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Synthesis, structural characterization and catalytic properties of a N-functionalized organoamide zirconium complex
Inorganic Chemistry Communications 65 (2016) 32–34
Contents lists available at ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
Short Communication
Synthesis, structural characterization and catalytic properties of a N-functionalized organoamide zirconium complex Lei Yan, Xiaoyang Wang, Meisu Zhou ⁎ Institute of Applied Chemistry, Shanxi University, Taiyuan 030006, People's Republic of China
a r t i c l e
i n f o
Article history: Received 10 December 2015 Received in revised form 4 January 2016 Accepted 20 January 2016 Available online 23 January 2016 Keywords: Zirconium Aminopyridine Structure Polymerization of ethylene
a b s t r a c t Treatment of anhydrous ZrCl4 with 3 equiv of lithium 2-(trimethylsilyl) amino-pyridine (TMS-Apy) afforded [(TMS-Apy)3ZrCl] (1) in high yield. The structure of 1 was characterized by spectroscopic and X-ray crystallographic method. The X-ray analysis revealed that 1 was a mononuclear zirconium complex with sevencoordinate metal center and the η2-coordinated aminopyridinato ligands arranged in a propeller-like fashion. Complex 1 activated with methylaluminoxane (MAO) showed good activity towards ethylene polymerization. © 2016 Elsevier B.V. All rights reserved.
Nitrogen-based ligands have attracted much interest as alternatives to cyclopentadienyl ligands in organometallic chemistry and catalysis chemistry [1,2]. Early transition metal complexes bearing such ligands have shown catalytic activity in olefin polymerization especially tripod ligand systems gained a lot of attention due to the formation of a reactive pocket [3,4]. Of which, the group 4 amidinate and guanidinate complexes have been shown to be promising catalysts for the polymerization of ethylene [5,6]. The chiral group 4 benzamidinate complex of C3 symmetry was found to be active for the highly stereospecific polymerization of propylene [7]. The related group 4 complex with aliphatic benzamidinato ligand was also used in the polymerization of olefins [8]. Very recently, a novel organoamido zirconium (IV) compound bearing 1, 3, 5-triazapentadienyl ligand was developed in our group and showed moderate activity in the polymerization of ethylene [9]. Although the synthesis and catalytic applications of titanium and some of the zirconium and hafnium aminopyridinato complexes in the polymerization of olefins were involved [10–17], to the best of knowledge, among the very rare examples of mononuclear tris(aminopyridinato) group 4 metal complexes [4,18,19], none of the catalytic applications was involved. Herein is reported the synthesis, characterization and catalytic behaviors towards ethylene polymerization of a novel
⁎ Corresponding author. E-mail address: [email protected] (M. Zhou).
http://dx.doi.org/10.1016/j.inoche.2016.01.010 1387-7003/© 2016 Elsevier B.V. All rights reserved.
tris(aminopyridinato) zirconium (IV) complex 1 (Eq. (1)).
ð1Þ Compound 1 was easily prepared in moderate yield according to Eq. (1). Thus, treatment of ZrCl4 with three equivalents of the lithium reagent resulted in the isolation of the 3:1 orange complex [(TMSApy)3ZrCl] (1) [20]. Complex 1 has been characterized by 1H and 3C NMR, elemental analysis. Suitable crystals for X-ray diffraction analysis [21] of 1 can be obtained by slowly cooling a saturated dichloromethane solution to −20 °C for 20 days. Compound 1 crystallizes in the trigonal space group P3. There are three chemically similar, crystallographically independent molecules in the crystal lattice and the bond distances and angles have no significant differences. The coordination environment about the sevencoordinate zirconium atom is described best as a mono-capped octahedral structure with three bidentate TMS-Apy ligands and a terminal chloride ligand, where the atoms N1, N2, N1A and N2B occupy the central plane (with a mean deviation of 0.16 Å), and atoms N1B and Cl occupy the axis position and atom N2A occupies the capping site (Fig. 1).
L. Yan et al. / Inorganic Chemistry Communications 65 (2016) 32–34
33
Table 3 Ethylene polymerization activity for 1 and its analogues I and II. Catalyst
1
I
II
Activitya
1.47 × 105
8.6b
1.05 × 104c
a b c
Fig. 1. Molecular structure of [(TMS-Apy)3ZrCl] (1). Thermal ellipsoids are plotted at 30% probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (deg): Zr(1)–N(1) 2.314(2), Zr(1)–N(2) 2.178(2), Zr(1)–Cl(1) 2.478(1); N(1)– Zr(1)–N(2) 59.51(9), N(1)–C(5)–N(2) 110.8(2), Zr(1)–N(1)–C(5) 90.91(18), Zr(1)– N(2)–C(5) 97.06(18).
The bond length of Zr − Cl is from 2.478(1) to 2.484(1) Å. The bond lengths of Zr − Namide are in the range of 2.178(2)–2.188(2) Å, shorter than those of similar organoamido amidinate or guanidinate zirconium(IV) complexes such as [N(SiMe3)C(C6H4Me-4)NPh]3ZrCl (I) [6] or [PhNC(NMe2)NSiMe3]3ZrCl (II) [5]. The bond lengths of Zr−Npy in 1 are in the range of 2.301(2)–2.314(2) Å. The atoms N1, C5, N2 and Zr1 are coplanar (mean deviation 0.063 Å) and the dihedral angles between the NCNZr planes are 91.8, 88.2 and 88.2°, respectively. In the backbone of NCNM, the mean bond angle of N–M–N is 59.51°, larger than those in I [59.03°] and II [59.22°]. The mean Namide–C–Npyridyl angle of 110.6°, narrower than 113.1 and 113.0° of I and II, much narrower than the desired 120°, indicates the Table 1 Comparison of selected bond lengths (Å) and angles (°) for 1 and its seven-coordinate analogues. Parameters
1
I
II
Zr–Cl Zr–Namide N–Zr–N N–C–N βb
2.480 2.182 59.51 110.6a 89.4
2.462 2.260 59.03 113.1 –
2.515 2.253 59.22 113.0 90.4
a b
Angle of Namide–C–Npyridyl. Angle between the NZrN planes.
Entry
P/atm
T/°C
Al/Zr
Yield(mg)
Activityb
1 2 3 4 5 6
10 10 10 10 10 10
30 30 30 30 50 70
1000 1500 2000 2500 2000 2000
63.1 133 190 38.8 367 195
2.52 × 104 5.34 × 104 7.61 × 104 1.55 × 104 1.47 × 105 7.81 × 104
b
highly strained tweezers-like bonding mode [19]. A comparison of 1 with its analogues I and II is presented in Table 1. Compound 1 was investigated for its catalytic behavior of ethylene polymerization [22] activated with cocatalyst methylaluminoxane (MAO), which has been known to play roles in initiating the polymerization reactions by creating an empty site on the catalyst for the insertion of an ethylene monomer. The optimum conditions were shown in Table 2. The amount of MAO used in ethylene polymerization reaction was critical for the catalyst to exhibit high activity. At the temperature of 30 °C, with the increase of the molar ratios of Al to Zr from 1000 to 2500 (Entries 1–4), the optimum Al/Zr ratio was 2000, and the catalytic performance was 7.61 × 104 g PE/mol Zr h. Further increase of the Al/Zr ratio impaired the activity of the catalyst (Entry 4). The explanation for this observation is that, with the proper ratio of MAO to the zirconium complex, the formation and stabilization of the active species are achieved. With reaction temperatures in the range 30–70 °C at 10 atm of ethylene pressure with an Al/Zr molar ratio of 2000, the catalytic activity showed a maximum value of 1.47 × 105 g PE/mol Zr h at 50 °C (Entry 5 in Table 2). Proper increase of reaction temperature will accelerate the formation of the active species. The activity of complex 1 is higher than its amidinate and guanidinate analogues I and II (Table 3), but comparable to those of zirconium complexes with N-alkyl aminopyridinato ligands [14] or very bulky aminopyridinato ligands [17]. This behavior is thought to be due to their structural differences. The highly Lewis acidicity of the metal center fulfilled by the strong basicity of amide and pyridine ligands and the chelating strained η2-coordiantion of the aminopyridinato ligands made complex 1 more active. In conclusion, a N-functionalized organoamide zirconium complex [(TMS-Apy)3ZrCl] (1) was readily prepared via the reaction of lithium 2-(trimethylsilyl)amino-pyridine with zirconium tetrachloride. Complex 1 is mononuclear with seven-coordinate metal center and the η2strained-coordinated aminopyridinato ligands arrange in a propellerlike fashion. Complex 1 is active for ethylene polymerization with the activity of 1.47 × 105 g PE/mol Zr h. Acknowledgments We thank the Natural Science Foundation of China (No. 21371111), Shanxi Scholarship Council of China (No. 2013-025) and Shanxi Functional Organometallic Compound Information Net Project (No. 2013091022) for financial support. Appendix A. Supplementary material
Table 2 Data for ethylene polymerization catalyzed by complex 1/cocatalyst systema.
a
Complex/MAO system. kgPE/mol Zr h bar, Al/Zr = 500:1, 1 h [6]. gPE/mol Zr h, Al/Zr = 1000:1, 0.5 h, 10 atm [5].
Polymerization conditions: 5 μmol of Zr, Cocatalyst: MAO, 100 ml toluene, 0.5 h. g mol−1 h−1.
CCDC 1439583 contains the supplementary crystallographic data for 1. These data can be obtained free of charge via http://www.ccdc.cam. ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Center, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+ 44) 1223-336-033; or e-mail: [email protected]. Supplementary data associated with this article can be found in the online version, at http://dx.doi.org/10.1016/j.inoche.2016.01.010. References [1] F.T. Edelmann, Angew. Chem. Int. Ed. 34 (1995) 2466–2488. [2] M.S. Eisen, H. Mack, J. Organomet. Chem. 525 (1996) 81–87.
34 [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20]
L. Yan et al. / Inorganic Chemistry Communications 65 (2016) 32–34 T.L. Brown, K.J. Lee, Coord. Chem. Rev. 128 (1993) 89–116. R. Kempe, S. Brenner, P. Arndt, Organometallics 15 (1996) 1071–1074. M.S. Zhou, H.B. Tong, X.H. Wei, D.S. Liu, J. Organomet. Chem. 692 (2007) 5195–5202. P.B. Hitchcock, M.F. Lappert, P.G. Merle, Dalton Trans. (2007) 585–594. C. Averbuj, E. Tish, M.S. Eisen, J. Am. Chem. Soc. 120 (1998) 8640–8646. M. Fan, Q.K. Yang, H.B. Tong, S.F. Yuan, B. Jia, D.L. Guo, M.S. Zhou, D.S. Liu, RSC Adv. 2 (2012) 6599–6605. M.S. Zhou, Q.K. Yang, H.B. Tong, L. Yan, X.Y. Wang, RSC Adv. 5 (2015) 105292–105298. W.P. Kretschmer, B. Hessen, A. Noor, N.M. Scott, R. Kempe, J. Organomet. Chem. 692 (2007) 4569–4579. M. Talja, M. Klinga, M. Polamo, E. Aitola, M. Leskelä, Inorg. Chim. Acta 358 (2005) 1061–1067. M. Talja, T. Luhtanen, M. Polamo, M. Klinga, T.A. Pakkanen, M. Leskelä, Inorg. Chim. Acta 361 (2008) 2195–2202. M. Talja, M. Polamo, M. Leskelä, J. Mol. Catal. A Chem. 280 (2008) 102–105. C. Morton, P. O'Shaughnessy, P. Scott, Chem. Commun. (2000) 2099–2100. A. Noor, W.P. Kretschmer, G. Glatz, R. Kempe, Inorg. Chem. 50 (2011) 4598–4606. E. Smolensky, M. Kapon, J.D. Woollins, M.S. Eisen, Organometallics 24 (2005) 3255–3265. A. Noor, W.P. Kretschmer, G. Glatz, A. Meetsma, R. Kempe, Eur. J. Inorg. Chem. (2008) 5088–5098. C. Jones, P.C. Junk, S.G. Leary, N.A. Smithies, Inorg. Chem. Commun. 6 (2003) 1126–1128. R. Kempe, P. Arndt, Inorg. Chem. 35 (1996) 2644–2649. Preparation of 1: n-Butyllithium (1.10 mL, 2.42 mmol) was added to a solution of 2(trimethylsilylamido) pyridine (0.40 g, 2.42 mmol) in Et2O (30 mL) at 0 °C. The resulting mixture was warmed to ca. 20 °C and stirred overnight. ZrCl4 (0.19 g, 0.81 mmol) was added at −78 °C.The resulting mixture was warmed to ca. 20 °C
and stirred overnight. The volatiles were removed in vacuo and the residue was extracted with dichloromethane. Filtered and the filtrate was concentrated in vacuo to 10 mL and stored at −20 °C for 20 days, afforded orange block crystals of 1 (0.33 g, 65%). Mp 123–127 °C. Anal. calcd. for C24H39ClN6Si3Zr (%): C, 46.30; H, 6.31; N, 13.50. Found: C, 46.58; H, 6.01; N, 13.52. 1H NMR (C6D6): δ 0.43 (s, 9 H, SiMe3), 5.97–6.09 (m, 3 H, H-4), 6.28–6.41 (m, 3 H, H-5), 6.99–7.10 (m, 2 H, H-3), 8.23 (s, 3 H, H-6). 3C NMR (C6D6): δ − 0.08 (SiMe3), 109.8 (C-5), 112.9 (C-3), 136.8 (C-4), 148.3 (C-6), 165.9 (C-2). [21] Crystal data for 1: C24H39ClN6Si3Zr, M = 622.55, Trigonal, space group P3, T = 200 K, a = 18.7788(7) Å, b = 18.7788(7) Å, c = 7.8210(3) Å, V = 2388.5(2) Å3, Z = 3, Fooo = 972, GOF = 1.074, ρcalcd. = 1.298 g cm − 3, crystal size = 0.30 × 0.25 × 0.25 mm. Data were collected on a Bruker SMART APEX diffractometer/CCD area detector, using mono-chromated Mo-Kα radiation, λ = 0.71073 Å at 200 K. A total of 52987 reflections were collected, of which 7916 unique reflections (6492 with I N 2σ(I)) were for structure elucidation. The final R1 was 0.0350 for I N 2σ(I) and 0.0572 for all reflections. Absorption correction was performed using the multi-scan method. The structures were solved by direct methods and refined by full-matrix least squares on F2 using the SHELXTL-97 program package. [22] General procedure for polymerization of ethylene. Ethylene polymerization was carried out in a 500 mL autoclave stainless steel reactor equipped with a mechanical stirrer and a temperature controller. Briefly, toluene, the desired amount of cocatalyst, and a toluene solution of the catalytic precursor (the total volume was 100 mL) were added to the reactor in this order under an ethylene atmosphere. When the desired reaction temperature was reached, ethylene at 10 atm pressure was introduced to start the reaction, and the ethylene pressure was maintained by constant feeding of ethylene. After 30 min, the reaction was stopped. The solution was quenched with HCl-acidified ethanol (5%), and the precipitated polyethylene was filtered, washed with ethanol, and dried in vacuum at 60 °C to constant weight.
Contents lists available at ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
Short Communication
Synthesis, structural characterization and catalytic properties of a N-functionalized organoamide zirconium complex Lei Yan, Xiaoyang Wang, Meisu Zhou ⁎ Institute of Applied Chemistry, Shanxi University, Taiyuan 030006, People's Republic of China
a r t i c l e
i n f o
Article history: Received 10 December 2015 Received in revised form 4 January 2016 Accepted 20 January 2016 Available online 23 January 2016 Keywords: Zirconium Aminopyridine Structure Polymerization of ethylene
a b s t r a c t Treatment of anhydrous ZrCl4 with 3 equiv of lithium 2-(trimethylsilyl) amino-pyridine (TMS-Apy) afforded [(TMS-Apy)3ZrCl] (1) in high yield. The structure of 1 was characterized by spectroscopic and X-ray crystallographic method. The X-ray analysis revealed that 1 was a mononuclear zirconium complex with sevencoordinate metal center and the η2-coordinated aminopyridinato ligands arranged in a propeller-like fashion. Complex 1 activated with methylaluminoxane (MAO) showed good activity towards ethylene polymerization. © 2016 Elsevier B.V. All rights reserved.
Nitrogen-based ligands have attracted much interest as alternatives to cyclopentadienyl ligands in organometallic chemistry and catalysis chemistry [1,2]. Early transition metal complexes bearing such ligands have shown catalytic activity in olefin polymerization especially tripod ligand systems gained a lot of attention due to the formation of a reactive pocket [3,4]. Of which, the group 4 amidinate and guanidinate complexes have been shown to be promising catalysts for the polymerization of ethylene [5,6]. The chiral group 4 benzamidinate complex of C3 symmetry was found to be active for the highly stereospecific polymerization of propylene [7]. The related group 4 complex with aliphatic benzamidinato ligand was also used in the polymerization of olefins [8]. Very recently, a novel organoamido zirconium (IV) compound bearing 1, 3, 5-triazapentadienyl ligand was developed in our group and showed moderate activity in the polymerization of ethylene [9]. Although the synthesis and catalytic applications of titanium and some of the zirconium and hafnium aminopyridinato complexes in the polymerization of olefins were involved [10–17], to the best of knowledge, among the very rare examples of mononuclear tris(aminopyridinato) group 4 metal complexes [4,18,19], none of the catalytic applications was involved. Herein is reported the synthesis, characterization and catalytic behaviors towards ethylene polymerization of a novel
⁎ Corresponding author. E-mail address: [email protected] (M. Zhou).
http://dx.doi.org/10.1016/j.inoche.2016.01.010 1387-7003/© 2016 Elsevier B.V. All rights reserved.
tris(aminopyridinato) zirconium (IV) complex 1 (Eq. (1)).
ð1Þ Compound 1 was easily prepared in moderate yield according to Eq. (1). Thus, treatment of ZrCl4 with three equivalents of the lithium reagent resulted in the isolation of the 3:1 orange complex [(TMSApy)3ZrCl] (1) [20]. Complex 1 has been characterized by 1H and 3C NMR, elemental analysis. Suitable crystals for X-ray diffraction analysis [21] of 1 can be obtained by slowly cooling a saturated dichloromethane solution to −20 °C for 20 days. Compound 1 crystallizes in the trigonal space group P3. There are three chemically similar, crystallographically independent molecules in the crystal lattice and the bond distances and angles have no significant differences. The coordination environment about the sevencoordinate zirconium atom is described best as a mono-capped octahedral structure with three bidentate TMS-Apy ligands and a terminal chloride ligand, where the atoms N1, N2, N1A and N2B occupy the central plane (with a mean deviation of 0.16 Å), and atoms N1B and Cl occupy the axis position and atom N2A occupies the capping site (Fig. 1).
L. Yan et al. / Inorganic Chemistry Communications 65 (2016) 32–34
33
Table 3 Ethylene polymerization activity for 1 and its analogues I and II. Catalyst
1
I
II
Activitya
1.47 × 105
8.6b
1.05 × 104c
a b c
Fig. 1. Molecular structure of [(TMS-Apy)3ZrCl] (1). Thermal ellipsoids are plotted at 30% probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (deg): Zr(1)–N(1) 2.314(2), Zr(1)–N(2) 2.178(2), Zr(1)–Cl(1) 2.478(1); N(1)– Zr(1)–N(2) 59.51(9), N(1)–C(5)–N(2) 110.8(2), Zr(1)–N(1)–C(5) 90.91(18), Zr(1)– N(2)–C(5) 97.06(18).
The bond length of Zr − Cl is from 2.478(1) to 2.484(1) Å. The bond lengths of Zr − Namide are in the range of 2.178(2)–2.188(2) Å, shorter than those of similar organoamido amidinate or guanidinate zirconium(IV) complexes such as [N(SiMe3)C(C6H4Me-4)NPh]3ZrCl (I) [6] or [PhNC(NMe2)NSiMe3]3ZrCl (II) [5]. The bond lengths of Zr−Npy in 1 are in the range of 2.301(2)–2.314(2) Å. The atoms N1, C5, N2 and Zr1 are coplanar (mean deviation 0.063 Å) and the dihedral angles between the NCNZr planes are 91.8, 88.2 and 88.2°, respectively. In the backbone of NCNM, the mean bond angle of N–M–N is 59.51°, larger than those in I [59.03°] and II [59.22°]. The mean Namide–C–Npyridyl angle of 110.6°, narrower than 113.1 and 113.0° of I and II, much narrower than the desired 120°, indicates the Table 1 Comparison of selected bond lengths (Å) and angles (°) for 1 and its seven-coordinate analogues. Parameters
1
I
II
Zr–Cl Zr–Namide N–Zr–N N–C–N βb
2.480 2.182 59.51 110.6a 89.4
2.462 2.260 59.03 113.1 –
2.515 2.253 59.22 113.0 90.4
a b
Angle of Namide–C–Npyridyl. Angle between the NZrN planes.
Entry
P/atm
T/°C
Al/Zr
Yield(mg)
Activityb
1 2 3 4 5 6
10 10 10 10 10 10
30 30 30 30 50 70
1000 1500 2000 2500 2000 2000
63.1 133 190 38.8 367 195
2.52 × 104 5.34 × 104 7.61 × 104 1.55 × 104 1.47 × 105 7.81 × 104
b
highly strained tweezers-like bonding mode [19]. A comparison of 1 with its analogues I and II is presented in Table 1. Compound 1 was investigated for its catalytic behavior of ethylene polymerization [22] activated with cocatalyst methylaluminoxane (MAO), which has been known to play roles in initiating the polymerization reactions by creating an empty site on the catalyst for the insertion of an ethylene monomer. The optimum conditions were shown in Table 2. The amount of MAO used in ethylene polymerization reaction was critical for the catalyst to exhibit high activity. At the temperature of 30 °C, with the increase of the molar ratios of Al to Zr from 1000 to 2500 (Entries 1–4), the optimum Al/Zr ratio was 2000, and the catalytic performance was 7.61 × 104 g PE/mol Zr h. Further increase of the Al/Zr ratio impaired the activity of the catalyst (Entry 4). The explanation for this observation is that, with the proper ratio of MAO to the zirconium complex, the formation and stabilization of the active species are achieved. With reaction temperatures in the range 30–70 °C at 10 atm of ethylene pressure with an Al/Zr molar ratio of 2000, the catalytic activity showed a maximum value of 1.47 × 105 g PE/mol Zr h at 50 °C (Entry 5 in Table 2). Proper increase of reaction temperature will accelerate the formation of the active species. The activity of complex 1 is higher than its amidinate and guanidinate analogues I and II (Table 3), but comparable to those of zirconium complexes with N-alkyl aminopyridinato ligands [14] or very bulky aminopyridinato ligands [17]. This behavior is thought to be due to their structural differences. The highly Lewis acidicity of the metal center fulfilled by the strong basicity of amide and pyridine ligands and the chelating strained η2-coordiantion of the aminopyridinato ligands made complex 1 more active. In conclusion, a N-functionalized organoamide zirconium complex [(TMS-Apy)3ZrCl] (1) was readily prepared via the reaction of lithium 2-(trimethylsilyl)amino-pyridine with zirconium tetrachloride. Complex 1 is mononuclear with seven-coordinate metal center and the η2strained-coordinated aminopyridinato ligands arrange in a propellerlike fashion. Complex 1 is active for ethylene polymerization with the activity of 1.47 × 105 g PE/mol Zr h. Acknowledgments We thank the Natural Science Foundation of China (No. 21371111), Shanxi Scholarship Council of China (No. 2013-025) and Shanxi Functional Organometallic Compound Information Net Project (No. 2013091022) for financial support. Appendix A. Supplementary material
Table 2 Data for ethylene polymerization catalyzed by complex 1/cocatalyst systema.
a
Complex/MAO system. kgPE/mol Zr h bar, Al/Zr = 500:1, 1 h [6]. gPE/mol Zr h, Al/Zr = 1000:1, 0.5 h, 10 atm [5].
Polymerization conditions: 5 μmol of Zr, Cocatalyst: MAO, 100 ml toluene, 0.5 h. g mol−1 h−1.
CCDC 1439583 contains the supplementary crystallographic data for 1. These data can be obtained free of charge via http://www.ccdc.cam. ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Center, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+ 44) 1223-336-033; or e-mail: [email protected]. Supplementary data associated with this article can be found in the online version, at http://dx.doi.org/10.1016/j.inoche.2016.01.010. References [1] F.T. Edelmann, Angew. Chem. Int. Ed. 34 (1995) 2466–2488. [2] M.S. Eisen, H. Mack, J. Organomet. Chem. 525 (1996) 81–87.
34 [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20]
L. Yan et al. / Inorganic Chemistry Communications 65 (2016) 32–34 T.L. Brown, K.J. Lee, Coord. Chem. Rev. 128 (1993) 89–116. R. Kempe, S. Brenner, P. Arndt, Organometallics 15 (1996) 1071–1074. M.S. Zhou, H.B. Tong, X.H. Wei, D.S. Liu, J. Organomet. Chem. 692 (2007) 5195–5202. P.B. Hitchcock, M.F. Lappert, P.G. Merle, Dalton Trans. (2007) 585–594. C. Averbuj, E. Tish, M.S. Eisen, J. Am. Chem. Soc. 120 (1998) 8640–8646. M. Fan, Q.K. Yang, H.B. Tong, S.F. Yuan, B. Jia, D.L. Guo, M.S. Zhou, D.S. Liu, RSC Adv. 2 (2012) 6599–6605. M.S. Zhou, Q.K. Yang, H.B. Tong, L. Yan, X.Y. Wang, RSC Adv. 5 (2015) 105292–105298. W.P. Kretschmer, B. Hessen, A. Noor, N.M. Scott, R. Kempe, J. Organomet. Chem. 692 (2007) 4569–4579. M. Talja, M. Klinga, M. Polamo, E. Aitola, M. Leskelä, Inorg. Chim. Acta 358 (2005) 1061–1067. M. Talja, T. Luhtanen, M. Polamo, M. Klinga, T.A. Pakkanen, M. Leskelä, Inorg. Chim. Acta 361 (2008) 2195–2202. M. Talja, M. Polamo, M. Leskelä, J. Mol. Catal. A Chem. 280 (2008) 102–105. C. Morton, P. O'Shaughnessy, P. Scott, Chem. Commun. (2000) 2099–2100. A. Noor, W.P. Kretschmer, G. Glatz, R. Kempe, Inorg. Chem. 50 (2011) 4598–4606. E. Smolensky, M. Kapon, J.D. Woollins, M.S. Eisen, Organometallics 24 (2005) 3255–3265. A. Noor, W.P. Kretschmer, G. Glatz, A. Meetsma, R. Kempe, Eur. J. Inorg. Chem. (2008) 5088–5098. C. Jones, P.C. Junk, S.G. Leary, N.A. Smithies, Inorg. Chem. Commun. 6 (2003) 1126–1128. R. Kempe, P. Arndt, Inorg. Chem. 35 (1996) 2644–2649. Preparation of 1: n-Butyllithium (1.10 mL, 2.42 mmol) was added to a solution of 2(trimethylsilylamido) pyridine (0.40 g, 2.42 mmol) in Et2O (30 mL) at 0 °C. The resulting mixture was warmed to ca. 20 °C and stirred overnight. ZrCl4 (0.19 g, 0.81 mmol) was added at −78 °C.The resulting mixture was warmed to ca. 20 °C
and stirred overnight. The volatiles were removed in vacuo and the residue was extracted with dichloromethane. Filtered and the filtrate was concentrated in vacuo to 10 mL and stored at −20 °C for 20 days, afforded orange block crystals of 1 (0.33 g, 65%). Mp 123–127 °C. Anal. calcd. for C24H39ClN6Si3Zr (%): C, 46.30; H, 6.31; N, 13.50. Found: C, 46.58; H, 6.01; N, 13.52. 1H NMR (C6D6): δ 0.43 (s, 9 H, SiMe3), 5.97–6.09 (m, 3 H, H-4), 6.28–6.41 (m, 3 H, H-5), 6.99–7.10 (m, 2 H, H-3), 8.23 (s, 3 H, H-6). 3C NMR (C6D6): δ − 0.08 (SiMe3), 109.8 (C-5), 112.9 (C-3), 136.8 (C-4), 148.3 (C-6), 165.9 (C-2). [21] Crystal data for 1: C24H39ClN6Si3Zr, M = 622.55, Trigonal, space group P3, T = 200 K, a = 18.7788(7) Å, b = 18.7788(7) Å, c = 7.8210(3) Å, V = 2388.5(2) Å3, Z = 3, Fooo = 972, GOF = 1.074, ρcalcd. = 1.298 g cm − 3, crystal size = 0.30 × 0.25 × 0.25 mm. Data were collected on a Bruker SMART APEX diffractometer/CCD area detector, using mono-chromated Mo-Kα radiation, λ = 0.71073 Å at 200 K. A total of 52987 reflections were collected, of which 7916 unique reflections (6492 with I N 2σ(I)) were for structure elucidation. The final R1 was 0.0350 for I N 2σ(I) and 0.0572 for all reflections. Absorption correction was performed using the multi-scan method. The structures were solved by direct methods and refined by full-matrix least squares on F2 using the SHELXTL-97 program package. [22] General procedure for polymerization of ethylene. Ethylene polymerization was carried out in a 500 mL autoclave stainless steel reactor equipped with a mechanical stirrer and a temperature controller. Briefly, toluene, the desired amount of cocatalyst, and a toluene solution of the catalytic precursor (the total volume was 100 mL) were added to the reactor in this order under an ethylene atmosphere. When the desired reaction temperature was reached, ethylene at 10 atm pressure was introduced to start the reaction, and the ethylene pressure was maintained by constant feeding of ethylene. After 30 min, the reaction was stopped. The solution was quenched with HCl-acidified ethanol (5%), and the precipitated polyethylene was filtered, washed with ethanol, and dried in vacuum at 60 °C to constant weight.