{"id":{"repo_id":"cornell","oai_identifier":"oai:ecommons.cornell.edu:1813/29490"},"canonical_url":"https://search.dev.ndltd.org/etd/cornell/oai:ecommons.cornell.edu:1813/29490","repository":{"repo_id":"cornell","name":"Cornell University","base_url":"https://ecommons.cornell.edu/server/oai/request"},"display":{"title":"Ligand-Induced Cleavage Of Dinitrogen By A Hafnium Metallocene Complex","abstract":"Side-on bound dinitrogen complexes of zirconium and hafnium, [([eta]5C5Me3H2)2M]2([eta]2, [eta]2-N2) (M = Zr, Hf), have been prepared by alkali metal reduction of the corresponding diiodide precursors. UV-Visible spectroscopy and X-ray diffraction studies established a higher degree of N2 activation in these complexes than those of the type [([eta]5-C5Me4H)2M]2([eta]2, [eta]2-N2) (M = Zr, Hf), likely due to increased metal-nitrogen orbital overlap resulting from contracted metal-metal distances. Addition of four atmospheres of dihydrogen afforded the expected hydrido metallocene azenido complexes [([eta]5-C5Me3H2)2MH]2N2H2 (M = Zr, Hf). The iodo hafnocene azenido compound [([eta]5-C5Me3H2)2HfI]2N2H2 was obtained by treatment of the hydrido hafnocene azenido precursor with methyl iodide. The first example of an bridging hafnium nitride compound, [([eta]5-C5Me3H2)2Hf(DMAP)]([MICRO SIGN]-N)[([eta]5-C5Me3H2)2Hf(NCO)], was isolated upon treatment of [([eta]5-C5Me3H2)2Hf]2([eta]2, [eta]2-N2) with carbon monoxide gas in the presence of 4-dimethylaminopyridine. The molecule proved to be a source of the hafnium-nitride fragment, which reacted with terminal alkynes via 1,2-addition at elevated temperatures and furnished the [MICRO SIGN]-imido acetylido complexes [([eta]5C5Me3H2)2Hf(CCR)]([MICRO SIGN]-NH)[([eta]5-C5Me3H2)2Hf(NCO)] (R = Ph, SiMe3). The hafnium nitride has also been shown to react with an additional molecule of carbon monoxide to yield the [MICRO SIGN]-isocyanate isocyanato compound [([eta]5-C5Me3H2)2Hf]([eta]3, [eta]1, [MICRO SIGN]-NCO)[([eta]5C5Me3H2)2Hf(NCO)]. The hafnocene-N2 complex also undergoes a unique series of reactions with primary silanes, leading to the production of monosilylated dinitrogen units. Complete N-N bond scission is achieved upon thermoylsis of the mono-silylated compounds, and N-C bond formation can be achieved by upon treatment of the silylated compound with CO. Trapping of the hafnium [MICRO SIGN]-nitride and N2 functionalization with silanes are reactions which are unique to the 1,2,4-trimethylcyclopentadienyl hafnocene-N2 compound. The origin of this unique reactivity has been attributed to the reduced steric profile of the trisubstituted metallocene, which allows shorter metalmetal contact distances and produces a highly activated, but sterically accessible dinitrogen fragment.","abstract_html":"Side-on bound dinitrogen complexes of zirconium and hafnium, [([eta]5C5Me3H2)2M]2([eta]2, [eta]2-N2) (M = Zr, Hf), have been prepared by alkali metal reduction of the corresponding diiodide precursors. UV-Visible spectroscopy and X-ray diffraction studies established a higher degree of N2 activation in these complexes than those of the type [([eta]5-C5Me4H)2M]2([eta]2, [eta]2-N2) (M = Zr, Hf), likely due to increased metal-nitrogen orbital overlap resulting from contracted metal-metal distances. Addition of four atmospheres of dihydrogen afforded the expected hydrido metallocene azenido complexes [([eta]5-C5Me3H2)2MH]2N2H2 (M = Zr, Hf). The iodo hafnocene azenido compound [([eta]5-C5Me3H2)2HfI]2N2H2 was obtained by treatment of the hydrido hafnocene azenido precursor with methyl iodide. The first example of an bridging hafnium nitride compound, [([eta]5-C5Me3H2)2Hf(DMAP)]([MICRO SIGN]-N)[([eta]5-C5Me3H2)2Hf(NCO)], was isolated upon treatment of [([eta]5-C5Me3H2)2Hf]2([eta]2, [eta]2-N2) with carbon monoxide gas in the presence of 4-dimethylaminopyridine. The molecule proved to be a source of the hafnium-nitride fragment, which reacted with terminal alkynes via 1,2-addition at elevated temperatures and furnished the [MICRO SIGN]-imido acetylido complexes [([eta]5C5Me3H2)2Hf(CCR)]([MICRO SIGN]-NH)[([eta]5-C5Me3H2)2Hf(NCO)] (R = Ph, SiMe3). The hafnium nitride has also been shown to react with an additional molecule of carbon monoxide to yield the [MICRO SIGN]-isocyanate isocyanato compound [([eta]5-C5Me3H2)2Hf]([eta]3, [eta]1, [MICRO SIGN]-NCO)[([eta]5C5Me3H2)2Hf(NCO)]. The hafnocene-N2 complex also undergoes a unique series of reactions with primary silanes, leading to the production of monosilylated dinitrogen units. Complete N-N bond scission is achieved upon thermoylsis of the mono-silylated compounds, and N-C bond formation can be achieved by upon treatment of the silylated compound with CO. Trapping of the hafnium [MICRO SIGN]-nitride and N2 functionalization with silanes are reactions which are unique to the 1,2,4-trimethylcyclopentadienyl hafnocene-N2 compound. The origin of this unique reactivity has been attributed to the reduced steric profile of the trisubstituted metallocene, which allows shorter metalmetal contact distances and produces a highly activated, but sterically accessible dinitrogen fragment.","abstract_has_math":false,"creators":["Semproni, Scott"],"institution":"Cornell University","degree_name":"M.S., Chemistry and Chemical Biology","degree_level":"Master of Science","degree_discipline":"Chemistry and Chemical Biology","degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":["Wolczanski, Peter Thomas","George, Serena DeBeer"],"year":2011,"date_issued":"2011-01-31","date_published":"2011-01-31","updated_at":"2026-07-24T01:49:06Z","subjects":[],"languages":["en_US"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/1813/29490","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Wolczanski, Peter Thomas","George, Serena DeBeer"]},{"key":"dc:creator","label":"Author","values":["Semproni, Scott"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2012-06-28T20:57:37Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2016-06-01T06:15:43Z"]},{"key":"dc:date.issued","label":"Date","values":["2011-01-31"]},{"key":"dc:type","label":"Dc Type","values":["dissertation or thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Chemistry and Chemical Biology"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Master of Science"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S., Chemistry and Chemical Biology"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Cornell University"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en_US"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://hdl.handle.net/1813/29490"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Side-on bound dinitrogen complexes of zirconium and hafnium, [([eta]5C5Me3H2)2M]2([eta]2, [eta]2-N2) (M = Zr, Hf), have been prepared by alkali metal reduction of the corresponding diiodide precursors. UV-Visible spectroscopy and X-ray diffraction studies established a higher degree of N2 activation in these complexes than those of the type [([eta]5-C5Me4H)2M]2([eta]2, [eta]2-N2) (M = Zr, Hf), likely due to increased metal-nitrogen orbital overlap resulting from contracted metal-metal distances. Addition of four atmospheres of dihydrogen afforded the expected hydrido metallocene azenido complexes [([eta]5-C5Me3H2)2MH]2N2H2 (M = Zr, Hf). The iodo hafnocene azenido compound [([eta]5-C5Me3H2)2HfI]2N2H2 was obtained by treatment of the hydrido hafnocene azenido precursor with methyl iodide. The first example of an bridging hafnium nitride compound, [([eta]5-C5Me3H2)2Hf(DMAP)]([MICRO SIGN]-N)[([eta]5-C5Me3H2)2Hf(NCO)], was isolated upon treatment of [([eta]5-C5Me3H2)2Hf]2([eta]2, [eta]2-N2) with carbon monoxide gas in the presence of 4-dimethylaminopyridine. The molecule proved to be a source of the hafnium-nitride fragment, which reacted with terminal alkynes via 1,2-addition at elevated temperatures and furnished the [MICRO SIGN]-imido acetylido complexes [([eta]5C5Me3H2)2Hf(CCR)]([MICRO SIGN]-NH)[([eta]5-C5Me3H2)2Hf(NCO)] (R = Ph, SiMe3). The hafnium nitride has also been shown to react with an additional molecule of carbon monoxide to yield the [MICRO SIGN]-isocyanate isocyanato compound [([eta]5-C5Me3H2)2Hf]([eta]3, [eta]1, [MICRO SIGN]-NCO)[([eta]5C5Me3H2)2Hf(NCO)]. The hafnocene-N2 complex also undergoes a unique series of reactions with primary silanes, leading to the production of monosilylated dinitrogen units. Complete N-N bond scission is achieved upon thermoylsis of the mono-silylated compounds, and N-C bond formation can be achieved by upon treatment of the silylated compound with CO. Trapping of the hafnium [MICRO SIGN]-nitride and N2 functionalization with silanes are reactions which are unique to the 1,2,4-trimethylcyclopentadienyl hafnocene-N2 compound. The origin of this unique reactivity has been attributed to the reduced steric profile of the trisubstituted metallocene, which allows shorter metalmetal contact distances and produces a highly activated, but sterically accessible dinitrogen fragment."]},{"key":"dc:format.mimetype","label":"Dc Format Mimetype","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Ligand-Induced Cleavage Of Dinitrogen By A Hafnium Metallocene Complex"]}]}],"canonical_facts":{"dc:contributor.committeemember":["Wolczanski, Peter Thomas","George, Serena DeBeer"],"dc:creator":["Semproni, Scott"],"dc:date.accessioned":["2012-06-28T20:57:37Z"],"dc:date.available":["2016-06-01T06:15:43Z"],"dc:date.issued":["2011-01-31"],"dc:description.abstract":["Side-on bound dinitrogen complexes of zirconium and hafnium, [([eta]5C5Me3H2)2M]2([eta]2, [eta]2-N2) (M = Zr, Hf), have been prepared by alkali metal reduction of the corresponding diiodide precursors. UV-Visible spectroscopy and X-ray diffraction studies established a higher degree of N2 activation in these complexes than those of the type [([eta]5-C5Me4H)2M]2([eta]2, [eta]2-N2) (M = Zr, Hf), likely due to increased metal-nitrogen orbital overlap resulting from contracted metal-metal distances. Addition of four atmospheres of dihydrogen afforded the expected hydrido metallocene azenido complexes [([eta]5-C5Me3H2)2MH]2N2H2 (M = Zr, Hf). The iodo hafnocene azenido compound [([eta]5-C5Me3H2)2HfI]2N2H2 was obtained by treatment of the hydrido hafnocene azenido precursor with methyl iodide. The first example of an bridging hafnium nitride compound, [([eta]5-C5Me3H2)2Hf(DMAP)]([MICRO SIGN]-N)[([eta]5-C5Me3H2)2Hf(NCO)], was isolated upon treatment of [([eta]5-C5Me3H2)2Hf]2([eta]2, [eta]2-N2) with carbon monoxide gas in the presence of 4-dimethylaminopyridine. The molecule proved to be a source of the hafnium-nitride fragment, which reacted with terminal alkynes via 1,2-addition at elevated temperatures and furnished the [MICRO SIGN]-imido acetylido complexes [([eta]5C5Me3H2)2Hf(CCR)]([MICRO SIGN]-NH)[([eta]5-C5Me3H2)2Hf(NCO)] (R = Ph, SiMe3). The hafnium nitride has also been shown to react with an additional molecule of carbon monoxide to yield the [MICRO SIGN]-isocyanate isocyanato compound [([eta]5-C5Me3H2)2Hf]([eta]3, [eta]1, [MICRO SIGN]-NCO)[([eta]5C5Me3H2)2Hf(NCO)]. The hafnocene-N2 complex also undergoes a unique series of reactions with primary silanes, leading to the production of monosilylated dinitrogen units. Complete N-N bond scission is achieved upon thermoylsis of the mono-silylated compounds, and N-C bond formation can be achieved by upon treatment of the silylated compound with CO. Trapping of the hafnium [MICRO SIGN]-nitride and N2 functionalization with silanes are reactions which are unique to the 1,2,4-trimethylcyclopentadienyl hafnocene-N2 compound. The origin of this unique reactivity has been attributed to the reduced steric profile of the trisubstituted metallocene, which allows shorter metalmetal contact distances and produces a highly activated, but sterically accessible dinitrogen fragment."],"dc:format.mimetype":["application/pdf"],"dc:identifier.uri":["https://hdl.handle.net/1813/29490"],"dc:language.iso":["en_US"],"dc:title":["Ligand-Induced Cleavage Of Dinitrogen By A Hafnium Metallocene Complex"],"dc:type":["dissertation or thesis"],"thesis:degree_discipline":["Chemistry and Chemical Biology"],"thesis:degree_level":["Master of Science"],"thesis:degree_name":["M.S., Chemistry and Chemical Biology"],"thesis:institution_name":["Cornell University"]},"updated_at":"2026-07-24T01:49:06Z"}