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A Mononuclear and High-Spin Tetrahedral TiII Complex.
Anders Reinholdt1, Daniel Pividori2, Alexander L Laughlin3
1Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
Inorganic Chemistry
|December 1, 2020
Summary
A novel high-spin titanium(II) complex was synthesized and characterized. This titanium complex can activate nitrogen gas, forming a unique bridged dinitrogen complex, and react with other small molecules.
Area of Science:
- Organometallic Chemistry
- Inorganic Chemistry
- Coordination Chemistry
Background:
- Low-valent transition metal complexes are crucial for small molecule activation.
- Titanium complexes, particularly in low oxidation states, offer unique reactivity.
- Understanding the electronic and structural properties of titanium complexes is key to designing new catalysts.
Purpose of the Study:
- To synthesize and characterize a mononuclear high-spin titanium(II) complex.
- To investigate the reactivity of this titanium(II) complex towards small molecules like N2 and pi-acids.
- To explore the potential of this complex in atom- or group-transfer reactions.
Main Methods:
- Synthesis of titanium(II) complex via reduction of titanium(III) precursor.
- Characterization using high-frequency and -field electron paramagnetic resonance (HFEPR) spectroscopy.
- Magnetic studies (solution and solid-state), X-ray absorption spectroscopy (XAS).
- Computational studies (DFT, CASSCF), single-crystal X-ray diffraction.
- Infrared (IR) and Raman spectroscopies, electrochemistry.
Main Results:
- A high-spin, mononuclear titanium(II) complex, [(Tp*)TiCl], with a 3A2 ground state was successfully prepared and characterized.
- The titanium(II) complex binds THF but captures N2 in its absence, forming a diamagnetic complex with a linear Ti=N=N=Ti topology (two Ti(III) centers bridged by N2(2-)).
- Coordination of a pi-acid (CNAd) yields a high-spin, five-coordinate titanium(II) complex without spin pairing.
- The titanium(II) complex undergoes atom- or group-transfer reactions, providing access to various titanium(IV) complexes.
Conclusions:
- The synthesized titanium(II) complex exhibits unique reactivity, including N2 activation and coordination of pi-acids.
- The study demonstrates the versatility of low-valent titanium chemistry in small molecule activation and functionalization.
- This work provides a foundation for developing new titanium-based catalysts for challenging chemical transformations.
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