room temperature in BTF or toluene and gave the corresponding product in 99% and 88% chemical yields and 81% ee and 87% ee, respectively after the nonfluorous MOP complex gave the product in 95% yield and 99% ee in toluene at 0 °C [9]) [Eq. (1)]. When toluene was used as a solvent, the simple extraction of the reaction mixture with n-perfluorooctane (twice) allowed the complete removal of the ligand and of the palladium complex. However, the recovered palladium complex did not have catalytic activity for the reachon. 

Another fluorous palladium complex that was applied in a Mizoroki-Heck reaction is the SCS pincer palladium complex 24 (Table 15.1, entry 3) [67]. It was applied under thermal and microwave heating. No fluorous solvent was used and the insoluble catalyst dissolved at the reaction temperature of 140 °C. The catalyst was recovered after 30 to 45 min by solid-phase extraction with a fluorous silica gel. Depending on whether activated or nonactivated substrates were coupled, the yields ranged between 76 and 94%. 

The platinum group metals occur jointly as alloys and as mineral compounds in placer deposits of varying compositions. Ru and Os are separated from the PGM mix by distillation of their volatile oxides, whereas platinum, iridium, palladium, and rhodium are separated by repeated solution and precipitation as complex PGM chlorides, or by solvent extraction and thermal decomposition to sponge or powder. PGM scrap is recycled by melting with collector metals (lead, iron, or copper) followed by element-specific extraction. 

Neutral ionic liquids are excellent solvents for the palladium catalysed coupling of alkyl halides with alkenes (Heck reaction). The special advantage of using neutral ionic liquids is that many palladium complexes are soluble in ionic liquids and that the products or product of the reaction can be extracted with water or alkane solvents. So the expensive catalyst can be recycled compared to the routine Heck reaction in which the catalyst is lost at the end of the reaction (see Section 12.11). A typical Heck reaction is given (Scheme 7). 

D.iii.a. Standard Phosphine-Assisted Protocol. The process is done with palladium complexes with hydrophobic phosphine ligands and aqueous solution or a slurry of inorganic base in a biphasic system in which benzene or toluene is the most frequently used solvent. Therefore, it is evident that the process should involve phase transfer, because the precatalyst and organic halide reside in the organic phase, while boronate must be extracted to the aqueous phase. The most probable answer to the question of how the... 

Arsonium salts have found considerable use in analytical chemistry. One such use involves the extraction of a metal complex in aqueous solution with tetraphenyiarsonium chloride in an organic solvent. Titanium(IV) thiocyanate [35787-79-2] (157) and copper(II) thiocyanate [15192-76-4] (158) in hydrochloric acid solution have been extracted using tetraphenyiarsonium chloride in chloroform solution in this manner, and the Ti(IV) and Cu(II) thiocyanates deterrnined spectrophotometricaHy. Cobalt, palladium, tungsten, niobium, and molybdenum have been deterrnined in a similar manner. In addition to their use for the deterrnination of metals, anions such as perchlorate and perrhenate have been deterrnined as arsonium salts. Tetraphenyiarsonium permanganate is the only known insoluble salt of this anion. 

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