Bismuth Pyridine Dipyrrolide Complexes: a Transient Bi(II) Species Which Ring Opens Cyclic Ethers

Area of Science:

• Organometallic Chemistry
• Main Group Chemistry
• Redox Chemistry

Background:

• Group 15 pyridine dipyrrolide complexes (M^III) were synthesized and characterized.
• Traditional reductants (Mg, Zn, KC₈) resulted in over-reduction or ligand redistribution.

Purpose of the Study:

• To investigate the reduction of Group 15 M^III pyridine dipyrrolide complexes using novel soluble reductants.
• To explore the potential of these complexes in activating small molecules like cyclic ethers.

Main Methods:

• Preparation and full characterization of Group 15 M^III pyridine dipyrrolide complexes.
• Reduction studies using organosilanes as soluble reductants.
• Trapping of reaction intermediates using TEMPO (2,2,6,6-tetramethylpiperidinyloxyl).

Main Results:

• Organosilane reduction led to the ring opening and two-electron reduction of tetrahydrofuran (thf) solvent.
• Formation of bismuth-carbon (Bi-C) and silicon-oxygen (Si-O) bonds was observed.
• A proposed Bismuth(II) (Bi^II) intermediate was successfully trapped by TEMPO.

Conclusions:

• This study demonstrates a main group complex capable of cyclic ether ring opening without additional metal reducing agents.
• Organosilanes serve as effective soluble reductants for activating these complexes and the solvent.
• The findings open new avenues for main group mediated organic transformations.