Síntese de copolímeros pelo acoplamento da polimerização via adição e metátese de olefinas de norborneno por um catalisador heterobimetálico de Ni(II)/Ru(II)
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Data
2023-02-24
Autores
Santos, Douglas Henrique Nunes
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Universidade Estadual Paulista (Unesp)
Resumo
Com a necessidade de novos materiais poliméricos que pudessem satisfazer os avanços das tecnologias, a busca por polímeros com propriedades e arquiteturas sofisticadas tem se tornado cada vez mais atrativa. O grande desafio da área de catalise é o desenvolvimento de catalisadores capazes de acoplar reações mecanisticamente distintas em um único sistema. Os catalisadores heterobimetálicos vem ganhando grande ascensão nos últimos anos devido sua alta seletividade e aumento da possibilidade de modulação desses complexos frente as reações de polimerização. Nesse trabalho foi desenvolvido um catalisador heterobimetálico de rutênio(II) e Níquel(II) com atividade em reações de polimerização de ROMP e adição utilizando o norborneno (NBE) como monômero. O composto inédito 4-bromofenil-biciclo[2,2,1]hept-5-ene-2-carboxilato (NBE-Aril-Br) foi sintetizado através da esterificação de Steglich e utilizado como ligante para perfazer a esfera de coordenação do centro de níquel. O complexo heterobimetálico [RuCl2(6-p-cimeno)][(-Schiff-pip)Ni(Aril-NBE)(PPh3)] (Complexo 3) foi sintetizado a partir da reações entre os fragmentos [Ni(PPh3)2(Aril-NBE)Br] (Complexo 1) e [RuCl2(η6-p-cimeno)((4-metilamina)-piperidina)] (Complexo 2). As técnicas de UV-Vis, FTIR, RMN 1H, 13C, 13P{1H} e voltametria cíclica foram utilizadas para a caracterização do ligante NBE-Aril-Br e dos complexos 1, 2 e 3. O complexo 3 foi avaliado como pré-catalisador para as polimerizações de abertura de anel via metátese (ROMP), as reações foram conduzidas em 25 e 50 °C usando uma razão molar [NBE]/[Ru] = 5000, 3 L de EDA e um tempo de reação de 10 a 60 minutos. As melhores condições de reação proporcionadas por esse catalisador foi em 50 ºC e 60 min. Por fim, Complexo 3 também foi avaliado em polimerização de NBE via adição, usando o metilaluminoxano (MAO) como cocatalisador, variando a razão molar [Al]/[Ni] de 1000 a 3000 e a temperatura de 30 a 90 °C, fixando uma quantidade de 2,5 mol do complexo bimetálico. Os resultados das polimerizações obtidas nas reações individuais indicaram uma bifuncionalidade do Complexo 3 em reações de polimerização de NBE via ROMP e via adição.
With the need for new polymeric materials that could experience advances in technology, the search for polymers with sophisticated properties and architectures has become increasingly attractive. The great challenge in the area of catalysis is the development of catalysts capable of coupling mechanistically different reactions in a single system. Heterobimetallic catalysts have gained great ascension in recent years due to their high selectivity and increased possibility of modulating these complexes in the face of polymerization reactions. In this work, a heterobimetallic catalyst of Ruthenium(II) and Nickel(II) was developed with activity in ROMP and addition polymerization reactions using norbornene (NBE) as monomer. The unpublished compound 4-bromophenyl-bicyclo[2,2,1]hept-5-ene-2-carboxylate (NBE-Aryl-Br) was synthesized through Steglich esterification and used as a linker to make the center direction sphere of nickel. The heterobimetallic complex [RuCl2(6-p-cymene)][( -Schiff-pip)Ni(Aryl-NBE)(PPh3)] (Complex 3) was synthesized from the reactions between fragments [Ni(PPh3)2(Aryl-NBE)Br] (Complex 1) and [RuCl2(η6-p-cymene)((4-methylamino)-piperidine)] (Complex 2). UV-Vis, FTIR, 1H, 13C, 13P{1H} NMR and cyclic voltammetry techniques were used to characterize the NBE-Aryl-Br ligand and complexes 1, 2 and 3. Complex 3 was evaluated as a pre-catalyst for ring opening polymerizations via metathesis (ROMP), reactions were conducted at 25 and 50 °C using a molar ratio [NBE]/[Ru] = 5000, 3 L of EDA and a reaction time of 10 to 60 minutes. The best reaction conditions provided by this catalyst were at 50°C and 60 min. Finally, Complex 3 was also evaluated in polymerization of NBE via addition, using methylaluminoxane (MAO) as cocatalyst, varying the molar ratio [Al]/[Ni] from 1000 to 3000 and the temperature from 30 to 90 °C, fixing an amount of 2.5 mol of the bimetallic complex. The results of transient polymerizations in individual reactions indicated a bifunctionality of Complex 3 in NBE polymerization reactions via ROMP and via addition.
With the need for new polymeric materials that could experience advances in technology, the search for polymers with sophisticated properties and architectures has become increasingly attractive. The great challenge in the area of catalysis is the development of catalysts capable of coupling mechanistically different reactions in a single system. Heterobimetallic catalysts have gained great ascension in recent years due to their high selectivity and increased possibility of modulating these complexes in the face of polymerization reactions. In this work, a heterobimetallic catalyst of Ruthenium(II) and Nickel(II) was developed with activity in ROMP and addition polymerization reactions using norbornene (NBE) as monomer. The unpublished compound 4-bromophenyl-bicyclo[2,2,1]hept-5-ene-2-carboxylate (NBE-Aryl-Br) was synthesized through Steglich esterification and used as a linker to make the center direction sphere of nickel. The heterobimetallic complex [RuCl2(6-p-cymene)][( -Schiff-pip)Ni(Aryl-NBE)(PPh3)] (Complex 3) was synthesized from the reactions between fragments [Ni(PPh3)2(Aryl-NBE)Br] (Complex 1) and [RuCl2(η6-p-cymene)((4-methylamino)-piperidine)] (Complex 2). UV-Vis, FTIR, 1H, 13C, 13P{1H} NMR and cyclic voltammetry techniques were used to characterize the NBE-Aryl-Br ligand and complexes 1, 2 and 3. Complex 3 was evaluated as a pre-catalyst for ring opening polymerizations via metathesis (ROMP), reactions were conducted at 25 and 50 °C using a molar ratio [NBE]/[Ru] = 5000, 3 L of EDA and a reaction time of 10 to 60 minutes. The best reaction conditions provided by this catalyst were at 50°C and 60 min. Finally, Complex 3 was also evaluated in polymerization of NBE via addition, using methylaluminoxane (MAO) as cocatalyst, varying the molar ratio [Al]/[Ni] from 1000 to 3000 and the temperature from 30 to 90 °C, fixing an amount of 2.5 mol of the bimetallic complex. The results of transient polymerizations in individual reactions indicated a bifunctionality of Complex 3 in NBE polymerization reactions via ROMP and via addition.
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Palavras-chave
Complexo bimetálico, Catalisador bifuncional, ROMP, Norborneno, Polimerização via adição, Bimetallic complex, Bifunctional catalyst, Norbornene, Polymerization via addition