Alternating ethylene-norbornene copolymerization catalyzed by cationic organopalladium complexes bearing hemilabile bidentate ligands of α-amino-pyridines

Abstract

Cationic methylpalladium complexes with hemilabile bidentate ligands of alpha-amino-pyridines, in the form of {[R(1)HNCR(2)H(o-C(6)H(5)N)]Pd(Me)(NCMe)}(BF(4)) (R(1) = (i)Pr, (t)Bu, Ar R(2) = H, Me) have been found to be effective precursors for catalytic copolymerization of ethylene and norbornene under mild conditions. The copolymer products exhibit predominant alternating microstructures which are evidenced by NMR and mass spectrometry as well as a kinetic analysis according to the Finman-Ross relationship.

Kinetics, Mechanism and Theoretical Studies of Norbornene-Ethylene Alternating Copolymerization Catalyzed by Organopalladium(II) Complexes Bearing Hemilabile α-Amino–pyridine

“…The collection of C - 2e , which is of the kinetic product from N-insertion into 1e , is probably due to ready decomposition of the thermodynamically stable T - 2e , via C-H activation at i Pr 2 C 6 H 3 [ 92 , 93 ]. The bond lengths of Pd-N1(sp 2 ), Pd-N2(sp 3 ), and Pd-N3(sp) of 2b , e are comparable with the data of 1a – e [ 80 ]. All structural parameters collected in Table S1 are in agreement with the literature data [ 89 , 90 , 91 ].…”

“…T -{[RHNCH 2 ( o -C 6 H 4 N)]Pd(Et)(MeCN)}(BF 4 ) ( 5a – c ), with respective yields of 29%, 50%, and 24%, were also obtained. The absence of the C - 5a – c is presumably due to the conformational steric hindrance between the amino substituent and the ethyl ligand [ 80 , 98 ]. T -forms are of the more favored configurations in 1a’ – d’ and 5a’ – e’ , again, ascribed to the steric effect ( Table 3 ).…”

“…Although late-transition metal catalysts have been employed to generate functionalized polyolefins [ 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 ], the successful examples to produce COC are still limited [ 73 , 74 , 75 , 76 , 77 , 78 , 79 ], because of the occurrence of β-H elimination on the alkyl chain. We previously reported our finding of the alternating E–N copolymerization, induced by methylpalladium(II) cations and bearing hemilabile bidentate ligand of α-amino–pyridines without the assistance of MAO (as shown in Scheme 1 ) [ 80 ]. The general features of the copolymerization show M w ~10 4 , PDI~1.5, T g ~100–120 °C, and characteristic N%~50, indicating that the COCs have a predominated alternating E–N microstructure.…”

“…The general features of the copolymerization show M w ~10 4 , PDI~1.5, T g ~100–120 °C, and characteristic N%~50, indicating that the COCs have a predominated alternating E–N microstructure. Furthermore, the reactivity ratios obtained from the linear Fineman–Ross plot show both r 1 ( k EE / k EN ) and r 2 ( k NN / k NE) are smaller than 1, revealing that both EE- and NN-insertion would be more difficult than EN- or NE-insertion [ 80 ]. Synthesis of the alternating copolymer is important for optical applications, since the chemical homogeneous products generate high transparency.…”

Crystal structure of dichlorido[N-(pyridin-2-ylmethyl)aniline]zinc(II), C12H12Cl2N2Zn

“…All other H-atoms were placed in calculated positions and treated as riding: C-H = 0.93 or 0.97 Å, with U iso (H) = 1.2 U eq (C). Discussion a-amino-pyridines metal complexes, in particular those of gallium(III), nickel(II) and zinc(II), have a great potential to be developed into novel anticancer drugs [1][2][3], and its cationic palladium complexes can catalyze the copolymerization of ethylene and norbornene [4]. The title complex was prepared by the reaction of ZnCl 2 with the potentially bidentate ligand N-(pyridin-2-ylmethyl)aniline.…”