Lithium extractant compounds and their use in selective lithium extraction from aqueous solutions

An aqueous-insoluble hydrophobic solution useful for extracting lithium from an aqueous solution, comprising a chelating lithium extractant compound dissolved in an aqueous-insoluble hydrophobic solvent, wherein the lithium extractant compound has the following structure:

• wherein:
• Ra and Rb are independently selected from the group consisting of hydrocarbon groups (R), —OR, —NRR′, —SR, —SO2R, —SO2NR2, —C(O)R, —C(O)OR, —C(O)NRR′, —C(S)OR, —C(O)SR, and —C(S)NRR′;
• Rc is selected from R′ groups;
• wherein the hydrocarbon groups (R) independently contain 1-30 carbon atoms and are selected from alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, cycloalkenyl groups, aromatic groups, and heteroaromatic groups, any of which are optionally substituted with fluorine, and wherein said cycloalkyl groups, cycloalkenyl groups, aromatic groups, and heteroaromatic groups are further optionally substituted with one or more groups selected from the group consisting of alkyl (R″) groups containing 1-20 carbon atoms, —OH, —OR″, —NH2, —NHR″, —NR″2, —NO2, —SR″, —SO2R″, —SO2NR″2, —C(O)R″, —C(O)OR″, —C(O)NH2, —C(O)NHR″, —C(O)NR″2, —C(S)OR″, —C(O)SR″, —C(S)NH2, —C(S)NHR″, and —C(S)NR″2;
• R′ is selected from H and R groups;
• X is O or OH;
• Y is C or N, wherein, when Y is N, then Ra is R;
• the dotted lines indicate optional presence of carbon-carbon double bonds;
• Ra and Rc optionally interconnect via their R groups to form ring A, wherein ring A is optionally substituted with one or more groups selected from the group consisting of alkyl (R″) groups containing 1-20 carbon atoms, —OH, —OR″, —NH2, —NHR″, —NR″2, —NO2, —SR″, —SO2R″, —SO2NR″2, —C(O)R″, —C(O)OR″, —C(O)NH2, —C(O)NHR″, —C(O)NR″2, —C(S)OR″, —C(O)SR″, —C(S)NH2, —C(S)NHR″, and —C(S)NR″2;
• Rb and Rc optionally interconnect via their R groups to form ring B, wherein ring B is optionally substituted with one or more groups selected from the group consisting of alkyl (R″) groups containing 1-20 carbon atoms, —OH, —OR″, —NH2, —NHR″, —NR″2, —NO2, —SR″, —SO2R″, —SO2NR″2, —C(O)R″, —C(O)OR″, —C(O)NH2, —C(O)NHR″, —C(O)NR″2, —C(S)OR″, —C(O)SR″, —C(S)NH2, —C(S)NHR″, and —C(S)NR″2;
• and
• Ra, Rb, and Rc optionally interconnect via their R groups to form a fused bicyclic ring system, wherein the fused bicyclic ring system is optionally substituted with one or more groups selected from the group consisting of alkyl (R″) groups containing 1-20 carbon atoms, —OH, —OR″, —NH2, —NHR″, —NR″2, —NO2, —SR″, —SO2R″, —SO2NR″2, —C(O)R″, —C(O)OR″, —C(O)NH2, —C(O)NHR″, —C(O)NR″2, —C(S)OR″, —C(O)SR″, —C(S)NH2, —C(S)NHR″, and —C(S)NR″2;
• provided that Ra and Rb are not both alkyl groups, and if Ra is an alkyl group and Rb is an aromatic group, or if Ra and Rb are the same aromatic groups, then at least one of the aromatic groups is substituted with a group selected from the group consisting of alkyl (R″) groups containing 1-20 carbon atoms, —OH, —OR″, —NH2, —NHR″, —NR″2, —NO2, —SR″, —SO2R″, —SO2NR″2, —C(O)R″, —C(O)OR″, —C(O)NH2, —C(O)NHR″, —C(O)NR″2, —C(S)OR″, —C(O)SR″, —C(S)NH2, —C(S)NHR″, and —C(S)NR″2.

A method for extracting lithium from aqueous solution, the method comprising:

• (i) providing an aqueous solution containing lithium and having a pH sufficient to deprotonate a chelating lithium extractant compound according to Formula (1);
• (ii) contacting the aqueous solution with an aqueous-insoluble hydrophobic solution comprising the chelating lithium extractant compound dissolved in an aqueous-insoluble hydrophobic solvent to result in deprotonation of the chelating lithium extractant compound, chelation of lithium in the aqueous solution by the deprotonated form of the chelating lithium extractant compound, and resultant extraction of the lithium from the aqueous solution into the aqueous-insoluble hydrophobic solution, wherein the chelating lithium extractant compound has the following structure:
• wherein:
• Ra and Rb are independently selected from the group consisting of hydrocarbon groups (R), —OR, —NRR′, —SR, —SO2R, —SO2NR2, —C(O)R, —C(O)OR, —C(O)NRR′, —C(S)OR, —C(O)SR, and —C(S)NRR′;
• Rc is selected from R′ groups;
• wherein the hydrocarbon groups (R) independently contain 1-30 carbon atoms and are selected from alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, cycloalkenyl groups, aromatic groups, and heteroaromatic groups, any of which are optionally substituted with fluorine, and wherein said cycloalkyl groups, cycloalkenyl groups, aromatic groups, and heteroaromatic groups are further optionally substituted with one or more groups selected from the group consisting of alkyl (R″) groups containing 1-20 carbon atoms, —OH, —OR″, —NH2, —NHR″, —NR″2, —NO2, —SR″, —SO2R″, —SO2NR″2, —C(O)R″, —C(O)OR″, —C(O)NH2, —C(O)NHR″, —C(O)NR″2, —C(S)OR″, —C(O)SR″, —C(S)NH2, —C(S)NHR″, and —C(S)NR″2;
• R′ is selected from H and R groups;
• X is O or OH;
• Y is C or N, wherein, when Y is N, then Ra is R;
• the dotted lines indicate optional presence of carbon-carbon double bonds;
• Ra and Rc optionally interconnect via their R groups to form ring A, wherein ring A is optionally substituted with one or more groups selected from the group consisting of alkyl (R″) groups containing 1-20 carbon atoms, —OH, —OR″, —NH2, —NHR″, —NR″2, —NO2, —SR″, —SO2R″, —SO2NR″2, —C(O)R″, —C(O)OR″, —C(O)NH2, —C(O)NHR″, —C(O)NR″2, —C(S)OR″, —C(O)SR″, —C(S)NH2, —C(S)NHR″, and —C(S)NR″2;
• Rb and Rc optionally interconnect via their R groups to form ring B, wherein ring B is optionally substituted with one or more groups selected from the group consisting of alkyl (R″) groups containing 1-20 carbon atoms, —OH, —OR″, —NH2, —NHR″, —NR″2, —NO2, —SR″, —SO2R″, —SO2NR″2, —C(O)R″, —C(O)OR″, —C(O)NH2, —C(O)NHR″, —C(O)NR″2, —C(S)OR″, —C(O)SR″, —C(S)NH2, —C(S)NHR″, and —C(S)NR″2;
• and
• Ra, Rb, and Rc optionally interconnect via their R groups to form a fused bicyclic ring system, wherein the fused bicyclic ring system is optionally substituted with one or more groups selected from the group consisting of alkyl (R″) groups containing 1-20 carbon atoms, —OH, —OR″, —NH2, —NHR″, —NR″2, —NO2, —SR″, —SO2R″, —SO2NR″2, —C(O)R″, —C(O)OR″, —C(O)NH2, —C(O)NHR″, —C(O)NR″2, —C(S)OR″, —C(O)SR″, —C(S)NH2, —C(S)NHR″, and —C(S)NR″2;
• provided that Ra and Rb are not both alkyl groups, and if Ra is an alkyl group and Rb is an aromatic group, or if Ra and Rb are the same aromatic groups, then at least one of the aromatic groups is substituted with a group selected from the group consisting of alkyl (R″) groups containing 1-20 carbon atoms, —OH, —OR″, —NH2, —NHR″, —NR″2, —NO2, —SR″, —SO2R″, —SO2NR″2, —C(O)R″, —C(O)OR″, —C(O)NH2, —C(O)NHR″, —C(O)NR″2, —C(S)OR″, —C(O)SR″, —C(S)NH2, —C(S)NHR″, and —C(S)NR″2.