Palladium complexes thiolates

Related reactions of thiolate anions with ort/zo-chloromethyl-phenyl(diphenyl)phosphine have provided a range of ort/ o-alkyl and aryl-thiomethylphenyl(diphenyl)phosphines. " The reactions of 2-amino-alkylphosphines with isocyanates and isothiocyanates have provided routes to new chiral phosphinoalkyl-urea and -thiourea ligands. Similarly, treatment of hydroxy- or amino-functional arylphosphines with isocyanides in the presence of a cyclooctadienepalladium(II) complex results in the formation of bidentate arylphosphino-carbene palladium complexes. New chiral phosphinoarylphosphoramidite ligands, e.g.,... 

Kurosawa et al. have reported that the relative stability of the ti-allyl palladium thi-olate 39 and the allyl sulfide/Pd(0) was highly ligand dependent. In the presence of PPhs or P(OMe)3 the stability was in favor of reductive elimination (Eq. 7.28), while in the presence of olefin or in the absence of any additional ligand the stability was in favor of oxidative addition (Eq. 7.29) [38]. This can explain the reactivity of the n-allyl palladium thiolate 33 and 38 proposed in Eq. (7.24) and path (c) of Scheme 7-10. The complex 33 should react with PhSH, but C-S bond-forming reductive elimination has to be suppressed in order to obtain the desired product 32. On the other hand, the complex 38 requires the phosphine ligand to promote the C-S bond-forming reductive elimination. 

Several Pd11 complexes with thiolate or thioether derivative ligands have been studied to be applied in the hydroxycarbonylation reaction.394 Aminothiolate complexes of palladium with PPh3 catalyze the conversion of styrene to 2-phenylpropionic acid in high yield and excellent regioselectivity.644 Under mild conditions and in the presence of a catalytic amount of an S, TV-chelated palladium or//zo-amino-arenethiolate complex, styrene reacts with CO and oxalic acid or water to selectively give 2-phenylpropanic aid in high yield.645... 

The formation of complexes of l,2,3,4-thiatriazole-5-thiol has been well described in CHEC-II(1996) 1,2,3,4-thiatriazole-5-thiol can form complexes with various metals such as palladium, nickel, platinum, cobalt, zinc, etc. <1996CHEC-II(4)691>. These complexes can be prepared either by cycloaddition reactions of carbon disulfide with metal complexes of azide anion (Equation 20) or directly from the sodium salt of l,2,3,4-thiatriazole-5-thiol with metal salts. For instance, the palladium-thiatriazole complex 179 can be obtained as shown in Equation (20) or it may be formed from palladium(ll) nitrate, triphenylphosphine, and sodium thiatriazolate-5-thiolate. It should be noted that complexes of azide ion react with carbon disulfide much faster than sodium azide itself. 

AU -l,2,3,4-thiatriazolc-5-thiolate anions in a square-planar coordination geometry for the palladium atoms. The use of 1,2,3,4-thiatriazole complexes in analytical chemistry to determine the sulfite ion concentration was also reported <1996CHEC-II(4)691>. 

Four oxidation states of palladium are encountered in organometallic chemistry see Palladium Inorganic Coordination Chemistry) In order of importance, they are Pd , Pd , Pd, and Pd . With the reduction of palladium from Pd to Pd , the metal changes its reactivity from electrophile to nucleophile. However, unlike main group nucleophiles such as thiolates or cyanide, Pd complexes react with both alkyl halides and aryl or vinyl halides. Reactions of Pd complexes with these latter sp halides generate new Pd aryl or vinyl bonds through the process of oxidative addition. 

The coordination chemistry of palladium and platinum with large aromatic thiolates has been restricted to some studies with PFTPH, although there is an extensive reported chemistry of oligomeric complexes with smaller thiols. Halide complexes of Pd and Pt were shown to react with Tl(PFTP) to give the presumably monomeric, square planar anionic M(II) complexes [M(PFTP)4] (83). 

Substitution of the two diphenylphosphino substituents for thiolate groups affords a series of complexes, the structure of which is typically represented by that of dichloro[l,r-bis(ibutylsulfido)ferrocene]palladium(ii) shown in Fig. 7-53 [10]. The assembly is similar to that of the preceding bis (diphenylphosphino) complexes, except for the eclipsed and less tilted (1.9°) conformation of the cyclopentadienyl rings of the ferrocene group. 

Palladium(ll) and nickel(II) complexes containing the bridging pyrazolate ion as well as the thiolate based dinucleating ligand H,L12, [M2(Ll2)(pz )] (Hpz = Hpz or Hdmpz), were obtained (148). The complexes were easily prepared by treating the [M2(Ll2)(CH2COO)] species with Hpz. ... 

An interesting displacement of thiolate in nickel(II) and palladium(ll) complexes by secondary amines, Eq. (13), has been investigated. The reaction is... 

Several approaches have been used to prepare transition-metal-thiolate complexes. The most common synthetic route involves the metathesis reaction of a metal halide with an alkali metal thiolate salt. For instance, [(DPPE)Pd(Ar)(S-t-Bu)] was obtained by treatment of the (DPPE) palladium aryl iodide complex with sodium fprf-butyl thiolate (Equaticm 4.106). Additionally, these compoimds have been formed by proton exchange reactions of thiols with M-C (Equation 4.107), ° M-W and M-O, bonds (Equation 4.108). Finally, the oxidative addition of RSH, or alkyl and aryl disulfides - is a useful way... 

A few final comments should be made on the insertions of substrates containing C-C multiple bonds into the bonds between a transition metal and an electronegative heteroatom. First, insertions of olefins into related thiolate and phosphide complexes are as rare as insertions into alkoxo and amido complexes. Reactions of acrylonitrile into the metal-phosphorus bonds of palladium- and platinum-phosphido complexes to give products from formal insertions have been observed, and one example is showm in Equation 9.90. However, these reactions are more likely to occur by direct attack of the phosphorus on the electrophilic carbon of acrylonitrile than by migratory insertion. Second, the insertions of alkynes into metal-oxygen or metal-nitrogen covalent bonds are rare, even though the C-C ir-bond in an alkyne is weaker than the ir-bond in an alkene. 

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