Iridium alkyl

A special type of reaction is observed with the platinum(IV) complex [PtI(Me)3] which cleaves the Af,N,Af, A -tetraphenyltetraaminoethylene under reduction to form the dimeric cyclometallated mono(NHC) complex of platinum(II) iodide [Eq. (31)]. Cyclometallation with the same ligand is also observed for ruthe-nium. Additional cyclometallations with various substituents of NHCs have been reported for ruthenium(II), rhodium(III), iridium(I), palladium(II), " and platinum(II). In the case of iridium, alkyl groups can be activated twice. In rare cases like for nickel(II) /x-bridging NHCs have been obtained. ... 

The stable alkylmetal(III) porphyrins are accessible from the hydrides via their corresponding bases (i.e. Rh(I) or Ir(I) porphyrins) by action of alkyl halides (paths 1, m) or from the respective chlorometal(III) porphyrins by action of lithium alkyls (path c,n). They form a very important class of compounds in view of their close relation to the alkylcobalt corrinoids. Of course, the Rh or Ir alkyl group is much more stable than the corresponding Co alkyl group which, in the case of the porphyrins, is photolabile. A variety of axial ligands have been added to the iridium alkyl porphyrins (path o). 

Iridium alkoxides, synthesis, 7, 383 Iridium alkyl complexes reactivity, 7, 284-... 

IRIDIUM ALKYL (See Alkyl Complexes) AND ARYL COMPLEXES... 

More specifically, calculations have suggested that the ruthenium-alkyl complex in Equation 6.53 reacts with arene to exchange covalent ligands by a process closely related to a a-bond metathesis mechanism. Computational studies of the reactions of a simple iridium-alkyl and alkoxo complex with alkanes to generate new metal-alkyl complexes have also suggested that a mechanism is followed that involves many of the characteristics of a classic a-bond metathesis transition state. However, calculations of the mechanisms of these two processes imply that the transition state contains some degree of M-H bonding. 

The iridium alkyl complexes [Ir(R)(dppe),] (R=Me,n -CcH-) have been... 

Interest in iridium hydrocarbyl complexes has been fueled by the higher thermodynamic stability of both Ir-C and Ir-H bonds in comparison to related compounds of rhodium. Therefore, iridium alkyl and aryl complexes have been frequently and successfully used as kinetically inert models for a variety of rhodium-catalyzed reactions allowing to collect intriguing mechanistic information on important industrial processes and organometallic reactions of academic interest. 

Homo- or heterodinuclear A-frame complexes stabilized by a pair of bridging dppm ligands were used by Cowie and co-workers to synthesize iridium alkyl compounds.Then, alkylation of [RhIr(CO)3(dppm)2] 317 with MeOTf yields [RhIrMe(CO)3(dppm)2]OTf 127, having the Me group terminally bound to iridium as confirmed by X-ray diffraction analysis (Figure 26). ... 

Hydrosoluble iridium alkyl complexes may also be prepared by hydrolysis of alkynes and alkenes promoted by water-soluble precursors. The reaction with alkynes follows the well-known mechanism demonstrated by Bianchini et al. for ruthenium complexes.A reasonable mechanism, related to that of hydrolytic breakage, has been proposed by Chin etal. to account for the hydrolysis of ethene promoted by [Cp"lr(TPPMS)Cl2] 344 in the presence of silver salts in water. Scheme 37 describes the Chin s hydrolysis of alkynes, leading to [Cp Ir(TPPMS)(CO)(CH2R)] (69 R=Ph, Bz, Bu, />-Tol) via the aquo complex [Cp Ir(TPPMS)(OH2)OTf 345... 

Hydrogen elimination from iridium alkyl or alkoxide derivatives is also a general pathway to generate Ir-H species. The mechanism of the reversible /3-hydrogen elimination from square-planar Ir(i) alkoxide complexes has been studied in detail by Hartwig," Milstein," " " and their co-workers. 

Brown JM, Maddox PJ. Solution stmctures of iridium alkyl hydrides pertaining to asymmetric hydrogenation. J. Chem. Soc., Chem. Common. 1987 (17) 1276-1278. 

Several tertiary phosphine iridium-alkyl and -aryl complexes have been... 

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