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Dihydrogen Catalysis of the Reversible Formation and Cleavage of CH and NH Bonds of Aminopyridinate Ligands Bound to (η 5 ‐C 5 Me 5 )Ir III
Author(s) -
Zamorano Ana,
Rendón Nuria,
LópezSerrano Joaquín,
Valpuesta José E. V.,
Álvarez Eleuterio,
Carmona Ernesto
Publication year - 2015
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.201405340
Subject(s) - chemistry , electrophile , denticity , iridium , ligand (biochemistry) , cationic polymerization , stereochemistry , aryl , bond cleavage , cleavage (geology) , medicinal chemistry , catalysis , crystallography , ring (chemistry) , crystal structure , polymer chemistry , alkyl , biochemistry , receptor , geotechnical engineering , organic chemistry , fracture (geology) , engineering
This study focuses on a series of cationic complexes of iridium that contain aminopyridinate (Ap) ligands bound to an (η 5 ‐C 5 Me 5 )Ir III fragment. The new complexes have the chemical composition [Ir(Ap)(η 5 ‐C 5 Me 5 )] + , exist in the form of two isomers ( 1 + and 2 + ) and were isolated as salts of the BAr F − anion (BAr F =B[3,5‐(CF 3 ) 2 C 6 H 3 ] 4 ). Four Ap ligands that differ in the nature of their bulky aryl substituents at the amido nitrogen atom and pyridinic ring were employed. In the presence of H 2 , the electrophilicity of the Ir III centre of these complexes allows for a reversible prototropic rearrangement that changes the nature and coordination mode of the aminopyridinate ligand between the well‐known κ 2 ‐N , N ′‐bidentate binding in 1 + and the unprecedented κ‐ N ,η 3 ‐pseudo‐allyl‐coordination mode in isomers 2 + through activation of a benzylic CH bond and formal proton transfer to the amido nitrogen atom. Experimental and computational studies evidence that the overall rearrangement, which entails reversible formation and cleavage of HH, CH and NH bonds, is catalysed by dihydrogen under homogeneous conditions.