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LUND UNIVERSITY LIBRARIES

Aliphatic β-Blocked Ligands in POCOP Pincer Complex Synthesis

Hansson, Ruben LU (2025) KEMR30 20251
Department of Chemistry
Abstract
Introduction:
Synthesis of novel aliphatic POCOP pincer complexes with β-blocking alkyl groups.
Background:
An issue with Aliphatic POCOP pincer complexes is that the sought-after C=M bond is unstable with previous attempts forming aromatic groups or decomposing completely under heating. By introducing β-blocking elements to the aliphatic POCOP pincer ligands could this mitigate the decomposition and the C=M bond could be maintained in the pincer complexes.
Aim(s):
Can an aliphatic POCOP β-blocking pincer complex be similar in stability and catalytic activity when compared to aromatic POCOP pincer complexes?
Methods:
Due to the sensitivity of alkyl phosphines towards water and/or dioxygen all syntheses were conducted under inert... (More)
Introduction:
Synthesis of novel aliphatic POCOP pincer complexes with β-blocking alkyl groups.
Background:
An issue with Aliphatic POCOP pincer complexes is that the sought-after C=M bond is unstable with previous attempts forming aromatic groups or decomposing completely under heating. By introducing β-blocking elements to the aliphatic POCOP pincer ligands could this mitigate the decomposition and the C=M bond could be maintained in the pincer complexes.
Aim(s):
Can an aliphatic POCOP β-blocking pincer complex be similar in stability and catalytic activity when compared to aromatic POCOP pincer complexes?
Methods:
Due to the sensitivity of alkyl phosphines towards water and/or dioxygen all syntheses were conducted under inert conditions. The synthesised complexes were characterised by using 1H and 31P NMR and also with single crystal XRD when possible.
Results:
[Pd(II)Cl2(CNMe)2] metal precursor formed complexes 2, 3 and 4 when reacted with ligand 1 and 2 at room temperature in non-polar solvents such as benzene or toluene. Chlorido Ligand abstraction and substitution was successful using AgBF4, but no carbene-metal double bond was observed. Ni(II), Pt(II) and Ru(II) did not form pincer complexes after extensive investigation of reaction conditions.
Conclusion:
Complexation using aliphatic POCOP pincer ligands with β-blocking alkyl groups was possible with Pd(II) resulting in five novel complexes. But thermal instability coupled with few possibilities for ligand substitution leaves catalytic applications limited with current ligand structures. (Less)
Popular Abstract
Making all new catalysts
Throughout the day will most people encounter what is called a catalyst. Catalyst are chemicals that do not get consumed, but instead speeds up reactions. One example is catalytic converters that filter exhaust fumes from cars to make the exhaust less harmful. In the same way no one needs to refill the catalytic converter fluid; ideally no one needs to replace good catalysts. But catalytic converters get old and could lose some of their function. So sooner or later a real catalyst must be replaced. To come up with catalyst that does a better job for longer, new catalysts must be design, made and tested.
My work has been to make completely new catalysts that has not been attempted before. Because they have never... (More)
Making all new catalysts
Throughout the day will most people encounter what is called a catalyst. Catalyst are chemicals that do not get consumed, but instead speeds up reactions. One example is catalytic converters that filter exhaust fumes from cars to make the exhaust less harmful. In the same way no one needs to refill the catalytic converter fluid; ideally no one needs to replace good catalysts. But catalytic converters get old and could lose some of their function. So sooner or later a real catalyst must be replaced. To come up with catalyst that does a better job for longer, new catalysts must be design, made and tested.
My work has been to make completely new catalysts that has not been attempted before. Because they have never been made before will the focus of this work be investigating their reactivity and stability rather than applying them in catalysis. The catalysts were made in dry and oxygen free conditions, so they do not decompose while they are being made. The specific type of catalyst that has been made has two parts; one is a metal that will do all the catalysis and the other is a pincer ligand that attaches to the metal to hold it in place. The pincer will attach on tree spots, like a crab. This crab analogy is to better describe what is happening. With two claws and one mouth that pinches/bites down on the metal. By pinching and biting the metal it will hold the metal steady, making the catalyst work better.
The pincer ligand complex that was chosen to work with is unfortunately very selective with what metals it wants to attach to. Out of the many metals tested it only attached to palladium. It did not attach to other metals such as nickel and platinum. To encourage it to attach to these metals, the solution containing ligand and metals were shaken, heated up and the solvent was switched out. Shaking it did little, heating it to over room temperature only decomposed the complex and switching solvents made the complex behave strange, a few ligands picked up metals while most would decompose. Due to the palladium pincer complex being very sensitive to heat, it will have limited use cases as catalyst. But a greater understanding of how this type of pincer ligands behaves has been achieved while looking for better catalysts. (Less)
Please use this url to cite or link to this publication:
author
Hansson, Ruben LU
supervisor
organization
alternative title
Aliphatic beta-Blocked Ligands in POCOP Pincer Complex Synthesis
course
KEMR30 20251
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Aliphatic, β-blocking, Palladium, POCOP, Pincer complexes, Inorganic chemistry.
language
English
id
9205585
date added to LUP
2025-06-25 13:47:36
date last changed
2025-06-25 13:47:36
@misc{9205585,
  abstract     = {{Introduction: 
Synthesis of novel aliphatic POCOP pincer complexes with β-blocking alkyl groups.
Background: 
An issue with Aliphatic POCOP pincer complexes is that the sought-after C=M bond is unstable with previous attempts forming aromatic groups or decomposing completely under heating. By introducing β-blocking elements to the aliphatic POCOP pincer ligands could this mitigate the decomposition and the C=M bond could be maintained in the pincer complexes. 
Aim(s):
Can an aliphatic POCOP β-blocking pincer complex be similar in stability and catalytic activity when compared to aromatic POCOP pincer complexes?
Methods: 
Due to the sensitivity of alkyl phosphines towards water and/or dioxygen all syntheses were conducted under inert conditions. The synthesised complexes were characterised by using 1H and 31P NMR and also with single crystal XRD when possible. 
Results: 
[Pd(II)Cl2(CNMe)2] metal precursor formed complexes 2, 3 and 4 when reacted with ligand 1 and 2 at room temperature in non-polar solvents such as benzene or toluene. Chlorido Ligand abstraction and substitution was successful using AgBF4, but no carbene-metal double bond was observed. Ni(II), Pt(II) and Ru(II) did not form pincer complexes after extensive investigation of reaction conditions. 
Conclusion: 
Complexation using aliphatic POCOP pincer ligands with β-blocking alkyl groups was possible with Pd(II) resulting in five novel complexes. But thermal instability coupled with few possibilities for ligand substitution leaves catalytic applications limited with current ligand structures.}},
  author       = {{Hansson, Ruben}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Aliphatic β-Blocked Ligands in POCOP Pincer Complex Synthesis}},
  year         = {{2025}},
}