1- ethane, with iridium complexes

The dihydrido complex [RhH2(ri5-C5Me5)(PMe3)] forms C—H insertion products when irradiated in the presence of alkanes (ethane, propane).227,228 Reaction with CHBr3 leads to bromoalkylrhodium complexes, which on treatment with bromine give ethyl bromide or 1-bromopropane in 70-85% yield. The less stable iridium complex formed with neopentane could not be converted directly to neopentyl bromide.229 It gave, however, a mercury derivative that yielded the bromide after treatment with bromine. 

Iridium complexes such as Cp Ir(774-C6Me6) and Ir( 75-indene)(cod) themselves were inefficient, but addition of the small electron-donating phosphines such as PMe3 or the chelating l,2-bis(dimethylphosphino)ethane (dmpe) substantially increased the catalyst activity and TON (Equation (68)).344,346 The maximum TON achieved for benzene with HBpin at 150 °C was 4,500 TON. 

Ligand (94) or its C-methyl derivative [tris(pyrazol-l-yl)ethane] (represented by L) affords iridium complexes which react with carbon monoxide and methanol to yield alkoxycarbonyl derivatives [(L)IrH(C02Me)(C0)] (Equation (1)) <89JOM(366)245>. This constitutes an interesting example of alcohol activation. 

An iridium(I) complex with the l,2-bis(tcrt-butylmethylphosphino)ethane (4) and tetrakis(3,5-bis(trifluoromethyl)phenyl)borate as the counter anion catalyzes the hydrogenation of several acyclic aromatic Ai-arylimines under atmospheric hydrogen pressure at room temperature, giving the desired chiral amines with high-to-excellent enantioselectivities (up to 99%, Fig. 6) [19]. The authors also tested (S )-BINAP (Fig. 1) and (/ )-Ph-PHOX (PHOX = 2-[2-(diphenylphosphino) phenyl]-4,5-dihydrooxazole) hgands with lower enantioselectivities [19]. Both steric and electronic properties of the ligand and the combination with the BArF anion are in the base of the efficacy of this catalytic system. On the other hand, attempted hydrogenations of Ai-(2,2,2-trifluoro-l-phenylethylidene)aniline and M-(l,2,2-trimethyl-propylidene)aniline under the same conditions resulted in... 

The functionalized phosphine coordinates to the iridium center as a 6+2 electron donor ligand. This dihydrido iridium]111) complex reacts with ethene or propene to yield ethane or propane and formation of the iridium(l) complexes [(t -QH5CH2CH2PTr2-K-P)lr(CH2=CHR)]BF4 (R=H, Me) (Scheme 2.27). 

The iridium(III)-complex, [Ir(p-acac-0,0,C )(acac-0,0)(acac-C )]2, mediates the activation of unactivated aromatic C—H bond with unactivated alkenes to form anti-Markovnikov products [57]. The reaction of benzene 131 with propene 132 (0.78 MPa of propylene, 1.96 MPa of N2) leads to the formation of n-propylbenzene 133 in 61% selectivities (turnover number (TON) = 13 turnover frequency (TOE) = 0.0110 s ) (Equation 10.34). The reaction of benzene with ethane at 180 °C for 3h gave ethylbenzene (TON = 455 TOE = 0.0421s ). The anti-Markovnikov selectivity was also proven for the reaction with 1-hexane and isobutene, giving 1-phenyUiexane (69% selectivity) and isobutylbenzene (82% selectivity), respectively. 

F,SCH, Methanesulfonic acid, trifluoro-iridium, manganese and rhenium complexes, 26 114, 115, 120 platinum complex, 26 126 OiFeCgH, Iron, acetyl dicarbonyl (if -cyclopentadienyl)-, 26 239 0,FeN2C2 Hll(, Iron, tricarbonylbis(2-isocy-ano-l,3-dimethylbenzene)-, 26 54 0.iMoNaCHH5-2 C4H ,02, Molybdate 1 -), tricarbonyl(T) -cyclopentadienyl)-sodium, compd. with 1,2-dimethoxy-ethane-(l 2), 26 343 0,NaWC H5-2 C4H ,02, Tungstate(l -), tricarbonyl(ris-cyclopentadienyl)-... 

Hydrogen displacement syntheses often lead to some hydrogenation of the entering olefin as in in Eqs. (az) and (bm). Thus ethylene reacts with [Ir(PPr-i3)2H5] to form 1 mol of a bis(ethylene) complex and 1 mol of ethane for every mole of iridium ... 

IrsMo) prepared from the bimetallic carbonyl complex was somewhat more active for the -butane reaction at 488 K than a pure iridium catalyst, but high ethane selectivity was retained (1.43). The IraMoa complex gave a less active catalyst, with a lower value of S2 (1.08). The addition of zirconium to platinum (Pt7sZr25/C) lowered the rate of ethane hydrogenolysis about 20-fold, and raised the activation energy. ... 

In the case of white phosphorus, the reaction proceeds through the following elementary steps (i) ethane elimination, (ii) P-P bond activation at iridium forming the Ir(m) hydride [(triphos)IrH(77 -P4)] 921, (iii) isomerization of 921 to [(triphos)Ir( j -P4H)] 922 with selective delivery of the hydride atom to one of the coordinated P-atoms, and (iv) hydrogenation of the teraphosphidohydride ligand with PH3 generation and formation of the known cyclo-Vj, complex [(triphos)Ir( -P3)] 923. 

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