Platinum hydrido complexes

Yoshida and Otsuka found that platinum(O) complexes [PtLj] (26) (a L = PEtj b L = P Prj) and rhodium hydrido complexes such as [RhHLj] (L = P Prs 33, PEts), [RhiHidr-NJlPCyslJ (34), tram-[RhH(N2)(PPh Bu2)J, and [RhH(P Bu3)J, all of which carry electron-donating alkylphosphine ligands, can catalyze the water gas shift reaction under fairly mild conditions (100-150°C CO 20 kg/cm ) (Eq. 6.32) [23, 60]. Among these complexes, [RhH(P Pr3)3] (33) was the most active catalyst precursor. Several complexes were isolated from or detected in the reaction mixture... 

A New Class of Hydrido-Bridged Platinum Complex with Application in Catalysis... 

There is one interesting report of an inner sphere reductive migration in a platinum hydrido complex (equation 104). 

Mononuclear Hydroxo, Methoxo, and Hydrido Complexes of Platinum(ll)... 

Unexpectedly, the methoxo complex shows no tendency to decompose to a hydride by / -elimination, although it does react immediately with water to give the hydroxo complex. In contrast, cyclohexyne bis(triphenylphosphine)platinum(0) reacts with methanol to give a hydrido complex, presumably via an undetected intermediate methoxide (see Equation 3) ... 

Dimethylhydrazine, for semiconductor growth, 12, 7 Dimethylhydrazone, Grignard additions to, 9, 67 Dimethyl(hydrido) complexes, with platinum(IV), 8, 583 Dimethylhydrizomethylgallium, for semiconductor growth,... 

Addition of phenylacetylene to the platinum hydrido complexes R3Si PtH(PPh3)2 (entries 117 and 118) leads to reductive elimination of HSi R3 and formation of a Pt(0)-alkyne complex. A similar Pt(0) product is observed from the cyclic precursor in entry 119. 

Table I. Some Better Known Types of Hydrido Complex of the Platinum Metals"...

The feverish interest in hydrido complexes has, as its main cause, the tremendous potential of these reactions in catalytic systems. In a relatively short span of time, hydrido complexes have been found to play a role in a significant number of catalytic processes (6, 9)—e.g., oligomerization of olefins (rhodium), decarboxylation reactions (rhodium), and hydrogenation reactions (ruthenium, osmium, rhodium, iridium, and platinum). Discussion of these applications would go beyond the scope of the present treatment. 

The remainder of this review is devoted to giving a closer look at the hydrido complexes of iridium and their reactions. Iridium gives the most extensive and versatile range of hydrido complexes of any platinum metal (29). The main types of compounds known and some of their reactions are shown in Table II. To this, one must add the hydrogen abstraction reaction mentioned earlier. 

Platinum(IV) hydride chemistry has been reviewed recently. These are usually formed by oxidative addition to a Pt species and are rather unstable. The reaction shown in equation (5), for example, is readily reversible, because the product easily loses HCl. Hydrido complexes are often involved as intermediates in reactions in which the first step is oxidative addition of an H-X species to Pt. ... 

Hydrides. The hydrides have the trans-structure, and the cis-species appear not to exist.28 Most of the studies have been on platinum compounds since the comparable palladium (and also nickel) hydrido complexes are usually less stable thermally some compounds such as ra w-PdClH(PR3)2 with R = cyclohexyl or Ph have been made.29... 

Most commonly, P elimination occurs leading to the formation of a hydrido complex and an olefin. During decomposition reactions of platinum complexes of the type PtRR (PR3)2(R, R = Et, Pr , Pr, Bu Bu, and n-CsHn), jS elimination occurs first to give an olefin followed by subsequent reductive elimination of RH. ... 

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