Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2004 Feb 4;126(4):1018-9.
doi: 10.1021/ja0385944.

C-H bond activation of hydrocarbons by an imidozirconocene complex

Helen M Hoyt  1 , Forrest E Michael, Robert G Bergman
Affiliations

C-H bond activation of hydrocarbons by an imidozirconocene complex

Helen M Hoyt et al. J Am Chem Soc. .

Abstract

Monomeric imidozirconocene complexes of the type Cp2(L)Zr=NCMe3 (Cp = cyclopentadienyl, L = Lewis base) have been shown to activate the carbon-hydrogen bonds of benzene, but not the C-H bonds of saturated hydrocarbons. To our knowledge, this singularly important class of C-H activation reactions has heretofore not been observed in imidometallocene systems. The M=NR bond formed on heating the racemic ethylenebis(tetrahydro)indenyl methyl tert-butyl amide complex, however, cleanly and quantitatively activates a wide range of n-alkane, alkene, and arene C-H bonds. Mechanistic experiments support the proposal of intramolecular elimination of methane followed by a concerted addition of the hydrocarbon C-H bond. Products formed by activation of sp2 C-H bonds are generally more thermodynamically stable than those formed by activation of sp3 C-H bonds, and those resulting from reaction at primary C-H bonds are preferred over secondary sp3 C-H activation products. There is also evidence that thermodynamic selectivity among C-H bonds is sterically rather than electronically controlled.

PubMed Disclaimer

Figures

(1)
(1)
(2)
(2)
Figure 1
Figure 1
ORTEP diagrams for (a) complex 1c and (b) complex 1d with hydrogen atoms omitted for clarity.
Figure 2
Figure 2
ORTEP diagrams for (a) complex 3 and (b) complex 4 with hydrogen atoms omitted for clarity.
Scheme 1
Scheme 1
See this image and copyright information in PMC

References

    1. Duncan AP, Bergman RG. Chem Rec. 2002;2:431. - PubMed
    1. Walsh PJ, Hollander FJ, Bergman RG. J Am Chem Soc. 1988;110:8729.
    2. Cummins CC, Baxter SM, Wolczanski PT. J Am Chem Soc. 1988;110:8731.
    3. Schaller CP, Cummins CC, Wolczanski PT. J Am Chem Soc. 1996;118:591.
    4. Bennett JL, Wolczanski PT. J Am Chem Soc. 1997;119:10696.
    5. (e) For a V(= NR)2 example, see: De With J, Horton AD.Angew Chem, Int Ed Engl 199332903
    1. Sweeney ZK, Salsman JL, Andersen RA, Bergman RG. Angew Chem, Int Ed. 2000;39:2339. - PMC - PubMed
    2. Diamond GM, Jordan RF, Petersen JL. J Am Chem Soc. 1996;118:8024.
    1. Activation of benzylic sp3 and aryl sp2 C–H bonds is often competitive; preference for aryl or benzylic activation is highly system dependent (see refs 2c; 6a; Adams CS, Legzdins P, Tran E.Organometallics 2002211474
    1. We presume that secondary products, if formed, are less thermodynamically stable than primary products and are thus not observed.

Publication types