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-9828347-B2
Publication Date
2017-11-28
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 of synthesizing the same, as well as NHC carbene-metal complexes derived therefrom. The backfunctionalized imidazolinium salts have a specific formula where R1 is selected from ester, amide, or aromatic groups; R2 is hydrogen, ester, amide, or aromatic; R3 and R4 are aliphatic groups; and X is an anion. The synthesis method involves cyclization of a halogenated acrylate with Hünig's base in a solvent, including polar aprotic solvents such as toluene or diglyme.
The problem addressed by the invention arises in chemical vapor deposition (CVD) processes and supercritical fluid deposition (SFD) processes for metal coatings. Conventional CVD processes have limitations in coating internal or tortuous features of substrates. Existing SFD processes using hot-wall systems are wasteful because metal deposits on all interior surfaces of the processing chamber, not just on the substrate. Cold-wall processing systems improve efficiency but require organometallic precursors that are thermally stable and reducible at appropriate temperatures. Prior backfluorinated NHC carbene complexes, although useful, have synthesis limitations, particularly in achieving bulk quantities suitable for industrial use and enabling additional functionalization.
This invention provides improved methods for synthesizing backfunctionalized imidazolinium salts leading to NHC carbene-metal complexes that overcome prior synthesis challenges. The synthesis occurs at lower temperatures using less nucleophilic bases like Hünig's base, allowing the use of alternative bases such as triethylamine and facilitating a wider variety of functional groups, including aliphatic groups. The invention also allows preparation of ionic liquids and supports further functionalization and preparation of various metal complexes suitable for applications including supercritical fluid deposition and catalysis. The method affords versatility in ligand groups and metal coordination, improving solubility, stability, and applicability of the metal complexes.
Claims Coverage
The patent includes three independent claims focusing on the novel backfunctionalized imidazolinium salts and their specific chemical structures and configurations.
Backfunctionalized imidazolinium salt composition
A backfunctionalized imidazolinium salt comprising a defined chemical formula in which R1 is selected from ester, amide, and aromatic groups; R2 from hydrogen, ester, amide, and aromatic; R3 and R4 from aliphatic groups; and X is an anion, including halogen anions.
Anion specification
The backfunctionalized imidazolinium salt where the anion X is specifically a halogen anion.
Stereochemical configuration of substituents
The backfunctionalized imidazolinium salt with R1 and R2 substituents in a trans-configuration relative to each other on the imidazolinium ring.
The inventive features cover the chemical structure of backfunctionalized imidazolinium salts with specified substituents and anion identity, including stereochemical configuration, establishing novel compositions with defined functional groups and configurations.
Stated Advantages
The synthesis method occurs at lower temperatures and uses less nucleophilic bases such as Hünig's base, enabling use of alternative and potentially less costly bases like triethylamine, thus improving economic viability for bulk production.
The invention enables functionalization with both aromatic and aliphatic groups, which was not feasible with conventional methods limited to aromatic side chains.
The backfunctionalized NHC carbene-metal complexes produced are soluble in supercritical solvents, stable to hydrogen reduction at lower temperatures, and can effectively deposit metals on substrates while minimizing wasteful deposition on chamber walls.
The synthesis approach yields novel ionic liquids with desired solubility properties, which may serve as plasticizers in advanced propellant formulations.
The invention provides versatility for catalyst synthesis, including supported catalyst systems and improved catalyst stability and solubility in fluorinated solvents.
Documented Applications
Use of backfunctionalized imidazolinium salts and derived NHC carbene-metal complexes as precursors in supercritical fluid deposition (SCFD) processes to efficiently deposit noble metals onto substrates by cold-wall processing systems.
Use as ionic liquids that function as plasticizers for advanced propellant formulations such as ammonium perchlorate-based, ammonium dinitramide-based, and furazan-based propellants.
Application in catalysis, including the preparation of backfluorinated second generation Grubbs' and Grubbs-Hoveyda catalysts active in olefin metathesis and ring opening metathesis polymerization.
Supported catalyst systems synthesized by transesterification, including silica-supported backfunctionalized NHC carbene-metal complexes for heterogeneous catalysis.
Biphasic fluorous catalysis where the backfluorinated NHC carbene-metal complexes improve reaction efficiency and separation in fluorinated and non-fluorinated media.
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