Effect of Cyclopentadienyl Fragment in Copolymerization of Ethylene with Cyclic Olefins Catalyzed by Non‐Bridged (Aryloxo)(cyclopentadienyl)titanium(IV) Complexes

Abstract

Dedicated in honor to Prof. Richard R. Schrock on the occasion of his 60th birthday.Abstract: The effect of the cyclopentadienyl fragment in the copolymerization of ethylene with norbornene (NBE) by various non-bridged (aryloxo)(cyclopentadienyl)titanium(IV) complexes of the type, Cp'TiCl 2 -(OAr) [Cp' ¼ indenyl (1), C 5 Me 5 (Cp*, 2), t-BuC 5 H 4 (3), 1,2,4-Me 3 C 5 H 2 (4); OAr ¼ O-2,6-i-Pr 2 C 6 H 3 ], À MAO catalyst systems has been explored. The catalytic activity and the NBE incorporation were highly dependent upon substituent on Cp' employed, and 1 exhibited both a remarkable catalytic activity and an efficient NBE incorporation, affording high molecular weight polymers with unimodal molecular weight distributions. NBE repeat units were observed in the resultant poly(ethylene-co-NBE)s prepared by 1, 3, and 4, and the degree of NBE dyads as well as alternating sequences was strongly influenced by the Cp' employed. These complexes (1,3,4) also exhibited high catalytic activities for ethylene/cyclopentene (CPE) copolymerization, but the CPE incorporation by 1 was less efficient than the NBE incorporation under the same conditions. The ab initio density functional (DF) molecular orbital (MO) methods were utilized to explore the effect of substituents on Cp' toward the catalytic activity, the NBE incorporation and the monomer sequence distribution. Good correlations between the DE coord Et (coordination energy of ethylene) after NBE insertion and the activity, and between DE coord NBE (coordination energy of NBE) after ethylene (or NBE insertion) and NBE content were observed, strongly suggesting that the capability producing NBE repeat units was dependent upon DE coord NBE after NBE insertion.

Design of Efficient Molecular Catalysts for Synthesis of Cyclic Olefin Copolymers (COC) by Copolymerization of Ethylene and α-Olefins with Norbornene or Tetracyclododecene

“…This may also be explained by the fact that 7 showed remarkable catalytic activity for NBE homopolymerization. The resultant polymers possessed uniform compositions, confirmed by differential scanning calorimetry (DSC) thermograms as well as gel permeation chromatography (GPC) traces, and a linear relationship between glass transition temperatures and NBE content in the resultant poly(ethylene-co-NBE)s was observed [22][23][24][25].…”

“…; Y = anionic ancillary donor such as aryloxy, ketimide, imidazolin-2-iminato, etc. )-that efficient catalysts for the desired copolymerization can be tuned by the ligand modification on both the cyclopentadienyl fragment and nature (and substituents) of the anionic donor ligand employed, as demonstrated in the ethylene copolymerization with NBE [22][23][24], TCD [53], cyclohexene [72], cyclopentene [73], 2-methyl-1-pentene [74], and the others [39,41,45], as summarized in Scheme 6. We thus believe that the results demonstrated here are promising in terms of the synthesis of new polymers, and provides a better understanding not only for the polymer design (combination of monomers), but also for the catalyst design for efficient synthesis.…”

“…Aryloxo-modified half-titanocenes (exemplified as 5 and 6) have been known as effective catalysts in ethylene copolymerization, not only with α-olefin, but also with sterically encumbered olefins and cyclic olefins [39,41,45]; an efficient catalyst for the desired copolymerization can be tuned by the cyclopentadienyl fragment [39,41]. The indenyl-aryloxo analogue (6) showed efficient NBE incorporation with high catalytic activity, whereas the Cp*-aryloxo analogue (5) showed less efficient NBE incorporation than 6 [22,23], however, both the activity and the M n value decreased upon increasing the NBE content. The Cp'-pyrazolato analogue (10) exhibited efficient NBE incorporation with rather low NBE concentration (Table 1) to yield ultrahigh molecular weight copolymers with unimodal molecular weight distributions, but the activity decreased upon increasing the NBE concentration [25].…”

“…Many have reported on ethylene copolymerization with norbornene (NBE) using ordinary metallocenes [10][11][12][13][14][15][16][17], half-titanocenes [18][19][20][21][22][23][24][25][26], and others [27][28][29][30], however, successful examples of the efficient synthesis of random, high molecular weight copolymers with high Tg values (high NBE content) have been limited. Ethylene copolymers with tetracyclododecene (TCD, dimethanooctahydronaphthalene) are also known as promising materials [9], and are produced by using classical Ziegler-type vanadium catalyst systems (VOCl3, VO(OEt)Cl2-EtAlCl2•Et2AlCl, etc.)…”

On the Use of Quantum Chemistry for the Determination of Propagation, Copolymerization, and Secondary Reaction Kinetics in Free Radical Polymerization

“…Since then, many copolymer systems of common acrylates and methacrylates, styrene, and functional acrylates as well as of other common monomers were studied applying both the terminal model (TM) [108] and the penultimate unit effect (PUE) [109,110] model [101,107,[111][112][113][114][115], which are detailed in Figure 2. A list of relevant computational results for the copolymer systems studied by the application of QM methods is presented in Table 3.…”