Backfunctionalized imidazolinium salts and NHC carbene-metal complexes
Inventors
Blanski, Rusty L. • Grubbs, Robert H.
Assignees
United States Department of the Air Force
Publication Number
US-10919860-B2
Publication Date
2021-02-16
Expiration Date
2035-10-09
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Abstract
Backfunctionalized imidazolinium salts and methods of synthesizing the same and NHC carbene-metal complexes therefrom. For backfunctionalized imidazolinium salts of the formula: Wherein R1 is selected from the group consisting of an ester group, an amide group, and an aromatic group; R2 is selected from the group consisting of hydrogen, an ester group, an amide group, and an aromatic group; R3 and R4 are each an aliphatic group; and X is an anion; the method comprises cyclization of a halogenated acrylate with Hünig's base in a solvent.
Core Innovation
The invention relates to backfunctionalized imidazolinium salts and methods for synthesizing them, as well as N-heterocyclic carbene (NHC) carbene-metal complexes derived from such salts. The invention includes methods of cyclizing halogenated acrylates with Hünig's base in solvents to form backfunctionalized imidazolinium salts characterized by specific substituents on the imidazolinium ring. These salts serve as precursors to backfluorinated NHC carbene-metal complexes with applications in metal deposition and catalysis.
The problem addressed involves limitations in conventional chemical vapor deposition (CVD) and supercritical fluid deposition (SFD) methods for metal deposition, particularly challenges in coating substrates with tortuous internal surfaces effectively and economically. Existing backfluorinated NHC carbenes provide improvements but suffer from inefficient synthesis methods that restrict bulk preparation and functionalization potential. There is a specific need for more efficient and versatile synthesis routes to produce backfunctionalized NHC carbene complexes suitable for industrial applications.
This invention provides new synthesis methods for producing backfunctionalized imidazolinium salts using cyclization reactions at moderate temperatures involving halogenated acrylates or maleates with Hünig's base or alternative bases, expanding the scope to aliphatic and aromatic substituents. These salts can be converted into backfluorinated NHC carbene-metal complexes coordinated with various metals and ligands. Furthermore, the invention encompasses ionic liquids derived from such salts and modifications via transesterification, enabling tailored functionalities and supported catalyst systems, thereby advancing the utility of NHC complexes in supercritical fluid deposition and catalysis.
Claims Coverage
The claims include two independent claims focused respectively on an ionic liquid compound and its use as a plasticizer for propellant formulations. The inventive features involve the chemical structure of the ionic liquid and its functionality in propellant systems.
Ionic liquid having a specific imidazolinium salt formula
An ionic liquid characterized by a chemical structure consisting of an imidazolinium ring with substituents including hydrogen or methyl groups, ester, amide, or aromatic groups, with anions or halides balancing charge. This ionic liquid exemplified includes 2-ethylhexyl imidazolinium salt.
Plasticizer for propellant formulations comprising the ionic liquid
Utilization of the described ionic liquid as a plasticizer additive in propellant formulations. The propellant formulations explicitly include ammonium perchlorate-based, ammonium dinitramide-based, and furazan-based propellants, where the ionic liquid enhances properties of these energetic materials.
The claims principally cover the synthesized ionic liquid of defined imidazolinium composition and its application as a plasticizer in various propellant formulations, emphasizing both the chemical composition and its functional use in energetic material formulations.
Stated Advantages
The synthesis method produces backfunctionalized imidazolinium salts rapidly at lower temperatures than conventional methods, enabling the use of less nucleophilic and more economical bases such as Hünig's base and triethylamine.
The invention allows functionalization on the back of the imidazolinium ring, facilitating increased solubility and the possibility of additional ester or amide substituents, expanding utility.
The ability to produce ionic liquids that are soluble in non-polar solvents and behave as plasticizers for advanced propellant formulations.
The backfunctionalized NHC carbene-metal complexes synthesized via this method improve solubility in supercritical fluids and demonstrate stability to hydrogen reduction at lower temperatures, enhancing efficiency in supercritical fluid deposition processes.
Documented Applications
The backfunctionalized imidazolinium salts and corresponding NHC carbene-metal complexes are explicitly described for use as precursors in supercritical chemical fluid deposition (SCFD) to deposit metals such as noble metals onto substrates with complex geometries efficiently.
The ionic liquids produced are described as plasticizers in propellant formulations including ammonium perchlorate-based, ammonium dinitramide-based, and furazan-based propellants.
The NHC carbene-metal complexes are applicable in catalysis, including olefin metathesis and ring-opening metathesis polymerization, and serve as supported catalysts via transesterification and anchoring techniques.
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