10.1021/ic0518834.s004
Joseph M. Fritsch
Joseph M.
Fritsch
Noah D. Retka
Noah D.
Retka
Kristopher McNeill
Kristopher
McNeill
Synthesis, Structure, and Unusual Reactivity of β-Halovinyl Cobalt
Porphyrin Complexes
American Chemical Society
2006
cobalt halovinyl complexes
halide complexes
TCE
1.320 Å
1.211 Å
cobalt halide bonds
TPP
dichlorovinyl cobalt porphyrin
dissociative mechanism
vinyl group
halide substitution
Unusual Reactivity
group ability
CHCHX
chlorovinyl cobalt complexes
1.234 Å
cobalt acetylene
2006-03-06 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Synthesis_Structure_and_Unusual_Reactivity_of_Halovinyl_Cobalt_Porphyrin_Complexes/3234865
The preparation, structures, and reactivity of tetraphenylporphyrin (TPP) cobalt halovinyl complexes are reported.
β-Halovinyl complexes of (TPP)Co(<i>E</i>-CHCHX) (X = Br and I) were prepared from the insertion of acetylene into
the cobalt halide bonds of the corresponding halide complexes. The reactivity of these compounds and of the
previously reported (TPP)Co(<i>E</i>-CHCHCl), was studied in depth, and it was found that complex reactivity increased
with the leaving group ability of the halide. A <i>trans</i>-dichlorovinyl cobalt porphyrin complex, (TPP)Co(<i>Z</i>-CClCHCl),
was also prepared through the reaction of (TPP)CoNa and TCE. The structures of (TPP)Co(<i>E</i>-CHCHBr), (TPP)Co(<i>Z</i>-CClCHCl), and (TPP)Co(C<sub>2</sub>H) are reported. The C−C bond length of the vinyl group was found to vary for
the β-halovinyl complexes (TPP)Co(<i>E</i>-CHCHX) from 1.211 Å for X = Br to 1.234 Å for X = Cl and 1.320 Å for
(TPP)Co(<i>Z</i>-CClCHCl). A comparison of these structures to many chlorovinyl cobalt complexes shows that <i>trans</i>-2-halo substitution results in a dramatically decreased vinyl C−C bond length. The mechanism of halide substitution
for the β-halovinyl complexes was investigated with kinetic experiments that indicated a dissociative mechanism
and supported the intermediacy of a cobalt acetylene complex.