Easy and Reversible C−H Activation of a Substituted Benzene

Canepa, Giuseppe; Brandt, and Carsten D.; Werner, Helmut

doi:10.1021/om0010159

Cited by 22 publications

(31 citation statements)

References 14 publications

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“…This arylhydrido complex can also be obtained by treatment of the π -alkyne complex [( η 6 -C 6 H 5 CH 2 CH 2 P i Pr 2 -κ -P )Ir(PhC ˜ CPh)]BF 4 with excess of acetonitrile in acetone [22] . These observations support the concept that the insertion of a metal into one of the arene C ˆ H bonds is reversible, as was previously observed in related complexes [25] . The reaction of the arylhydrido complex [IrH(C 6 H 4 CH 2 CH 2 P i Pr 2 -κ 2 -C,P )(NCMe) 3 obtained by replacement of the propene analogue with Z -stilbene.…”

Section: Dihydrido Arene Iridium Triisopropylphosphine Complexes 31supporting

confidence: 90%

Dihydrido Iridium Triisopropylphosphine Complexes: From Organometallic Chemistry to Catalysis

Oro

2008

Iridium Complexes in Organic Synthesis

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2.1 IntroductionThe impressive developments of organometallic chemistry have allowed the preparation of a wide variety of soluble metal complexes useful for organic transformations under mild conditions. There is no question that much of the general knowledge on homogeneous catalysis has stemmed from studies of organometallic chemistry and homogeneous hydrogenation. Following the discovery of Wilkinson ' s hydrogenation catalyst, RhCl(PPh 3 ) 3 , in 1964 [1] -which is by far the most -studied homogeneous catalyst -Schrock and Osborn reported the catalytic potential of [Rh(diene)L 2 ] + complexes as hydrogenation catalysts. Under hydrogen, the diene is hydrogenated to generate the reactive [RhH 2 S 2 (PR 3 ) 2 ] + species which, in some cases, can be isolated relatively easily from coordinating solvents (S) such as acetone or ethanol [2] . In contrast to Wilkinson ' s catalyst, a large number of donor ligands can be used, while the use of a PR 3 : Rh ratio of 2 : 1 avoids the need for phosphine dissociation which is required with Wilkinson ' s catalyst.Interestingly, cationic diene iridium complexes of general formula [Ir(COD)(PR 3 ) 2 ] + (COD = 1,5 -cyclo -octadiene), mainly developed by Crabtree, may be even more active than the cationic diene rhodium complexes, particularly when dichloromethane ( DCM ) is used as solvent. The solvent is less coordinating and must be easily displaced by the substrates. Furthermore, its polarity favors the solubility of the ionic catalyst. As in the case of rhodium systems, [IrH 2 S 2 (PR 3 ) 2 ] + species can be observed by hydrogenation of the diene [3,4] . Another important discovery was the very active mixed ligand complex [Ir(COD)(py)(PCy 3 )] + (py = pyridine), usually known as Crabtree ' s catalyst, that in DCM as solvent effectively hydrogenates tetrasubstituted amido -alkenes [3] . The related benzonitrile (bzn) derivatives [Ir(COD)(bzn)(PR 3 )] + (PR 3 = PCy 3 or the chiral phosphines, neomenthyldiphenylphosphine or phenyl -( o -methoxyphenyl)methylphosphine) are also very active catalysts for the hydrogenation of prochiral didehydro amino acid derivatives [5] , although poor enantiomeric excess ( ee ) values are obtained with chiral monodentate phosphines. The effectiveness of the [Ir(COD)(L)(PR 3 )] + cations for

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Section: Dihydrido Arene Iridium Triisopropylphosphine Complexes 31supporting

confidence: 90%

Dihydrido Iridium Triisopropylphosphine Complexes: From Organometallic Chemistry to Catalysis

Oro

2008

Iridium Complexes in Organic Synthesis

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“…In the 1 H NMR spectrum a triplet at d À18.20 (1H) with a cis 1 He 31 P coupling constant of J(PH) ¼ 15.2 Hz, a singlet at d 0.55 that integrated as 9H is assigned to the t Bu group and two methyl environments for the Xantphos ligand were observed. Signals assigned to methylene groups at d 1.93 and 1.02 (2H each) were seen, while no signals characteristic to a coordinated tbe ligand [33,34] [38]), and that the Ir1eC1eC2 angle (116.8(4) ) is also much smaller than expected for a vinyl group (w130 [38]). The hydride ligand was located in the final difference map and sits trans to the MeCN ligand.…”

Section: Resultsmentioning

confidence: 91%

Cationic iridium complexes of the Xantphos ligand. Flexible coordination modes and the isolation of the hydride insertion product with an alkene

Pontiggia

Chaplin

Weller

2011

Journal of Organometallic Chemistry

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“…A preliminary communication has already appeared. [8] Results and Discussion Rhodium complexes obtained with iPr 2 PCH 2 CH 2 C 6 H 5 (L 1 ) as the substrate: Under conditions similar to those used for the preparation of 1, the reaction of [{RhCl(C 8 H 14 ) 2 } 2 ] (2) with a twofold excess of L 1 in pentane at room temperature results in the formation of a yellow solid, the analytical composition of which corresponds to 3 (Scheme 1). The product is thermally not exceedingly stable and decomposes in solution (benzene or dichloromethane) at 10 8C in a few hours.…”

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confidence: 99%

Rhodium(I) and Rhodium(III) Complexes Formed by Coordination and CH Activation of Bulky Functionalized Phosphanes

Canepa

Brandt

Ilg

et al. 2003

Chemistry A European J

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The reaction of [[RhCl(C(8)H(14))(2)](2)] (2) with iPr(2)PCH(2)CH(2)C(6)H(5) (L(1)) led, via the isolated dimer [[RhCl(C(8)H(14))(L(1))](2)] (3), to a mixture of three products 4 a-c, of which the dinuclear complex [[RhCl(L(1))(2)](2)] (4 a) was characterized by Xray crystallography. The mixture of 4a-c reacts with CO, ethene, and phenylacetylene to give the square-planar compounds trans-[RhCl(L)(L(1))(2)] (L=CO (5), C(2)H(4) (6), C=CHPh (9)). The corresponding allenylidene(chloro) complex trans-[RhCl(=C=C=CPh(2))(L(1))(2)] (11), obtained from 4 a-c and HC triple bond CC(OH)Ph(2) via trans-[RhCl[=C=CHC(OH)Ph(2)](L(1))(2)] (10), could be converted stepwise to the related hydroxo, cationic aqua, and cationic acetone derivatives 12-14, respectively. Treatment of 2 and [[RhCl(C(2)H(4))(2)](2)] (7) with two equivalents of tBu(2)PCH(2)CH(2)C(6)H(5) (L(2)) gave the dimers [[RhCl(C(8)H(14))(L(2))](2)] (15) and [[RhCl(C(2)H(4))(L(2))](2)] (16), which both react with L(2) in the molar ratio of 1:2 to afford the five-coordinate aryl(hydrido)rhodium(III) complex [RhHCl(C(6)H(4)CH(2)CH(2)PtBu(2)-kappa(2)C,P)(L(2))] (17) by C-H activation. The course of the reactions of 17 with CO, H(2), PhC triple bond CH, HCl, and AgPF(6), leading to the compounds 19-21, 24, and 25 a, respectively, indicate that the coordinatively unsaturated isomer of 17 with the supposed composition [RhCl(L(2))(2)] is the reactive species. Labeling experiments using D(2), DCl, and PhC triple bond CD support this proposal. With either [Rh(C(8)H(14))(eta(6)-L(2)-kappaP]PF(6) or [Rh(C(2)H(4))(eta(6)-L(n)-kappaP]PF(6) (n=1 and 2) as the starting materials, the corresponding halfsandwich-type complexes 27, 28, and 32 were obtained. The nonchelating counterpart of the dihydrido compound 32 with the composition [RhH(2)(PiPr(3))(eta(6)-C(6)H(6))]PF(6) (35) was prepared stepwise from [Rh(C(2)H(4))(PiPr(3))(eta(6)-C(6)H(6))]PF(6) and H(2) in acetone via the tris(solvato) species [RhH(2)(PiPr(3))(acetone)(3)]PF(6) (34) as intermediate. The synthesis of the bis(chelate) complex [Rh(eta(4)-C(8)H(12))(C(6)H(5)OCH(2)CH(2)PtBu(2)-kappa(2)O,P)]BF(4) (39) is also described. Besides 4 a, the compounds 17, 25 a, and 39 have been characterized by Xray crystal structure analysis.

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Easy and Reversible C−H Activation of a Substituted Benzene

Cited by 22 publications

References 14 publications

Dihydrido Iridium Triisopropylphosphine Complexes: From Organometallic Chemistry to Catalysis

Dihydrido Iridium Triisopropylphosphine Complexes: From Organometallic Chemistry to Catalysis

Cationic iridium complexes of the Xantphos ligand. Flexible coordination modes and the isolation of the hydride insertion product with an alkene

Rhodium(I) and Rhodium(III) Complexes Formed by Coordination and CH Activation of Bulky Functionalized Phosphanes

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