Easy access to the copper(III) anion [Cu(CF3 )4 ](-)

Area of Science:

• Organometallic Chemistry
• Fluorine Chemistry
• Coordination Chemistry

Background:

• Trifluoromethyl (CF3) ligands are crucial in organometallic chemistry, influencing reactivity and stability.
• Copper complexes, particularly those involving CF3 ligands, are of interest for catalytic applications.
• Efficient synthesis of well-defined copper-trifluoromethyl species is essential for further research.

Purpose of the Study:

• To develop a robust synthetic route for the [Cu(CF3)4](-) complex.
• To explore the reactivity of [Cu(CF3)4](-) as a precursor for novel copper complexes.
• To characterize new copper(III) complexes and investigate their properties.

Main Methods:

• Reaction of CuCl or CuCF3 with CF3SiMe3/KF in DMF under air to yield [Cu(CF3)4](-).
• Isolation and characterization of various [Cu(CF3)4](-) salts (PPN+, Me4N+, Bu4N+, Ph4P+) using spectroscopy and X-ray diffraction.
• Synthesis and characterization of a novel Cu(III) complex, [(bpy)Cu(CF3)3], via ligand exchange from [Cu(CF3)4](-).

Main Results:

• Quantitative synthesis of [Cu(CF3)4](-) achieved, with isolated salts in high yields (82-99%).
• X-ray structures confirmed the molecular geometry of several [Cu(CF3)4](-) salts.
• A novel, fluxional Cu(III) complex, [(bpy)Cu(CF3)3], was synthesized and characterized, exhibiting a low isomerization barrier (2.3 kcal mol(-1)).
• NPA studies indicated a higher electron density on copper in the fluorinated [Cu(CF3)4](-) compared to its non-fluorinated analog.

Conclusions:

• A facile and high-yielding synthesis of the [Cu(CF3)4](-) complex has been established.
• The [Cu(CF3)4](-) complex serves as a versatile precursor for synthesizing new copper complexes, including Cu(III) species.
• The electronic properties of copper are significantly influenced by trifluoromethyl ligands, impacting complex stability and reactivity.