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-10975038-B2
Publication Date
2021-04-13
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; andX 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 the same, as well as NHC carbene-metal complexes derived from these salts. Specifically, it describes backfunctionalized imidazolinium salts with functional groups such as ester, amide, or aromatic groups attached at the 4 or 5 positions of the imidazolinium ring. The synthesis involves cyclization of a halogenated acrylate with Hünig's base (N,N-diisopropylethylamine) in solvents like toluene or acetone, enabling mild reaction conditions compared to conventional methods.
The problem addressed is the limitation of conventional chemical vapor deposition methods, particularly in depositing metal coatings on internal or tortuous surfaces efficiently. While supercritical chemical fluid deposition (SFD) offers advantages in coating complex surfaces, existing backfluorinated NHC carbene complexes suffer from inefficient synthesis methods limiting bulk production and functionality. This invention aims to provide more efficient synthesis methods for backfunctionalized NHC carbene complexes suitable for industrial-scale applications.
Claims Coverage
The patent includes independent claims directed to backfunctionalized imidazolinium salts, their metal complexes, and methods for their synthesis. The claims focus on chemical structures, coordination to metals, and specific synthesis steps.
Backfunctionalized imidazolinium salts chemical structure
Backfunctionalized imidazolinium salts having ester, amide, or aromatic groups at defined positions and various R groups with X as an anion, selectable in cis or trans configurations.
N-heterocyclic carbene-metal complexes composition
Complexes comprising a metal from a defined group coordinated with one or two backfunctionalized NHC carbenes and additional ligands such as acetylacetonate, alkoxy, alkyl, aryl, aryloxy, carbonyl, halide, imido, oxo, pyridine, trialkylphosphine, or triarylphosphine.
Method of synthesizing backfunctionalized imidazolinium salts
Cyclization of a halogenated acrylate ester with Hünig's base in a solvent (toluene or acetone), optionally introducing bases selected from triethylamine, formamidine, and Hünig's base during cyclization, including preparing halogenated acrylate ester from acrylate ester.
The independent claims cover the chemical structures of novel backfunctionalized imidazolinium salts and their metal complexes, as well as efficient synthesis methods involving cyclization with Hünig's base and alternative bases under mild conditions, enabling broad applicability and improved industrial production.
Stated Advantages
The synthesis method allows for milder reaction conditions than conventional methods, requiring lower temperatures and shorter reaction times.
Use of less nucleophilic bases like Hünig's base or aromatic formamidines facilitates successful cyclization where conventional bases fail at elevated temperatures.
The methods enable preparation of bulk quantities of backfunctionalized NHC carbene complexes, supporting scalability for industrial applications.
The backfunctionalized salts exhibit versatility with various functional groups and can lead to ionic liquids useful as plasticizers for advanced propellant formulations.
Backfunctionalized NHC carbene-metal complexes are soluble in supercritical solvents like CO2, stable to hydrogen at lower temperatures, and effective for selective metal deposition in supercritical fluid deposition methods.
Documented Applications
Use as precursors in supercritical chemical fluid deposition (SCFD) for coating metals onto substrates with complex internal features.
Synthesis of backfluorinated second generation Grubbs' and Grubbs-Hoveyda catalysts for olefin metathesis and ring-opening metathesis polymerization.
Supported catalysis with backfunctionalized NHC carbene-metal complexes anchored on surfaces via transesterification.
Use of obtained ionic liquids as plasticizers in advanced propellant formulations including ammonium perchlorate-based, ammonium dinitramide-based, and furazan-based propellants.
Biphase fluorous catalysis where the backfluorinated NHC carbene-metal complexes enable reaction efficiency and catalyst-product separation in fluorinated solvents.
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