Related Experiment Video
Updated: Sep 8, 2025
06:26
Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source
Published on: August 17, 2018
10.1K
Reactivity of titanium pyrazolates towards CO2, CS2 and N2O
Felix Kracht1, Sophie Mayer1, Cäcilia Maichle-Mössmer1
1Institut für Anorganische Chemie, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany. reiner.anwander(at)uni-tuebingen.de.
Dalton Transactions (Cambridge, England : 2003)
|July 1, 2025
Summary
Titanium pyrazolate complexes reversibly insert carbon dioxide at ambient conditions. Tetravalent titanium complexes show stability, while trivalent ones react with N2O, releasing nitrogen gas.
Area of Science:
- Organometallic Chemistry
- Coordination Chemistry
- Materials Science
Background:
- Titanium pyrazolate complexes are known for their diverse reactivity.
- The activation and functionalization of small molecules like CO2 are crucial in catalysis and materials science.
- Understanding the reactivity of titanium complexes with heteroallenes is essential for developing new chemical transformations.
Purpose of the Study:
- To investigate the reactivity of tetravalent and trivalent titanium pyrazolate complexes with carbon dioxide (CO2) and carbon disulfide (CS2).
- To explore the stability and transformation pathways of the resulting metal-CO2 and metal-CS2 adducts.
- To examine the reaction of titanium pyrazolates with nitrous oxide (N2O).
Main Methods:
- Synthesis and characterization of titanium pyrazolate complexes.
- Reactions with CO2, CS2, and N2O under varying conditions.
- Thermogravimetric analysis (TGA) to study thermal stability and reversibility.
- Spectroscopic and structural analysis of reaction products.
Main Results:
- Tetravalent Ti(pzMe2)4 instantly inserts two CO2 molecules, forming a stable complex, with reversible CO2 release observed via TGA.
- The tetravalent complex undergoes deoxygenation in solution to form oxo-bridged species.
- Trivalent Ti(pztBu2)3 also inserts two CO2 molecules, with complete de-insertion occurring at 70 °C.
- Ti(pzMe2)4 does not react with N2O, whereas Ti(pztBu2)3 reacts to form an oxo-bridged species with N2 release.
Conclusions:
- Titanium pyrazolates, both tetravalent and trivalent, exhibit significant reactivity towards CO2 insertion.
- The stability and reaction pathways of these adducts are dependent on the titanium oxidation state and reaction conditions.
- Trivalent titanium pyrazolates demonstrate unique reactivity with N2O, leading to oxo-bridged complexes and nitrogen gas evolution.
Related Concept Videos
01:22Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction
1.9K
The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.
1.9K
01:11ortho–para-Directing Activators: –CH3, –OH, –NH2, –OCH3
6.3K
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
6.3K
01:10Radical Reactivity: Steric Effects
2.0K
The presence of electron-donating, electron-withdrawing, or conjugating groups adjacent to a radical center, imparts electronic stabilization to the radicals. Examples of such electronically-stabilized radicals are triphenylmethyl, tetramethylpiperidine‐N‐oxide, and 2,2‐diphenyl‐1‐picrylhydrazyl. These radicals are remarkably stable and are known as persistent radicals. Some of the persistent radicals can even be isolated and purified.
Along with electronic...
Along with electronic...
2.0K
01:20Radical Reactivity: Concentration Effects
1.5K
In a radical reaction, the concentration of starting materials governs the selectivity of a radical. For example, the reaction between an alkyl halide and an alkene, in the presence of tin hydride and AIBN, begins with the generation of a tin radical. The generated radical then abstracts halogen from the alkyl halide, producing an alkyl radical. This alkyl radical can either react with tin hydride, yielding an alkane, or add to an alkene, generating a nitrile-stabilized radical, eventually...
1.5K
01:11Radical Reactivity: Overview
2.2K
Radicals, the highly reactive species, gain stability by undergoing three different reactions. The first reaction involves a radical-radical coupling, in which a radical combines with another radical, forming a spin‐paired molecule. The second reaction is between a radical and a spin‐paired molecule, generating a new radical and a new spin‐paired molecule. The third reaction is radical decomposition in a unimolecular reaction, forming a new radical and a spin‐paired...
2.2K
01:13meta-Directing Deactivators: –NO2, –CN, –CHO, –CO2R, –COR, –CO2H
5.7K
All meta-directing substituents are deactivating groups. These substituents withdraw electrons from the aromatic ring, making the ring less reactive toward electrophilic substitution. For example, the nitration of nitrobenzene is 100,000 times slower than that of benzene because of the deactivating effect of the nitro group. The first step in an electrophilic aromatic substitution is the addition of an electrophile to form a resonance-stabilized carbocation. The energy diagrams for...
5.7K