Pyridine iridium complexes

Catalyst 58, in which the oxazoline ring has been replaced with an imidazoline, gave ee-values in the low 90% region for substrates 36 and 38-40 [42]. However, for certain substrates (see Section 30.5), replacement of the oxazoline by an imidazoline has resulted in significantly higher enantioselectivity. Recently, a number of pyridine- and quinoline-derived iridium complexes 59-62 have been developed, which gave promising enantioselectivities with substrates 36-39 [43, 44]. However, these catalysts cannot yet compete with the most efficient oxazoline-based complexes and complex 14. 

During a discussion with G Pannetier (Universite Paris VI) in Paris, he mentioned that he thought he had seen evidence for mixed pyridine-phosphine derivatives of the type [(cod)Rh(PPh3)(C5H5N)]BF4 in the Rh series. On returning to Gif, I confirmed this result by isolating the compound and mentioned it to Morris, who tried to obtain the iridium complex. Our initial idea was that a 1 1 phosphine to metal catalyst might be even more active than the 2 1 species. 

CsHuN, Ethanamine, A-ethyl-A-methyl-tungsten complex, 26 40, 42 C6HF5, Benzene, pentafluoro-gold complexes, 26 86-90 C H4I2, Benzene, 1,2-diido-iridium complex, 26 125 CJT, Phenyl platinum complex, 26 136 C,H,N, Pyridine osmium complex, 26 291 OHtS, Benzenethiol osmium complex, 26 304 QH7P, Phosphine, phenyl-cobalt-iron complex, 26 353 QH 1-Butyne, 3,3-dimethyl-mercury-molybdenum-ruthenium complex, 26 329-335 C6H 4P, Phosphine, triethyl-platinum complex, 26 126 platinum complexes, 26 135-140 CsHisPO, Triethyl phosphite iron complex, 26 61... 

C2H,N, Pyridine, 3,5-dimethyl-palladium complex, 26 210 CbHsNO, Benzoyl isocyanide chromium com-C HbO, Ethanone, 1-phenyl-manganese complex, 26 156-158 CBH, 02, Methyl benzoate chromium complex, 26 32 C H i, o-Xylylene magnesium complex, 26 147 ChH P, Phosphine, dimethylphenyl-iron complex, 26 61 ruthenium complex, 26 273 ChH12, 1,5-Cyclooctadiene iridium complex, 26 122 ruthenium complexes, 26 69-72, 253-256 ChH OjPS, 2-Butenedioic acid, 2-(dimethylphosphinothioyl)-dimethyl ester, manganese complex, 26 163... 

Ruthenium complexes mediate the hydroamination of ethylene with pyridine.589 The reaction, however, is not catalytic, because of strong complexation of the amine to metal sites. Iridium complexes with chiral diphosphine ligands and a small amount of fluoride cocatalyst are effective in inducing asymmetric alkene hydroamination reaction of norbomene with aniline [the best enantiomeric excess (ee) values exceed 90%].590 Strained methylenecyclopropanes react with ring opening to yield isomeric allylic enamines 591... 

Cyclometallated iridium complexes, for OLEDs, 12, 145 Cyclometallated palladium(II) complexes from amines and pyridines, 8, 280 with C,C-chelating ligands, 8, 291 enantioselective synthesis, 8, 296 ferrocene-based palladacycles, 8, 292 four-membered palladacycles, 8, 297 imine- and oxime-based complexes, 8, 285 with N-N and N=N bonds, 8, 288 palladacycle catalysis, 8, 297... 

In another example, the cyclometalated iridium complex [Ir(ppy)2(4-vinylpyridine)Cl] has been attached via hydrosilation see Hydrosilation) to hydride-terminated poly(dimethylsiloxane) to produce a luminescent material. Evaluation of this material as a luminescent oxygen sensor revealed significantly improved sensitivity over dispersions of the original vinyl pyridine complex in poly(dimethylsiloxane). The luminescent material was blended with polystyrene to give a new sensor that exhibited increased sensitivity and maintained short response times to rapid changes in air pressure. 

The complex has enjoyed relatively little use in organic synthesis. For iridium-catalyzed homogeneous hydrogenation of alkenes, Crabtree s iridium complex ((1,5-Cycloocta-diene)(tricyclohexylphosphine)(pyridine)iridium(I) Hexafluoro-phosphate) is generally preferred, although this readily prepared Ir complex is active. It is more reactive than its rhodium counterpart in the catalytic isomerization of butenyl- to allylsilanes. ... 

Photoaquation of a number of iridium complexes has been observed, including transformations of cis-[IrCU(py)2] to give both fac-cis and mer-cis isomers, and also of [IrCl2(H20)(py)3] to give the cis, cis, traits isomer. Photoisomerization of cis- to tratts-[IrCl2(py)4] has been reported together with photo-pyridination of the three complexes IrCl3(H20)(py)2. ... 

The (acac-<9,0)2Ir(acac-C3) pyridine complex is quite soluble in methanol, dichloromethane, and chloroform, and moderately soluble in THF. It is slightly soluble in water, benzene, and toluene. The complex is also soluble in acetic and trifluoroacetic acids. It is insoluble in hexanes and diethyl ether. The complex is air and water stable for extended periods. Addition of pyridine to complex from procedure A or B in organic or acid media leads to formation of (acac-(9,<9)2Ir (acac-C3)pyridine in situ, which drastically inhibits C-H activation however, it does not stop it completely. Pyridine binds strongly through o-donation to help stabilize the electrophilic iridium(III). 

Asymmetric reductions of aiylalkylketones by hydride transfer from i-PrOH are catalyzed by iridium complexes, and the most efficient chiral ligands are bis-oxazolines 3.57 (R = i-Pr) and pyridine derivatives 3.63 and 3.64 [339, 873,942],... 

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