User:Pg1885h/Jonathan rajaseelan

Rajaseelan, Jonathan.

"N-Heterocyclic Carbene Complexes of Rhodium and Iridium: Steric Effects on Molecular Conformation." Gary S. Nichol,*[a] Jonathan Rajaseelan,[b] Laura J. Anna,[c] and Edward Rajaseelan[c] Keywords: Carbene ligands / Nitrogen heterocycles / Rhodium / Iridium / Polymorphism

Abstract A series of new RhI triazole-based N-heterocyclic carbene (NHC) complexes [(cod)Rh(NHC)Cl] 2a-c were obtained by transmetallation from AgI complexes using n-butyl, benzyl and neopentyl NHC wing tip substituents. The corresponding new RhI ionic complexes (3a-c) were synthesized bytreating compounds 2a-c with triphenylphosphane and AgBF4. 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··· interactions and steric crowding of the PPh3 ligand.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)