Hydrides fluxionality

Trinuclear osmium clusters have received considerable attention recently. The green isomer of [Os3(//-H)2(CO)9(CNBu )], in contrast to the previously known red isomers, contains the CNBu ligand bonded in an axial site to the Os atom not associated with bridging hydrides. Fluxionality is associated with 3-fold rotation of the carbonyls of the Os(CO)3 units, the hydride ligands and carbonyls of the Os(CO)3(CNBu ) remaining unaffected. In the complex [ (OC)4(Bu NC)Os Os3(CO)u] there is evidence of restricted rotation about one of the Os—Os bonds at... 

Reactions leading to a series of remarkable dizirconium alkyls and hydrides are outlined in Scheme 213. In solution, the tetrahydride undergoes a rapid fluxional process (observed by NMR spectroscopy) that exchanges the four hydrides. At low temperature three distinct hydrides can be observed, which is consistent with either a dibridged structure, or a tri-bridged species undergoing... 

These nano-objects display an organometalhc surface chemistry comparable to usual organometalhc moieties and which can be studied by classical spectroscopic methods substitution reactions leading to structural changes in the particles, the fluxional or non-fluxional behavior of surface hgands, the formation and observation of surface hydride species, the monitoring of catalytic reactions etc. 

Protonation of IrH5(Pcy3)2 affords a fluxional complex thought to be IrH6(Pcy3)2 with two (7y2-H2) ligands and two classical hydrides (Figure 2.99) from the H NMR (6 = -8.3 ppm at room temperature ... 

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