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-10150738-B2
Publication Date
2018-12-11
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 these salts and NHC carbene-metal complexes derived from them. The invention includes backfunctionalized imidazolinium salts of a specific formula wherein R1, R2, R3, R4, and anion X groups are defined with selections from ester, amide, aromatic, aliphatic, and fluorinated groups. The synthesis method comprises cyclization of a halogenated acrylate with Hünig's base in a solvent, including polar aprotic solvents like ethylene glycol dimethyl ethers and toluene.
The background describes challenges in chemical vapor deposition (CVD) and supercritical fluid deposition (SFD), particularly the inefficiencies in coating complex internal surfaces and the limitations of hot-wall and cold-wall processing systems. While backfluorinated NHC carbene complexes have been useful to overcome some deposition issues, there remains a need for more efficient methods to synthesize bulk quantities and methods allowing additional functionalization of the complexes.
The invention addresses these needs by providing alternative synthesis methods operating at lower temperatures using less nucleophilic bases like Hünig's base, enabling the preparation of backfunctionalized imidazolinium salts with aromatic and aliphatic side chains. These methods allow the formation of new classes of imidazolinium salts that behave as ionic liquids and facilitate easier coordination with metal centers to form stable backfluorinated NHC carbene-metal complexes suitable for various applications including supercritical chemical fluid deposition and catalysis.
Claims Coverage
The patent includes two independent claims focused on methods of synthesizing backfunctionalized imidazolinium salts with specified substituent groups and cyclization conditions.
Method of synthesizing backfunctionalized imidazolinium salt by cyclization with Hünig's base
The method comprises cyclization of a halogenated acrylate with Hünig's base in a solvent selected from acetone or toluene, optionally introducing a secondary base such as triethylamine during cyclization, with R3 and R4 groups selected from a group consisting of C1-C20 alkyl, partially fluorinated alkyl, aryl groups with para CF3 functionality, and partially fluorinated aliphatic groups. The solvent can be a polar aprotic solvent including ethylene glycol dimethyl ethers, and X is a halogen anion in the formula.
Method of synthesizing backfunctionalized imidazolinium salt with defined configurations and base usage
This method involves cyclization under similar substituent definitions as the first, with R1 group in trans-configuration relative to R2, using polar aprotic solvents like ethylene glycol dimethyl ethers, and optionally introducing triethylamine as a secondary base to effect cyclization.
The independent claims principally claim methods of synthesizing backfunctionalized imidazolinium salts via cyclization of halogenated precursors with Hünig's base or secondary bases in specified solvents, defining substituents that allow for functionalization and improved synthesis conditions for subsequent complex formation.
Stated Advantages
Synthesis at lower temperatures reduces the risk of nucleophilic side reactions and allows use of less nucleophilic and more economical bases like Hünig's base and triethylamine.
The methods allow preparation of backfunctionalized imidazolinium salts with both aromatic and aliphatic side chains, overcoming limitations of conventional methods.
Backfunctionalized imidazolinium salts synthesized may behave as ionic liquids, which have potential use as plasticizers in propellant formulations.
The invention enables more efficient bulk synthesis of backfluorinated NHC carbene complexes suitable for industrial use and additional functionalization, facilitating easier coordination to metal centers.
Improved solubility of the NHC carbene-metal complexes in supercritical fluids at lower pressures, enhancing their utility in supercritical chemical fluid deposition processes.
Documented Applications
Use of backfunctionalized imidazolinium salts and their derived backfluorinated NHC carbene-metal complexes as organometallic precursors in supercritical chemical fluid deposition (SCFD) for metal coating on substrates, particularly in cold-wall processing systems.
Application of backfluorinated NHC carbene-metal complexes as catalysts in olefin metathesis and ring-opening metathesis polymerization, including preparation of second-generation Grubbs and Grubbs-Hoveyda catalysts.
Use as ionic liquids serving as plasticizers for advanced propellant formulations including ammonium perchlorate-based, ammonium dinitramide-based, and furazan-based propellants.
Applications in supported catalyst systems via transesterification to anchor the salts to surfaces for heterogeneous catalysis.
Use in biphase fluorous catalysis where backfluorinated NHC carbene-metal complexes facilitate efficient chemical reaction separation in fluorinated solvents.
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