Reductive elimination of hydrogen

S-H bond to the gold surface, followed by the reductive elimination of hydrogen, as shown in Eq. (2) [37],... 

Successive hydrogen transfers within 60, followed by coordination of olefin and then H2 (an unsaturate route), constitute the catalytic cycle, while isomerization is effected through HFe(CO)3(7r-allyl) formed from 59. Loss of H2 from 60 was also considered to be photoinduced, and several hydrides, including neutral and cationic dihydrides of iridium(III) (385, 450, 451), ruthenium(II) (452) and a bis(7j-cyclopentadienyltungsten) dihydride (453), have been shown to undergo such reductive elimination of hydrogen. Photoassisted oxidative addition of H2 has also been dem-... 

Few studies have been made of the reactions of this class of complex. The action of bases upon the complexes brings about reductive elimination of hydrogen halide (equation 207).973 However, if this reaction is carried out in dichloromethane it appears that the hydrido ligand reduces the solvent since, although the base hydrochloride is formed, a rhodium(III) complex results (equation 208).953 The action of bromine989 or S02953 also produces hydrogen halide (equations 209 and 210). (The reaction with concentrated nitric acid has already been mentioned in Section 48.6.3.3,ii above.953)... 

Oxidative addition of hydrogen halides is most extensively studied with Ir complexes. Stereochemical, mechanistic and thermochemical data are known. The trans-IrCl(CO)(PRj)2 compounds demonstrate the clearest examples of oxidative addition because the products HIr(X)Cl(CO)(PR3)j are stable complexes. The analogous Rh complexes are unstable with respect to the reductive elimination of hydrogen halide. 

PtH3(Tp )] has also been synthesized through the sequence of clean reactions reported in Fig. 2.125. The acid-assisted reductive elimination of hydrogen from [PtH3(Tp )] and of methane and hydrogen from [PtMeH2(Tp )] has been examined by the same authors,... 

Trinuclear clusters of platinum carbonyls are more common. These have been prepared by the reaction of [Pt(CO)2L with phosphine ligands the reduction of PtHXL2 with hydrazine in the presence of CO, and the reductive elimination of hydrogen from fra s-PtH2(PCy3)2 in the presence of The initially formed Pt3(CO)4L4 has been isolated for L = PPh3,... 

The photochemically induced reductive eliminations of hydrogen from [IrClH2-(PPh3)a] and [IrHs(PPh3)3] appear to be concerted processes since in the presence of deuteriated analogues no HD is produced. The photoactive excited state is believed to involve population of an iridium-Ha antibonding orbital which explains the easy hydrogen loss. 

Transition metal hydride complexes of the second- and third-row transition are common, and frequently thermally stable under ambient conditions. They can be synthesized by reactions involving hydrides, protons, or by the oxidative addition of hydrogen to a low valent complex. Hydride complexes of these metals will often undergo reductive elimination of hydrogen under photolytic conditions, which is the reverse of the oxidative addition reaction that can be used in their synthesis ... 

These reactions involve the reductive elimination of hydrogen from both dihydride and polyhydride complexes. For polyhydrides it is found that the photolysis reactions involve either a single or a multiple loss of H2. In some cases the reductive elimination of H2 results in the formation of a coordinate unsaturated complex, but in other cases the photolysis is carried out in the presence of a coordinating ligand that complexes to give a coordinately saturated complex as the final product. 

The photoinduced reductive elimination of hydrogen occurs by a concerted / reaction rather than by a stepwise sequence. This concerted pathway is supported by the experimental observation that photolysis of a solution containing a mixture of IrClH2(PPh3)3 and IrClD2(PPh3)3 gave only H2 and D2, with no formation of the crossover product Several explanations have been offered for the photoin-... 

Organometallic hydride complexes, like those of other transition metal complexes, undergo photochemical reactions. Organometallic hydrides are known that contain either a single M-H bond, or two bonds to hydrogen in complexes of type MH2. A common reaction of the latter type is the photoinduced reductive elimination of hydrogen ... 

A study of the reductive elimination of hydrogen from ( / -cp)2MoH2 has concluded that the pathway likely involves a direct concerted loss of hydrogen. This conclusion was reached by carrying out the photolysis of ( / -cp)2MoH2 in the presence of toluene-d . Less than 10% of HD is detected. " Such an observation makes it unlikely that the elimination occurs in a stepwise manner because the free... 

The kinetics of reductive elimination of hydrogen from iridium(i) have been investigated, mainly in chloroform solution ... 

The mechanism shown in the Scheme is suggested for the reaction of hydridoplatinum(n) complexes with tetracyanoethylene, which involves reductive elimination of hydrogen chloride from the platinum. 

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