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Synthetic and X-ray structural studies of pentabenzylcyclopentadienyl transition metal complexes
Abstract
An improved synthetic route to pentabenzylcyclopentadiene, $\rm C\sb5Bz\sb5H$, has been developed. Both pentabenzylcyclopentadiene and an isomer were obtained depending on the reaction conditions. Structural assignments of both compounds have been investigated based on $\sp1$H NMR, $\sp{13}$C NMR, $\sp1$N 2D COSY NMR spectral and X-ray crystallographic studies. Pentabenzylcyclopentadienyl-lithium, $\rm C\sb5Bz\sb5Li$, was readily prepared from pentabenzylcyclopentadiene and n-butyl-lithium. Both $\rm C\sb5Bz\sb5H$ and $\rm C\sb5Bz\sb5Li$ have been used in the syntheses of the "sandwich" compounds: decabenzyl-, pentabenzyl-, and pentamethylpenta-benzyl-ferrocene, as well as the preparation of the "half-sandwich" compound: $(h\sp5$-$\rm C\sb5Bz\sb5)Mn(CO)\sb3$, $(h\sp5$-$\rm C\sb5Bz\sb5)Re(CO)\sb3$, $\lbrack (h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2\rbrack \sb2$, $(h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2R$ (where R = H, Me, SiMe$\sb3$, SnMe$\sb3$, Cl, I), and $(h\sp5$-$\rm C\sb5Bz\sb5)TiCl\sb3$. The reaction of pentabenzylcyclopentadiene and Fe(CO)$\sb5$ produced a mixture of $(h\sp4$-$\rm C\sb5Bz\sb5H)Fe(CO)\sb3$ and $\lbrack (h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2\rbrack \sb2$. Treatment of $\lbrack (h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2\rbrack \sb2$ with Na/Hg generated $(h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2\sp-Na\sp+$. Subsequent reactions of this anion with CH$\sb3$COOH, MeI, SiMe$\sb3$Cl, or SnMe$\sb3$Cl, produced $(h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2$-R (where R = H, Me, SiMe$\sb3$, SnMe$\sb3$, respectively) in good yield. A reaction of $(h\sp4$-$\rm C\sb5Bz\sb5H)Fe(CO)\sb3$ with trityl cation led to the formation of $\lbrack (h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb3\rbrack \sp+$; following by the addition of LiCl, $(h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2$Cl was obtained. $(h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2$I can also be prepared from the reaction of $(h\sp4$-$\rm C\sb5Bz\sb5H)Fe(CO)\sb3$ with n-BuLi, followed by the addition of MeI in THF. A reaction between trimethylsilylindene and TiCl$\sb4$ in hexane formed (indenyl)titanium trichloride in 52% yield. All the above compounds have been well-characterized by $\sp1$H NMR, $\sp{13}$C NMR, IR, and mass spectrometry, as well as by elemental analyses. Many of the new compounds were obtained as single crystals, and X-ray crystallographic studies of several of them are described. Some of the compounds, such as the isomer of pentabenzylcyclopentadiene and $\lbrack (h\sp5$-$\rm C\sb5Bz\sb5)Fe(CO)\sb2\rbrack \sb2$, cannot be completely elucidated in terms of their structures at the present time, however.
Subject Area
Inorganic chemistry|Physical chemistry|Chemistry
Recommended Citation
Tsai, Woei-Min, "Synthetic and X-ray structural studies of pentabenzylcyclopentadienyl transition metal complexes" (1991). Doctoral Dissertations Available from Proquest. AAI9207465.
https://scholarworks.umass.edu/dissertations/AAI9207465