Synthesis, crystal structure and hydrogen bonding of a Cp*Rh(III) complex bearing pyridyl azine ligands: a combined experimental and DFT approach

Abstract

We report the synthesis of a Cp*Rh complex bearing a pyridyl azine ligand with a free amine (NH2) group. The reaction of [Cp*RhCl2]2 with ligand (L) formed a cationic complex with the formula [RhIII(η5-C5Me5)(L)к2 (N,N’)Cl]SbF6 (1) that was characterized by IR, UV-Vis, 1H, 13C{1H} NMR, etc. The SC-XRD analysis of the complex revealed the condensation of an acetone molecule with the azine NH2 group, thus forming an imine –C=N– bond in the ligand, giving [RhIII(η5-C5Me5)(L’)к2 (N,N’)Cl]SbF6 (2). The coordination geometry around rhodium in 2 is pseudo-tetrahedral with coordination sites occupied by a Cp* moiety in an η5 manner, a terminal chloride, and a pyridyl azine ligand in a bidentate N,N’ fashion through N(pyridine) and N(azine) nitrogen atoms occupying the four vertices of the tetrahedron. The crystal packing is mainly directed by moderate and weak hydrogen bonds including C–H⋯F, C–H⋯Cl, N–H⋯Cl and C–H⋯N interactions. The overall crystal packing and the significant role of hydrogen bonding in the supramolecular assembly has been discussed by performing Atoms-In-Molecules (AIM) and Natural Bond Orbital (NBO) analyses.