Phosphine species

Apart from Ru(CO)5 and other carbonyls, there are mixed carbonyl-phosphine species and a few simple phosphine complexes like Ru(PF3)5 and Ru[P(OMe)3]5 [61a]. 

Red phosphorus in an aqueous basic medium has also been used in the preparation of a-hydroxyphosphonites (Figure 2.7).23 Aromatic and a,p-unsaturated aldehydes added to the reaction mixture undergo nucleophilic attack by the intermediate phosphine species in a manner reminiscent of the approach of Pudovik and Arbuzov24 using partially esterified phosphites and aldehydes. Reaction of the red phosphorus suspension is noted to be enhanced by the use of ultrasonication an excess of elemental phosphorus is used, and excess unreacted red phosphorus must be removed by filtration in the product isolation process. 

The simplest and the least technically demanding method of isolating S,S-CHIRAPHOS from the reaction mixture is by the formation of its very insoluble bis(thiocyanato-N)nickel(II) complex. The nickel selectively separates the S.S-CHIRAPHOS from other phosphine species in the reaction mixture. 

The first-generation catalyst, a cobalt carbonyl ligand, was employed in the BASF process. In the next generation, phosphine species were added to milden the reaction conditions and to optimize the linear to branched ratio. In the third... 

A kinetic study of the hydroformylation of soybean oil was undertaken by Kandanarachchi [25] the pressure was varied between 40 and 110 bar, and the conversion rate increased with the pressure. The activation energy was calculated both for a rhodium system with (PhO)3P and with (Ph)3P showing that the phosphine species has a lower activation energy. Also, the temperature effect was studied, and it was found that the reaction rate increased until 100°C. Above that, the high temperature apparently inhibited the reaction due to phosphido-bridged clusters which are favored at higher temperatures. 

When aryl halides were applied in catalytic coupling reactions, the mechanistic evidence points to initial SET reduction by low-valent nickel phosphine species (selected investigations in [23, 24]). The competition of cage collapse to ArNi(PR3)2X vs. dissociation of the aryl halide radical anion to a free radical and Ni(I) complexes determines the cross-coupling manifolds. Thus, Ni(0)-Ni(II) and Ni(I)-Ni(III) catalytic cycles can occur interwoven with each other and a distinction may be difficult. Common to both is that the coupling process with aryl halides is likely to occur by a two-electron oxidative addition/reductive elimination pathway. 

In some cases the ensuing reactivity of the complex is changed upon substitution. For example, the Bi[Co(CO)3L]3 L = phosphine species have exhibited no tendency to form c/oso-tetrahedral molecules like the parent L = CO complex. Presumably, the steric crowding imposed by the phosphines prevents the formation of BiCo3(CO)6L3 species. 

A substantial number of these have been reported for osmium, particularly with AsPh3. Predictably the chemistry is quite similar to that for the analogous phosphine species. 

The precise nature of the product obtained depends on the cation used and also on the halide and the solvent. There is a variety of halide complexes with other ligands present such as Mnl2(thf)3, trnns-[MnCl4(H20)2]2 , and amine and phosphine species. Homoleptic pseudohalide complexes are represented by [Mn(NCS)6]4 and [Mn(CN)6]4, as well as Prussian blue-like analogues, e.g., K2Mnu[Mnn(CN)6], that are ferrimagnetic.3... 

In these cases the catalytic cycle differs from the one discussed previously in that the first hydrogen transfer to C=C takes place prior to H2 addition. The cycle for RhH(CO)(PPh3)3 is shown in Fig. 22-2. The 18-electron precursor complex dissociates in benzene to a 16-electron square bis(phosphine) species which is capable of binding the olefin. In agreement with the assumption of a ligand dissociation step, catalysis is suppressed by the addition of excess PPh3. 

Similarly, a Pd[(S,S)-N0RPH0S]( 7 -C3H5) Cl04 precursor prepared from 2-acetoxy-4,4-diphenylbut-3-ene has been shown to react with sodium dimethylmalonate, a soft nucleophile. The corresponding [Pd (chiral phosphine)] species is thereby generated in situ, which serves to initiate the catalytic cycle that results in allylic alkylation of the nucleophile. The resulting allylation product is formed in 76% ee (eq 8). ... 

Platinum dihydride complexes with small monodentate phosphines may also be prepared. Photolysis of the oxalate complexes [Pt(C204)(PR3)2] (R = Me, Et) generates the coordlnatively unsaturated bis(phosphine) species, to which H2 may add oxidatively ... 

The Initiation Mechanism with Phosphonium Compounds. Although further experimental data are needed to give a fuller understanding of the reaction mechanisms involved in the latent acceleration effect of these quaternary phosphonium compounds in epoxyanhydride resins, there is definite indication, at this stage, that the mechanism does not involve the decomposition of the phosphonium compound to the free phosphine species (16). The initiation mechanism probably involves the formation of hydrogen-bonded phosphonium-epoxy or phosphonium-anhydride complexes which rearrange on the application of heat to form activated species resulting in polymerization of the epoxy-anhydride components ( > ... 

Recently, phosphine compounds have been vised as catalysts in the epoxy-phenolic or epoxy-anhydride reactions. There is indication that the mechanism does not involve the decomposition of the phosphonium compound to the free phosphine species. The... 

Treatment of (phosphine)gold(I) halides or tris(phosphinegold(I))oxonium salts with sodium tetraphenylborate affords arylgold(I) phosphine species through an unusual phenyl transfer reaction. Examples of this novel synthetic route are given in equations 22104 and 23105. 

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