Macrocyclic Ligands for Bifunctional Catalysis
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Solution Overview
Problem
There is a continued need for the development of novel ligands and catalysts in homogeneous catalysis, particularly for applications such as hydrogenation and transfer hydrogenation of unsaturated organic compounds, where existing ligands may not offer sufficient efficiency or selectivity.
Innovation Solution
The development of polydentate macrocyclic ligands and their transition metal complexes, specifically designed for catalytic reactions, where the ligands are synthesized through cyclization reactions and coordinated with transition metals to enhance catalytic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional polydentate chelating ligands are used in homogeneous catalysis, then catalytic reactions can proceed with reasonable activity, but the catalytic activity and selectivity are insufficient for many applications
Solution Approach 1:
The patent introduces N-H functional groups at specific positions within the polydentate ligand structure. These local N-H sites provide hydrogen bonding capability and participate in bifunctional catalysis, enhancing both activity and selectivity. The N-H groups create localized active sites that can simultaneously activate substrates and stabilize transition states, resolving the contradiction between overall catalytic activity and specific reaction selectivity.
Solution Approach 2:
The patent combines multiple donor atom types (N, P, O, S) and functional groups (N-H, chelating sites) within a single polydentate ligand framework. This composite ligand structure integrates various catalytic functions - the polydentate chelating provides stable metal coordination while N-H groups provide hydrogen bonding and bifunctional catalysis. This composite approach enables the catalyst to achieve both high activity through stable coordination and high selectivity through directional hydrogen bonding interactions.
2Ease of manufacture
If existing ligand structures are used, then synthesis is relatively straightforward, but the ligands do not provide sufficient catalytic efficiency or selectivity
Solution Approach 1:
The patent designs polydentate ligands as assembled structures composed of multiple donor atom sites (N, P, O, S) and N-H functional groups that can be constructed through stepwise synthesis. The ligand framework is segmented into chelating portions that bind metal and N-H portions that provide catalytic functionality. This segmentation allows modular synthesis where different donor atom combinations can be systematically constructed to optimize catalytic efficiency while maintaining reasonable synthetic accessibility.
3Reliability
If traditional ligands are used in bifunctional molecular catalysis, then the ligand can stabilize transition states through hydrogen bonding, but the catalytic performance is limited
Solution Approach 1:
The patent creates polydentate ligands that perform multiple catalytic functions simultaneously. The ligand provides: (1) polydentate chelating to stabilize metal coordination, (2) N-H groups for hydrogen bonding to stabilize transition states, and (3) participation in bifunctional catalysis cycles. This multi-functionality allows a single ligand structure to address multiple catalytic requirements, enhancing overall catalytic performance beyond what traditional single-function ligands can achieve while maintaining transition state stabilization capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These macrocyclic ligands and metal complexes demonstrate improved catalytic activity in hydrogenation, transfer hydrogenation, and other reactions, such as dehydrogenation and asymmetric Michael-type additions, offering enhanced selectivity and efficiency compared to traditional ligands.
Implementation Method 1
polydentate macrocyclic ligands and their transition metal complexes, specifically designed for catalytic reactions, where the ligands are synthesized through cyclization reactions and coordinated with transition metals
Implementation Method 2
the ligand facilitates the catalytic reaction via stabilization of rate-determining transition states, for example, through N—H . . . O hydrogen bonding interactions
Data Source
AI summary
Disclosed herein are embodiments of chiral and achiral macrocyclic polydentate ligands and methods of preparing the same. Disclosed herein are also embodiments of metal coordination complexes derived from these macrocyclic polydentate ligands and methods of preparing the same. The metal coordination complexes described herein, can be used for a variety of catalytic reactions, including hydrogenation and transfer hydrogenation of unsaturated organic compounds, dehydrogenation of alcohols and boranes, an asymmetric Michael-type addition reaction, or an aerobic oxidative kinetic resolution of an organic compound, dehydrogenative couplings and other catalytic transformations.