Cyclometalation of Primary Benzyl Amines by Ruthenium(II), Rhodium(III), and Iridium(III) Complexes

• Published in: Organometallics 2007-04, Vol.26 (8), p.1856-1867
• Main Authors: Sortais, Jean-Baptiste, Pannetier, Nicolas, Holuigue, Alexandre, Barloy, Laurent, Sirlin, Claude, Pfeffer, Michel, Kyritsakas, Nathalie
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Coordination chemistry
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om060973t

The cyclometalation of chiral and achiral primary amines occurred readily with Ru(II), Rh(III), and Ir(III) derivatives. Thus, the metalation of (R)-1-phenylethylamine by [(η 6-benzene)RuCl2]2, [(η 5-Cp*)RhCl2]2, and [(η 5-Cp*)IrCl2]2 was studied. Good yields of the expected cationic products in which the phenyl group was ortho-metalated were obtained for the rhodium and the ruthenium derivatives, whereas a mixture of products was formed in the case of the iridium complex. Benzylamine, (R)-1-phenylpropylamine, (R)-1-(1-naphthyl)ethylamine, and (R)-1-aminotetraline afforded also the cycloruthenation products whose general formula is [(η 6-benzene)Ru(N−C)(NCMe)]PF6 where N−C represents the ortho-metalated ligands. Substitution of the acetonitrile ligand by PMe2Ph occurred readily on the ruthenium complexes, affording stable compounds that were characterized by X-ray diffraction studies on single crystals, thus ascertaining the existence of the cycloruthenated five-membered rings. Accurate analyses of the structure of the complexes were implemented in solution and in the solid state. The (S) configuration at the metal was usually associated with a δ conformation of the metallacycle, and conversely, the (R) configuration with the λ conformation. The study of the conformation of the five-membered rings revealed that the orientation of the NH2 group is such that one NH unit is oriented toward the η 6-benzene ring (roughly parallel to the Ru−centroid benzene vector), whereas the second NH is parallel to the Ru−L bond, L = NCMe or PMe2Ph.