84624-47-5Relevant academic research and scientific papers
Isolation of chloro-bridged arylpalladium complexes, [Pd2Ar 2(μ-Cl)2(PR3)2], in palladium catalyzed C-C cross coupling reaction of triarylbismuth with arylhalides
Chaudhari, Kamal R.,Wadawale, Amey P.,Jain, Vimal K.
, p. 15 - 21 (2012/02/04)
The reaction of [Pd2Cl2(μ-Cl)2(PR 3)2] with triarylbismuth in dichloromethane at room temperature afforded chloro-bridged arylpalladium complexes, [Pd 2Ar2(μ-Cl)2(PR3)2] (Ar = Ph or 4-MeC6H4 (tol)) in 85-90% yield as a yellow crystalline powder. These complexes were characterized by elemental analysis and NMR spectroscopy. Molecular structures of [Pd2tol 2(μ-Cl)2(PEt3)2] and [Pd 2Ph2(μ-Cl)2(PMePh2)2] were established by single crystal X-ray crystallography. These complexes are centrosymmetric dimers with trans configuration. The C-C coupling reaction between triarylbismuth and an arylhalide in the presence of a base is catalyzed by [Pd2Cl2(μ-Cl)2(PR3) 2]. The reactions proceed via an arylpalladium complex formed by transmetallation reaction between [Pd2Cl2(μ-Cl) 2(PR3)2] and Ar3Bi. Probable reaction routes for C-C coupling have been discussed.
Reactions of free radicals with η3-allylpalladium(II) complexes: Phenyl and trityl radicals
Reid, Simon J.,Baird, Michael C.
, p. 3975 - 3980 (2007/10/03)
The compounds (η3-allyl)PdCl(PPh3) and [(η3-allyl)Pd(PPh3)2]Cl react with phenyl and trityl radicals generated from the thermal decomposition of phenylazotriphenylmethane (PhN=NCPh3, PAT) in benzene at 60°C. The products are the palladium phenyl compounds, [PdPhCl(PPh3)]2 and trans-PdPhCl(PPh3)2, respectively, and 4,4,4-triphenyl-1-butene, the latter being the result of coupling of the trityl radical with the allyl ligands. In contrast, [(η3-allyl)PdCl]2 reacts with phenyl and trityl radicals under the same conditions to form palladium metal, trityl chloride and 3-phenylpropene, which is subsequently catalytically isomerized to 1-phenylpropene. These disparate results are interpreted in all cases in terms of initial attack by phenyl radicals on the palladium(II) to give phenyl-palladium(III) intermediates, and it is the secondary reactions, influenced by the presence or absence of coordinated PPh3 ligands, which provide variety in the products. The reaction of [(4-methoxy-1,3-η3-cyclohexenyl)PdCl]2 gives a mixture of trans-3-methoxy-6-phenylcyclohexene and trans-4-methoxy-3-phenylcyclohexene, consistent with initial formation of a phenyl-palladium(III) intermediate followed by phenyl migration to the η3-cyclohexenyl ligand (reductive elimination).
Thermal stability, decomposition paths, and Ph/Ph exchange reactions of [(Ph3P)2Pd(Ph)X] (X = I, Br, Cl, F, and HF2)
Grushin, Vladimir V.
, p. 1888 - 1900 (2008/10/08)
Complexes of the type [(Ph3P)2Pd(Ph)X], where X = I (1), Br (2), Cl (3), F (4), and HF2 (5), possess different thermal stability and reactivity toward the Pd-Ph/P-Ph exchange reactions. While 1 decomposed (16 h) in toluene at 110 °C to [Ph4P]I, Pd metal, and Ph3P, complexes 2 and 3 exhibited no sign of decomposition under these conditions. Kinetic studies of the aryl-aryl exchange reactions of [(Ph3P)2Pd(C6D5)X] in benzene-de demonstrated that the rate of exchange decreases in the order 1 > 2 > 3, the observed rate constant ratio, kI:kBr:kCl, in benzene at 75 °C being ca. 100:4:1 for 1-d5, 2-d5, and 3-d5. The exchange was facilitated by a decrease in the concentration of the complex, polar media, and a Lewis acid, e.g., Et2O·BF3. Unlike [Bu4N]PF6, which speeded up the exchange reaction of 2-d5, [Bu4N]-Br inhibited it due to the formation of anionic four-coordinate [(Ph3P)Pd(C6D5)Br2]-. The latter and its iodo analogue were generated in dichloromethane and benzene upon addition of [Bu4N]X or PPN Cl to [(Ph3P)2Pd2(Ph)2(μ-X) 2] (X = I, Br, or Cl) and characterized in solution by 1H and 31P NMR spectral data. The mechanism of the aryl-aryl exchange reactions of [(Ph3P)2Pd(C6D5)X] in noncoordinating solvents of low polarity may not require Pd-X ionization but rather involves phosphine dissociation, the ease of which decreases in the order X = I > Br > Cl, as suggested by crystallographic data. Two mechanisms govern the thermal reactions of [(Ph3P)2Pd(Ph)F], 4. One of them is similar to the aryl-aryl exchange and decomposition path for 1-3, involving a tight ion pair intermediate, [Ph4P][(Ph3P)PdF], within which two processes were shown to occur. At 75 °C, the C-P oxidative addition restores the original neutral complex (4). At 90 °C, reversible fluoride transfer from Pd to the phosphonium cation resulted in the formation of covalent [Ph4PF] and [(Ph3P)Pd], which was trapped by PhI to produce [(Ph3P)2Pd2(Ph)2(μ-I) 2]. The other decomposition path of 4 leads to the formation of [(Ph3P)3Pd], Pd, Ph2 , Ph3PF2, and Ph2P-PPh2 as main products. Unlike the aryl-aryl exchange, this decomposition reaction is not inhibited by free phosphine. The formation of biphenyl was shown to occur due to PdPh/PPh coupling on the metal center. Mechanisms accounting for the formation of these products are proposed and discussed. The facile (4 h at 75 °C) thermal decomposition of [(Ph3P)2Pd(Ph)(FHF)] (5) in benzene resulted in the clean formation of PhH, Ph3PF2, Pd metal, and [(Ph3P)3Pd].
Preparation of chloride-bridged organopalladium(II) dimers and their role in the carbonylation of trans-[PdClR1(PR3)2]
Anderson, Gordon K.
, p. 665 - 668 (2008/10/08)
Complexes of the type [Pd2(μ-Cl)2R2L2] (R = Ph, C6H4Me-p, or CH2Ph; L = PPh3, PMePh2, or PBu3) are prepared by the reaction of R2Hg with [Pd2(μ-Cl)2Cl2L2] in benzene and have been characterized by elemental analysis and NMR spectroscopy. Reaction with L gives the corresponding bis(phosphine)palladium complex, while treatment with CO yields [Pd2(μ-Cl)2(COR)2L2]. Carbonylation of trans- [PdClRL2] or bridge cleavage of [Pd2(μ-Cl)2(COR)2L2] with L produces trans-[PdCl(COR)L2]. The rates of these processes are considered, and the intermediacy of the dimeric complexes in the carbonylation of trans-[PdClRL2] is discussed.
