Iridium(III) and Rhodium(III) compounds of dipyridyl-N-alkylimine and dipyridyl-NH-ketimine: Spectral characterization and crystal structure

Abstract

Pentamethylcyclopentadienyl iridium(III) and rhodium(III) complexes of formulation [(η 5-C 5Me 5)M{(C 5 H 4N) 2 C=NR)}Cl]PF 6 were prepared by the reaction of [MCl 2(η 5-C 5Me 5)] 2(M = Ir or Rh) with dipyridyl-N-alkylimine ligands, (C 5 H 4N) 2 C=NR (R = Me or Et) in the presence of NH 4 PF 6 at room temperature. The reaction also produced an unexpected dipyridyl-NH-ketimine organometallic compound [(η 5-C 5Me 5)M {(C 5 H 4N) 2 C=NH}Cl]PF 6 as minor product when the reaction was performed under refluxing acetonitrile. The NH-ketimine compounds were formed via N-C single bond cleavage of imine ligand resulting in coordination of the transformed ligand, (C 5 H 4N) 2 C=NH to the metal centre. Complexes were obtained as their hexafluorophosphate salts and characterized based on IR, NMR and ESI-MS spectroscopic data. Authenticity of NH-ketimine organometallic compound was established by single crystal X-ray analysis of a representative compound, which crystallized in orthorhombic space group Pbcn and has a pseudo-octahedral geometry around the metal ion. Pentamethylcyclopentadienyl iridium(III) and rhodium(III) complexes containing dipyridyl-N-alkylimine and dipyridyl-NH-ketimine ligands of formulation [(η 5-C5Me5)M{(C5H4N)2C=NR}Cl]PF6 and [(η 5-C5Me5)M{(C5H4N)2C=NH}Cl]PF6 were synthesized and characterized on the basis of spectroscopic data. Solid state structure of one representative NH-ketimine compound [6]PF 6 has been determined by X-ray crystallography