Neutral trans-Dioxorhenium(V) Complexes with the Anionic Tetrakis(pyrazolyl)borate Ligand

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Coordination Chemistry

Background:

• Rhenium complexes are of interest due to their diverse applications in catalysis and medicine.
• Synthesis of specific rhenium oxidation states and coordination geometries can be challenging.
• The use of poly(pyrazolyl)borate ligands offers unique coordination possibilities.

Purpose of the Study:

• To develop a convenient and efficient synthetic route to neutral dioxorhenium(V) complexes.
• To explore the reactivity of rhenium(III) oxo precursors with triphenylphosphine and various ligands.
• To characterize the resulting rhenium(V) complexes using spectroscopic and crystallographic methods.

Main Methods:

• Reduction of rhenium(V) oxo complexes using triphenylphosphine (PPh3) in the presence of sigma-donor ligands.
• Synthesis of complexes trans-[ReO(2){eta(2)-B(pz)(4)}(L)(2)] and trans-[ReO(2){eta(2)-B(pz)(4)}(P&arcraise;P)].
• Characterization by Infrared (IR), Nuclear Magnetic Resonance (NMR) spectroscopy, and X-ray crystallography.

Main Results:

• Successful synthesis of neutral dioxorhenium(V) complexes with tetrakis(pyrazolyl)borate and related ligands.
• Identification of complexes trans-[ReO(2){eta(2)-B(pz)(4)}(L)(2)] (L=pyridine, imidazole derivatives) and trans-[ReO(2){eta(2)-B(pz)(4)}(diphosphine)].
• Characterization confirmed the structures, including X-ray crystallographic data for key compounds.

Conclusions:

• The PPh3-mediated reduction provides a versatile method for synthesizing neutral dioxorhenium(V) complexes.
• The study expands the library of characterized rhenium(V) complexes with poly(pyrazolyl)borate ligands.
• The findings contribute to the understanding of rhenium oxo chemistry and ligand effects.