Coordinatively unsaturated W(IV)-bis(pyridine) complexes, a reactive source of W(IV)

Area of Science:

• Organometallic Chemistry
• Tungsten Chemistry
• Coordination Chemistry

Background:

• Tungsten complexes with diamide ligands are of interest due to their unique electronic and steric properties.
• Understanding ligand dynamics and coordination behavior is crucial for developing novel catalytic systems.

Purpose of the Study:

• To synthesize and characterize novel tungsten(IV) complexes incorporating sigma-donor ligands.
• To investigate the steric and electronic effects of diamide ligands on tungsten coordination.
• To explore the reactivity of coordinatively unsaturated tungsten complexes.

Main Methods:

• Synthesis of tungsten(IV) complexes via ligand addition to precursor tungsten compounds.
• Preparation of complexes through reductive methods using sodium.
• Characterization of synthesized compounds using spectroscopic techniques and analysis of ligand rotation.

Main Results:

• Successfully synthesized three new W(IV) complexes: [W(NPh)(o-(Me3SiN)2C6H4)(C5H5N)2] (5), [W(NPh)(o-(Me3SiN)2C6H4)(p-C6H7N)2] (6), and [W(NPh)(o-(Me3SiN)2C6H4)(C9H7N)2] (7).
• Observed hindered rotation of sigma-donor ligands (pyridine, 4-picoline, quinoline) due to steric hindrance from trimethylsilyl (Me3Si) groups.
• Demonstrated the reactivity of coordinatively unsaturated complexes 5 and 6 with carbon monoxide (CO) and trimethylphosphine (PMe3) to form six-coordinate adducts.

Conclusions:

• The steric bulk of the Me3Si groups in the diamide ligand significantly influences ligand dynamics in tungsten complexes.
• The synthesized tungsten(IV) complexes serve as valuable platforms for studying coordination unsaturation and reactivity.
• This study expands the scope of tungsten organometallic chemistry, highlighting the role of ligand design in controlling complex properties.