%0 Journal Article
%A Polson, Suzette M.
%A Hansen, Lory
%A Marzilli, Luigi G.
%D 1997
%T The First X-ray Structural Evidence Demonstrating Thiolate Coordination in an
Organocobalt B12 Model Complex: Implications for Methionine Synthase
%U https://acs.figshare.com/articles/journal_contribution/The_First_X-ray_Structural_Evidence_Demonstrating_Thiolate_Coordination_in_an_Organocobalt_B_sub_12_sub_Model_Complex_Implications_for_Methionine_Synthase/3617241
%R 10.1021/ic961019z.s001
%2 https://acs.figshare.com/ndownloader/files/5705829
%K trans influence alkyl ligand
%K trans influence
%K NMR
%K bond
%K CH 3 ligand
%K thiolate
%K Co
%K DH
%K organocobalt B 12 models
%X Enzyme-bound methyl-B12 transfers its methyl group to
homocysteine during methionine synthesis. However,
treatment of several types of organocobalt B12 models with
arene- and alkanethiolates under ambient conditions
leads only to thiolate ligation. The structure of
[AsPh4][EtSCo(DH)2CH3] (DH
= monoanion of dimethylglyoxime),
the first characterization by X-ray crystallography of an organocobalt
complex containing a unidentate coordinated
thiolate, demonstrates unambiguously the S-ligation of ethanethiolate
to Co, trans to the CH3 ligand. This
compound
contains a very long Co−S bond (2.342(2) Å). However, the
length of the Co−C bond (2.005(7) Å) is typical;
this result strongly supports reported FT-Raman spectroscopic data
indicating that the thiolate-type ligand does
not have a strong trans influence and does not significantly
weaken the Co−C bond in the ground state.
Since
a strong trans influence alkyl ligand weakens the
trans Co−C bond, we examined the effect of
EtS- on Co((DO)(DOH)pn)(CH3)2
[(DO)(DOH)pn =
N2,N2‘-propanediylbis(2,3-butanedione
2-imine 3-oxime) is an imine/oxime quadridentate ligand]. Even for this compound, no attack on
the Co−C bond was observed, although
independently synthesized
EtSCo((DO)(DOH)pn)CH3 was stable.
Furthermore, thiolate did not cleave the Co−C
bond of an organocobalt complex with a highly distorted Co−C group.
Several new spectroscopic and ligand-exchange reactions were observed in this study. Ligand-responsive
NMR shift trends in these other new complexes
also indicate that thiolate ligands have a weak trans
influence.
%I ACS Publications