Synthetic Inorganic and Organometallic Research
We study the chemistry of Mn(III) halide and pseudohalide compounds
Overview: Mn(III) halide and pseudohalide compounds are known for their high reactivity, which has traditionally limited their applications beyond Mn(III) acetate. One major challenge has been the instability of MnCl3, which decomposes at temperatures above -35 °C. However, our research has shown that by coordinating MnCl3 with carefully selected ligands, we can achieve a “Goldilocks” level of reactivity—striking a balance between stability and reactivity. This has allowed us to explore the unique properties of Mn(III) halide and pseudohalide complexes, which are now being applied in diverse fields such as drug synthesis, materials chemistry, and biomimetic studies. Below are some highlights from our research.
• A powerful oxidant for chemists
Removing electrons, or single-electron oxidation, is one of the most common and fundamental reactions in chemistry. In choosing the right oxidant, chemists must balance a series of properties including the strength of the oxidant, its compatibility with the system, and the ease of preparation or handling. This is where our most recent innovation comes to the rescue. We developed a bench-stable powerful oxidant that can be prepared on gram-scale using simple Schlenk-line technique using commercially available materials. This new oxidant, [Mn(NO3)3(OPPh3)2], is soluble in most common organic solvents and does not react with various functional groups commonly encountered. It is very easy to make and use. Finally, its reduction potential is 1.02 V positive of ferrocenium making it one of the strongest stoichiometric oxidants in organic solvent available to chemists
• publication
https://doi.org/10.1021/jacs.4c03411
• A new bench-stable Cl-atom transfer reagent
The Lacy group discovered a new bench-stable Mn(III)Cl3 precursor that can be prepared in a single step from commercially available starting materials. This compound is a revolutionary advancement because there are very few available molecular starting materials for high-valent Mn.
• publications…
https://doi.org/10.1021/jacs.2c08509
https://doi.org/10.1021/jacs.3c03651
• News articles on discovery…
https://www.chemistryviews.org/bench-stable-manganeseiii-chloride-source/
https://www.nature.com/articles/s44160-022-00181-7#citeas
https://www.buffalo.edu/news/releases/2022/10/001.html
• E-selective alkyne semihydrogenation with bench-stable Mn(I) catalysts
We discovered a new class of manganese-based bench-stable hydrogenation catalysts that can be prepared gram-scale from commercially available starting materials in a single step. These are useful in stoichiometric or catalytic alkyne semi-hydrogenation (1 atm H2) and they selectively form the trans E-isomer.
• Check out our review and research articles on this unique class of molecules…
https://doi.org/10.1002/chem.202300518
https://doi.org/10.1002/chem.202201766
https://doi.org/10.1021/acs.organomet.1c00603
• Coordination chemistry of Mn(I), Fe, Zn, and Ru hydrogenation catalysts
Making catalysts in situ has its advantages. Therefore, we invented an additive free method of generating active Mn(I) 16-e- catalysts in the presence of substrate(s). This was accomplished using Mn(I) alkyl precursors, namely the bench-stable compound MeMn(CO)5. This convenient methodology was first demonstrated by us in 2019, and has since been used by others in “additive free” Mn(I) catalyzed hydrogenation reactions.
• Check out our two publications that highlight this methodology…
https://doi.org/10.1039/C9DT00529C
https://doi.org/10.1021/acs.organomet.9b00692
• We have also studied the coordination chemistry of Mn(I), Ru(II), Zn(II) and Fe(II) hydrogenation catalysts. A few selected examples are linked below…
Mn(I)
https://doi.org/10.1016/B978-0-12-820206-7.00060-3
https://doi.org/10.1021/acs.inorgchem.9b00941
https://doi.org/10.1021/acs.organomet.1c00606
https://doi.org/10.1039/C8DT02933D
Ru(II)
https://doi.org/10.1021/acs.organomet.0c00327
https://doi.org/10.1021/acs.organomet.1c00648
Zn(II) & Fe(II)
https://doi.org/10.1002/chem.202201042
https://doi.org/10.1002/ejic.202300757
• A CO rich molecule
The Lacy group had its beginnings studying the properties of an organomanganese tetramer, [Mn(CO)3(µ3-OH)]4. Our early work on this molecule detailed its synthesis, photochemical properties, and chemical properties. Recently, we considered the use of [Mn(CO)3(µ3-OH)]4 as a water soluble CO releasing molecule (CORM) in cancer cell anti-proliferation. Since [Mn(CO)3(µ3-OH)]4 has twelve CO ligands, it has advantages over other CORMs that only deliver one to three CO molecules.
• Our studies on this interesting molecule are linked below…
https://doi.org/10.1016/j.poly.2024.116859
https://doi.org/10.1021/acs.inorgchem.9b00322
https://doi.org/10.1021/acs.inorgchem.7b01483
https://doi.org/10.1021/acs.inorgchem.7b01438
• O2 activation with non-heme iron(II) complexes
Molecular oxygen, or O2, constitutes about 21% of the air that we breath, and without it, life on Earth as we know it would not exist. Therefore, understanding the complexities of how O2 reacts with various molecules is a very important subfield of chemical research. The Lacy group was interested in how a special class of enzymes called non-heme oxygenases take O2 from the air and use it in biochemical processes. The goal was to develop new catalysts that could mimic this reactivity and harness it for applications in organic synthesis. Our strategy was to design synthetic molecular complexes inspired from the active site structures of the enzymes in question. What we found is that simple, solvated molecules, like Fe(II) ions in acetonitrile, outperform some of the best synthetic models with complicated chelating ligands; these findings were too controversial for some reviewers and so the results and interpretation had to be tucked away so as not to offend anyone. We also found an interesting relationship between the kinetics of O2 reduction by Fe(II) complexes and the binding energy of superoxide with Fe(III) complexes. Our publications on this project are linked below…
https://doi.org/10.1002/ejic.202000984
https://doi.org/10.1080/00958972.2021.1878353
https://doi.org/10.1039/C8SC01621F
https://doi.org/10.1039/C9QI00828D