Polyhydride complexes

Bayse, C.A. and Hall, M.B. (1999) Prediction of the Geometries of Simple Transition Metal Polyhydride Complexes hy Symmetry Analysis. Journal of the American Chemical Society, 121, 1348-1358. 

Generation of Reactive Intermediates via Photolysis of Transition-Metal Polyhydride Complexes... 

The photochemical properties of several transition metal polyhydride complexes are described. Irradiation of [MoH Cdppe) ] (dppe =... 

A number of studies have demonstrated that photolysis of transition metal di- and polyhydride complexes can lead to the generation of very reactive intermediates, generally via photo-induced loss of H9 Cl, 2). Two such examples are shown in eqs 1 (3) and 2 (4-8). Z... 

Photoinduced reductive elimination of from polyhydride complexes, HxMLn (x > 3) can, in principle, lead to the generation... 

In this regard a more significant determination should be obtained from a study of the polyhydride complexes [ReH7(PR3)2], in that (i) if the complex is a classical hydride the rhenium atom would be in its maximum oxidation state (+ 7) and, therefore, could not undergo further oxidation processes (ii) if the complex is a non-classical hydride, the rhenium atom would be in a lower oxidation state and, consequently, could display oxidation processes. 

Moreover, Dimeric and trimeric Ir(III) polyhydride complexes (Fig. 5) were formed from the reaction of [lr(3)(COD)]PF6 with molecular hydrogen at atmospheric pressure and were found to inhibit catalytic activity. 

Substituent effects opposite to those found for silane a-complexes were observed for the complexes with IHI, where the presence of one electron-withdrawing group trans to the hydride switches the IHI on in comparison with a silyl SiRs with the donating R s only. However, the IHI weakens with the further increase of the number of electron-withdrawing substituents at silicon. It also appears that electron-donating groups on silicon decrease the extent of H Si interactions in the recently discovered class of polyhydride complexes with multicenter H Si interactions. 

Table I. Schematic of Polyhydride Complexes H7ReL2 HeOsL.2 HsIrL ...

The subject of polyhydride complexes was included as part of a larger, comprehensive review of metal hydride complexes by Kaesz and Saillant (19), and their interesting NMR behavior has been summarized by Jesson (20). The... 

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