Fine-Tuning the Energy Barrier for Metal-Mediated
Dinitrogen NN Bond Cleavage
Andrew
J. Keane
Brendan L. Yonke
Masakazu Hirotsu
Peter Y. Zavalij
Lawrence R. Sita
10.1021/ja505309j.s002
https://acs.figshare.com/articles/dataset/Fine_Tuning_the_Energy_Barrier_for_Metal_Mediated_Dinitrogen_N_N_Bond_Cleavage/2273986
Experimental data support a mechanism for NN bond cleavage
within a series of group 5 bimetallic dinitrogen complexes of general
formula, {Cp*M[N(<sup><i>i</i></sup>Pr)C(R)N(<sup><i>i</i></sup>Pr)]}<sub>2</sub>(μ-N<sub>2</sub>) (Cp* = η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>) (M = Nb, Ta), that proceeds
in solution through an intramolecular “end-on-bridged”
(μ-η<sup>1</sup>:η<sup>1</sup>-N<sub>2</sub>) to
“side-on-bridged” (μ-η<sup>2</sup>:η<sup>2</sup>-N<sub>2</sub>) isomerization process to quantitatively provide
the corresponding bimetallic bis(μ-nitrido) complexes, {Cp*M[N(<sup><i>i</i></sup>Pr)C(R)N(<sup><i>i</i></sup>Pr)](μ-N)}<sub>2</sub>. It is further demonstrated that subtle changes in the steric
and electronic features of the distal R-substituent, where R = Me,
Ph and NMe<sub>2</sub>, can serve to modulate the magnitude of the
free energy barrier height for NN bond cleavage as assessed
by kinetic studies and experimentally derived activation parameters.
The origin of the contrasting kinetic stability of the first-row congener,
{Cp*V[N(<sup><i>i</i></sup>Pr)C(Me)N(<sup><i>i</i></sup>Pr)]}<sub>2</sub>(μ-η<sup>1</sup>:η<sup>1</sup>-N<sub>2</sub>) toward NN bond cleavage is rationalized in
terms of a ground-state electronic structure that favors a significantly
less-reduced μ-N<sub>2</sub> fragment.
2014-07-16 00:00:00
activation parameters
cleavage
bond
Energy Barrier
energy barrier height
Cp
group 5 bimetallic dinitrogen complexes