{"id":{"repo_id":"aachen","oai_identifier":"oai:publications.rwth-aachen.de:61701"},"canonical_url":"https://search.dev.ndltd.org/etd/aachen/oai:publications.rwth-aachen.de:61701","repository":{"repo_id":"aachen","name":"RWTH Aachen University","base_url":"https://publications.rwth-aachen.de/oai2d"},"display":{"title":"Organometallic and coordination chemistry of (Tetramethylcyclobutadiene)cobalt sandwich and halfsandwich complexes","abstract":"This thesis consists of two parts. Part one is devoted to the development of (tetramethylcyclobutadiene)cobalt (Cb*Co) tris(ligand) complexes [Cb*Co(L)3]+. An improved synthesis of the starting materials [Cb*Co(CO)3]BF4, Cb*CoI(CO)2 and [Cb*Co(C6H6)]PF6 was developed. Photolysis of [Cb*Co(C6H6)]PF6 in acetonitrile produced [Cb*Co(NCMe)3]PF6. Alternatively, the tris(acetonitrile) complex was obtained via thermal substitution of benzene by acetonitrile when heating [Cb*Co(C6H6)]PF6 in acetonitrile. Complex cation [Cb*Co(NCMe)3]+ is substitutionally labile and reacts with Lewis bases to form cations of the type [Cb*CoL3]+, notably L3 = Cp-. The first structural characterizations of tris(ligand) complex cations [Cb*CoL3]+ with L = CO and MeCN are presented. The second part of the thesis describes reaction chemistry of the novel sigma,eta4-butadienyl (carbenoid) complex ion [CpCo(sigma,eta4-C4HsynMe4)]+, formed by protonation of CpCoCb*, and chemistry of a number of products derived thereof. Above -10°C the carbenoid cation undergoes a thermal rearrangement to produce the half-open cobaltocenium ion [CpCo(eta5-C5H4Me3)]+. The protonation of CpCoCb* was shown to be reversible under conditions of low proton activity. Thus deprotonation of the s,h4-butadienyl complex with one equivalent of NEt3 mainly gave CpCoCb*, whereas reaction with excess NEt3 afforded a hexatriene complex CpCo[eta4-C4HsynMe3(CH2)]. The carbenoid complex underwent nucleophilic addition reactions. Addition of CNtBu produced a (tert-butylamino)cobaltocenium ion [CpCo{eta5-C5Me4(NHtBu)}]+. Addition of excess PPh3 gave a phosphonio cation [CpCo{eta4-C4HantiMe4(PPh3)}]+. With pyridine four reaction channels were revealed: i) reversible deprotonation to the hexatriene complex; ii) reversible nucleophilic addition at the carbenoid center to form [CpCo{eta4-C4HsynMe4(NC5H5)}]+; iii) stereoisomerization to form a more stable isomer, [CpCo{eta4-C4HantiMe4(NC5H5)}]+; iv) very slow formation of the CpCoCb*. The more stable isomeric pyridine addition product underwent nucleophilic substitution reactions with 4-picoline to afforded the 4-picoline addition product and with CN– to yield a hexa-2,4-dienenitrile complex [CpCo(eta4-C4HantiMe4CN)]. The latter on protonation gave an aminocobaltocenium ion [CpCo{eta5-C5Me4(NH2)}]+. With CNtBu [CpCo{eta5-C5Me4(NHtBu)}]+ was formed. Acid removes pyridine from [CpCo{eta4-C4HantiMe4(NC5H5)}]+ to produce an isomeric carbenoid ion [CpCo(sigma,eta4-C4HantiMe4)]+, which again could be reacted with excess NEt3 to afford the isomeric hexatriene complex CpCo[eta4-C4HantiMe3(CH2)]. Thermolyses of CpCo[eta4-C4HsynMe3(CH2)] and CpCo[eta4-C4HantiMe3(CH2)] show that the later is the lower-energy isomer and produce a dinuclear complex (my-C5H3Me3)(CoCp)2 (Co–Co) with a bridging penta-2,4-dienylidene ligand.","abstract_html":"This thesis consists of two parts. Part one is devoted to the development of (tetramethylcyclobutadiene)cobalt (Cb*Co) tris(ligand) complexes [Cb*Co(L)3]+. An improved synthesis of the starting materials [Cb*Co(CO)3]BF4, Cb*CoI(CO)2 and [Cb*Co(C6H6)]PF6 was developed. Photolysis of [Cb*Co(C6H6)]PF6 in acetonitrile produced [Cb*Co(NCMe)3]PF6. Alternatively, the tris(acetonitrile) complex was obtained via thermal substitution of benzene by acetonitrile when heating [Cb*Co(C6H6)]PF6 in acetonitrile. Complex cation [Cb*Co(NCMe)3]+ is substitutionally labile and reacts with Lewis bases to form cations of the type [Cb*CoL3]+, notably L3 = Cp-. The first structural characterizations of tris(ligand) complex cations [Cb*CoL3]+ with L = CO and MeCN are presented. The second part of the thesis describes reaction chemistry of the novel sigma,eta4-butadienyl (carbenoid) complex ion [CpCo(sigma,eta4-C4HsynMe4)]+, formed by protonation of CpCoCb*, and chemistry of a number of products derived thereof. Above -10°C the carbenoid cation undergoes a thermal rearrangement to produce the half-open cobaltocenium ion [CpCo(eta5-C5H4Me3)]+. The protonation of CpCoCb* was shown to be reversible under conditions of low proton activity. Thus deprotonation of the s,h4-butadienyl complex with one equivalent of NEt3 mainly gave CpCoCb*, whereas reaction with excess NEt3 afforded a hexatriene complex CpCo[eta4-C4HsynMe3(CH2)]. The carbenoid complex underwent nucleophilic addition reactions. Addition of CNtBu produced a (tert-butylamino)cobaltocenium ion [CpCo{eta5-C5Me4(NHtBu)}]+. Addition of excess PPh3 gave a phosphonio cation [CpCo{eta4-C4HantiMe4(PPh3)}]+. With pyridine four reaction channels were revealed: i) reversible deprotonation to the hexatriene complex; ii) reversible nucleophilic addition at the carbenoid center to form [CpCo{eta4-C4HsynMe4(NC5H5)}]+; iii) stereoisomerization to form a more stable isomer, [CpCo{eta4-C4HantiMe4(NC5H5)}]+; iv) very slow formation of the CpCoCb*. The more stable isomeric pyridine addition product underwent nucleophilic substitution reactions with 4-picoline to afforded the 4-picoline addition product and with CN– to yield a hexa-2,4-dienenitrile complex [CpCo(eta4-C4HantiMe4CN)]. The latter on protonation gave an aminocobaltocenium ion [CpCo{eta5-C5Me4(NH2)}]+. With CNtBu [CpCo{eta5-C5Me4(NHtBu)}]+ was formed. Acid removes pyridine from [CpCo{eta4-C4HantiMe4(NC5H5)}]+ to produce an isomeric carbenoid ion [CpCo(sigma,eta4-C4HantiMe4)]+, which again could be reacted with excess NEt3 to afford the isomeric hexatriene complex CpCo[eta4-C4HantiMe3(CH2)]. Thermolyses of CpCo[eta4-C4HsynMe3(CH2)] and CpCo[eta4-C4HantiMe3(CH2)] show that the later is the lower-energy isomer and produce a dinuclear complex (my-C5H3Me3)(CoCp)2 (Co–Co) with a bridging penta-2,4-dienylidene ligand.","abstract_has_math":false,"creators":["Butovskiy, Mikhail V."],"institution":"Publikationsserver der RWTH Aachen University","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Kölle, Ulrich"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2007,"date_issued":"2007","date_published":"2007","updated_at":"2026-07-30T19:43:10Z","subjects":["info:eu-repo/classification/ddc/540","Chemie","Cobalt","Cyclobutadiene","Butadiene","Butadienyl","Carbene complexes","Metallo-electrophiles"],"languages":["eng"],"rights":["info:eu-repo/semantics/openAccess"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123336%22"],"render_values":[{"text":"https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123336%22","href":"https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123336%22","code":true}]}]},"links":{"outbound_url":"https://publications.rwth-aachen.de/record/61701","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Kölle, Ulrich"]},{"key":"dc:creator","label":"Author","values":["Butovskiy, Mikhail V."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:coverage","label":"Dc Coverage","values":["DE"]},{"key":"dc:date","label":"Dc Date","values":["2007"]},{"key":"dc:publisher","label":"Institution","values":["Publikationsserver der RWTH Aachen University"]},{"key":"dc:relation","label":"Dc Relation","values":["info:eu-repo/semantics/altIdentifier/urn/urn:nbn:de:hbz:82-opus-12576"]},{"key":"dc:type","label":"Dc Type","values":["info:eu-repo/semantics/doctoralThesis","info:eu-repo/semantics/publishedVersion"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["info:eu-repo/classification/ddc/540","Chemie","Cobalt","Cyclobutadiene","Butadiene","Butadienyl","Carbene complexes","Metallo-electrophiles"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["info:eu-repo/semantics/openAccess"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://publications.rwth-aachen.de/record/61701","https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123336%22"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["This thesis consists of two parts. Part one is devoted to the development of (tetramethylcyclobutadiene)cobalt (Cb*Co) tris(ligand) complexes [Cb*Co(L)3]+. An improved synthesis of the starting materials [Cb*Co(CO)3]BF4, Cb*CoI(CO)2 and [Cb*Co(C6H6)]PF6 was developed. Photolysis of [Cb*Co(C6H6)]PF6 in acetonitrile produced [Cb*Co(NCMe)3]PF6. Alternatively, the tris(acetonitrile) complex was obtained via thermal substitution of benzene by acetonitrile when heating [Cb*Co(C6H6)]PF6 in acetonitrile. Complex cation [Cb*Co(NCMe)3]+ is substitutionally labile and reacts with Lewis bases to form cations of the type [Cb*CoL3]+, notably L3 = Cp-. The first structural characterizations of tris(ligand) complex cations [Cb*CoL3]+ with L = CO and MeCN are presented. The second part of the thesis describes reaction chemistry of the novel sigma,eta4-butadienyl (carbenoid) complex ion [CpCo(sigma,eta4-C4HsynMe4)]+, formed by protonation of CpCoCb*, and chemistry of a number of products derived thereof. Above -10°C the carbenoid cation undergoes a thermal rearrangement to produce the half-open cobaltocenium ion [CpCo(eta5-C5H4Me3)]+. The protonation of CpCoCb* was shown to be reversible under conditions of low proton activity. Thus deprotonation of the s,h4-butadienyl complex with one equivalent of NEt3 mainly gave CpCoCb*, whereas reaction with excess NEt3 afforded a hexatriene complex CpCo[eta4-C4HsynMe3(CH2)]. The carbenoid complex underwent nucleophilic addition reactions. Addition of CNtBu produced a (tert-butylamino)cobaltocenium ion [CpCo{eta5-C5Me4(NHtBu)}]+. Addition of excess PPh3 gave a phosphonio cation [CpCo{eta4-C4HantiMe4(PPh3)}]+. With pyridine four reaction channels were revealed: i) reversible deprotonation to the hexatriene complex; ii) reversible nucleophilic addition at the carbenoid center to form [CpCo{eta4-C4HsynMe4(NC5H5)}]+; iii) stereoisomerization to form a more stable isomer, [CpCo{eta4-C4HantiMe4(NC5H5)}]+; iv) very slow formation of the CpCoCb*. The more stable isomeric pyridine addition product underwent nucleophilic substitution reactions with 4-picoline to afforded the 4-picoline addition product and with CN– to yield a hexa-2,4-dienenitrile complex [CpCo(eta4-C4HantiMe4CN)]. The latter on protonation gave an aminocobaltocenium ion [CpCo{eta5-C5Me4(NH2)}]+. With CNtBu [CpCo{eta5-C5Me4(NHtBu)}]+ was formed. Acid removes pyridine from [CpCo{eta4-C4HantiMe4(NC5H5)}]+ to produce an isomeric carbenoid ion [CpCo(sigma,eta4-C4HantiMe4)]+, which again could be reacted with excess NEt3 to afford the isomeric hexatriene complex CpCo[eta4-C4HantiMe3(CH2)]. Thermolyses of CpCo[eta4-C4HsynMe3(CH2)] and CpCo[eta4-C4HantiMe3(CH2)] show that the later is the lower-energy isomer and produce a dinuclear complex (my-C5H3Me3)(CoCp)2 (Co–Co) with a bridging penta-2,4-dienylidene ligand."]},{"key":"dc:source","label":"Dc Source","values":["Aachen : Publikationsserver der RWTH Aachen University VI, 180 S. : graph. Darst. (2007). = Aachen, Techn. Hochsch., Diss., 2005"]},{"key":"dc:title","label":"Title","values":["Organometallic and coordination chemistry of (Tetramethylcyclobutadiene)cobalt sandwich and halfsandwich complexes"]}]}],"canonical_facts":{"dc:contributor":["Kölle, Ulrich"],"dc:coverage":["DE"],"dc:creator":["Butovskiy, Mikhail V."],"dc:date":["2007"],"dc:description":["This thesis consists of two parts. Part one is devoted to the development of (tetramethylcyclobutadiene)cobalt (Cb*Co) tris(ligand) complexes [Cb*Co(L)3]+. An improved synthesis of the starting materials [Cb*Co(CO)3]BF4, Cb*CoI(CO)2 and [Cb*Co(C6H6)]PF6 was developed. Photolysis of [Cb*Co(C6H6)]PF6 in acetonitrile produced [Cb*Co(NCMe)3]PF6. Alternatively, the tris(acetonitrile) complex was obtained via thermal substitution of benzene by acetonitrile when heating [Cb*Co(C6H6)]PF6 in acetonitrile. Complex cation [Cb*Co(NCMe)3]+ is substitutionally labile and reacts with Lewis bases to form cations of the type [Cb*CoL3]+, notably L3 = Cp-. The first structural characterizations of tris(ligand) complex cations [Cb*CoL3]+ with L = CO and MeCN are presented. The second part of the thesis describes reaction chemistry of the novel sigma,eta4-butadienyl (carbenoid) complex ion [CpCo(sigma,eta4-C4HsynMe4)]+, formed by protonation of CpCoCb*, and chemistry of a number of products derived thereof. Above -10°C the carbenoid cation undergoes a thermal rearrangement to produce the half-open cobaltocenium ion [CpCo(eta5-C5H4Me3)]+. The protonation of CpCoCb* was shown to be reversible under conditions of low proton activity. Thus deprotonation of the s,h4-butadienyl complex with one equivalent of NEt3 mainly gave CpCoCb*, whereas reaction with excess NEt3 afforded a hexatriene complex CpCo[eta4-C4HsynMe3(CH2)]. The carbenoid complex underwent nucleophilic addition reactions. Addition of CNtBu produced a (tert-butylamino)cobaltocenium ion [CpCo{eta5-C5Me4(NHtBu)}]+. Addition of excess PPh3 gave a phosphonio cation [CpCo{eta4-C4HantiMe4(PPh3)}]+. With pyridine four reaction channels were revealed: i) reversible deprotonation to the hexatriene complex; ii) reversible nucleophilic addition at the carbenoid center to form [CpCo{eta4-C4HsynMe4(NC5H5)}]+; iii) stereoisomerization to form a more stable isomer, [CpCo{eta4-C4HantiMe4(NC5H5)}]+; iv) very slow formation of the CpCoCb*. The more stable isomeric pyridine addition product underwent nucleophilic substitution reactions with 4-picoline to afforded the 4-picoline addition product and with CN– to yield a hexa-2,4-dienenitrile complex [CpCo(eta4-C4HantiMe4CN)]. The latter on protonation gave an aminocobaltocenium ion [CpCo{eta5-C5Me4(NH2)}]+. With CNtBu [CpCo{eta5-C5Me4(NHtBu)}]+ was formed. Acid removes pyridine from [CpCo{eta4-C4HantiMe4(NC5H5)}]+ to produce an isomeric carbenoid ion [CpCo(sigma,eta4-C4HantiMe4)]+, which again could be reacted with excess NEt3 to afford the isomeric hexatriene complex CpCo[eta4-C4HantiMe3(CH2)]. Thermolyses of CpCo[eta4-C4HsynMe3(CH2)] and CpCo[eta4-C4HantiMe3(CH2)] show that the later is the lower-energy isomer and produce a dinuclear complex (my-C5H3Me3)(CoCp)2 (Co–Co) with a bridging penta-2,4-dienylidene ligand."],"dc:identifier":["https://publications.rwth-aachen.de/record/61701","https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123336%22"],"dc:language":["eng"],"dc:publisher":["Publikationsserver der RWTH Aachen University"],"dc:relation":["info:eu-repo/semantics/altIdentifier/urn/urn:nbn:de:hbz:82-opus-12576"],"dc:rights":["info:eu-repo/semantics/openAccess"],"dc:source":["Aachen : Publikationsserver der RWTH Aachen University VI, 180 S. : graph. Darst. (2007). = Aachen, Techn. Hochsch., Diss., 2005"],"dc:subject":["info:eu-repo/classification/ddc/540","Chemie","Cobalt","Cyclobutadiene","Butadiene","Butadienyl","Carbene complexes","Metallo-electrophiles"],"dc:title":["Organometallic and coordination chemistry of (Tetramethylcyclobutadiene)cobalt sandwich and halfsandwich complexes"],"dc:type":["info:eu-repo/semantics/doctoralThesis","info:eu-repo/semantics/publishedVersion"]},"updated_at":"2026-07-30T19:43:10Z"}