C-H bond activation of hydrocarbons by an imidozirconocene complex.
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.
Hoyt
Helen M
HM
Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, USA.
Michael
Forrest E
FE
Bergman
Robert G
RG
D018360:Crystallography, X-Ray; D006838:Hydrocarbons / Q000737:chemistry*; D007094:Imides / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry*
D006838:Hydrocarbons; D007094:Imides; D009942:Organometallic Compounds; D015040:Zirconium