Enhanced Understanding of Structure-Function Relationships for Oxomanganese(IV) Complexes.
Priya Singh1, Yuri Lee1, Jaycee R Mayfield1
1The University of Kansas, Department of Chemistry and Center for Environmentally Beneficial Catalysis, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States.
Inorganic Chemistry
|June 14, 2023
Summary
This study synthesized manganese-oxo complexes with varying ligand fields to explore their reactivity. Ligand field strength and steric factors significantly influence the oxidation rates of hydrocarbons and thioanisole.
Area of Science:
- Inorganic Chemistry
- Organometallic Chemistry
- Catalysis
Background:
- Manganese-oxo complexes are crucial in various oxidation reactions.
- Understanding the influence of ligand environment on reactivity is key for catalyst design.
Purpose of the Study:
- To synthesize and characterize manganese(II) and oxomanganese(IV) complexes with diverse equatorial ligand field strengths.
- To investigate how variations in ligand field strength and steric bulk affect the oxidative reactivity of these complexes.
Main Methods:
- Synthesis and structural characterization of manganese complexes.
- Spectroscopic analysis, including electronic absorption spectroscopy.
- Reactivity studies using hydrocarbon and thioanisole oxidation.
- Computational analysis using density functional theory (DFT) to compute bond dissociation free energies (BDFEs).
Main Results:
- Complexes with varied equatorial ligand field strengths were successfully synthesized and characterized.
- [MnIV(O)(N4pyMe2)]2+ exhibited the weakest equatorial ligand field, while [MnIV(O)(N2py2I)]2+ showed the strongest.
- The [MnIV(O)(N3pyQ)]2+ complex demonstrated high reactivity in C-H bond and thioanisole oxidation.
- Steric factors, not just ligand field strength, were found to dampen the reactivity of the [MnIV(O)(N4pyMe2)]2+ complex.
- DFT-computed BDFEs correlated well with thioanisole oxidation rates (MnIV═O BDFEs) and showed scatter with hydrocarbon oxidation rates (MnIIIO-H BDFEs).
Conclusions:
- Ligand field strength and steric bulk are critical determinants of manganese-oxo complex reactivity.
- The correlation between computational BDFEs and experimental oxidation rates provides insights into reaction mechanisms.
- This work contributes to the rational design of efficient manganese-based oxidation catalysts.
More Related Videos
Related Concept Videos
02:42Valence Bond Theory
8.8K
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
8.8K
02:34Structural Isomerism
19.5K
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can...
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can...
19.5K
03:02Colors and Magnetism
12.0K
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
12.0K
02:57Coordination Number and Geometry
16.2K
For transition metal complexes, the coordination number determines the geometry around the central metal ion. Table 1 compares coordination numbers to molecular geometry. The most common structures of the complexes in coordination compounds are octahedral, tetrahedral, and square planar.
16.2K
02:54Coordination Compounds and Nomenclature
21.7K
In most main group element compounds, the valence electrons of the isolated atoms combine to form chemical bonds that satisfy the octet rule. For instance, the four valence electrons of carbon overlap with electrons from four hydrogen atoms to form CH4. The one valence electron leaves sodium and adds to the seven valence electrons of chlorine to form the ionic formula unit NaCl (Figure 1a). Transition metals do not normally bond in this fashion. They primarily form coordinate covalent bonds, a...
21.7K