Dirhodium formamidinate compounds with bidentate nitrogen chelating ligands

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Materials Science

Background:

• Rhodium(II) dimers are versatile precursors in catalysis and materials science.
• The N,N'-di-p-tolylformamidinate (DTolF) ligand offers unique steric and electronic properties.
• Substitution reactions of acetonitrile ligands in rhodium complexes are crucial for synthesizing novel structures.

Purpose of the Study:

• To investigate the reactivity of the rhodium(II) dimer [Rh(2)(DTolF)(2)(CH(3)CN)(6)][BF(4)](2) with N-N chelating ligands.
• To characterize the resulting products, focusing on ligand coordination modes and structural features.
• To understand the influence of steric effects from the formamidinate ligand on the coordination geometry.

Main Methods:

• Synthesis of rhodium(II) complexes.
• Reaction of the rhodium dimer with 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen).
• Full characterization using X-ray crystallography and 1H NMR spectroscopy.

Main Results:

• Substitution of acetonitrile ligands by bpy and phen, leading to equatorial-equatorial (eq-eq) chelation.
• Formation of various products depending on the stoichiometry of the N-N ligand.
• Crystallographic data confirmed the structures of [Rh(2)(DTolF)(2)(bpy)(CH(3)CN)(3)][BF(4)](2) (2a), [Rh(2)(DTolF)(2)(bpy)(CH(3)CN)(4)][BF(4)](2) (2b), [Rh(2)(DTolF)(2)(bpy)(2)(CH(3)CN)][BF(4)](2) (3), and [Rh(2)(DTolF)(2)(phen)(CH(3)CN)(3)][BF(4)](2).2C(2)H(5)OC(2)H(5) (4).
• A notable observation is the presence of only one axial acetonitrile ligand in cations 2a, 3, and 4.

Conclusions:

• The steric bulk of the DTolF ligand influences the coordination sphere of the rhodium dimer.
• The observed equatorial-equatorial chelation mode is favored in these reactions.
• The study provides insights into the synthesis and structural diversity of rhodium(II) complexes with N-N ligands.