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Synthesis, characterization and catalytic activity of some organolanthanides in ethylene polymerization
Inorganic Chemistry Communications 4 (2001) 582±584
www.elsevier.com/locate/inoche
Synthesis, characterization and catalytic activity of some organolanthanides in ethylene polymerization Vitor Lavini a, Alessandra de Souza Maia a, Icaro Sampaio Paulino b, Ulf Schuchardt b, Wanda de Oliveira a,* a
b
Instituto de Quõmica, Universidade de S~ ao Paulo, CP 26077, 05599-970, S~ ao Paulo, SP, Brazil Instituto de Quõmica, Universidade Estadual de, Campinas, CP 6154, 13083-970, Campinas, SP, Brazil Received 8 April 2001; received in revised form 12 July 2001; accepted 18 July 2001
Abstract The synthesis and characterization of a new class of organolanthanide compounds containing the bromide and cyclopentadienyl anions together with a pyrazinamide ligand are presented. The compounds were characterized by elemental analyses, complexometric titration with EDTA, thermal analyses, vibrational spectra in the infrared region. The catalytic activity of these compounds in ethylene polymerization was examined. Ó 2001 Elsevier Science B.V. All rights reserved. Keywords: Organolanthanides; Pyrazinamide; Cyclopentadienyl; Polymerization
1. Introduction It is well known that ole®ns such as ethylene, propylene and 1-butene can be polymerized in the presence of certain metallic catalysts, particularly by transition metal- and lanthanide organometallic compounds. The ®rst reports on the application of organolanthanide compounds in ethylene polymerization appeared in 1978. Ballard et al. [1] at ICI reported moderate catalytic activities at 100 °C (82 g mmol 1 h 1 bar 1 ) using an alkyl metallocene complex of erbium. In the last few years a variety of bis(substituted cyclopentadienyl) alkyl and hydride complexes of lanthanide metals have been shown to be active for ethylene polymerization [2]. In an attempt to contribute to the application of organolanthanides as catalysts for ole®n polymerization, we report the synthesis and catalytic activity of the organolanthanide complexes cyclopentadienyllanthanidedibromidemonopyrazin [LnCpBr2 PzA], Ln La, Nd and Sm. Elemental analysis, thermal analyses, and infrared spectra characterized these compounds. The
*
Corresponding author. Tel.: +55-11-3818-3847. E-mail address: [email protected] (W. de Oliveira).
catalytic activity of such compounds was veri®ed for ethylene polymerization. 2. Experimental details All manipulations were performed under prepuri®ed argon. Solvents were dried by standard techniques and thoroughly deoxygenated before use. Microanalysis (%C, %H, %N) was performed on a Perkin±Elmer CHN 2400. %Ln was determined by complexometric titration with EDTA (%Ln) [3]. Thermal analyses were recorded on a Shimadzu Thermogravimetric Analyzer-TGA-50, with an applied heating rate of 20 °C/min in air (¯ow rate: 50.0 ml/ min) using 2±5 mg samples in a platinum pan. Infrared spectra were recorded on an FTIR-BOMEM model MB-102, from 4000 to 200 cm 1 using Nujol or Fluorolube mulls between cesium iodide windows. Dierential scanning calorimetry (DSC) measurements were performed on a DSC 2910 TA Instrument. The samples were heated from 150 to 200 °C at a heating rate of 10 °C/min. The melting temperature values (Tm ) and the heat of fusion (DHf ) were taken from the second heating curve. The degree of crystallinity was calculated from DHf using the equation kDCS DHf 100=288.
1387-7003/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII: S 1 3 8 7 - 7 0 0 3 ( 0 1 ) 0 0 2 8 2 - 9
V. Lavini et al. / Inorganic Chemistry Communications 4 (2001) 582±584
583
Table 1 Results of the thermal analyses studies of the compounds [LnBr2 CpPzA] Ln
Weight lost (%)
M initial (mg)
M residue (mg)
Residue
MM exp. (g/mol)
MM calcd. (g/mol)
La Nd Sm
50.59 51.72 50.83
3.130 4.871 1.256
1.547 2.352 0.617
LaOBr NdOBr SmOBr
487 492 498
503 498 501
2.1. Synthesis and characterization of compounds 2.1.1. [LnBr3 PzA3 ] A solution of pyrazinamide (4 mmol) in tetrahydrofuran (THF) was added to a solution of hydrated lanthanide bromide (1 mmol) in ethanol (as described in the literature [4]). The resulting solution was stirred for 24 h at room temperature and evaporated until dryness. The compounds were dried under vacuum for 6 h at 60 °C to give the anhydrous compounds LnBr3 PzA3 , Ln La, Nd, Sm and Er. Yield 75%. Calc. Anal. for: LaBr3 PzA3 : C, 24.08; H, 2.02; N, 16.85; La, 18.57. Found: C, 24.12; H, 2.10; N, 16.78; La, 18.67; For: NdBr3 PzA3 : C, 23.91; H, 2.00; N, 16.73; Nd, 19.14. Found: C, 23.42; H, 2.08; N, 16.26; Nd, 19.60; For SmBr3 PzA3 : C, 23.72; H, 1.99; N, 16.59; Sm, 19.80. Found: C, 23.27; H, 2.04; N, 16.48; Sm, 19.20. 2.1.2. [LnCpBr2 PzA] These compounds were prepared by the reaction between NaCp (3 mmol) in THF and LnBr3 PzA3 (1 mmol). This mixture was stirred for 24 h. THF was removed under vacuum and the compound was washed by ethanol. The remaining solid was dried under vacuum. Yield 40±50%. Calc. Anal.: [LaCpBr2 PzA]: C, 24.66; H, 2.07; N, 8.63; La, 28.52. Found: C, 24.03; H, 2.18; N, 8.55; La, 28.50; For: [NdCpBr2 PzA]: C, 24.34; H, 2.05; N, 8.54; Nd, 29.30. Found: C, 24.64; H, 2.25; N, 8.27; Nd, 29.19; For [SmCp2 BrPzA]: C, 24.09; H, 2.02; N,
8.43; Sm, 30.17. Found: C, 24.05; H, 2.26; N, 8.31; Sm, 30.18. 2.2. Catalytic polymerization of ethylene The polymerization was carried out in a B uchi autoclave at 70 °C and 3 bar of ethylene using 3.5±4.5 mg of organolanthanide compound and 3.0 ml of MAO (10% in toluene) in 50 ml of toluene.
3. Results and discussion Cyclopentadienyl sodium salt (NaCp) reacts with LnBr3 PzA3 in THF at room temperature to aord the compounds [LnCpBr2 PzA], Ln La, Nd and Sm. These compounds are practically insoluble in acetone, acetonitrile, benzene, chloroform, ethanol, methanol, nitromethane and THF. The compound [LnCpBr2 PzA], Ln La, Nd, Sm showed similar decomposition characteristics in the thermal analyses measurements, losing weight gradually with increasing temperature from ca. 30 to 850 °C . At this temperature LnOBr (Ln La, Nd, Sm) is formed (Table 1). Infrared spectra of the compounds [LnCpBr2 PzA], Ln La, Nd, Sm (Table 2) show shifts of the m(C@O) for free pyrazinamide of 1680 cm 1 to 1611±1614 cm 1 in organolanthanide compounds, indicating coordina-
Table 2 Infrared frequencies (cm 1 ) of organolanthanide compounds
a
LaCpBr2 PzA2 a
NdCpBr2 PzA2 a
SmCpBr2 PzA2 a
Assignment
3405 w 3271 w 3175 w±m 1612 s 1573 m 1519 w±m 1303 w 1160 w±m 1050 m 966 w 793 w±m 724 m 612 s 455 m 427 w
3400 w 3258 w 3169 w±m 1611 s 1575 m 1523 w±m 1305 w 1165 w±m 1052 m 969 w 794 w±m 722 m±s 619 s 452 w±m 429 w
3401w 3226 w 3169 w±m 1613 s 1574 m 1522 w±m 1305 w 1159 w±m 1052 m 970 w 795 w±m 724 m±s 613 s 457 w±m 428 w
mas (NH) (PzA) ms (NH) (PzA) mas (CH) (Cp) m (C@O) (PzA) Ring vibration (PzA) Ring vibration (PzA) m C@C (Cp) d CH3 (Cp) cs (C±H) (Cp) d (CH) (Cp) qr (CH) (Cp) mas (CH) (Cp) c (C±H) (Cp) Ring vibration (PzA) m (NC) (PzA) Ring vibration (PzA)
v, very; s, strong; m, medium; w, weak; sh, shoulder.
584
V. Lavini et al. / Inorganic Chemistry Communications 4 (2001) 582±584
tion of the pyrazinamide to the lanthanide ion via oxygen of the carbonyl group [5±7]. The assignments of cyclopentadienyl vibrational modes indicated a r-centered coordination to the lanthanide(III) ions under C5V local symmetry with ionic character [8]. The compounds [LnCpBr2 PzA], Ln La, Nd, Sm possess catalytic activities, respectively, of 1.1, 4.3 and 4:6 kg PE mol Ln 1 bar 1 h 1 at 70 °C with Al/Ln ratios of ca. 1000. These activities are in the range of those observed by Bazan et al. [9] for Cp g5 -C4 H4 B±N CHMe2 2 TaCl2 (2.0 g PE mmol 1 Ta 1 h 1 bar 1 ) and by Ballard et al. [1] for Y g-C5 H4 SiMe3 2 Me2 (5.1 g PE mmol 1 Y 1 h 1 bar 1 , 70 °C). Infrared spectra of the polyethylene product showed bands at 1461, 1360 and 1337 cm 1 , which are assigned to deformation modes of the methylene groups; and bands at 730 and 719 cm 1 , which are assigned to rocking modes of the methylene groups. The polyethylene absorption band at 730 cm 1 is ascribed to crystalline product and the 721 cm 1 band indicates the presence of both crystalline and amorphous [10] polyethylene. These infrared data are supported by melting points of 135±136 °C for the obtained polyethylene by DSC measurements, which showed 18±40% crystalline product. 4. Conclusions We conclude that the organometallic compounds [LnCpBr2 PzA], Ln La, Nd, Sm have been prepared in
good yields by the reaction of cyclopentadienylsodium with [LnBr3 PzA3 ] in the appropriate molar ratio. These organolanthanide compounds show catalytic activity for ethylene polymerization at 70 °C; and the polyethylene product is obtained with low crystallinity.
Acknowledgements We thank CNPq (Conselho Nacional de Pesquisa) and FAPESP (Fundacß~ao de Amparo a Pesquisa do Estado de S~ao Paulo) for ®nancial support.
References [1] D.G.H. Ballard, A. Courtis, J. Holton, J. McMeeking, R. Pearce, J. Chem. Soc. Chem. Commun. (1978) 994. [2] D.P. Long, P.A. Bianconi, J. Am. Chem. Soc. 118 (1996) 12 453, and references within. [3] S.J. Lyle, Md.M. Rahman, Talanta (1963) 257. [4] S. Brown, S. Fletcher, D.G. Holah, J. Chem. Soc. (A) (1968) 1889. [5] P.P. Singh, J.N. Seth, J. Inorg. Nucl. Chem 37 (1975) 593. [6] G. de Sa, M.A.V. de Almeida, J. Coord. Chem. 10 (1980) 35. [7] J.R. Allan, A.D. Paton, K. Turvey, H.J. Bowley, D.L. Gerrard, J. Coord. Chem. 17 (1988) 255. [8] H.P. Fritz, Adv. Organomet. Chem. 1 (1964) 239. [9] G.C. Bazan, S.J. Donnely, G. Rodriguez, J. Am. Chem. Soc. 117 (1995) 2671. [10] S.L. Aggarwal, O.J. Sweeting, Chem. Rev. 57 (1957) 665.
www.elsevier.com/locate/inoche
Synthesis, characterization and catalytic activity of some organolanthanides in ethylene polymerization Vitor Lavini a, Alessandra de Souza Maia a, Icaro Sampaio Paulino b, Ulf Schuchardt b, Wanda de Oliveira a,* a
b
Instituto de Quõmica, Universidade de S~ ao Paulo, CP 26077, 05599-970, S~ ao Paulo, SP, Brazil Instituto de Quõmica, Universidade Estadual de, Campinas, CP 6154, 13083-970, Campinas, SP, Brazil Received 8 April 2001; received in revised form 12 July 2001; accepted 18 July 2001
Abstract The synthesis and characterization of a new class of organolanthanide compounds containing the bromide and cyclopentadienyl anions together with a pyrazinamide ligand are presented. The compounds were characterized by elemental analyses, complexometric titration with EDTA, thermal analyses, vibrational spectra in the infrared region. The catalytic activity of these compounds in ethylene polymerization was examined. Ó 2001 Elsevier Science B.V. All rights reserved. Keywords: Organolanthanides; Pyrazinamide; Cyclopentadienyl; Polymerization
1. Introduction It is well known that ole®ns such as ethylene, propylene and 1-butene can be polymerized in the presence of certain metallic catalysts, particularly by transition metal- and lanthanide organometallic compounds. The ®rst reports on the application of organolanthanide compounds in ethylene polymerization appeared in 1978. Ballard et al. [1] at ICI reported moderate catalytic activities at 100 °C (82 g mmol 1 h 1 bar 1 ) using an alkyl metallocene complex of erbium. In the last few years a variety of bis(substituted cyclopentadienyl) alkyl and hydride complexes of lanthanide metals have been shown to be active for ethylene polymerization [2]. In an attempt to contribute to the application of organolanthanides as catalysts for ole®n polymerization, we report the synthesis and catalytic activity of the organolanthanide complexes cyclopentadienyllanthanidedibromidemonopyrazin [LnCpBr2 PzA], Ln La, Nd and Sm. Elemental analysis, thermal analyses, and infrared spectra characterized these compounds. The
*
Corresponding author. Tel.: +55-11-3818-3847. E-mail address: [email protected] (W. de Oliveira).
catalytic activity of such compounds was veri®ed for ethylene polymerization. 2. Experimental details All manipulations were performed under prepuri®ed argon. Solvents were dried by standard techniques and thoroughly deoxygenated before use. Microanalysis (%C, %H, %N) was performed on a Perkin±Elmer CHN 2400. %Ln was determined by complexometric titration with EDTA (%Ln) [3]. Thermal analyses were recorded on a Shimadzu Thermogravimetric Analyzer-TGA-50, with an applied heating rate of 20 °C/min in air (¯ow rate: 50.0 ml/ min) using 2±5 mg samples in a platinum pan. Infrared spectra were recorded on an FTIR-BOMEM model MB-102, from 4000 to 200 cm 1 using Nujol or Fluorolube mulls between cesium iodide windows. Dierential scanning calorimetry (DSC) measurements were performed on a DSC 2910 TA Instrument. The samples were heated from 150 to 200 °C at a heating rate of 10 °C/min. The melting temperature values (Tm ) and the heat of fusion (DHf ) were taken from the second heating curve. The degree of crystallinity was calculated from DHf using the equation kDCS DHf 100=288.
1387-7003/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII: S 1 3 8 7 - 7 0 0 3 ( 0 1 ) 0 0 2 8 2 - 9
V. Lavini et al. / Inorganic Chemistry Communications 4 (2001) 582±584
583
Table 1 Results of the thermal analyses studies of the compounds [LnBr2 CpPzA] Ln
Weight lost (%)
M initial (mg)
M residue (mg)
Residue
MM exp. (g/mol)
MM calcd. (g/mol)
La Nd Sm
50.59 51.72 50.83
3.130 4.871 1.256
1.547 2.352 0.617
LaOBr NdOBr SmOBr
487 492 498
503 498 501
2.1. Synthesis and characterization of compounds 2.1.1. [LnBr3 PzA3 ] A solution of pyrazinamide (4 mmol) in tetrahydrofuran (THF) was added to a solution of hydrated lanthanide bromide (1 mmol) in ethanol (as described in the literature [4]). The resulting solution was stirred for 24 h at room temperature and evaporated until dryness. The compounds were dried under vacuum for 6 h at 60 °C to give the anhydrous compounds LnBr3 PzA3 , Ln La, Nd, Sm and Er. Yield 75%. Calc. Anal. for: LaBr3 PzA3 : C, 24.08; H, 2.02; N, 16.85; La, 18.57. Found: C, 24.12; H, 2.10; N, 16.78; La, 18.67; For: NdBr3 PzA3 : C, 23.91; H, 2.00; N, 16.73; Nd, 19.14. Found: C, 23.42; H, 2.08; N, 16.26; Nd, 19.60; For SmBr3 PzA3 : C, 23.72; H, 1.99; N, 16.59; Sm, 19.80. Found: C, 23.27; H, 2.04; N, 16.48; Sm, 19.20. 2.1.2. [LnCpBr2 PzA] These compounds were prepared by the reaction between NaCp (3 mmol) in THF and LnBr3 PzA3 (1 mmol). This mixture was stirred for 24 h. THF was removed under vacuum and the compound was washed by ethanol. The remaining solid was dried under vacuum. Yield 40±50%. Calc. Anal.: [LaCpBr2 PzA]: C, 24.66; H, 2.07; N, 8.63; La, 28.52. Found: C, 24.03; H, 2.18; N, 8.55; La, 28.50; For: [NdCpBr2 PzA]: C, 24.34; H, 2.05; N, 8.54; Nd, 29.30. Found: C, 24.64; H, 2.25; N, 8.27; Nd, 29.19; For [SmCp2 BrPzA]: C, 24.09; H, 2.02; N,
8.43; Sm, 30.17. Found: C, 24.05; H, 2.26; N, 8.31; Sm, 30.18. 2.2. Catalytic polymerization of ethylene The polymerization was carried out in a B uchi autoclave at 70 °C and 3 bar of ethylene using 3.5±4.5 mg of organolanthanide compound and 3.0 ml of MAO (10% in toluene) in 50 ml of toluene.
3. Results and discussion Cyclopentadienyl sodium salt (NaCp) reacts with LnBr3 PzA3 in THF at room temperature to aord the compounds [LnCpBr2 PzA], Ln La, Nd and Sm. These compounds are practically insoluble in acetone, acetonitrile, benzene, chloroform, ethanol, methanol, nitromethane and THF. The compound [LnCpBr2 PzA], Ln La, Nd, Sm showed similar decomposition characteristics in the thermal analyses measurements, losing weight gradually with increasing temperature from ca. 30 to 850 °C . At this temperature LnOBr (Ln La, Nd, Sm) is formed (Table 1). Infrared spectra of the compounds [LnCpBr2 PzA], Ln La, Nd, Sm (Table 2) show shifts of the m(C@O) for free pyrazinamide of 1680 cm 1 to 1611±1614 cm 1 in organolanthanide compounds, indicating coordina-
Table 2 Infrared frequencies (cm 1 ) of organolanthanide compounds
a
LaCpBr2 PzA2 a
NdCpBr2 PzA2 a
SmCpBr2 PzA2 a
Assignment
3405 w 3271 w 3175 w±m 1612 s 1573 m 1519 w±m 1303 w 1160 w±m 1050 m 966 w 793 w±m 724 m 612 s 455 m 427 w
3400 w 3258 w 3169 w±m 1611 s 1575 m 1523 w±m 1305 w 1165 w±m 1052 m 969 w 794 w±m 722 m±s 619 s 452 w±m 429 w
3401w 3226 w 3169 w±m 1613 s 1574 m 1522 w±m 1305 w 1159 w±m 1052 m 970 w 795 w±m 724 m±s 613 s 457 w±m 428 w
mas (NH) (PzA) ms (NH) (PzA) mas (CH) (Cp) m (C@O) (PzA) Ring vibration (PzA) Ring vibration (PzA) m C@C (Cp) d CH3 (Cp) cs (C±H) (Cp) d (CH) (Cp) qr (CH) (Cp) mas (CH) (Cp) c (C±H) (Cp) Ring vibration (PzA) m (NC) (PzA) Ring vibration (PzA)
v, very; s, strong; m, medium; w, weak; sh, shoulder.
584
V. Lavini et al. / Inorganic Chemistry Communications 4 (2001) 582±584
tion of the pyrazinamide to the lanthanide ion via oxygen of the carbonyl group [5±7]. The assignments of cyclopentadienyl vibrational modes indicated a r-centered coordination to the lanthanide(III) ions under C5V local symmetry with ionic character [8]. The compounds [LnCpBr2 PzA], Ln La, Nd, Sm possess catalytic activities, respectively, of 1.1, 4.3 and 4:6 kg PE mol Ln 1 bar 1 h 1 at 70 °C with Al/Ln ratios of ca. 1000. These activities are in the range of those observed by Bazan et al. [9] for Cp g5 -C4 H4 B±N CHMe2 2 TaCl2 (2.0 g PE mmol 1 Ta 1 h 1 bar 1 ) and by Ballard et al. [1] for Y g-C5 H4 SiMe3 2 Me2 (5.1 g PE mmol 1 Y 1 h 1 bar 1 , 70 °C). Infrared spectra of the polyethylene product showed bands at 1461, 1360 and 1337 cm 1 , which are assigned to deformation modes of the methylene groups; and bands at 730 and 719 cm 1 , which are assigned to rocking modes of the methylene groups. The polyethylene absorption band at 730 cm 1 is ascribed to crystalline product and the 721 cm 1 band indicates the presence of both crystalline and amorphous [10] polyethylene. These infrared data are supported by melting points of 135±136 °C for the obtained polyethylene by DSC measurements, which showed 18±40% crystalline product. 4. Conclusions We conclude that the organometallic compounds [LnCpBr2 PzA], Ln La, Nd, Sm have been prepared in
good yields by the reaction of cyclopentadienylsodium with [LnBr3 PzA3 ] in the appropriate molar ratio. These organolanthanide compounds show catalytic activity for ethylene polymerization at 70 °C; and the polyethylene product is obtained with low crystallinity.
Acknowledgements We thank CNPq (Conselho Nacional de Pesquisa) and FAPESP (Fundacß~ao de Amparo a Pesquisa do Estado de S~ao Paulo) for ®nancial support.
References [1] D.G.H. Ballard, A. Courtis, J. Holton, J. McMeeking, R. Pearce, J. Chem. Soc. Chem. Commun. (1978) 994. [2] D.P. Long, P.A. Bianconi, J. Am. Chem. Soc. 118 (1996) 12 453, and references within. [3] S.J. Lyle, Md.M. Rahman, Talanta (1963) 257. [4] S. Brown, S. Fletcher, D.G. Holah, J. Chem. Soc. (A) (1968) 1889. [5] P.P. Singh, J.N. Seth, J. Inorg. Nucl. Chem 37 (1975) 593. [6] G. de Sa, M.A.V. de Almeida, J. Coord. Chem. 10 (1980) 35. [7] J.R. Allan, A.D. Paton, K. Turvey, H.J. Bowley, D.L. Gerrard, J. Coord. Chem. 17 (1988) 255. [8] H.P. Fritz, Adv. Organomet. Chem. 1 (1964) 239. [9] G.C. Bazan, S.J. Donnely, G. Rodriguez, J. Am. Chem. Soc. 117 (1995) 2671. [10] S.L. Aggarwal, O.J. Sweeting, Chem. Rev. 57 (1957) 665.