Why did incorporation of acrylonitrile to a linear polyethylene become possible? Comparison of phosphine-sulfonate ligand with diphosphine and imine-phenolate ligands in the Pd-catalyzed ethylene/acrylonitrile copolymerization

Kyoko Nozaki, Shuhei Kusumoto, Shusuke Noda, Takuya Kochi, Lung Wa Chung, Keiji Morokuma

Research output: Contribution to journalArticle

57 Citations (Scopus)

Abstract

Palladium-catalyzed coordination-insertion copolymerization of ethylene with acrylonitrile (AN) proceeded only by using phosphine-sulfonate (P-SO 3) as a ligand among the neutral and anionic ligands we examined, those are phosphine-sulfonate (P-SO3), diphosphine (P-P), and imine-phenolate (N-O). In order to answer a question that is unique for P-SO3, theoretical and experimental studies were carried out for the three catalyst systems. By comparing P-SO3 and P-P, it was elucidated that (i) the π-acrylonitrile complex [(L-L′)PdPr(π-AN)] is less stable than the corresponding σ-complex [(L-L′)PdPr(σ-AN)] in both the phosphine-sulfonato complex (L-L′ = P-SO3) and the diphosphine complex (L-L′ = P-P) and (ii) the energetic difference between the π-complex and the σ-complex is smaller in the P-SO3 complexes than in the P-P complexes. Thus, the energies of the transition states for both AN insertion and its subsequent ethylene insertion relative to the most stable species [(L-L′)PdPr(σ-AN)] are lower for P-SO 3 than for P-P. The results nicely explain the difference between these two types of ligands. That is, ethylene insertion subsequent to AN insertion was detected for P-SO3, while aggregate formation was reported for cationic [(L-L)Pd(CHCNCH2CH3)] complex. Aggregate formation with the cationic complex can be considered as a result of the retarded ethylene insertion to [(L-L)Pd(CHCNCH2CH3)]. In contrast, theoretical comparison between P-SO3 and N-O did not show a significant energetic difference in both AN insertion and its subsequent ethylene insertion, implying that ethylene/AN copolymerization might be possible. However, our experiment using [(N-O)PdMe(lutidine)] complex revealed that β-hydride elimination terminated the ethylene oligomerization and, more importantly, that the resulting Pd-H species lead to formation of free N-OH and Pd(0) particles. The β-hydride elimination process was further studied theoretically to clarify the difference between the two anionic ligands, P-SO3 and N-O.

Original languageEnglish
Pages (from-to)16030-16042
Number of pages13
JournalJournal of the American Chemical Society
Volume132
Issue number45
DOIs
Publication statusPublished - 2010 Nov 17

Fingerprint

phosphine
Acrylonitrile
Imines
Polyethylene
Copolymerization
Polyethylenes
Ethylene
Ligands
Hydrides
Oligomerization
ethylene
Palladium

ASJC Scopus subject areas

  • Chemistry(all)
  • Catalysis
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

@article{7bf7fc59c15347ae90283024b5237f21,
title = "Why did incorporation of acrylonitrile to a linear polyethylene become possible? Comparison of phosphine-sulfonate ligand with diphosphine and imine-phenolate ligands in the Pd-catalyzed ethylene/acrylonitrile copolymerization",
abstract = "Palladium-catalyzed coordination-insertion copolymerization of ethylene with acrylonitrile (AN) proceeded only by using phosphine-sulfonate (P-SO 3) as a ligand among the neutral and anionic ligands we examined, those are phosphine-sulfonate (P-SO3), diphosphine (P-P), and imine-phenolate (N-O). In order to answer a question that is unique for P-SO3, theoretical and experimental studies were carried out for the three catalyst systems. By comparing P-SO3 and P-P, it was elucidated that (i) the π-acrylonitrile complex [(L-L′)PdPr(π-AN)] is less stable than the corresponding σ-complex [(L-L′)PdPr(σ-AN)] in both the phosphine-sulfonato complex (L-L′ = P-SO3) and the diphosphine complex (L-L′ = P-P) and (ii) the energetic difference between the π-complex and the σ-complex is smaller in the P-SO3 complexes than in the P-P complexes. Thus, the energies of the transition states for both AN insertion and its subsequent ethylene insertion relative to the most stable species [(L-L′)PdPr(σ-AN)] are lower for P-SO 3 than for P-P. The results nicely explain the difference between these two types of ligands. That is, ethylene insertion subsequent to AN insertion was detected for P-SO3, while aggregate formation was reported for cationic [(L-L)Pd(CHCNCH2CH3)] complex. Aggregate formation with the cationic complex can be considered as a result of the retarded ethylene insertion to [(L-L)Pd(CHCNCH2CH3)]. In contrast, theoretical comparison between P-SO3 and N-O did not show a significant energetic difference in both AN insertion and its subsequent ethylene insertion, implying that ethylene/AN copolymerization might be possible. However, our experiment using [(N-O)PdMe(lutidine)] complex revealed that β-hydride elimination terminated the ethylene oligomerization and, more importantly, that the resulting Pd-H species lead to formation of free N-OH and Pd(0) particles. The β-hydride elimination process was further studied theoretically to clarify the difference between the two anionic ligands, P-SO3 and N-O.",
author = "Kyoko Nozaki and Shuhei Kusumoto and Shusuke Noda and Takuya Kochi and Chung, {Lung Wa} and Keiji Morokuma",
year = "2010",
month = "11",
day = "17",
doi = "10.1021/ja104837h",
language = "English",
volume = "132",
pages = "16030--16042",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "45",

}

TY - JOUR

T1 - Why did incorporation of acrylonitrile to a linear polyethylene become possible? Comparison of phosphine-sulfonate ligand with diphosphine and imine-phenolate ligands in the Pd-catalyzed ethylene/acrylonitrile copolymerization

AU - Nozaki, Kyoko

AU - Kusumoto, Shuhei

AU - Noda, Shusuke

AU - Kochi, Takuya

AU - Chung, Lung Wa

AU - Morokuma, Keiji

PY - 2010/11/17

Y1 - 2010/11/17

N2 - Palladium-catalyzed coordination-insertion copolymerization of ethylene with acrylonitrile (AN) proceeded only by using phosphine-sulfonate (P-SO 3) as a ligand among the neutral and anionic ligands we examined, those are phosphine-sulfonate (P-SO3), diphosphine (P-P), and imine-phenolate (N-O). In order to answer a question that is unique for P-SO3, theoretical and experimental studies were carried out for the three catalyst systems. By comparing P-SO3 and P-P, it was elucidated that (i) the π-acrylonitrile complex [(L-L′)PdPr(π-AN)] is less stable than the corresponding σ-complex [(L-L′)PdPr(σ-AN)] in both the phosphine-sulfonato complex (L-L′ = P-SO3) and the diphosphine complex (L-L′ = P-P) and (ii) the energetic difference between the π-complex and the σ-complex is smaller in the P-SO3 complexes than in the P-P complexes. Thus, the energies of the transition states for both AN insertion and its subsequent ethylene insertion relative to the most stable species [(L-L′)PdPr(σ-AN)] are lower for P-SO 3 than for P-P. The results nicely explain the difference between these two types of ligands. That is, ethylene insertion subsequent to AN insertion was detected for P-SO3, while aggregate formation was reported for cationic [(L-L)Pd(CHCNCH2CH3)] complex. Aggregate formation with the cationic complex can be considered as a result of the retarded ethylene insertion to [(L-L)Pd(CHCNCH2CH3)]. In contrast, theoretical comparison between P-SO3 and N-O did not show a significant energetic difference in both AN insertion and its subsequent ethylene insertion, implying that ethylene/AN copolymerization might be possible. However, our experiment using [(N-O)PdMe(lutidine)] complex revealed that β-hydride elimination terminated the ethylene oligomerization and, more importantly, that the resulting Pd-H species lead to formation of free N-OH and Pd(0) particles. The β-hydride elimination process was further studied theoretically to clarify the difference between the two anionic ligands, P-SO3 and N-O.

AB - Palladium-catalyzed coordination-insertion copolymerization of ethylene with acrylonitrile (AN) proceeded only by using phosphine-sulfonate (P-SO 3) as a ligand among the neutral and anionic ligands we examined, those are phosphine-sulfonate (P-SO3), diphosphine (P-P), and imine-phenolate (N-O). In order to answer a question that is unique for P-SO3, theoretical and experimental studies were carried out for the three catalyst systems. By comparing P-SO3 and P-P, it was elucidated that (i) the π-acrylonitrile complex [(L-L′)PdPr(π-AN)] is less stable than the corresponding σ-complex [(L-L′)PdPr(σ-AN)] in both the phosphine-sulfonato complex (L-L′ = P-SO3) and the diphosphine complex (L-L′ = P-P) and (ii) the energetic difference between the π-complex and the σ-complex is smaller in the P-SO3 complexes than in the P-P complexes. Thus, the energies of the transition states for both AN insertion and its subsequent ethylene insertion relative to the most stable species [(L-L′)PdPr(σ-AN)] are lower for P-SO 3 than for P-P. The results nicely explain the difference between these two types of ligands. That is, ethylene insertion subsequent to AN insertion was detected for P-SO3, while aggregate formation was reported for cationic [(L-L)Pd(CHCNCH2CH3)] complex. Aggregate formation with the cationic complex can be considered as a result of the retarded ethylene insertion to [(L-L)Pd(CHCNCH2CH3)]. In contrast, theoretical comparison between P-SO3 and N-O did not show a significant energetic difference in both AN insertion and its subsequent ethylene insertion, implying that ethylene/AN copolymerization might be possible. However, our experiment using [(N-O)PdMe(lutidine)] complex revealed that β-hydride elimination terminated the ethylene oligomerization and, more importantly, that the resulting Pd-H species lead to formation of free N-OH and Pd(0) particles. The β-hydride elimination process was further studied theoretically to clarify the difference between the two anionic ligands, P-SO3 and N-O.

UR - http://www.scopus.com/inward/record.url?scp=78449250069&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=78449250069&partnerID=8YFLogxK

U2 - 10.1021/ja104837h

DO - 10.1021/ja104837h

M3 - Article

C2 - 20973530

AN - SCOPUS:78449250069

VL - 132

SP - 16030

EP - 16042

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 45

ER -