C-H bond activation of benzene by unsaturated η2-cyclopropene and η2-benzyne complexes of niobium.
We report the synthesis of a niobium cyclopropyl complex, Tp(Me2)NbMe(c-C(3)H(5))(MeCCMe), and show that thermal loss of methane from this compound generates an intermediate that is capable of activating both aliphatic and aromatic C-H bonds. Isotopic labeling, trapping studies, a detailed kinetic analysis, and density functional theory all suggest that the active intermediate is an η(2)-cyclopropene complex formed via β-hydrogen abstraction rather than an isomeric cyclopropylidene species. C-H activation chemistry of this type represents a rather unusual reactivity pattern for η(2)-alkene complexes but is favored in this case by the strain in the C(3) ring which prevents the decomposition of the key intermediate via loss of cyclopropene.
Boulho
Cédric
C
CNRS, Laboratoire de Chimie de Coordination, 205 Route de Narbonne, F-31077 Toulouse, France.
Oulié
Pascal
P
Vendier
Laure
L
Etienne
Michel
M
Pimienta
Véronique
V
Locati
Abel
A
Bessac
Fabienne
F
Maseras
Feliu
F
Pantazis
Dimitrios A
DA
McGrady
John E
JE