Pd salts

In Du Pont patents (116) the catalyst is prepared by spray-drying a mixture of colloidal siUca or other carriers and Pt/Pd salts. Aqueous hydrogen peroxide solutions up to 20 wt % ate reported for reaction conditions of 10—17°C and 13.7 MPa (140 kg/cm ) with 60—70% of the hydrogen feed selectively forming hydrogen peroxide. 

A review26 with 787 references on Pt and Pd salts and coordination compounds covering literature cited in Chemical Abstracts, Vol. 97 (issue 21) to Vol. 99 (issue 24) is presented. 

The reduction steps on active Co sites are strongly affected by activated hydrogen transferred from promoter metal particles (Pt and Ru). Several indications for the existence and importance of hetero-bimetallic centers have been obtained.63 [Cp Co(CO)2] in the presence of PEt3 and Mel catalyzes the carbonylation of methanol with initial rates up to 44 mol L 1 h 1 before decaying to a second catalytic phase with rates of 3 mol L 1 h-1.64 HOAc-AcOMe mixtures were prepared by reaction of MeOH with CO in the presence of Co(II) acetate, iodine, and additional Pt or Pd salts, e.g., [(Ph3P)2PdCl2] at 120-80 °C and 160-250 atm.65... 

Simple Pd salts and complexes which contain neither phosphines nor any other deliberately added ligands are well known to provide catalytic activity in cross-coupling reactions. Such catalytic systems (often referred to as ligand-free catalysts ) often require the use of water as a component of the reaction medium.17 In the majority of cases such systems are applicable to electrophiles easily undergoing the oxidative addition (aryl iodides and activated bromides), although there are examples of effective reactions with unactivated substrates (electron-rich aiyl bromides, and some aryl chlorides).18,470... 

The palladium-catalyzed coupling of aiyl and vinyl halides to organotin compounds, known as Stille coupling, is one of the most important catalytic methods of carbon-carbon bond formation. The reaction is generally conducted in polar organic solvents, such as dimethylformamide, with tertiary phosphine complexes of palladium, although phosphine-free complexes or simple Pd-salts are also frequently used as catalysts [8]. 

Pd salts and CC14 in the presence of K2CO3,362 or (3) RuH PPluV363 Primary alcohols RCH2OH can be directly oxidized to acyl fluorides RCOF with cesium fluoroxysulfate.364 Lactones can be prepared by oxidizing diols in which at least one OH is primary.365... 

Heterogeneous catalysts that exhibit good characteristics are silica-supported mixed Mo-V heteropoly acids and their Pd salts,1317 Pd on titania,1318 supported H3PMO12O40, and heteropoly acids and salts with Pd(OAc)21320 or PdCl2.1321... 

Potassium tetrachloropalladate(II) reacts with 1 to give CH3C1 and metallic Pd as products (48). This reaction apparently follows the same mechanism as the Hg(II) system, with reported rate constants K (= kj A 4) = 150 and k2 = 7.7 x 10 3 M sec-1. Additional support for the proposed methylpalladium(II) intermediate comes from the report of such a species, detected by proton NMR spectroscopy, in the reaction of PdCir with (CH3)3Sn+ (44). There has been a separate study on the base-off complex formed between PdCl4 and 1 (49). Attempts to react K2PdCl6 with 1 proved futile, due to the extremely rapid decomposition of the Pd salt under reaction conditions (46). 

The palladium(II)-mediated oxidative coupling of olefins with oxygen-nucleophiles (ROH water, alcohols, carboxylic acids) is a stoichiometric reaction with respect to Pd(II), resulting in an oxygenated product and Pd(0). To convert Pd(0) back to Pd(II) and start a new reaction cycle, a reoxidation reaction (which can itself be stoichiometric or catalytic) using a terminal oxidant is required. In this way, the overall process becomes catalytic with respect to the expensive Pd salt. 

The available evidence indicates a nonconcerted mechanism which is depicted in Scheme 14. Oxidation of a Pd(0) species by the carbon-nitrogen bond of the allyle-nammonium ion gives cleavage to the 7r-allylpalladium complex and an enamine. Nucleophilic reaction by the enamine on the Pd salt then forms resultant imines after a loss of a proton. The role of co-catalyst CF3C02H is to form the N-allylenammonium ion, which reacts readily with the Pd(0) species. 

Other electron-acceptor ligands can take the place of CO, for example S02. There is a series of higher clusters Pd (CO)x(PR3), (n = 3-8, 10, 16, and 23) they form on reduction of Pd salts in the presence of CO and PR3. Mixed-valence clusters may also arise in a self-assembly fashion, for example, (18-H-III) is formed from palladium acetate, CO, H+, and Ph2PCH2PPh2 (dppm).4... 

Reaction of 1,3-butadienes and Pd salts give munerous C4 and Cg products, depending on the exact reaction conditions. Either r-allyl C4 complexes or bis-7r-allyl Cg dimers form, which can undergo ftirther reactions with nucleophiles, CO, or solvent (Scheme 26). 

While the reaction of acid chlorides with organoz-inc halide compounds is relatively inefficient, the reaction with the corresponding copper-zinc reagents or the catalysis with Pd salts represents a smooth route for the preparation of ketones in very good yields (equation 58). 

When ggm-dimetallic reagents contain zinc and a metal of different nature MX (MX = MgBr, Li), they can react successively with two different electrophiles see Electrophile) Ei+ and E2+, with the more reactive C M bond reacting first (Scheme 36). Consequently, the vinylation of 1,1-borio zincioalkanes, catalyzed by Pd salts, is an excellent procedure for the preparation of reactive allylboranes (equation 83). 

Transmetallation of organomercurials by Pd and subsequent ligand insertion is also useful in organic synthesis e.g., the reaction of alkenes, organomercurials and Pd salts is used to replace a vinyl hydrogen by an alkyl or aryl moiety ... 

The O2F indeed must rival KrF2 fluorine atom source. It was not able to excite Pd however, and attempts to obtain the previously claimed O Pd Fg, all gave O Pd Fs, which is the probable formulation for the supposed Pd salt. 

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