Synthesis and structural characterization of two novel N-heterocyclic carbene complexes of Rh(I)

Two new N-heterocyclic carbene (NHC) ligands with p-methylphenyl and p-methoxyphenyl substituents on 4,5-positions and methoxyethyl pendants on N atoms of the imidazole ring were complexed together with cyclooctadiene and an iodide ion to Rh(I) to give 4a and 4b, respectively. The complexes were characterized by elemental analyses, NMR and IR spectroscopy. In addition, molecular and crystal structure of 4a was determined by single-crystal X-ray methods. In 4a the rhodium ion has distorted square planar coordination geometry chelating with cyclooctadiene (COD) ligand. Molecules of 4a form polymeric chains along the c axis through C-H...I hydrogen bonds.