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 [Rh^III(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 [Rh^III(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.

KEYWORDS:

• Rhodium
• azine
• hydrogen bonding
• packing
• DFT

Acknowledgements

S.A. thanks Dr. Saumitra Bhowmik of IISER Kolkata for useful help and suggestions for single crystal X-ray diffraction.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

S.A. thanks the financial support received from Madhav University and we extend our sincere thanks to the University. A.C. thanks Sharda University (Grant number: SU/SF/2022/08) for providing financial support.