Disproportionation, of metal

Photochemical disproportionation of metal-metal bonded carbonyl dimers. A. E. Stiegman and D. R. Tyler, Coord. Chem. Rev., 1985, 63, 217 (59). 

Ethylene gave cyclopropane and methylcyclopropane in very low yields. Isomerization was also observed. The term disproportionation was used for the reaction because of the analogy with disproportionation of metal ions into different oxidation states. The reaction has a more general nature, however, and consequently the terms dismutation3 and olefin metathesis4 were introduced. 

Reviews have appeared of photochemical disproportionation of metal-metal bonded carbonyl dimersphotofragmentation of transition metal cluster carbonyls in the gas phase, and f-element photochemistry. ... 

Ligand functional groups on the polymer first form a soluble macromolecular complex. The loss of CO transforms complexes into polymer-immobilized cluster particles M . The subsequent growth of these particles leads to the formation of a nanoparticle. Initiation, growth of particles, and termination by simple disproportionation of metal carbonyl on the particle surface all occur. 

Lees, A. J. Luminescence Properties of Organometallic Complexes, Chem. Revs. 1987, 87,711-743. Stiegman, A. E. lyier, D. R. "Photochemical Disproportionation of Metal>Metal Bonded Carbonyl Dimers, Coord. Chem. Revs. 1985,63, 217-240. 

Other methods for preparing tertiary arsiaes have been employed, but they have limited usefiilness. These methods include the cleavage of quaternary arsonium compounds (68), the cyclodehydrohalogenation of haloarsines (69), the reaction of dia2onium salts with arsenic trichloride in the presence of a metal such as 2inc or iron (70), and the disproportionation of halo- or dihaloarsines (71). 

Consequently, the coke cools down and the steam must be intermittently replaced by a flow of air to reheat the coke. At high temperatures, particularly in the presence of metal catalysts, CO undergoes reversible disproportionation ... 

More complex is the hydrolytic disproportionation of the molecular halogens themselves in aqueous alkali which is a commercial route to several alkali-metal halides ... 

The product is the dihydrogen orthoperiodate N33H2I06, which is a convenient starting point for many further preparations (see Scheme on next page). Paraperiodates of the alkaline earth metals can be made by the thermal disproportionation of the corresponding iodates, e g. ... 

Disproportionation of Pu(IV). There are several needs associated witn the occurrence, detection, and mitigation of the disproportionation of Pu(IV) in applied plutonium recovery/ purification procedures. First, there is a great need for much more detailed information concerning the effect of typical process conditions [e.g., temperature, concentration of plutonium, hydrogen ion, nitrate ion, nitrite ion, fluoride ion, other metal ions (e.g., A13+, Fe3+, etc.), etc.] on the occurrence and extent of the reaction ... 

Use the information in Appendix 2B to determine the equilibrium constant for the disproportionation of copper(l) ions in aqueous solution at 25°C to copper metal and copper(ll) ions. 

The compounds discussed in 6.2.3 are significant as examples of metal-meta bonding in group IIIB, but their value for chemical utilization is restricted by their insolubility and their tendency to disproportionate to E(0) or E(I) and E(III) states. 

For the most electronegative ligand, fluorine, we expect a relativistic destabilization in the Au—F bond, which was indeed determined to be —0.36eV at the coupled cluster level [182,183], Nevertheless, AuF has a sufficiently high dissociation energy of about 3.17 eV and has been identified recently in the gas phase [184]. In solution or in the solid state it would disproportionate to metallic Au and compounds of Au (AuF3 for the solid). However, a carbene-stabilized Au(I) fluoride was synthesized only very recently (see discussion in the next section) [185]. 

The multifarious character of -orbital symmetry provides a possibility of explaining the catalytic action of transition metal compounds. One example is the catalytic disproportionation of olefins 101>. 

Unsually short NMR T, relaxation values were observed for the metal-bonded H-ligands in HCo(dppe)2, [Co(H2)(dppe)]+ (dppe = l,2-bis(diphenylphosphino)ethane), and CoH(CO) (PPh3)3.176 A theoretical analysis incorporating proton-meta) dipole-dipole interactions was able to reproduce these 7) values if an rCo H distance of 1.5 A was present, a value consistent with X-ray crystallographic experiments. A detailed structural and thermodynamic study of the complexes [H2Co(dppe)2]+, HCo(dppe)2, [HCo(dppe)2(MeCN)]+, and [Co(dppe)2(MeCN)]2+ has been reported.177 Equilibrium and electrochemical measurements enabled a thorough thermodynamic description of the system. Disproportionation of divalent [HCo(dppe)2]+ to [Co(dppe)2]+ and [H2Co(dppe)2]+ was examined as well as the reaction of [Co(dppe)2]+ with H2. 

Thus partial evaporation of HC1 during the synthesis of [Tc2C18]3 by the method of Eakins et al. [24] and by the autoclave method [22,42,43] creates favorable conditions (from the standpoint of the acidity of the solution and the concentration of technetium ions in it) for the formation of the octachloro-ditechnetates (+2.5), since, on the one hand, the rate of reduction of the technetium(IV) ions increases owing to their hydrolysis [42] and, on the other hand, the stability of the hydrolyzed cluster ions formed increases in relation to the reactions involving disproportionation and oxidation by atmospheric oxygen [9,52,80,87]. We may note that under the conditions of more pronounced hydrolysis, the rate of reduction of technetium(IV) increases so much that the formation of metallic technetium becomes possible. 

These processes include (1) phase transitions (2) disproportionation reactions with rupture of metal-metal bonds (3) the Anderson reaction. 

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