Palladium complexes containing ligands

The first examples of highly active olefin polymerization catalysts based on late transition metals were nickel and palladium complexes containing bulky diimine ligands.310 312 For example, complex (120) was found to polymerize ethylene with an activity of ll,000gmmol h bar A range of PE materials with molecular weights up to 106 and... 

Catalytic enantioselective synthesis of 4,4-dimethyl-l-phenyl-l,2-pentadiene from 4,4-dimethyl-1,2-pentadiene and iodobenzene using 0.4 to 1 mol % of palladium complexes containing chiral phosphane ligands as the catalyst for the enantioselective cross coupling134 is the only example of substoichiometric transition metal catalyzed enantioselective allene synthesis. 

Dicarboxylic acids form monomeric complexes with palladium(II), K2[Pd(X2)2] (X2 = oxalate, malonate, etc,).153154 They may be prepared by warming a suspension of palladium(II) chloride with a concentrated solution of the alkali metal dicarboxylate or by using other palladium complexes containing readily substituted ligands such as [Pd(OH)2], [Pd(N03)2(H20)2] or [Pd(02CMe)2]3-155 These complexes are claimed to have useful antitumour properties.155 Complexes [Pd(X2)L2] (X2 = dicarboxylate L = amine or L2 = diamine) may be prepared by reaction of the dichloro complex with a carboxylate salt.156,128... 

Reactions and Structures of Palladium Complexes Containing Bis(diphenylphosphino)methane as a Bridging Ligand... 

Better catalytic behavior was observed in the copolymerization of CO and norbornadiene with palladium complexes containing a hemilabile pyridyl-carbene ligand [23]. The choice of a pyridine-functionalized carbene can be explained by the fact that the hemilabile arm in such a ligand is capable of reversible dissociation from the metal center, leading to vacant coordination sites for the complexation of the substrates while the strong donor moiety remains bound to the metal. 

Burmeister has recently shown that this metathetical reaction is a convenient method for the preparation of some palladium(II) complexes which cannot be synthesized by direct reaction of the ligand with tetrachloropalladate(II) ion. By this method he has prepared dichloro(diphenylphosphinoethane)palladium (II), as well as complexes containing ligands other than those of the organophosphorus type, for example, dichlorobis(thiourea)-palladium(II), [PdChl (NH2)2CS 2], and dichlorobis(2,3,5,6-tetraphenylpyridine)palladium(II), [PdCh(C5NHPh4)2]."... 

Extensive mechanistic studies have been conducted on the oxidative addition of aryl halides to Pd(0) complexes ligated by PPh3 in different media and with different additives175, 176. However, palladium complexes containing these ligands are not active catalysts for amination. Instead, one must consider the addition of aryl halides to palladium complexes bound by ligands relevant to amination. Studies of the mechanism of oxidative addition to palladium(O) complexes of P(tol-o)3, DPPF, BINAP, Q-phos, P(Bu-f)3 and an /V-heterocyclic carbene ligand have been reported. 

Palladium complexes containing basic, bulky phosphines (dippp, dippe, dippb, i-Pr3P) have been demonstrated to efficiently catalyze the hydrodechlorination reaction of chloroarenes with methanol or sodium formate (Eq. 14) [102]. Of the ligands examined, dippp exhibited the highest catalytic activity. 

A more robust process, suitable for the production of a greater scope of heterocycle, was later developed using SEM-protected azoles that could be readily converted to the N-H counterparts under a variety of conditions (Scheme 13a) [27], Palladium complexes containing imidazyl carbene ligands were utilized to improve the stability of palladium throughout the catalytic cycle, modulate reactivity and disfavour biphenyl formation. 

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