Electrophilic C-H activation at {Cp*Ir}:: Ancillary-ligand control of the mechanism of C-H activation

被引:241
作者
Davies, DL [1 ]
Donald, SMA
Al-Duaij, O
Macgregor, SA
Pölleth, M
机构
[1] Univ Leicester, Dept Chem, Leicester LE1 7RH, Leics, England
[2] Heriot Watt Univ, Sch Engn & Phys Engn, Edinburgh EH14 4AS, Midlothian, Scotland
关键词
D O I
10.1021/ja060173+
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Density functional calculations on the low-temperature cyclometalation of dimethylbenzylamine with [IrCl2Cp*]2/NaOAc have characterized a novel electrophilic activation pathway for C-H bond activation. C-H activation occurs from [Ir(DMBA-H)(k2-OAc)Cp*]+, and OAc plays a central role in determining the barrier for reaction. Dissociation of the proximal OAc arm sets up a facile intramolecular deprotonation via a geometrically convenient six-membered transition state. Dissociation of the distal OAc arm, however, leads to a higher energy four-membered (σ-bond metathesis) transition state, while oxidative addition is even higher in energy. For this Ir3+ system, these three mechanisms appear to lie within a continuum in which the participation of the metal center and an H-accepting ancillary ligand are inversely related. The ability of the ancillary ligand to act as a proton acceptor is the key factor in determining which mechanism pertains. Copyright © 2006 American Chemical Society.
引用
收藏
页码:4210 / 4211
页数:2
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