A structural, kinetic and thermodynamic study of the reversible thermal carbon-hydrogen bond activation/reductive elimination of alkanes at iridium

Buchanan, J. M.; Stryker, Jeffrey M.; Bergman, Robert G.

doi:10.1021/ja00267a025

Cited by 244 publications

(156 citation statements)

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“…This result is indicative of an inverse isotope effect (k H /k D ϭ 0.625) for the elimination of acetonitrile from the metal system. Inverse isotope effects for alkane reductive eliminations of Cp and TpЈ complexes have been seen (39)(40)(41)(42)(43)(44)(45).…”

Section: Resultsmentioning

confidence: 98%

The activation of alkyl cyanides using a rhodiumtrispyrazolylborate complex

Vetter

Rieth

Jones

2007

Proc. Natl. Acad. Sci. U.S.A.

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O rganometallic complexes of the cyclopentadienyl (Cp) and trispyrazolylborate (Tp) type have been shown to activate a variety of COH bonds in alkanes and arenes (1-9). However, studies on the activation of alkanes and arenes containing reactive functional groups have received far less attention in the literature. Hartwig and coworkers (10-12) have been successful in the hydroborylation of mono-and disubstituted arenes using transition metal catalysts. The borylation of the arene ring is believed to occur after oxidative addition of the ring COH bond without interference of reaction with the functional group. Smith (13,14) has even shown that haloarenes can be borylated and functionalized without affecting the carbon-halogen bond. Although numerous examples are presented for the functionalization of substituted arenes (15), the functionalization of alkanes containing reactive functional groups is somewhat restricted, perhaps because some of the functional groups on the alkanes are more reactive toward the catalysts and do not allow for COH activation. In addition, some functional groups (e.g., OH) are known to make the adjacent COH bonds more reactive in alkanes (16).We recently reported the activation of 1-, 2-, and 3-chloropentanes using a trispyrazolylborate rhodium complex (17). It was determined that the [TpЈRh(L)] fragment did not oxidatively cleave the COCl bond of the chloroalkane, as would have been expected given the relative bond strengths of COH (Ϸ100 kcal) vs. COCl (80 kcal) bonds (18) and the literature precedence that exists for the oxidative addition of COCl bonds to Rh(I) and Ir(I) metal systems (15,19). Surprisingly, the [TpЈRh(L)] fragment reacted exclusively with the terminal COH bonds of the alkane to give the substituted haloalkyl hydride complex. Here, we extend the investigation of the activation of hydrocarbon COH bonds to include substrates containing the nitrile functional group (OC'N).The COH bond activation of acetonitrile has been documented in the past. Teuben and coworkers (20) have reported the COH activation of acetonitrile via a -bond metathesis using Cp* 2 LnCH(SiMe 3 ) 2 . Jesson and coworkers (21) have also documented the formation of the cyanomethyl hydride as a result of activation of acetonitrile using (dmpe) 2 M(Np)H (M ϭ Fe, Ru; Np ϭ 2-naphthyl). The scission of the COCN bond of acetonitrile has also been reported by Parkin and coworkers (22), Brookhart and coworkers (23, 24), Nakazawa et al. (25), and Jones and coworkers (26). Of particular interest is the work by Brookhart using a similar Cp*Rh(PMe 3 ) system (23), which is known to undergo COH bond activation in the presence of alkanes and arenes (3,27). However, in the presence of nitriles and triphenylsilane, the complex promotes the cleavage of the COCN bond.To demonstrate the diversity of nitrile reactivity with low valent metals, our group has also investigated the reactions of aromatic, allylic, and alkyl nitriles using [(dippe)NiH] 2 (28-30). In these studies, 2 coordination of the CN bond to the Ni metal cent...

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Section: Resultsmentioning

confidence: 98%

The activation of alkyl cyanides using a rhodiumtrispyrazolylborate complex

Vetter

Rieth

Jones

2007

Proc. Natl. Acad. Sci. U.S.A.

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“…A particularly good review has been written by Jones; E881 for saturated hydrocarbons the order is CH4 > 1" C > 2" C > 3" C. For Iridium complexes, the kinetic produce is stable at room temperature, and a distribution of primary and secondary C-H bonds are broken in an alkane. [89] When the solution is heated above 100°C, the product converts to the primary C-H activated form. For Rhodium complexes, the secondary and higher products are much less stable, and are never isolated.…”

Section: Effect Of Alkane Structure On C-h Bond Activat Ionmentioning

confidence: 99%

Time resolved infrared studies of C-H bond activation by organometallics

Asplund¹

1998

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' Lhe Govermient reserves for itself and others acting on its behalf a ruyalty free, nonexclusive, irrev-le, world-wide license for governmental purpses to publish, distribute, translate, duplicate, exhibit, and perform a q such data aopyrighted by the amtractor.The U.S. Department of Energy has the right to use this document for any purpose whatsoever, including the right to reproduce all or any part thereof. Much of the study of these C-H activation reactions has focussed on the spectroscopy of the CO ligands. We have shown the spectroscopy of several non-CO modes in the system. Spectroscopy of the Rh-H stretch at 2080 cm-lhas allowed for the unambiguous assignment of the time scale of final C-H bond breaking step.

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“…In addition to metal alkyl compounds, there are also metal alkane compounds, so-called -complexes (15), where the alkane is attached to the metal by an agostic interaction (16)(17)(18)(19), i.e., a 3-center-2-electron M-H-C interaction. By comparison with agostic alkyl compounds, however, metal alkane compounds have very limited stability, and bona fide examples have not been isolated in the solid state (20,21).…”

Section: Introduction and Historical Perspectivementioning

confidence: 99%