Taking TiF4 complexes to extremes--the first examples with phosphine co-ligands

Area of Science:

• Inorganic Chemistry
• Coordination Chemistry
• Materials Science

Background:

• Titanium tetrafluoride (TiF(4)) is a Lewis acidic compound with limited exploration in forming stable adducts with soft donor ligands.
• Understanding the coordination behavior of TiF(4) with various ligands is crucial for developing new titanium-based materials and catalysts.

Purpose of the Study:

• To synthesize and characterize the first soft donor adducts of TiF(4) with diphosphine ligands.
• To investigate the structural features and bonding in these novel titanium(IV) complexes.
• To explore the reactivity of TiF(4) with a range of soft and hard donor ligands.

Main Methods:

• Synthesis of TiF(4) adducts under rigorously anhydrous conditions.
• Characterization using multinuclear NMR ((1)H, (31)P, (19)F), IR, and UV/vis spectroscopy.
• Single-crystal X-ray diffraction for structural determination of key complexes.

Main Results:

• Successful preparation of moisture-sensitive [TiF(4)(diphosphine)] adducts.
• Crystal structure of [TiF(4){Et(2)P(CH(2))(2)PEt(2)}] reveals distorted six-coordinate geometry with disparate Ti-F and Ti-P bond lengths.
• Formation of unexpected fluorotitanate(IV) salts with diprotonated diphosphine ligands, including the first authenticated structure of a diprotonated o-phenylene-diphosphine.

Conclusions:

• TiF(4) readily forms adducts with soft diphosphine ligands, although these complexes are highly sensitive to moisture.
• The coordination environment around titanium is influenced by the nature of the donor atoms, leading to distorted geometries.
• The study highlights the potential for unexpected reactivity, such as the formation of protonated ligand salts, expanding the known chemistry of titanium fluorides.