Premium
The Synthesis of Iridabenzenes by the Coupling of Iridacyclopentadienes and Olefins
Author(s) -
Paneque Margarita,
Poveda Manuel L.,
Rendón Nuria,
Álvarez Eleuterio,
Carmona Ernesto
Publication year - 2007
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200601257
Subject(s) - chemistry , propene , hydride , metallacycle , ligand (biochemistry) , iridium , moiety , regioselectivity , medicinal chemistry , stereochemistry , infrared spectroscopy , acetonitrile , metal , x ray crystallography , catalysis , organic chemistry , biochemistry , physics , receptor , optics , diffraction
The iridacyclopentadiene [(Tp Me2 )Ir{C 1 (R)=C(R)C(R)=C 4 (R)}(H 2 O)( Ir–C 4 )] ( 1 ; R = CO 2 Me) reacts with propene at 60 °C to give the iridabenzene [(Tp Me2 )Ir{C 1 (Et)C(R)C(R)C(R)C 5 (R)}(H)( Ir–C 5 )] ( 6 ), which also contains a hydride ligand, as the main product, accompanied by complexes 7 and 8 derived from the insertion of propene into the Ir–C bonds of 1 . In contrast, the closely related metallacycle [(Tp Me2 )Ir{C 1 (R)=C(H)C(R)=C 4 (R)}(H 2 O)( Ir–C 4 )] ( 1‐H ) gives the iridabenzene [(Tp Me2 )Ir{C 1 (Me)C(R)C(H)C(R)C 5 (R)}(Me)( Ir–C 5 )] ( 13 ), which contains an iridium‐bonded methyl group, upon treatment with propene at 20 °C. The proposed mechanism for the formation of metallabenzenes 6 and 13 postulates Ir–propene → Ir=CHEt or Ir–propene → Ir=CMe 2 isomerisations, followed by insertion of the alkylidene ligand into an Ir–C(R) bond (regioselective for 1‐H ) and α‐H or α‐Me elimination from the resulting alkyliridium moiety. At 25 °C, neat acetonitrile induces stereoselective hydride migration onto both the Ir[pb2]C bonds of 6 to give a kinetic mixture (6:1 ratio) of the isomeric adducts [(Tp Me2 )Ir{C 1 H(Et)C(R)=C(R)C(R)=C 5 (R)}(MeCN)( Ir–C 5 )] ( 9 ) and [(Tp Me2 )Ir{C 1 H(R)C(R)=C(R)C(R)=C 5 (Et)}(MeCN)( Ir–C 5 )] ( 10 ), with the latter being the thermodynamically preferred product. In contrast, complex 13 is stable in acetonitrile up to 100 °C, where it mainly experiences ring fragmentation to give the iridacyclopentadiene 1‐H as its MeCN adduct. All new compounds have been fully characterised by microanalysis and spectroscopy. Additionally, the solid‐state structures of 5 , 6 and 13 have been determined by X‐ray crystallography. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)