Iridium, pentamethylcyclopentadienyl complexes

Pentamethylcyclopentadienyl complexes CpjAnX, 4, 207 Cp AnX2 and Cp AnX, 4, 206 Cp MX compounds, 4, 62 with iridium amidinates, 7, 366 mono(Cp ) actinide(IV) compounds, 4, 207 with Ni-C cr-bonded ligands, 8, 108-109 with rhodium, 7, 152 with ruthenium, 6, 632 tris(Cp ) actinide(IV) compounds, 4, 219 with zirconium amidinates, 12, 730 l, 2, 3, 4, 5 -Pentamethyl-l-formylruthenocene, preparation, 6, 643... 

The pentamethylcyclopentadienyl complex of iridium relative to the iridium complexes that activate alkanes via typical oxidative addition, also reacts [33] with arenes by an unknown mechanism ... 

Given that previous studies had shown that the iridium(iii) complex [IrCl2Cp ]2 (Cp = pentamethylcyclopentadienyl) is an active catalyst for the p-alkylation of secondary alcohols with primary alcohols, a series of iridi-um(iii) complexes 35-36 bearing a Cp unit tethered to an imidazolylidene, as well as complex 37 containing a chelating NHC-pyrimidine ligand, were synthesised (Figure 8.3). ... 

A (pentamethylcyclopentadienyl)iridium chelating guanidinate complex has been conveniently prepared by treatment of [Cp IrCl2]2 with N,N, N"-th-p-tolylguanidine and base in THF at room temperature followed by recrystallization of the green product from toluene and pentane (Scheme 154). Insertion reactions of the product with heterocumulenes (diaryl carbodiimides, aryl isocyanates) have been investigated. It was found that the complex serves as highly active catalyst for the metathesis of diaryl carbodiimides with each other and for the more difficult metathesis of diaryl carbodiimides with aryl isocyanates (cf. Section V.C). ... 

The dichlororuthenium arene dimers are conveniently prepared by refluxing ethanolic ruthenium trichloride in the appropriate cyclohexadiene [19]. The di-chloro(pentamethylcyclopentadienyl) rhodium dimer is prepared by refluxing Dewar benzene and rhodium trichloride, whilst the dichloro(pentamethylcyclo-pentadienyl)iridium dimer is prepared by reaction of the cyclopentadiene with iridium trichloride [20]. Alternatively, the complexes can be purchased from most precious-metal suppliers. It should be noted that these ruthenium, rhodium and iridium arenes are all fine, dusty, solids and are potential respiratory sensitizers. Hence, the materials should be handled with great care, especially when weighing or charging operations are being carried out. Appropriate protective clothing and air extraction facilities should be used at all times. 

M. J. Wax, J. M. Stryker, J. M. Buchanan, C. A. Kovac, and R. G. Bergman, Reversible C—H Insertion/Reductive Elimination in ( 5-Pentamethylcyclopentadienyl)(trimethyl-phosphine)iridium Complexes. Use in Determining Relative Metal-Carbon Bond Energies and Thermally Activating Methane, J. Am. Chem. Soc. 106, 1121-1122 (1984). 

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. ... 

Pentamethylcyclopentadienyl)iridium complexes (pzH = (7) and dmpzH = (19)) [(CsMes) Ir(pz)2(Hpz)] and [(C5Me5)Ir(dmpz)2(Hdmpz)] show prototropism in solution depending on the substituents on the pyrazole rings <86AG(E)iii4>. The dynamic properties of the complex [rf-p-... 

Recently, it was also shown [74] that pentamethylcyclopentadienyl rhodium and iridium complexes with labile dative ligands catalyze the borylation of alkanes at the terminal position under thermal conditions (Scheme 9). It was proposed that Ir(V) and Rh(V) boryl complexes act as intermediates in these reactions. Reaction of Cp IrH4 with HBpin gives Cp Ir(Bpin)(H)3 and Cp Ir(Bpin)2(H)2. Both of the two Ir(V) boryl complexes react with octane to give octylboronate ester [75], though it is still unclear regarding the role... 

A method which uses a primary amine - diol pair in AT-heterocyclization has been developed. It features the catalytic activity of an iridium complex bearing pentamethylcyclopentadienyl (Cp ) ligands, and produces only water as a byproduct. The method was used in the two-step asymmetric synthesis of (S )-2-phenylpiperidine 145 from (7 )-phenylethylamine 146 <04OL3525>. 

Angelici and coworkers have demonstrated that coordination of thiophenes to an IrCp fragment (Cp = pentamethylcyclopentadienyl) in the mode leads to enhanced reactivity of the heterocycle as a donor. The monoiridium complex [Cp Ir(// -2,5-Me2C4H2S)] (33) reacts with triply-bonded [MoCp(00)2)2 to afford a cluster (34) in which the Mo-Mo bond is bridged by the thiophene sulfur.l l The iridium moiety remains attached to the thiophene in the same fashion as in the starting material. Reaction of the same iridium precursor with [Fc2(CO)9] or [Fe2(CO)8] also gives a product (35) with a fi2-S Fe2) thiophene. A... 

Partial or complete displacement of the coordinated acetonitrile ligands may be achieved with monodentate ligands (e.g., phosphines ), bidentate ligands (e.g., dienes), or tridentate ligands, providing a convenient entry to a range of (i -pentamethylcyclopentadienyl)rhodium and -iridium complexes. 

Pentamethylcyclopentadienyl-Rhodium and -Iridium Complexes as Catalysts for Olefin and Arene Hydrogenation... 

The binuclear complexes derived from the dimerization of Cp (q -allyl)hydride iridium fragments (Cp = r] -pentamethylcyclopentadienyl) reported by Bergman provide noteworthy examples of CSp -H bond activation (Scheme 20) [105]. 

In the case of rhodium and iridium, cyclopentadienyl compounds for high oxidation states ( + 5) of the metals are known. These complexes, like rhodium(III) and iridium(III) compounds, with the pentamethylcyclopentadienyl ligand... 

Ir Aryl halides (X=I, Br) were believed to be unsuitable substrates for the visible light photoredox chemistry because of their high redox potentials. However, when the reaction with Arl was carried out in benzene in the presence of the Ir complex [Cp IrHCl]2,(Cp =q -pentamethylcyclopentadienyl) as catalyst and KOBu at 80°C, the biaryls were obtained in a 43-73% yield [69]. In addition, in the photostimulated reaction with Ir(ppy)j (tris(2-phenylp3Tidine)iridium) as catalyst, biphenyls were obtained at room temperature (rt) from Arl or within the range it to 90°C from ArBr (Eq. 9.18) [70] ... 

Rigby W, Bailey PM, McCleverty JA, MaitUs PM (1979) Pentamethylcyclopentadienyl-rhodium and -iridium complexes 19. Preparation and reactions of azido-, cyanato-, tMocya-nato-, nitrito-, and nitrato-rhodium complexes. J Chem Soc Dalton Trans 371—381... 

Direct C-H activation at abnormal carbene positions was achieved by heteroatom-directed cyclometalation reactions using pyridyl-functionalized azolium salts and [IrCp Cl2]2 (Cp = pentamethylcyclopentadienyl Scheme 3.4). Cyclometalation proceeded well with both triazolium salt 20 and imidazolium salt 22 and yielded iridium complexes 21 and 23 in good yields. Transmetalation from silver was not efficient in either case. The imidazolium precursor underwent activation and oxidation of the exocyclic C2-bound CH3 group, whereas triazolium salt 20 formed a mixture of compounds upon reaction with Ag20, probably due to poor selectivity and competitive coordination of the pyridyl nitrogen. 

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