Presentation Title

Nickel Nitrosyl Complexes with Bidentate N-heterocyclic Carbene Ligands

Faculty Mentor

Dr. S. Chantal E. Stieber

Start Date

17-11-2018 9:45 AM

End Date

17-11-2018 10:00 AM

Location

C323

Session

Oral 2

Type of Presentation

Oral Talk

Subject Area

physical_mathematical_sciences

Abstract

Nitrous oxide (N2O) is a greenhouse gas mainly produced from human activities, and it has a warming potential up to 310 times that of carbon dioxide. Soil micro-organism such as Geobacillus stearothermophilus can reduce N2O and transform N2O into N2 gas, which is 78% of the air we breathe; however, the mechanism of the reaction is unknown. To understand the enzyme mechanisms and develop methods to reduce N2O, oxidation and reduction mechanisms were studied with nickel complexes. Nickel(0) complexes with bidentate N-heterocyclic carbene ligands were synthesized and structurally characterized by X-ray diffraction. 1-(2,4,6-trimethylphenyl)-1H-imidazole was synthesized and reacted with dibromomethane to make a mesityl bisimidazolium salt. Both products were characterized with 1H NMR spectroscopy. The bisimidazolium salt was deprotonated with potassium bis(trimethylsilyl)amide (KHMDS) and reacted with bis(1,5-cyclooctadiene)nickel(0) (Ni(COD)2) to make a new nickel(0)cyclooctadiene complex with bidentate N-heterocyclic carbene ligands (MesNHC2Me)Ni(COD). This complex was recently published. A new Ni-NO complex was made by adding one equivalent of nitrosonium tetrafluoroborate [NO][BF4] to (MesNHC2Me)Ni(COD). The presence of a new Ni-NO bond and a BF41- counterion was confirmed by infrared spectroscopy. Future directions will include reducing the nickel nitrosyl complexes and testing reactivity.

Summary of research results to be presented

Mesitylimidazole (1-(2,4,6-trimethylphenyl)-1H-imidazole) was synthesized and used as a ligand precursor and was characterized by 1H NMR spectroscopy. The mesityl bisimidazolium salt was synthesized with dibromomethane in toluene and characterized with 1H NMR spectroscopy. The bisimidazolium salt was deprotonated with potassium bis(trimethylsilyl)amide (KHMDS) in THF. A new complex nickel(0)cyclooctadiene with bidentate N-heterocyclic carbene ligands (MesNHC2Me)Ni(COD) was synthesized from bis(1,5-cyclooctadiene)nickel(0) (Ni(COD)2) in THF and published in a research paper on which I am a coauthor. A new Ni-NO complex was made by adding one equivalent of nitrosonium tetrafluoroborate [NO][BF4] to (MesNHC2Me)Ni(COD). The presence of a new Ni-NO bond and a BF41- counterion was confirmed by infrared spectroscopy.

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Nov 17th, 9:45 AM Nov 17th, 10:00 AM

Nickel Nitrosyl Complexes with Bidentate N-heterocyclic Carbene Ligands

C323

Nitrous oxide (N2O) is a greenhouse gas mainly produced from human activities, and it has a warming potential up to 310 times that of carbon dioxide. Soil micro-organism such as Geobacillus stearothermophilus can reduce N2O and transform N2O into N2 gas, which is 78% of the air we breathe; however, the mechanism of the reaction is unknown. To understand the enzyme mechanisms and develop methods to reduce N2O, oxidation and reduction mechanisms were studied with nickel complexes. Nickel(0) complexes with bidentate N-heterocyclic carbene ligands were synthesized and structurally characterized by X-ray diffraction. 1-(2,4,6-trimethylphenyl)-1H-imidazole was synthesized and reacted with dibromomethane to make a mesityl bisimidazolium salt. Both products were characterized with 1H NMR spectroscopy. The bisimidazolium salt was deprotonated with potassium bis(trimethylsilyl)amide (KHMDS) and reacted with bis(1,5-cyclooctadiene)nickel(0) (Ni(COD)2) to make a new nickel(0)cyclooctadiene complex with bidentate N-heterocyclic carbene ligands (MesNHC2Me)Ni(COD). This complex was recently published. A new Ni-NO complex was made by adding one equivalent of nitrosonium tetrafluoroborate [NO][BF4] to (MesNHC2Me)Ni(COD). The presence of a new Ni-NO bond and a BF41- counterion was confirmed by infrared spectroscopy. Future directions will include reducing the nickel nitrosyl complexes and testing reactivity.