Fine-tuning the energy barrier for metal-mediated dinitrogen N≡N bond cleavage.
J Am Chem Soc
; 136(28): 9906-9, 2014 Jul 16.
Article
em En
| MEDLINE
| ID: mdl-24960112
ABSTRACT
Experimental data support a mechanism for N≡N bond cleavage within a series of group 5 bimetallic dinitrogen complexes of general formula, {Cp*M[N((i)Pr)C(R)N((i)Pr)]}2(µ-N2) (Cp* = η(5)-C5Me5) (M = Nb, Ta), that proceeds in solution through an intramolecular "end-on-bridged" (µ-η(1)η(1)-N2) to "side-on-bridged" (µ-η(2)η(2)-N2) isomerization process to quantitatively provide the corresponding bimetallic bis(µ-nitrido) complexes, {Cp*M[N((i)Pr)C(R)N((i)Pr)](µ-N)}2. It is further demonstrated that subtle changes in the steric and electronic features of the distal R-substituent, where R = Me, Ph and NMe2, can serve to modulate the magnitude of the free energy barrier height for N≡N 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((i)Pr)C(Me)N((i)Pr)]}2(µ-η(1)η(1)-N2) toward N≡N bond cleavage is rationalized in terms of a ground-state electronic structure that favors a significantly less-reduced µ-N2 fragment.
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MEDLINE
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Metais
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Nitrogênio
Idioma:
En
Ano de publicação:
2014
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Article