Oxidation of PPh

MeOC6H4CHO) has been synthesized and characterized, and the compounds tested as catalysts for the aerobic oxidation of PPhs. " " The study follows earlier studies of similar complexes... 

Cp Cr(0)Br2 was an early example, but its potential as an oxidant was not explored extensively [14]. The complex was reported to catalyze the aerobic oxidation of PPhs, but it does not react with Et2S. According to a footnote, less electron rich CpCr(0)Br2 did oxygenate Et2S , but no further detail was given. 

For the range of samples tested, the oxidation of PPH films and filaments is independent of morphological differences, but the concentrations of UV-absorbing photo-initiators vary with production conditions. 

The above scheme does not involve direct oxygen transfer from the metal-dioxygen adduct to the substrate. Trace protic impurities may make this mechanism operative in nominally aprotic solvents such as benzene [6,7,9]. The oxidation of PPh catalyzed by Ru(NCS)(NO)(PPh ) ... 

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. 

The W(VI) oxo-peroxo complex W(C=CC=CPh)(02)(0)Cp (10 Scheme 3) is obtained by oxidation of W(C=CC=CPh)(CO)3Cp with hydrogen peroxide in strongly acidic media. Subsequent treatment with PPhs gave the dioxo-diynyl W(C=CCsCPh)(0)2Cp (11)." The terminal diynyl di-oxo complex can be prepared similar fashion." ... 

The complexes traTO-[ReO(OH)(N N)2] (N N = bipy or 4,4 -dimethyl-bipy) and trans-[Re02(N N)2]" (N N = 1,10-phenanthroline) are synthesized by reacting Rc207 with PPhs in the presence of the relevant ligands. Decomposition of the complexes occurs in aqueous media by slow oxidation of the coordinated bipyridine ligands to form the corresponding A-oxides." ... 

Osmium(VI) hydrazido complexes can be generated by electrochemical oxidation of the corresponding osmium(V) hydrazido complexes (Section 5.6.5.3.1). The complex trans-[0s (tpy)(Cl)2(NN(CH2)40)] " (83) is able to oxidize benzyl alcohol to benzaldehyde. It also oxidizes PPhs to PPh30, and R2S to give R2SO the source of O atoms is presumably H2O in the solvent. 

There are very few osmium(IV) 0x0 species. There is evidence that the Os =0 species is more reactive than the corresponding Os (0)2 species. [Os (0)2(phenba)] (see Figure 12 for structure of ligand) is able to oxidize benzyl alcohol in the presence of one equivalent of PPhs, the active... 

The system (4- Bu-pyH)3[Ru(0)3Cl ]/NM0/PMS/CH2Cl3 catalysed the oxidation of primary alcohols to aldehydes and of secondary alcohols to ketones like TRAP (Tables 2.1 and 2.2), such oxidations did not attack double bonds. As stoich. trans-(PPh )2[Ru(0)2Cl ] -/CH3CN it is a two electron oxidant for alcohols [561]. For tran -[Ru(0)2Cy - in solution the effective oxidant or oxidant precursor is [Ru(0)2Cl3]", and this species is coordinatively unsaturated. That this is the case is suggested by the observation that addition of extra Cl" (as (PPh )Cl) to the green [Ru(0)2Cl3]" in solution (Eq. 1.4) generating the red franx-[Ru(0)3Cl ] ", a markedly less effective catalytic oxidant for alcohols than [Ru(0) Cl ]" [561]. 

The generation of oxo(hydroxo)-Mo(V) species, for example, Tp MoO(OH)X, in the reactions of Tp Mo02X with half an equivalent of PPhs in wet solvents is interpreted in terms of combined OAT/CEPT reactions. Thus, water is an effective ligand for the binding site of putative Tp MoOX, formed upon OAT from Mo to phosphine, and unreacted Tp Mo02X is an effective oxidant for Tp MoOX(OH2). Hence, compropor-tionation (equation 17) mimics oxidation of reduced enzymes by external oxidants. " ... 

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