An anion-dependent switch in selectivity results from a change of C-H activation mechanism in the reaction of an imidazolium salt with IrH5(PPh3)(2)

Appelhans, L. N.; ZUCCACCIA, Daniele; Kovacevic, A.; Chianese, A. R.; Miecznikowski, J. R.; Macchioni, A.; Clot, E.; Eisenstein, O.; Crabtree, R. H.

doi:10.1021/ja055317j

CINECA IRIS Institutional Research Information System

IRIS è la piattaforma adottata dall’Università degli Studi di Udine per gestire l’archivio aperto dei prodotti della ricerca. L’archivio contiene articoli, contributi in volume, monografie, interventi pubblicati in atti di convegno, Tesi di dottorato e altri materiali.

Changing the counteranion along the series Br, BF4, PF6, SbF6 in their ion-paired 2-pyridylmethyl imidazolium salts causes the kinetic reaction products with IrH5(PPh3)(2) to switch from chelating N-heterocyclic carbenes (NHCs) having normal C2 (N path) to abnormal C5 binding (AN path). Computational work (DFT) suggests that the AN path involves C-H oxidative addition to Ir-III to give Ir-V with little anion dependence. The N path, in contrast, goes by heterolytic C-H activation with proton transfer to the adjacent hydride. The proton that is transferred is accompanied by the counteranion in an anion-coupled proton transfer, leading to an anion dependence of the N path, and therefore of the N/AN selectivity. The N path goes via Ir-III, not Ir-V, because the normal NHC is a much less strong donor ligand than the abnormal NHC. PGSE NMR experiments support the formation of ion-pair in both the reactants and the products. F-19,H-1-HOESY NMR experiments indicate an ion-pair structure for the products that is consistent with the computational prediction (ONIOM(B3PW91/UFF)).

Titolo:	An anion-dependent switch in selectivity results from a change of C-H activation mechanism in the reaction of an imidazolium salt with IrH5(PPh3)(2)
Autori:	L. N. Appelhans ZUCCACCIA, Daniele A. Kovacevic A. R. Chianese J. R. Miecznikowski A. Macchioni E. Clot O. Eisenstein R. H. Crabtree mostra contributor esterni nascondi contributor esterni
Data di pubblicazione:	2005
Rivista:	JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
Citazione:	An anion-dependent switch in selectivity results from a change of C-H activation mechanism in the reaction of an imidazolium salt with IrH5(PPh3)(2) / L. N. Appelhans;D. Zuccaccia;A. Kovacevic;A. R. Chianese;J. R. Miecznikowski;A. Macchioni;E. Clot;O. Eisenstein;R. H. Crabtree. - In: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY. - ISSN 0002-7863. - STAMPA. - 127(2005), pp. 16299-16311.
Abstract:	Changing the counteranion along the series Br, BF4, PF6, SbF6 in their ion-paired 2-pyridylmethyl imidazolium salts causes the kinetic reaction products with IrH5(PPh3)(2) to switch from chelating N-heterocyclic carbenes (NHCs) having normal C2 (N path) to abnormal C5 binding (AN path). Computational work (DFT) suggests that the AN path involves C-H oxidative addition to Ir-III to give Ir-V with little anion dependence. The N path, in contrast, goes by heterolytic C-H activation with proton transfer to the adjacent hydride. The proton that is transferred is accompanied by the counteranion in an anion-coupled proton transfer, leading to an anion dependence of the N path, and therefore of the N/AN selectivity. The N path goes via Ir-III, not Ir-V, because the normal NHC is a much less strong donor ligand than the abnormal NHC. PGSE NMR experiments support the formation of ion-pair in both the reactants and the products. F-19,H-1-HOESY NMR experiments indicate an ion-pair structure for the products that is consistent with the computational prediction (ONIOM(B3PW91/UFF)).
Handle:	http://hdl.handle.net/11390/949782
Appare nelle tipologie:	1.1 Articolo in rivista

File in questo prodotto:

Non ci sono file associati a questo prodotto.

Utilizza questo identificativo per citare o creare un link a questo documento:
http://hdl.handle.net/11390/949782

Citazioni

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.