2 research outputs found
Identifying and Rationalizing the Conditions for the Isomerization of 1,5-Cyclooctadiene in Iridium Complexes by Experimental and Theoretical Mechanistic Studies
The
independent synthesis of the biscarbene complexes [IrÂ(cod)Â(vegi<sup>R</sup>)]ÂPF<sub>6</sub> (<b>2</b>) (cod =1,5-cyclooctadiene,
vegi<sup>R</sup> = bidentate N-heterocyclic carbene) as well as their
isomerized complexes [IrÂ(1-κ-4,5,6-η-C<sub>8</sub>H<sub>12</sub>)Â(NCCH<sub>3</sub>)Â(vegi<sup>R</sup>)]ÂPF<sub>6</sub> (<b>3</b>) is described. We elucidated acetic acid as the catalyst
and coordinated acetonitrile as the thermodynamic driving force for
this cod-isomerization. By using the stronger trifluoroacetic acid,
we isolated complex [IrÂ(cod)Â(F<sub>3</sub>CCO<sub>2</sub>)Â(H)Â(vegi<sup><i>n</i>Pr</sup>)]ÂPF<sub>6</sub> (<b>7a</b>) as an
intermediate of the isomerization. From H/D exchange experiments as
well as DFT calculations, we conclude that after formation of the
Ir–H complex, an olefin insertion, followed by a concerted
metalation-deprotonation step and a coordination of acetonitrile,
is the mechanistic pathway. On the basis of our findings, we were
able to carry out the cod-isomerization for the first time also for
the less-electron-rich complex [IrÂ(2,2′-bipy)Â(cod)]ÂPF<sub>6</sub> (<b>8</b>) (2,2-bipy = 2,2′-bipyridine)
Identifying and Rationalizing the Conditions for the Isomerization of 1,5-Cyclooctadiene in Iridium Complexes by Experimental and Theoretical Mechanistic Studies
The
independent synthesis of the biscarbene complexes [IrÂ(cod)Â(vegi<sup>R</sup>)]ÂPF<sub>6</sub> (<b>2</b>) (cod =1,5-cyclooctadiene,
vegi<sup>R</sup> = bidentate N-heterocyclic carbene) as well as their
isomerized complexes [IrÂ(1-κ-4,5,6-η-C<sub>8</sub>H<sub>12</sub>)Â(NCCH<sub>3</sub>)Â(vegi<sup>R</sup>)]ÂPF<sub>6</sub> (<b>3</b>) is described. We elucidated acetic acid as the catalyst
and coordinated acetonitrile as the thermodynamic driving force for
this cod-isomerization. By using the stronger trifluoroacetic acid,
we isolated complex [IrÂ(cod)Â(F<sub>3</sub>CCO<sub>2</sub>)Â(H)Â(vegi<sup><i>n</i>Pr</sup>)]ÂPF<sub>6</sub> (<b>7a</b>) as an
intermediate of the isomerization. From H/D exchange experiments as
well as DFT calculations, we conclude that after formation of the
Ir–H complex, an olefin insertion, followed by a concerted
metalation-deprotonation step and a coordination of acetonitrile,
is the mechanistic pathway. On the basis of our findings, we were
able to carry out the cod-isomerization for the first time also for
the less-electron-rich complex [IrÂ(2,2′-bipy)Â(cod)]ÂPF<sub>6</sub> (<b>8</b>) (2,2-bipy = 2,2′-bipyridine)