Phosphine, triphenyl metal complexes

The active metal complex could be quantitatively stripped from the silica support material by washing with methanol, and consequently, the receptor (the silica support) could be used in several, different reaction cycles. The rhodium catalyst was reused in 11 consecutive runs in batch mode for the hydroformylation of oct-l-ene (80 °C, 20-50 bar) there was no noticeable loss of activity (<0.1% per run) when a xantphos derivative was used as a ligand, and there was an approximate loss of 1% per run when a triphenyl-phosphine-derived monodentate ligand was used (Figure 32). Turnover... 

A variety of organophosphine transition-metal complexes have been used for the detection of SO2 [149]. Cook et al. used triphenyl- and tribenzyl phosphine compounds as ligands bound to Cu and Mn. Varying the ligand affects the Lewis acid strength of the metal complex, and hence, its ability to bind SO2. One complex (bis(tribenzylphosphine)copper(II) thiophenolate — [Cu(PBz3)2)SPh]) exhibited a reversible response to SO2 that was linear in the range of lO-KKK) mg/L. 

Trialkyl and triphenyl substituted tertiary arsines and stibines are, like the phosphine analogues, suitable as ligands in transition metal complexes in several oxidation states, due to their low reduction potentials (cf Table 7 in Section III.A.l) and relatively high oxidation potentials (cf Table 14 in Section V.A). 

Not only noble metal complexes, but also nickel complexes undergo oxidative addition reactions. Fahey found that a variety of vinyl and aryl halides react with (R3P)2Ni(C2H4) to form a stable carbon-metal o-bond 24). Forex-ample, tetrachloroethylene affords /ran. -chloro(trichlorovinyl)bi s(triphenyl-phosphine)nickel. 

The ATP process developed by Sawamoto and coworkers [226], uses an initiating system consisting of carbon tetrachloride, dichlorotri(triphenyl-phosphine)-ruthenium (II) and methylaluminum bis(2,6-di-fe/"f-butylphenoxide) to polymerize methyl methacrylate [226]. The polymerization involves reversible and homolytic cleavages of carbon-halogen terminal groups assisted by transition metal complexes [226]. 

Thiocarbonyl and selenocarbonyl metal complexes are generally prepared from carbon disulfide, CS2 thiophosgene, CSCI2 and carbon diselenide, CSc2, as well as from transition metal complexes such as metal carbonyls. Commonly, triphenyl-phosphine is utilized to eliminate sulfur or selenium ... 

More limited investigations of the oxidation of triorganoarsines in the presence of transition metal complexes have been carried out but it appears that many of the same complexes which catalyze phosphine oxidation are also effective for arsines. The ruthenium complex, [Ru(NCSXN0XPPh3)2(02)], for example, has been found to be an efficient catalyst for the oxidation of triphenylarsine [79] the initial rate of oxidation being three to four times greater than the corresponding rate for triphenyl-phosphine oxidation under the same conditions. However, the rate of this oxidation was rapidly diminished by decomposition of the catalyst so that in a short time ca. 30 min) the catalyst was virtually ineffective. 

Br(CH2>2Br (CH3)2NCH0 CeHsCOCgHs Reaction of RCHgX with triphenyl phosphine resin (viii), followed by treatment with a base Reaction of the metal complex (ML ) with the triphenyl polymer (viii) From the lithiated polymer, by the reaction sequence ... 

Catalytic forms of copper, mercury and silver acetylides, supported on alumina, carbon or silica and used for polymerisation of alkanes, are relatively stable [3], In contact with acetylene, silver and mercury salts will also give explosive acetylides, the mercury derivatives being complex [4], Many of the metal acetylides react violently with oxidants. Impact sensitivities of the dry copper derivatives of acetylene, buten-3-yne and l,3-hexadien-5-yne were determined as 2.4, 2.4 and 4.0 kg m, respectively. The copper derivative of a polyacetylene mixture generated by low-temperature polymerisation of acetylene detonated under 1.2 kg m impact. Sensitivities were much lower for the moist compounds [5], Explosive copper and silver derivatives give non-explosive complexes with trimethyl-, tributyl- or triphenyl-phosphine [6], Formation of silver acetylide on silver-containing solders needs higher acetylene and ammonia concentrations than for formation of copper acetylide. Acetylides are always formed on brass and copper or on silver-containing solders in an atmosphere of acetylene derived from calcium carbide (and which contains traces of phosphine). Silver acetylide is a more efficient explosion initiator than copper acetylide [7],... 

The use of a basic solvent (in this case diethylamine) is important to stabilize acetylenic anions.(9) The third catalyst system component, triphenyl phosphine, is presumably added to help replace lost triphenyl phosphine ligands on the palladium complex and thus prevent metal agglomeration. 

In the case of phosphine, especially tri-n-butyl and triphenyl phosphines, an active phosphine complex is formed in the reaction medium via reaction with nickel carbonyl. This complex is a very active species provided that the optimum concentration of phosphine is used. Low phosphine concentration results in a loss of the effective nickel concentration through the formation of nickel tetra-carbonyl, nickel metal or nickel iodide. The absolute concentration of phosphine is less important than the P/Ni ratio. In addition to form the stable Ni-P catalyst, the phosphine has to compete with other ligands in the reaction mixture for nickel. With high carbon monoxide partial pressure, there is more CO in solution to compete with phosphine favoring the formation of the carbonyl, which is inactive under the reaction conditions. Hence with high carbon mon-... 

The stabilizing effect of an axial ligand has been previously observed in the synthesis of cobalt corrolates. Such an effect has been used to synthesize the complex where no peripheral p substituents are present on the macrocycle, which decomposes if attempts are made to isolate it in the absence of triphenyl-phosphine [10]. The behavior of rhodium closely resembled that of cobalt and it seems to be even more sensitive to the presence of axial ligands. [Rh(CO)2Cl]2 has also used as a metal carrier with such a starting material a hexacoordinated derivative has been isolated. The reaction follows a pathway similar to that observed for rhodium porphyrinates the first product is a Rh+ complex which is then oxidized to a Rh3+ derivative [29]. 

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