Trinuclear complex iridium

A new class of binuclear nitrido complexes of tetravalent osmium and ruthenium is described in which the metal atoms are symmetrically bridged by a nitride ligand to give a linear M-N—M unit They have the stoichiometries M2NX8(H20)2]3 and [M2N(NH3)8Y2]3+ (M = Os, Ru X = Cl, Br Y = Cl, Br, etc.). Studies are reported on their vibrational spectra, structures, and bonding. Preliminary studies are reported also on trinuclear complexes of osmium and iridium. Finally, the use of vibrational spectroscopy in the study of metal-nitrido and metal-oxo complexes is discussed briefly. 

The superiority of iridium photosensitizers was established by Chen and coworkers who assembled a derivative of PS2 and a phosphine-modified diiron catalyst through an amide linkage (Figure 9.13). The highest efficiency so far reported for a diiron-based photocatalyst was achieved by trinuclear complex 15... 

Binuclear iridium hydrides like 8 often form as off-loop species that can result in decreasing of the catalytic activity. Formation of trinuclear complexes completely deactivating the catalyst has been also observed. Nevertheless, the dimeric hydrides formed reversibly before the elimination of the proton are catalytically active, since they can recover mononuclear dihydrides via reversible dissociation. ... 

Imidazolium ligands, in Rh complexes, 7, 126 Imidazolium salts iridium binding, 7, 349 in silver(I) carbene synthesis, 2, 206 Imidazol-2-ylidene carbenes, with tungsten carbonyls, 5, 678 (Imidazol-2-ylidene)gold(I) complexes, preparation, 2, 289 Imidazopyridine, in trinuclear Ru and Os clusters, 6, 727 Imidazo[l,2-a]-pyridines, iodo-substituted, in Grignard reagent preparation, 9, 37—38 Imido alkyl complexes, with tantalum, 5, 118—120 Imido-amido half-sandwich compounds, with tantalum, 5,183 /13-Imido clusters, with trinuclear Ru clusters, 6, 733 Imido complexes with bis-Gp Ti, 4, 579 with monoalkyl Ti(IV), 4, 336 with mono-Gp Ti(IV), 4, 419 with Ru half-sandwiches, 6, 519—520 with tantalum, 5, 110 with titanium(IV) dialkyls, 4, 352 with titanocenes, 4, 566 with tungsten... 

The counterion as well was found to strongly influence catalyst performance. Initial experiments with Ir-PHOX complexes gave high enantioselectivity and full conversion, but only at high catalyst loadings of 4 mol% (Scheme 2b) [9]. Lower catalyst loadings resulted in decreased conversion due to catalyst deactivation [14] with concomitant formation of an inactive trinuclear iridium hydride cluster 8 (Scheme 4) [15], analogous to the deactivation products observed with the Crabtree catalyst 6 [16]. 

Schau-Magnussen M, Malcho P, Herbst K, Brorson M, Bendix J (2011) Synthesis and X-ray crystal structure of a novel organometallic (p3-oxido)(p3-imido) trinuclear iridium complex. Dalton Trans 40 4212-4216... 

Smidt, S. R Pfaltz, A. Martmez-Viviente, E. Pregosin, P. S. Albinati, A. X-ray and NOE studies on trinuclear iridium hydride phosphino oxazoline (PHOX) complexes. Organometallics 2003,22,1000-1009. 

Trinuclear and Larger Clusters - Addition of sodium sulfide to [Cp M(MeCN)3] yields sulfido-capped [Cp 3M3(p -S)2l (M=Rh,Ir), the iridium complex also being isolated from... 

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