Synthesis of Methylene-bridged Binuclear Metallocene Complexes and Application for Propylene Syndiospecific Polymerization†

doi:10.7503/cjcu20180781

Abstract

Abstract:

In order to investigate the differences between binuclear metallocene catalysts and mononuclear catalysts for propylene syndiotactic polymerization, binuclear metallocene complexes [μ,μ-(CH₂)₃]·{[C(H)(η⁵-C₅H₄)(η⁵-C₁₃H₈)](MCl₂)}₂[M=Zr or Ti](4, 5), and [μ,μ-(CH₂)₃]·{[C(H)(η⁵-C₅H₄)·(η⁵-C₉H₆)](MCl₂)}₂[M=Zr or Ti](6, 7) were synthesized and characterized by ¹H NMR, ¹³C NMR, mass spectra and elemental analysis. When combined with methylaluminoxane(MAO), these metallocene complexes shown high catalytic activity for the polymerization of ethylene and propylene, the activity of polyethylene(PE) reaches up to 7.5×10⁶ g PE/(mol Zr·h)(complex 6) and 10×10⁵ g sPP/(mol Zr·h)(complex 4) for polypropylene(PP). The syndiotacticity index(SI) of polypropylene(sPP) by complex 4 was more than 90%. It is found that, under the same conditions, binuclear complexes’ catalytic activity, M_w(>100000) and molecular weight distribution(MWD>2.5) are higher than that of corresponding mononuclear metallocene complexes(M_w<70000, MWD≤2), which suggests that there are cooperation effect in binuclear system.

Key words: Binuclear metallocene catalyst, Syndiotacticity index of polypropylene, Effect of binuclear

CLC Number:

O631
O614.8

TrendMD:

SHAO Lu,LIANG Chunchao,XU Sheng,MI Puke,WANG Tinglan,YI Jianjun. Synthesis of Methylene-bridged Binuclear Metallocene Complexes and Application for Propylene Syndiospecific Polymerization^†[J]. Chem. J. Chinese Universities, 2019, 40(6): 1324.

Figures/Tables 12

Fig.1 Structures of complexes C1—C7

Scheme 1 Synthesis of ligands Ⅰand Ⅲ

Scheme 2 Synthesis of complexes 4—7

Fig.2 Structures of mononuclear complexes 8—11

Table 1 Results of ethylene polymerization with complexes 1—11*

Catalyst	Activity/[10⁶g polymer/(molM·h)]	10^-4 M_n	10^-5 M_w	MWD
4(FZr₂)	3.2	8.36	4.88	5.84
8(FZr₁)	2.5	7.32	1.23	1.68
5(FTi₂)	1.7	10.90	5.42	4.97
9(FTi₁)	1.3	5.80	1.09	1.88
6(IZr₂)	7.5	10.00	5.57	5.56
10(IZr₁)	2.1	14.70	2.52	1.71
7(ITi₂)	1.2	13.80	7.51	5.43
11(ITi₁)	0.8	26.40	5.05	1.91

Table 2 Polymerization results of propylene with catalysts 4—11a

Entry	Catalyst	Activity/[10⁵ g polymer/(mol Zr·h)]	10^-4 $M η b$	10^-4 $M w b$	MWD	r(%)
1	4(FZr₂)	10.0		13.0	3.1	90
2	8(FZr₁)	8.0		5.2	1.8	92
3	5(FTi₂)	2.8	16.0			70
4	9(FTi₁)	1.9	12.5			76
5	6(IZr₂)	12.0		10.0	2.9	45
6	10(IZr₁)	8.5		4.5	1.8	56
7	7(ITi₂)	4.5	12.0			30
8	11(ITi₁)	3.2	9.7			40

Table 2 Polymerization results of propylene with catalysts 4—11a

Entry	Catalyst	Activity/[10⁵ g polymer/(mol Zr·h)]	10^-4 $M η b$	10^-4 $M w b$	MWD	r(%)
1	4(FZr₂)	10.0		13.0	3.1	90
2	8(FZr₁)	8.0		5.2	1.8	92
3	5(FTi₂)	2.8	16.0			70
4	9(FTi₁)	1.9	12.5			76
5	6(IZr₂)	12.0		10.0	2.9	45
6	10(IZr₁)	8.5		4.5	1.8	56
7	7(ITi₂)	4.5	12.0			30
8	11(ITi₁)	3.2	9.7			40

Fig.3 13C NMR spectrum of polymer Polymerization conditions: n(Al)/n(Zr)=2000∶1, 25 ℃, 0.3 MPa; solvent: toluene; catalyst: complex 4.

Fig.4 Influence of catalyst concentrstion on polymerization activity and molecular weight Polymerization conditions: n(Al)/n(Zr)=2000, 0.5 h, 60 ℃, 0.4 MPa, V(toluene)=100 mL.

Fig.5 Influence of polymerization temperature on polymerization activity and molecular weight Polymerization conditions: 1×10-5 mol Zr/L, n(Al)/n(Zr)=2000, 0.5 h, 0.4 MPa, V(toluene)=100 mL.

Fig.6 Influence of polymerization temperature on polymer syndiotactic degree Polymerization conditions: 1×10-5 mol Zr/L, n(Al)/n(Zr)=2000, 0.5 h, 0.4 MPa, V(toluene)=100 mL.

Fig.7 Influence of n(MAO)/n(Zr) on polymerization activity and polymer molecular weight Polymerization conditions: 1×10-5 mol Zr/L, 60 ℃, 0.5 h, 0.4 MPa, V(toluene)=100 mL.

Fig.8 Influence of n(MAO)/n(Zr) on polymer syndiotactic degree Polymerization conditions: 1×10-5 mol Zr/L, 60 ℃, 0.5 h, 0.4 MPa, V(toluene)=100 mL.

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