Phosphine complexes, and oxides

Phosphazene polymers, 773-775 Phosphazenes, 769-773 Phosphine complexes, and oxides, 871... 

Y. Z. Yuan, A. P. Kozlova, K. Asakura, H. L. Wan, K. Tsai, and Y. Iwasawa, Supported Au catalysts prepared from Au phosphine complexes and As-precipitated metal hydroxides Characterization and low-temperature CO oxidation, J. Catal. 170(1), 191-199 (1997). 

Even in an excess of ligands capable of stabilizing low oxidation state transition metal ions in aqueous systems, one may often observe the reduction of the central ion of a catalyst complex to the metallic state. In many cases this leads to a loss of catalytic activity, however, in certain systems an active and selective catalyst mixture is formed. Such is the case when a solution of RhCU in water methanol = 1 1 is refluxed in the presence of three equivalents of TPPTS. Evaporation to dryness gives a brown solid which is an active catalyst for the hydrogenation of a wide range of olefins in aqueous solution or in two-phase reaction systems. This solid contains a mixture of Rh(I)-phosphine complexes, TPPTS oxide and colloidal rhodium. Patin and co-workers developed a preparative scale method for biphasic hydrogenation of olefins [61], some of the substrates and products are shown on Scheme 3.3. The reaction is strongly influenced by steric effects. 

Tertiary Phosphine Complexes Intermediate Oxidation States and... 

It is a singular circumstance that the known chemistry of the tertiary phosphite complexes of osmium differs quite significantly from that of the tertiary phosphines, arsines and stibines. The closest analogue to P(OR)3 in osmium coordination chemistry would seem to be PF3, but even here the similarities are not marked. The oxidation states found are 0, II, III and IV (there are no established zerovalent unsubstituted osmium phosphine complexes), and the phosphites form unsubstituted species of the type OsL and [OsL ] " which have no counterparts in phosphine chemistry. The reason for these differences must be associated in part at least with the different cone angles and basicities of P(OR)3 ligands as against PR3. Further similarities and differences between the chemistries of osmium phosphines, phosphites and phosphorus trihalide complexes would obviously constitute a worthwhile study. 

The primary focus of research using transition metal phosphine complexes for oxidations is in the complexation and activation of molecular oxygen. These oxygen complexes have been variously regarded as complexes of coordinated peroxide, superoxide, or singlet oxygen, and their reactivity with reduced substrate has been interpreted on such a basis. In this chapter, we will focus on the chemical reactivity of these compounds for oxygen atom transfer oxidation reactions, with a particular emphasis on the mechanistic features of these processes. 

As a final generalization, it should be mentioned that these radical chain processes are common when transition metal compounds other than phosphine complexes are used. Catalytic oxidations have been carried out with a wide range of metal complexes, and a comparison has been observed between reactions catalyzed by phosphine complexes and those with acetyl-acetonate or other ligands. 

Agostic C-P interactions occur in phosphine complexes and in a trinuclear Ru cluster with a /r-phosphido interaction. Reaction with H2 cleaves P-Cph to give benzene and a /tg-phosphinidene complex shows that the C-P bond is activated as for other a complexes. Si-Si bonds also coordinate, including a unique tripalladium complex with six Si in the coordination sphere of the central Pd and initially believed to have an unprecedented Pd oxidation state. DFT studies showed formulation as a Pd Si-Si a complex (also unprecendented) was correct, underscoring both the multifarious and often well-concealed nature of H2 and a bond coordination. 

The following experiments were made concerning the mechanism of the coupling reaction mediated by metallic nickel. The reaction of iodopentafluorobenzene with nickel powder prepared from nickel iodide was investigated in detail. Iodopentafluorobenzene was found to react with nickel at room temperature however, decafluorobiphenyl could not be detected in the reaction mixture. Triphenylphosphine (2 equiv) was then added to the mixture to trap the arylnickel intermediate as the phosphine complex, and a usual workup afforded bis(triphenylphosphine) bis(pentafluorophenyl)nickel(II) in 45% yield. As the diarylnickel(II) species seemed to be derived by disproportionation from an initially formed oxidative adduct, (pentafluorophenyl)nickel(II) iodide, the trapping of the arylnickel(II) iodide was tried. In the presence of 2 equiv of triethylphos-phine, the reaction of iodopentafluorobenzene with nickel was carried out at room temperature, and bis(triethylphosphine)(pentafluorophenyl)-nickel(II) iodide was isolated in 15% yield. 

G. M. Williams, K. I. Gell, and J. Schwartz, J. Am. Chem. Soc., 1980,102, 3660. Competitive oxidation processes in the reaction between zirconocene bis(phosphine) complexes and alkyl halides. 

Use of alcohol as a solvent for carbonylation with reduced Pd catalysts gives vinyl esters. A variety of acrylamides can be made through oxidative addition of carbon monoxide [630-08-0] CO, and various amines to vinyl chloride in the presence of phosphine complexes of Pd or other precious metals as catalyst (14). 

Alkyl- and aryl-pyridazines can be prepared by cross-coupling reactions between chloropyridazines and Grignard reagents in the presence of nickel-phosphine complexes as catalysts. Dichloro[l,2-bis(diphenylphosphino)propane]nickel is used for alkylation and dichloro[l,2-bis(diphenylphosphino)ethane]nickel for arylation (78CPB2550). 3-Alkynyl-pyridazines and their A-oxides are prepared from 3-chloropyridazines and their A-oxides and alkynes using a Pd(PPh3)Cl2-Cu complex and triethylamine (78H(9)1397). 

Codeposition of silver vapor with perfluoroalkyl iodides at -196 °C provides an alternative route to nonsolvated primary perfluoroalkylsilvers [272] Phosphine complexes of trifluaromethylsilver are formed from the reaction of trimethyl-phosphme, silver acetate, and bis(trifluoromethyl)cadmium glyme [755] The per-fluoroalkylsilver compounds react with halogens [270], carbon dioxide [274], allyl halides [270, 274], mineral acids and water [275], and nitrosyl chloride [276] to give the expected products Oxidation with dioxygen gives ketones [270] or acyl halides [270] Sulfur reacts via insertion of sulfur into the carbon-silver bond [270] (equation 188)... 

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