Activation of carbon-hydrogen bonds in alkanes and other organic molecules using organotransition metal complexes
The potential for using alkanes-which are among the most chemically inert organic molecules-as feedstocks in chemical synthesis has stimulated a search for metal complexes capable of undergoing the C-H oxidative addition process shown in eq. (1), so that alkane chemistry more selective than that available using free radical reagents might be developed. Intramolecular C-H oxidative addition to metal centers has been known for some time, but despite M + R-H {yields} R-M-H (1) many efforts a direct observation of the corresponding intermolecular C-H oxidative addition process illustrated in eq. (1) was not uncovered until 1982. At that time our group and Graham's independently found that irradiation of complexes such as Cp*(L)lrH{sub 2}(1, Cp* = ({eta}{sup 5}-C{sub 5}Me{sub 5}). L = PMe{sub 3}) and Cp*lr(CO){sub 2} causes successful insertion of the Cp*lrL fragment into C-H bonds in alkanes, leading to stable alkyliridium hydride complexes Cp*(L)lr(R)(H)(2). This reaction is exceedingly general. So far no organic liquid in which Cp*(L)lrH{sub 2} has been irradiated has failed to react with the intermediate generated in the reaction. Much has been learned about the scope and mechanism of this reaction. Following the initial studies with iridium, alkane C-H oxidative addition has been observed at several other third-row transition metal centers (where M-H and M-R bonds are expected to be relatively strong), such as rhodium, rhenium, platinum, and osmium and even at one first-row metal (iron). The selectivity of the iridium and rhodium C-H oxidative addition reaction has been investigated by carrying out competition studies with various hydrocarbon substrates. Although the absolute magnitudes of the selectivities are different for lr and Rh, their trends are parallel, indicating that C-H oxidative additions proceed by similar mechanisms at these two metal centers, but that the Rh reactions are less exothermic than their lr counterparts. 14 refs., 1 fig.
- Research Organization:
- Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5740693
- Report Number(s):
- LBL-30592; CONF-9004314-1; ON: DE91013780
- Resource Relation:
- Journal Volume: 230; Conference: New science in homogeneous transition metal catalyzed reactions conference, Boston, MA (USA), 25 Apr 1990
- Country of Publication:
- United States
- Language:
- English
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Activation of carbon-hydrogen bonds in alkanes and other organic molecules using organotransition metal complexes
Activation of carbon-hydrogen bonds in alkanes and other organic molecules using organotransition metal complexes
Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALKANES
CHEMICAL ACTIVATION
CHEMICAL BONDS
CHEMICAL REACTION KINETICS
ORGANOMETALLIC COMPOUNDS
OXIDATION
PHOTOCHEMICAL REACTIONS
RARE GASES
REACTION INTERMEDIATES
TRANSITION ELEMENT COMPLEXES
CHEMICAL REACTIONS
COMPLEXES
ELEMENTS
FLUIDS
GASES
HYDROCARBONS
KINETICS
NONMETALS
ORGANIC COMPOUNDS
REACTION KINETICS
400201* - Chemical & Physicochemical Properties
400500 - Photochemistry