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Matthew
Kita
Author
Department of Chemistry
College of Arts and Sciences
CATION TUNABLE REACTIVITY AND CATALYSIS WITH IRIDIUM PINCER-CROWN ETHER COMPLEXES
Iridium complexes of a new multidentate ligand combining a rigid, strongly donating pincer scaffold with a flexible, weakly donating aza-crown ether moiety are reported. The “pincer-crown ether ligand” exhibits tridentate, tetradentate, and pentadentate coordination modes. The coordination mode can be changed by Lewis base displacement of the chelating ethers, with binding equilibria dramatically altered through cation–macrocycle interactions. Cation-promoted hydrogen activation was accomplished by an iridium monohydride cation ligated in a pentadentate fashion by the pincer-crown ether ligand. The rate can be controlled on the basis of the choice of cation, and the concentration of cation.
Using the same complex, rapid, selective, and highly controllable iridium-catalyzed allylbenzene isomerization is described, enabled by tunable hemilability based on alkali metal cation binding with the macrocyclic pincer-crown ether ligand. An inactive chloride-ligated complex can be activated by halide abstraction with sodium salts, with the resulting catalyst [κ5-(15c5NCOPiPr)Ir(H)]+ exhibiting modest activity. Addition of Li+ provides a further boost in activity, with up to 1000-fold rate enhancement. Ethers and chloride salts dampen or turn off reactivity, leading to three distinct catalyst states with activity spanning several orders of magnitude. Mechanistic studies suggest that the large rate enhancement and high degree of tunability stem from control over substrate binding.
Methods to convert CO2 to formate using iridium pincer-crown ether complexes are discussed. The synthesis of iridium dihydride pincer-crown ether complexes is attempted. Electrochemistry of pincer-crown ether complexes reveal very negative iridium reduction potentials. Lastly, CO2 hydrogenation to formate is accomplished in bicarbonate solutions with turn over numbers up to 1000.
Summer 2017
2017
Inorganic chemistry
Chemistry
hemilability, homogeneous catalysis, hydrogen activation, olefin isomerization, switchable catalysis
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Chemistry
Alexander
Miller
Thesis advisor
Cynthia
Schauer
Thesis advisor
Maurice
Brookhart
Thesis advisor
Frank
Leibfarth
Thesis advisor
Simon
Meek
Thesis advisor
text
Matthew
Kita
Author
Department of Chemistry
College of Arts and Sciences
Cation Tunable Reactivity and Catalysis with Iridium Pincer-Crown Ether Complexes
Iridium complexes of a new multidentate ligand combining a rigid, strongly donating pincer scaffold with a flexible, weakly donating aza-crown ether moiety are reported. The “pincer-crown ether ligand” exhibits tridentate, tetradentate, and pentadentate coordination modes. The coordination mode can be changed by Lewis base displacement of the chelating ethers, with binding equilibria dramatically altered through cation–macrocycle interactions. Cation-promoted hydrogen activation was accomplished by an iridium monohydride cation ligated in a pentadentate fashion by the pincer-crown ether ligand. The rate can be controlled on the basis of the choice of cation, and the concentration of cation.
Using the same complex, rapid, selective, and highly controllable iridium-catalyzed allylbenzene isomerization is described, enabled by tunable hemilability based on alkali metal cation binding with the macrocyclic pincer-crown ether ligand. An inactive chloride-ligated complex can be activated by halide abstraction with sodium salts, with the resulting catalyst [κ5-(15c5NCOPiPr)Ir(H)]+ exhibiting modest activity. Addition of Li+ provides a further boost in activity, with up to 1000-fold rate enhancement. Ethers and chloride salts dampen or turn off reactivity, leading to three distinct catalyst states with activity spanning several orders of magnitude. Mechanistic studies suggest that the large rate enhancement and high degree of tunability stem from control over substrate binding.
Methods to convert CO2 to formate using iridium pincer-crown ether complexes are discussed. The synthesis of iridium dihydride pincer-crown ether complexes is attempted. Electrochemistry of pincer-crown ether complexes reveal very negative iridium reduction potentials. Lastly, CO2 hydrogenation to formate is accomplished in bicarbonate solutions with turn over numbers up to 1000.
Summer 2017
2017
Inorganic chemistry
Chemistry
hemilability, homogeneous catalysis, hydrogen activation, olefin isomerization, switchable catalysis
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Chemistry
Alexander
Miller
Thesis advisor
Cynthia
Schauer
Thesis advisor
Maurice
Brookhart
Thesis advisor
Frank
Leibfarth
Thesis advisor
Simon
Meek
Thesis advisor
text
Matthew
Kita
Creator
Department of Chemistry
College of Arts and Sciences
Cation Tunable Reactivity and Catalysis with Iridium Pincer-Crown Ether
Complexes
Iridium complexes of a new multidentate ligand combining a rigid, strongly
donating pincer scaffold with a flexible, weakly donating aza-crown ether moiety are
reported. The “pincer-crown ether ligand” exhibits tridentate, tetradentate, and
pentadentate coordination modes. The coordination mode can be changed by Lewis base
displacement of the chelating ethers, with binding equilibria dramatically altered through
cation–macrocycle interactions. Cation-promoted hydrogen activation was accomplished by an
iridium monohydride cation ligated in a pentadentate fashion by the pincer-crown ether
ligand. The rate can be controlled on the basis of the choice of cation, and the
concentration of cation. Using the same complex, rapid, selective, and highly controllable
iridium-catalyzed allylbenzene isomerization is described, enabled by tunable hemilability
based on alkali metal cation binding with the macrocyclic pincer-crown ether ligand. An
inactive chloride-ligated complex can be activated by halide abstraction with sodium
salts, with the resulting catalyst [κ5-(15c5NCOPiPr)Ir(H)]+ exhibiting modest activity.
Addition of Li+ provides a further boost in activity, with up to 1000-fold rate
enhancement. Ethers and chloride salts dampen or turn off reactivity, leading to three
distinct catalyst states with activity spanning several orders of magnitude. Mechanistic
studies suggest that the large rate enhancement and high degree of tunability stem from
control over substrate binding. Methods to convert CO2 to formate using iridium
pincer-crown ether complexes are discussed. The synthesis of iridium dihydride
pincer-crown ether complexes is attempted. Electrochemistry of pincer-crown ether
complexes reveal very negative iridium reduction potentials. Lastly, CO2 hydrogenation to
formate is accomplished in bicarbonate solutions with turn over numbers up to
1000.
Summer 2017
2017
Inorganic chemistry
Chemistry
hemilability, homogeneous catalysis, hydrogen activation,
olefin isomerization, switchable catalysis
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting
institution
Chemistry
Alexander
Miller
Thesis advisor
Cynthia
Schauer
Thesis advisor
Maurice
Brookhart
Thesis advisor
Frank
Leibfarth
Thesis advisor
Simon
Meek
Thesis advisor
text
Matthew
Kita
Creator
Department of Chemistry
College of Arts and Sciences
Cation Tunable Reactivity and Catalysis with Iridium Pincer-Crown Ether Complexes
Iridium complexes of a new multidentate ligand combining a rigid, strongly donating pincer scaffold with a flexible, weakly donating aza-crown ether moiety are reported. The “pincer-crown ether ligand” exhibits tridentate, tetradentate, and pentadentate coordination modes. The coordination mode can be changed by Lewis base displacement of the chelating ethers, with binding equilibria dramatically altered through cation–macrocycle interactions. Cation-promoted hydrogen activation was accomplished by an iridium monohydride cation ligated in a pentadentate fashion by the pincer-crown ether ligand. The rate can be controlled on the basis of the choice of cation, and the concentration of cation. Using the same complex, rapid, selective, and highly controllable iridium-catalyzed allylbenzene isomerization is described, enabled by tunable hemilability based on alkali metal cation binding with the macrocyclic pincer-crown ether ligand. An inactive chloride-ligated complex can be activated by halide abstraction with sodium salts, with the resulting catalyst [κ5-(15c5NCOPiPr)Ir(H)]+ exhibiting modest activity. Addition of Li+ provides a further boost in activity, with up to 1000-fold rate enhancement. Ethers and chloride salts dampen or turn off reactivity, leading to three distinct catalyst states with activity spanning several orders of magnitude. Mechanistic studies suggest that the large rate enhancement and high degree of tunability stem from control over substrate binding. Methods to convert CO2 to formate using iridium pincer-crown ether complexes are discussed. The synthesis of iridium dihydride pincer-crown ether complexes is attempted. Electrochemistry of pincer-crown ether complexes reveal very negative iridium reduction potentials. Lastly, CO2 hydrogenation to formate is accomplished in bicarbonate solutions with turn over numbers up to 1000.
Summer 2017
2017
Inorganic chemistry
Chemistry
hemilability, homogeneous catalysis, hydrogen activation, olefin isomerization, switchable catalysis
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Chemistry
Alexander
Miller
Thesis advisor
Cynthia
Schauer
Thesis advisor
Maurice
Brookhart
Thesis advisor
Frank
Leibfarth
Thesis advisor
Simon
Meek
Thesis advisor
text
Matthew
Kita
Creator
Department of Chemistry
College of Arts and Sciences
Cation Tunable Reactivity and Catalysis with Iridium Pincer-Crown Ether Complexes
Iridium complexes of a new multidentate ligand combining a rigid, strongly donating pincer scaffold with a flexible, weakly donating aza-crown ether moiety are reported. The “pincer-crown ether ligand” exhibits tridentate, tetradentate, and pentadentate coordination modes. The coordination mode can be changed by Lewis base displacement of the chelating ethers, with binding equilibria dramatically altered through cation–macrocycle interactions. Cation-promoted hydrogen activation was accomplished by an iridium monohydride cation ligated in a pentadentate fashion by the pincer-crown ether ligand. The rate can be controlled on the basis of the choice of cation, and the concentration of cation. Using the same complex, rapid, selective, and highly controllable iridium-catalyzed allylbenzene isomerization is described, enabled by tunable hemilability based on alkali metal cation binding with the macrocyclic pincer-crown ether ligand. An inactive chloride-ligated complex can be activated by halide abstraction with sodium salts, with the resulting catalyst [κ5-(15c5NCOPiPr)Ir(H)]+ exhibiting modest activity. Addition of Li+ provides a further boost in activity, with up to 1000-fold rate enhancement. Ethers and chloride salts dampen or turn off reactivity, leading to three distinct catalyst states with activity spanning several orders of magnitude. Mechanistic studies suggest that the large rate enhancement and high degree of tunability stem from control over substrate binding. Methods to convert CO2 to formate using iridium pincer-crown ether complexes are discussed. The synthesis of iridium dihydride pincer-crown ether complexes is attempted. Electrochemistry of pincer-crown ether complexes reveal very negative iridium reduction potentials. Lastly, CO2 hydrogenation to formate is accomplished in bicarbonate solutions with turn over numbers up to 1000.
2017-08
2017
Inorganic chemistry
Chemistry
hemilability, homogeneous catalysis, hydrogen activation, olefin isomerization, switchable catalysis
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Chemistry
Alexander
Miller
Thesis advisor
Cynthia
Schauer
Thesis advisor
Maurice
Brookhart
Thesis advisor
Frank
Leibfarth
Thesis advisor
Simon
Meek
Thesis advisor
text
Matthew
Kita
Creator
Department of Chemistry
College of Arts and Sciences
Cation Tunable Reactivity and Catalysis with Iridium Pincer-Crown Ether Complexes
Iridium complexes of a new multidentate ligand combining a rigid, strongly donating pincer scaffold with a flexible, weakly donating aza-crown ether moiety are reported. The “pincer-crown ether ligand” exhibits tridentate, tetradentate, and pentadentate coordination modes. The coordination mode can be changed by Lewis base displacement of the chelating ethers, with binding equilibria dramatically altered through cation–macrocycle interactions. Cation-promoted hydrogen activation was accomplished by an iridium monohydride cation ligated in a pentadentate fashion by the pincer-crown ether ligand. The rate can be controlled on the basis of the choice of cation, and the concentration of cation. Using the same complex, rapid, selective, and highly controllable iridium-catalyzed allylbenzene isomerization is described, enabled by tunable hemilability based on alkali metal cation binding with the macrocyclic pincer-crown ether ligand. An inactive chloride-ligated complex can be activated by halide abstraction with sodium salts, with the resulting catalyst [κ5-(15c5NCOPiPr)Ir(H)]+ exhibiting modest activity. Addition of Li+ provides a further boost in activity, with up to 1000-fold rate enhancement. Ethers and chloride salts dampen or turn off reactivity, leading to three distinct catalyst states with activity spanning several orders of magnitude. Mechanistic studies suggest that the large rate enhancement and high degree of tunability stem from control over substrate binding. Methods to convert CO2 to formate using iridium pincer-crown ether complexes are discussed. The synthesis of iridium dihydride pincer-crown ether complexes is attempted. Electrochemistry of pincer-crown ether complexes reveal very negative iridium reduction potentials. Lastly, CO2 hydrogenation to formate is accomplished in bicarbonate solutions with turn over numbers up to 1000.
2017
Inorganic chemistry
Chemistry
hemilability, homogeneous catalysis, hydrogen activation, olefin isomerization, switchable catalysis
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Chemistry
Alexander
Miller
Thesis advisor
Cynthia
Schauer
Thesis advisor
Maurice
Brookhart
Thesis advisor
Frank
Leibfarth
Thesis advisor
Simon
Meek
Thesis advisor
text
2017-08
Matthew
Kita
Creator
Department of Chemistry
College of Arts and Sciences
Cation Tunable Reactivity and Catalysis with Iridium Pincer-Crown Ether Complexes
Iridium complexes of a new multidentate ligand combining a rigid, strongly donating pincer scaffold with a flexible, weakly donating aza-crown ether moiety are reported. The “pincer-crown ether ligand” exhibits tridentate, tetradentate, and pentadentate coordination modes. The coordination mode can be changed by Lewis base displacement of the chelating ethers, with binding equilibria dramatically altered through cation–macrocycle interactions. Cation-promoted hydrogen activation was accomplished by an iridium monohydride cation ligated in a pentadentate fashion by the pincer-crown ether ligand. The rate can be controlled on the basis of the choice of cation, and the concentration of cation. Using the same complex, rapid, selective, and highly controllable iridium-catalyzed allylbenzene isomerization is described, enabled by tunable hemilability based on alkali metal cation binding with the macrocyclic pincer-crown ether ligand. An inactive chloride-ligated complex can be activated by halide abstraction with sodium salts, with the resulting catalyst [κ5-(15c5NCOPiPr)Ir(H)]+ exhibiting modest activity. Addition of Li+ provides a further boost in activity, with up to 1000-fold rate enhancement. Ethers and chloride salts dampen or turn off reactivity, leading to three distinct catalyst states with activity spanning several orders of magnitude. Mechanistic studies suggest that the large rate enhancement and high degree of tunability stem from control over substrate binding. Methods to convert CO2 to formate using iridium pincer-crown ether complexes are discussed. The synthesis of iridium dihydride pincer-crown ether complexes is attempted. Electrochemistry of pincer-crown ether complexes reveal very negative iridium reduction potentials. Lastly, CO2 hydrogenation to formate is accomplished in bicarbonate solutions with turn over numbers up to 1000.
2017
Inorganic chemistry
Chemistry
hemilability, homogeneous catalysis, hydrogen activation, olefin isomerization, switchable catalysis
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Chemistry
Alexander
Miller
Thesis advisor
Cynthia
Schauer
Thesis advisor
Maurice
Brookhart
Thesis advisor
Frank
Leibfarth
Thesis advisor
Simon
Meek
Thesis advisor
text
2017-08
Matthew
Kita
Creator
Department of Chemistry
College of Arts and Sciences
Cation Tunable Reactivity and Catalysis with Iridium Pincer-Crown Ether Complexes
Iridium complexes of a new multidentate ligand combining a rigid, strongly donating pincer scaffold with a flexible, weakly donating aza-crown ether moiety are reported. The “pincer-crown ether ligand” exhibits tridentate, tetradentate, and pentadentate coordination modes. The coordination mode can be changed by Lewis base displacement of the chelating ethers, with binding equilibria dramatically altered through cation–macrocycle interactions. Cation-promoted hydrogen activation was accomplished by an iridium monohydride cation ligated in a pentadentate fashion by the pincer-crown ether ligand. The rate can be controlled on the basis of the choice of cation, and the concentration of cation. Using the same complex, rapid, selective, and highly controllable iridium-catalyzed allylbenzene isomerization is described, enabled by tunable hemilability based on alkali metal cation binding with the macrocyclic pincer-crown ether ligand. An inactive chloride-ligated complex can be activated by halide abstraction with sodium salts, with the resulting catalyst [κ5-(15c5NCOPiPr)Ir(H)]+ exhibiting modest activity. Addition of Li+ provides a further boost in activity, with up to 1000-fold rate enhancement. Ethers and chloride salts dampen or turn off reactivity, leading to three distinct catalyst states with activity spanning several orders of magnitude. Mechanistic studies suggest that the large rate enhancement and high degree of tunability stem from control over substrate binding. Methods to convert CO2 to formate using iridium pincer-crown ether complexes are discussed. The synthesis of iridium dihydride pincer-crown ether complexes is attempted. Electrochemistry of pincer-crown ether complexes reveal very negative iridium reduction potentials. Lastly, CO2 hydrogenation to formate is accomplished in bicarbonate solutions with turn over numbers up to 1000.
2017
Inorganic chemistry
Chemistry
hemilability, homogeneous catalysis, hydrogen activation, olefin isomerization, switchable catalysis
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Chemistry
Alexander
Miller
Thesis advisor
Cynthia
Schauer
Thesis advisor
Maurice
Brookhart
Thesis advisor
Frank
Leibfarth
Thesis advisor
Simon
Meek
Thesis advisor
text
2017-08
Matthew
Kita
Creator
Department of Chemistry
College of Arts and Sciences
Cation Tunable Reactivity and Catalysis with Iridium Pincer-Crown Ether Complexes
Iridium complexes of a new multidentate ligand combining a rigid, strongly donating pincer scaffold with a flexible, weakly donating aza-crown ether moiety are reported. The “pincer-crown ether ligand” exhibits tridentate, tetradentate, and pentadentate coordination modes. The coordination mode can be changed by Lewis base displacement of the chelating ethers, with binding equilibria dramatically altered through cation–macrocycle interactions. Cation-promoted hydrogen activation was accomplished by an iridium monohydride cation ligated in a pentadentate fashion by the pincer-crown ether ligand. The rate can be controlled on the basis of the choice of cation, and the concentration of cation. Using the same complex, rapid, selective, and highly controllable iridium-catalyzed allylbenzene isomerization is described, enabled by tunable hemilability based on alkali metal cation binding with the macrocyclic pincer-crown ether ligand. An inactive chloride-ligated complex can be activated by halide abstraction with sodium salts, with the resulting catalyst [κ5-(15c5NCOPiPr)Ir(H)]+ exhibiting modest activity. Addition of Li+ provides a further boost in activity, with up to 1000-fold rate enhancement. Ethers and chloride salts dampen or turn off reactivity, leading to three distinct catalyst states with activity spanning several orders of magnitude. Mechanistic studies suggest that the large rate enhancement and high degree of tunability stem from control over substrate binding. Methods to convert CO2 to formate using iridium pincer-crown ether complexes are discussed. The synthesis of iridium dihydride pincer-crown ether complexes is attempted. Electrochemistry of pincer-crown ether complexes reveal very negative iridium reduction potentials. Lastly, CO2 hydrogenation to formate is accomplished in bicarbonate solutions with turn over numbers up to 1000.
2017
Inorganic chemistry
Chemistry
hemilability, homogeneous catalysis, hydrogen activation, olefin isomerization, switchable catalysis
eng
Doctor of Philosophy
Dissertation
Chemistry
Alexander
Miller
Thesis advisor
Cynthia
Schauer
Thesis advisor
Maurice
Brookhart
Thesis advisor
Frank
Leibfarth
Thesis advisor
Simon
Meek
Thesis advisor
text
2017-08
University of North Carolina at Chapel Hill
Degree granting institution
Matthew
Kita
Creator
Department of Chemistry
College of Arts and Sciences
Cation Tunable Reactivity and Catalysis with Iridium Pincer-Crown Ether Complexes
Iridium complexes of a new multidentate ligand combining a rigid, strongly donating pincer scaffold with a flexible, weakly donating aza-crown ether moiety are reported. The “pincer-crown ether ligand” exhibits tridentate, tetradentate, and pentadentate coordination modes. The coordination mode can be changed by Lewis base displacement of the chelating ethers, with binding equilibria dramatically altered through cation–macrocycle interactions. Cation-promoted hydrogen activation was accomplished by an iridium monohydride cation ligated in a pentadentate fashion by the pincer-crown ether ligand. The rate can be controlled on the basis of the choice of cation, and the concentration of cation. Using the same complex, rapid, selective, and highly controllable iridium-catalyzed allylbenzene isomerization is described, enabled by tunable hemilability based on alkali metal cation binding with the macrocyclic pincer-crown ether ligand. An inactive chloride-ligated complex can be activated by halide abstraction with sodium salts, with the resulting catalyst [κ5-(15c5NCOPiPr)Ir(H)]+ exhibiting modest activity. Addition of Li+ provides a further boost in activity, with up to 1000-fold rate enhancement. Ethers and chloride salts dampen or turn off reactivity, leading to three distinct catalyst states with activity spanning several orders of magnitude. Mechanistic studies suggest that the large rate enhancement and high degree of tunability stem from control over substrate binding. Methods to convert CO2 to formate using iridium pincer-crown ether complexes are discussed. The synthesis of iridium dihydride pincer-crown ether complexes is attempted. Electrochemistry of pincer-crown ether complexes reveal very negative iridium reduction potentials. Lastly, CO2 hydrogenation to formate is accomplished in bicarbonate solutions with turn over numbers up to 1000.
2017
Inorganic chemistry
Chemistry
hemilability; homogeneous catalysis; hydrogen activation; olefin isomerization; switchable catalysis
eng
Doctor of Philosophy
Dissertation
Chemistry
Alexander
Miller
Thesis advisor
Cynthia
Schauer
Thesis advisor
Maurice
Brookhart
Thesis advisor
Frank
Leibfarth
Thesis advisor
Simon
Meek
Thesis advisor
text
2017-08
University of North Carolina at Chapel Hill
Degree granting institution
Matthew
Kita
Creator
Department of Chemistry
College of Arts and Sciences
Cation Tunable Reactivity and Catalysis with Iridium Pincer-Crown Ether Complexes
Iridium complexes of a new multidentate ligand combining a rigid, strongly donating pincer scaffold with a flexible, weakly donating aza-crown ether moiety are reported. The “pincer-crown ether ligand” exhibits tridentate, tetradentate, and pentadentate coordination modes. The coordination mode can be changed by Lewis base displacement of the chelating ethers, with binding equilibria dramatically altered through cation–macrocycle interactions. Cation-promoted hydrogen activation was accomplished by an iridium monohydride cation ligated in a pentadentate fashion by the pincer-crown ether ligand. The rate can be controlled on the basis of the choice of cation, and the concentration of cation. Using the same complex, rapid, selective, and highly controllable iridium-catalyzed allylbenzene isomerization is described, enabled by tunable hemilability based on alkali metal cation binding with the macrocyclic pincer-crown ether ligand. An inactive chloride-ligated complex can be activated by halide abstraction with sodium salts, with the resulting catalyst [κ5-(15c5NCOPiPr)Ir(H)]+ exhibiting modest activity. Addition of Li+ provides a further boost in activity, with up to 1000-fold rate enhancement. Ethers and chloride salts dampen or turn off reactivity, leading to three distinct catalyst states with activity spanning several orders of magnitude. Mechanistic studies suggest that the large rate enhancement and high degree of tunability stem from control over substrate binding. Methods to convert CO2 to formate using iridium pincer-crown ether complexes are discussed. The synthesis of iridium dihydride pincer-crown ether complexes is attempted. Electrochemistry of pincer-crown ether complexes reveal very negative iridium reduction potentials. Lastly, CO2 hydrogenation to formate is accomplished in bicarbonate solutions with turn over numbers up to 1000.
2017
Inorganic chemistry
Chemistry
hemilability, homogeneous catalysis, hydrogen activation, olefin isomerization, switchable catalysis
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Chemistry
Alexander
Miller
Thesis advisor
Cynthia
Schauer
Thesis advisor
Maurice
Brookhart
Thesis advisor
Frank
Leibfarth
Thesis advisor
Simon
Meek
Thesis advisor
text
2017-08
Matthew
Kita
Creator
Department of Chemistry
College of Arts and Sciences
Cation Tunable Reactivity and Catalysis with Iridium Pincer-Crown Ether Complexes
Iridium complexes of a new multidentate ligand combining a rigid, strongly donating pincer scaffold with a flexible, weakly donating aza-crown ether moiety are reported. The “pincer-crown ether ligand” exhibits tridentate, tetradentate, and pentadentate coordination modes. The coordination mode can be changed by Lewis base displacement of the chelating ethers, with binding equilibria dramatically altered through cation–macrocycle interactions. Cation-promoted hydrogen activation was accomplished by an iridium monohydride cation ligated in a pentadentate fashion by the pincer-crown ether ligand. The rate can be controlled on the basis of the choice of cation, and the concentration of cation. Using the same complex, rapid, selective, and highly controllable iridium-catalyzed allylbenzene isomerization is described, enabled by tunable hemilability based on alkali metal cation binding with the macrocyclic pincer-crown ether ligand. An inactive chloride-ligated complex can be activated by halide abstraction with sodium salts, with the resulting catalyst [κ5-(15c5NCOPiPr)Ir(H)]+ exhibiting modest activity. Addition of Li+ provides a further boost in activity, with up to 1000-fold rate enhancement. Ethers and chloride salts dampen or turn off reactivity, leading to three distinct catalyst states with activity spanning several orders of magnitude. Mechanistic studies suggest that the large rate enhancement and high degree of tunability stem from control over substrate binding. Methods to convert CO2 to formate using iridium pincer-crown ether complexes are discussed. The synthesis of iridium dihydride pincer-crown ether complexes is attempted. Electrochemistry of pincer-crown ether complexes reveal very negative iridium reduction potentials. Lastly, CO2 hydrogenation to formate is accomplished in bicarbonate solutions with turn over numbers up to 1000.
2017
Inorganic chemistry
Chemistry
hemilability; homogeneous catalysis; hydrogen activation; olefin isomerization; switchable catalysis
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Alexander
Miller
Thesis advisor
Cynthia
Schauer
Thesis advisor
Maurice
Brookhart
Thesis advisor
Frank
Leibfarth
Thesis advisor
Simon
Meek
Thesis advisor
text
2017-08
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