Phosphines and Arsines

The mechanisms of the oxidation of phosphines and arsines by chromium(VI) have been examined both in solution and on a diatomite support. Kinetic parameters are presented for both supported and solution reactions. A ruthenium complex of 1,4,8,1 l-tetramethyl-l,4,8,ll-tetraazacyclotetradecane has been utilized to oxidize triphenylphosphine in acetonitrile. Although a limited temperature range was utilized, a AH value of 8.7 0.8 kcal mor and a A5 value of -20 2 cal K mor were calculated. The secondary phosphine oxides, HP(0)R (R = n-butyl, isobutyl, cyclohexyl) and 9H-9-phosphabicyclononane-9-oxide, react with cobaltocene to yield dihydrogen and cobalt(I) compounds. With the less bulky phosphorus ligands at elevated temperatures trinuclear cobalt(III, II) complexes may be obtained. Arsenious acid may be utilized to catalyze the oxygen atom 

A study of the superoxide anion radical, Oj, reacting as an oxidant toward 

Reaction with O2 produces OJ. A series of rigidly structured Ni(II) macrocyclic and acyclic complexes has been shown to react rapidly with hydroxyl radicals and aquated electrons.Addition of e generates a Ni(I) transient except when the ligand incorporates a nitro group. Reaction with OH leads to a longer-lived Ni(III) species. OH radicals have also been shown to react with Pu(III) with a specific rate of oxidation of 1.83 0.78 x 10 Ms at pH Comparison has been 

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Osmium(II) forms no hexaaquo complex and [Os(NH3)g] +, which may possibly be present in potassium/liquid NH3 solutions, is also unstable. [Os(NH3)5N2] and other dinitrogen complexes are known but only ligands with good 7r-acceptor properties, such as CN, bipy, phen, phosphines and arsines, really stabilize Os , and these form complexes similar to their Ru analogues. 

The osmium(IV) complexes are only obtained by this route with fairly unreactive phosphines and arsines (e.g. PBu2Ph) but they are conveniently made by oxidation of mer-OsX3(QR3)3 (Q = P, As) with the halogen in CHC13, or CCI4 and refluxing. 

Rhodium(III) forms a wide range of complexes with tertiary phosphines and arsines [108, 109], though in some cases other oxidation states are possible. Table 2.5 summarizes the complexes produced from reaction of RhCl3 with stoichiometric quantities of the phosphine. 

A considerable number of the tertiary phosphine and arsine complexes of iridium(III) have been synthesized [4, 8] they generally contain 6-coordinate iridium and are conventionally prepared by refluxing Na2IrCl6 with the phosphine in ethanol or 2-methoxyethanol [154]... 

Many, but not all, bidentate phosphine and arsine ligands form 2 1 complexes with these metals. M(diars)2X2 (diars = o-C6H4(AsMe3)2) contain 6-coordinate metals frans-Pd(diars)2I2 has long Pd-I bonds (3.52 A). These complexes are 1 1 electrolytes in solution, suggesting the presence of 5-coordinate M(diars)2X+ ions. 

Complexes are similarly formed by polydentate phosphine and arsine ligands synthetic routes involve oxidation of the platinum(II) complex, either with the halogen or with nitric acid ... 

The limited stability of these compounds is shown by the fact that other tertiary phosphines and arsines do not yield isolable products. 

With chelating phosphine and arsine ligands, two types of complex have been isolated ... 

The phosphine and arsine complexes of gold(I) have been intensively studied since the early 1970s. The possibilities of coordination numbers between 2 and 4 have been explored, though the use of bulky ligands is less essential than with the isoelectronic M(PR3)2 (M = Pd, Pt) compounds and the coordination numbers depend on both steric and electronic factors [71]. 

While tertiary phosphines and arsines tend to reduce gold(III) to gold(I), the reverse reactions can be used synthetically [126] ... 

Gold (I) complexes of bidentate phosphines and arsines like... 

Reactions involving transition metal ions and tripodal phosphines and arsines. F. Mani and L. Sac-coni, Comments Inorg. Chem., 1983, 2, 157-186 (73). 

An investigation of the chelate effect the binding of bidentate phosphine and arsine chelates in square-planar transition metal complexes. D. M. A. Minahan, W. E. Hill and C. A. McAuliffe, Coord. Chem. Rev., 1984, 55, 31-54 (153). 

However, in contrast to the chloroalane-stibine adduct, the phosphine and arsine adducts could be converted into the corresponding heterocycles by thermal activation (Scheme 10) [73]. 

CdjPj and CdjAs are low band gap semiconductors (0.5 and 0.1 eV, respectively). The bulk materials are black and start to absorb in the infrared. These materials have been prepared as colloids in alkaline solution by precipitation of Cd with phosphine and arsine Depending on the conditions of preparation, particles of different sizes (between about 2 and 10 nm) were obtained, which could also be recovered in the solid state after evaporation of the solvent. The color of these materials ranged from black to colorless with decreasing particle size, with all kinds of intermediate colors in the visible. 

Platinum(IV) complexes of phosphine and arsine ligands formed by oxidation with chlorine or bromine are well known. Chloro complexes such as ci5-[PtCl2(PEt3)4]2+ can be generated by electrolysis of the platinum(II) complex c -[PtCl2(PEt3)2].433 Similar platinum(IV) complexes... 

Although reports on silver(i) cr-alkynyl complexes have appeared for more than a century, the number of examples was still very limited prior to the past decade, and many of them were referred to as insoluble homoleptic polymeric [Ag(C=CR)]oo. Molecular alkynylsilver(i) complexes were often heteroleptic in nature and were achieved commonly through the stabilization by an extra coordination with strong cr-donor ligands such as amines, phosphines, and arsines. 

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