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N‐Heterocyclic Carbene Complexes of Rhodium and Iridium: Steric Effects on Molecular Conformation
Author(s) -
Nichol Gary S.,
Rajaseelan Jonathan,
Anna Laura J.,
Rajaseelan Edward
Publication year - 2009
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.200900480
Subject(s) - chemistry , carbene , steric effects , iridium , rhodium , intramolecular force , stereochemistry , transmetalation , ionic bonding , ligand (biochemistry) , crystallography , catalysis , organic chemistry , ion , biochemistry , receptor
A series of new Rh I triazole‐based N‐heterocyclic carbene (NHC) complexes [(cod)Rh(NHC)Cl] 2a – c were obtained by transmetallation from Ag I complexes using n ‐butyl, benzyl and neopentyl NHC wing tip substituents. The corresponding new Rh I ionic complexes ( 3a‐c ) were synthesized bytreating compounds 2a – c with triphenylphosphane and AgBF 4 . These complexes were characterized by nmr spectroscopy and the structures of 2c , 3a , 3b , and 3c were determined by single‐crystal X‐ray diffraction. Compound 3b formed two polymorphs, the first reported incidence of polymorphism in this type of NHC. Ir analogues, 4 , of complexes 3a – c were also synthesized; two complexes are isomorphous with the Rh analogues 4b and 4c while 4a has a different structure. Differences in syn and anti molecular conformation of the NHC ligands is rationalized in terms of stabilizing intramolecular C–H ··· π interactions and steric crowding of the PPh 3 ligand.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)