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Formation of Hydrido–η 3 ‐Allyl Complexes of Ir III by Sequential Olefinic CH Bond Activation and CC Coupling of Alkenyl and Olefin Ligands
Author(s) -
Alvarado Ysaias,
Boutry Olivier,
Gutiérrez Enrique,
Monge Angeles,
Nicasio M. Carmen,
Poveda Manuel L.,
Pérez Pedro J.,
Ruíz Caridad,
Bianchini Claudio,
Carmona Ernesto
Publication year - 1997
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.19970030606
Subject(s) - allylic rearrangement , chemistry , allene , alkene , olefin fiber , propene , ligand (biochemistry) , double bond , stereochemistry , medicinal chemistry , photochemistry , catalysis , polymer chemistry , organic chemistry , biochemistry , receptor
The bis(ethene) complex [Tp * Ir‐(C 2 H 4 ) 2 ] ( 1 * ) (Tp * = tris(3,5‐dimethyl‐1‐pyrazol‐1‐yl)hydroborato) undergoes thermal rearrangement to the hydrido–allyl complex [Tp * IrH(π 3 ‐C 3 H 4 Me)] ( 6 * ), through the intermediacy of the hydrido–vinyl complex [Tp * IrH(C 2 H 3 )(C 2 H 4 )] ( 2 * ). The overall conversion of 1 * into 6 * corresponds formally to the dimerisation of ethene by an unprecedented pathway that involves sequential C–H bond activation of a coordinated olefin molecule and C–C bond formation by coupling of the resulting vinyl and ethene moieties. Similar transformations have been observed for monosubstituted olefins like propene and 1‐butene, while the internal alkene cis −2‐butene experiences allylic activation of an sp 3 C–H bond, which provides an alternative route to 6 * . The extension of these investigations to the analogous complexes of the unsubstituted tris(pyrazolyl)hydroborato ligand Tp is also reported. Mechanistic studies on the formation of the C–C bond by coupling of the vinyl and the olefin ligands suggest the participation of a vinylidene complex (formed by α‐H abstraction from the vinyl group), which then rearranges to an allene species. Evidence for the involvement of these and other key reaction intermediates is provided.