61396-34-7Relevant academic research and scientific papers
Aliphatic and aromatic carbon-fluorine bond activation with Cp*2ZrH2: Mechanisms of hydrodefluorination
Kraft,Lachicotte,Jones
, p. 10973 - 10979 (2001)
Cp*2ZrH2 (1) (Cp* = pentamethylcyclopentadienyl) reacts with primary, secondary, and tertiary monofluorinated aliphatic hydrocarbons to give Cp*2ZrHF (2) and/or Cp*2ZrF2 and alkane quantitatively through a radical chain mechanism. The reactivity of monofluorinated aliphatic C-F bonds decreases in the order 1° > 2° > 3°. The rate of hydrodefluorination was also greatly reduced with -CF2H and -CF3 groups attached to the hydrocarbon. An atmosphere of H2 is required to stabilize 1 against C-H activation of the Cp*-methyl groups and subsequent dimerization under the thermal conditions employed in these reactions. Reaction of 1 with fluorobenzene cleanly forms a mixture of Cp*2ZrHF, benzene, and Cp*2Zr(C6H5)F. Detailed studies indicate that radicals are not involved in this aromatic C-F activation reaction and that dual hydrodefluorination pathways are operative. In one mechanism, hydridic attack by Cp*2ZrH2 on the aromatic ring and fluoride abstraction is involved. In the second mechanism, an initial ortho C-H activation occurs, followed by β-fluoride elimination to generate a benzyne complex, which then inserts into the zirconium-hydride bond.
Activation of benzene carbon-hydrogen bonds via photolysis or thermolysis of (η5-C5Me5)2Zr(alkyl)H. Isolation of (η5-C5Me5)2Zr(C 6H5)H and its conversion to a complex containing a tetramethylfulvene ligand
Miller, Frederick D.,Sanner, Robert D.
, p. 818 - 825 (2008/10/08)
A new high-yield synthesis of Cp*2ZrH2 (Cp* = η5-C5Me5) is described, and olefin insertion into its Zr-H bond is used to prepare several new Cp*2Zr(alkyl)H complexes. Photolysis or thermolysis of Cp*2Zr(alkyl)H in benzene yields the respective alkane by intramolecular reductive elimination of the cis alkyl and hydride ligands, as well as the benzene C-H bond activation product Cp*2Zr(C6H5)H. Photochemically induced reductive elimination is also observed for Cp*2Zr(C6H5)H and Cp*2ZrH2. Deuterium-labeling experiments show that hydrogen exchange between the hydride and Cp* methyl groups occurs in both Cp*2Zr(H)CH2CH(CH3)2 and Cp*2Zr(C6H5)H. An additional exchange process in Cp*2Zr(C6H5)H involves the hydride ligand and an ortho phenyl hydrogen atom. Thermolysis of Cp*2Zr(C6H5)H in benzene causes quantitative evolution of dihydrogen and reversibly forms the tetramethylfulvene complex Cp*(η6-C5Me4CH2)Zr(C 6H5). Reaction of this compound with iodine produces the Cp* ring substituted phenyl iodide Cp*(η5-C5Me4CH2I)Zr(C 6H5)I. Several of the transformations involving Cp*2Zr(C6H5)H are believed to proceed via β-hydrogen elimination from the phenyl group to yield a benzyne dihydride intermediate.
