Secondary Deuterium Kinetic Isotope Effect for Aquation, Solvolysis,
and Isomerization Reactions of <i>trans</i>-[Co(en)<sub>2</sub>(OSMe<sub>2</sub>)N<sub>3</sub>]<sup>2+</sup>, and the
Resolution of a Mechanistic Anomaly
W. G. Jackson
10.1021/ic030271l.s001
https://acs.figshare.com/articles/journal_contribution/Secondary_Deuterium_Kinetic_Isotope_Effect_for_Aquation_Solvolysis_and_Isomerization_Reactions_of_i_trans_i_Co_en_sub_2_sub_OSMe_sub_2_sub_N_sub_3_sub_sup_2_sup_and_the_Resolution_of_a_Mechanistic_Anomaly/3342334
The two closely spaced NH signals in the <sup>1</sup>H NMR spectrum of <i>trans</i>-[Co(en)<sub>2</sub>(OSMe<sub>2</sub>)(N<sub>3</sub>)]<sup>2+</sup> have been reassigned
using 2D NMR and other techniques. Thus, the unusual syn to anti (to Co−N<sub>3</sub>) NH rearrangement on base catalyzed
substitution of the selectively deuterated complex in ND<sub>3</sub>(l) has been reinterpreted as “normal”, with inversion of
the effective deprotonation site accompanying the act of substitution. The re-examination of this system required
a repeat study of the secondary isotope effect for the acid hydrolysis reaction, previously used to assign syn and
anti amine sites, and this has been extended to other solvents (Me<sub>2</sub>SO, MeCN). The relative NH proton exchange
rates are also reconsidered. A systematic rate reduction for Me<sub>2</sub>SO substitution is observed for deuterium incorporation
into the <i>cis</i>-NH centers, irrespective of whether these are syn or anti, and the effect is much greater in Me<sub>2</sub>SO than
in water. The results are interpreted in terms of zero point energy effects and coupled vibrations.
2004-04-19 00:00:00
point energy effects
rate reduction
Isomerization Reactions
NH signals
acid hydrolysis reaction
Co
tran
N 3
deuterium incorporation
1 H NMR spectrum
substitution
NH centers
2 D NMR
NH proton exchange rates
deprotonation site
Secondary Deuterium Kinetic Isotope Effect
NH rearrangement
ND 3
syn
OSMe 2
isotope effect
Mechanistic Anomaly
amine sites