Iridium polyhydride complexes

The photochemical studies of transition metal hydride complexes that have appeared in the chemical literature are reviewed, with primary emphasis on studies of iridium and ruthenium that were conducted by our research group. The photochemistry of the molybdenum hydride complexes Mo(tj5-C5H5)2M2] and [MoH4(dppe)2] (dppe = Ph2PCH2CH2PPh2), which eliminate H2 upon photolysis, is discussed in detail. The photoinduced elimination of molecular hydrogen from di-and polyhydride complexes of the transition elements is proposed to be a general reaction pathway. 

Mo(r75-C5H5)2H2] and [MoH dppe ]. Our studies of the di- and trihydride complexes of ruthenium and iridium, described above and published previously (27,35), and those of other workers (discussed at the beginning of this chapter), indicate that photoinduced elimination of molecular hydrogen is a common reaction pathway for di- and polyhydride complexes. To demonstrate the photoreaction s generality and its utility for generating otherwise unattainable, extremely reactive metal complexes, we have begun to study the photochemistry of polyhydride complexes of the early transition metals. We focused initially... 

Iridium nanoparticles, preparation, 12, 82 Iridium(III) O-ligated complexes, preparation, 7, 315 Iridium polyhydrides, preparation and characteristics, 7, 405 Iridium pyrrolyl derivatives, reactivity, 7, 282 Iridium tetrahydrides, characteristics, 7, 407-408 Iridium trihydrides, preparation, 7, 405 Iridium vinylidenes, synthesis and characteristics, 7, 352 Iridium xyliphos complexes, properties, 7, 442 Iridoids, via Pauson-Khand reaction, 11, 360 Iron(arene) (cyclopentadienyl) cations, preparation and reactivity, 6, 166... 

Cross-Alkane Metathesis In a parallel study on cross-alkane metathesis using supported, Ta polyhydrides [34], Schrock and coworkers recently reported the dual-catalytic, homogenous, cross-alkane metathesis of n-octane, and ethylbenzene. The authors [136] employed various W-monoaryloxide pyrrolide complexes in combination with several iridium pincer complexes. For example, employing Ir-2(H2) and W-1 with a ratio of n-octane/ethylbenzene (1 1.33, in v/v) produced the best productivity toward alkylbenzenes, with good selectivity over linear alkanes (Scheme 2.20). 

Tetrahydrido(i -pentamethylcyclopentadienyl)iridium was synthesized in 1982, and proved to be a useful precursor for several iridium complexes of varied oxidation state.The tetrahydride and its derivatives are among the very few iridium(V) polyhydrides that do not contain phosphine ligands. No alternative preparation of the title complex has been reported. The key feature of the synthesis described here is the oxidation of the iridium(III) intermediate to the iridium(V) product during work-up of the reaction mixture. ... 

Eisenberg has studied the reductive elimination behavior of several polyhydrides of iridium relevant to catalytic hydrogenation and hydrofor-mylation/ Ethyl and propionyl complexes (10) and (11) in Scheme 3... 

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