A Single-Crystal Model for MgCl2–Electron Donor Support Materials

Article pubs.acs.org/Organometallics

A Single-Crystal Model for MgCl2−Electron Donor Support Materials: [Mg3Cl5(THF)4Bu]2 (Bu = n‑Butyl) Sami Pirinen,† Igor O. Koshevoy,† Peter Denifl,‡ and Tuula T. Pakkanen*,† †

Department of Chemistry, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland Borealis Polymers Oy, P.O. Box 330, FI-06101 Porvoo, Finland

‡

S Supporting Information *

ABSTRACT: The influence of the electron donor tetrahydrofuran (THF) on the formation of the crystalline morphology of MgCl2 was studied. MgCl2 was synthesized from magnesium and 1-chlorobutane in the presence of THF with the THF/Mg molar ratio ranging from 0.063 to 2.0. With the highest amounts of THF crystalline particles were formed, as evidenced from scanning electron microscopy images. The X-ray structure analysis of these single crystals revealed the new organometallic Mg compound [Mg3Cl5(THF)4Bu]2 (Bu = n-butyl), which has an open dicubanelike structure with four octahedrally and two tetrahedrally coordinated Mg atoms. The compound also contains two butyl groups directly bound to the Mg atoms at the opposite corners of the dicubane structure. With the lowest THF amounts, structurally disordered MgCl2/THF complexes were formed. The transition from single crystals toward particles with an amorphous morphology appeared to occur through an intermediate type of morphology with a three-dimensional network structure. The network structure is formed from a thin (30−100 nm) fiberlike MgCl2/THF material. Infrared and solid-state 13C nuclear magnetic resonance spectroscopy measurements revealed different types of Mg sites present in the MgCl2/THF complexes.

■

INTRODUCTION MgCl2-supported Ti-based Ziegler−Natta catalysts are widely used in olefin polymerization. These catalysts are especially important in the production of polyethylene and polypropylene. A typical Ziegler−Natta (Z-N) catalyst is comprised of MgCl2, TiCl4, electron donors, and aluminum trialkyl.1 MgCl2 with a layered structure is in its “activated” form when it is used as a support. This “activated” or δ form of MgCl2 is characterized by a highly disordered structure.2−4 The preparation of δ-MgCl2 can be done by mechanical or chemical means or by a combination of these two.5,6 In the mechanical route, crystalline MgCl2 (typically α form) is ground with a vibratory mill using steel balls under a dry nitrogen atmosphere.7 The grinding process breaks down the lattices of the MgCl2 and results in a disordered structure. Additionally, a Lewis base is usually added in the milling process to produce even higher disorder.8,9 In the chemical route the α-MgCl2 can be dissolved in a suitable Lewis base and after precipitation δMgCl2 can be obtained.10,11 MgCl2 can also be obtained by chemical synthesis. Examples of these are the reaction of Mg with RCl and the reaction of MgR2 with HCl, where R is an alkyl group.12−15 In addition to the importance of the MgCl2 support as part of the Z-N catalyst, also the role of the internal electron donor is significant. The electron donor, typically a phthalate or a 1,3diether, has an impact on the formation of the active sites for polymerization. The electron donor can block surface sites © 2013 American Chemical Society

where Ti species would otherwise form nonstereospecific centers or modify the surroundings of the Ti species bound on the MgCl2 surface and aid the formation of active and stereospecific centers.16,17 These catalytically relevant surfaces are (104) with five-coordinated Mg atoms and (110) with fourcoordinated Mg atoms.18 The electron donor can have an influence on the growth of the MgCl2 crystals. It has been shown that in the presence of 1,3-diether hexagonal MgCl2 single crystals are formed, indicating the formation of either (104) or (110) surfaces.19 Most likely the surfaces formed are (110) faces, because according to theoretical and experimental studies diethers have been found to bind preferably on the (110) surface.1,16,20 In addition, single crystals of MgCl2/tetrahydrofuran21,22 complexes have been prepared. The structures of the MgCl2/ tetrahydrofuran complexes depend on the molar ratio of tetrahydrofuran; [MgCl2(THF)2] has a linear polymeric structure, [MgCl2 (THF) 4 ] is a molecular crystal, and [MgCl2(THF)1.5] has been proposed to have the open dicubane-like structure [Mg4(μ3-Cl)2(μ2-Cl)4Cl2(THF)6].23,24 Knowledge of the structure of these complexes can provide information about the role of electron donors in the formation of different crystalline morphologies of MgCl2. This information can be helpful in the preparation of Z-N precatalysts from Received: May 8, 2013 Published: July 17, 2013 4208

dx.doi.org/10.1021/om400407p | Organometallics 2013, 32, 4208−4213

Organometallics

Article

have a slightly porous structure (Figure 1a). Samples 1 and 2 had a morphology (see Figure S1 in the Supporting Information) similar to that of sample 3, even though the amount of THF in sample 3 is markedly larger than in samples 1 and 2 (see Table 1). Sample 4 with a higher THF/Mg ratio has a three-dimensional network type morphology (Figure 1b), which is clearly different from that of samples 1−3. The porous network type structure of sample 4 is formed from thin (30− 100 nm) fibers that are entangled and connected to each other. Samples 5 and 6, which have the highest amount of THF, have morphologies completely different from those of other samples. These samples contain small amounts of amorphous material, but the particles are mainly crystalline. The crystals in sample 5 (Figure 1c) have a diamond shape, and the angles of the crystal facets are around 63 and 117°. In addition, some crystals with a 90° angle are observed. The length and the width of the crystals varied mainly from 2 to 35 μm (on the basis of SEM images) and the thickness from 1 to 5 μm. In sample 5 some remains from the network type morphology observed in sample 4 is still present, as some of the crystals are covered with a similar fiberlike material. In sample 6 (Figure 1d) crystals having the same shape as the crystals in sample 5 are observed, but the size of the crystals is slightly larger, varying mainly from 5 to 55 μm in length and width and from 2 to 5 μm in thickness. Furthermore, sample 6 does not contain any fiberlike material. Considering the high amount of THF in samples 5 and 6 (see Table 1), it is likely that the crystals are stoichiometric MgCl2/THF complexes. Structure of the Complexes. The crystal structure of MgCl2/THF complex 6 (shown in Figure 2) was solved by an

MgCl2/THF complexes. These types of precatalysts are active in the polymerization of ethylene and in the copolymerization of ethylene and α-olefins.25,26 In this article, an insight into the formation of MgCl2/ tetrahydrofuran complexes synthesized in autoclave reactions at 130 °C is given. Characterization of the complexes shows the effect of the amount of tetrahydrofuran on the crystalline morphology and on the structure of the complexes. With a suitable amount of tetrahydrofuran the reaction yields single crystals, for which the X-ray diffraction method gave an extended MgCl2−dicubane structure, a previously unknown complex. Spectroscopic characterization methods (DRIFT and 13 C CP/MAS) were used to study the bonding of tetrahydrofuran on the MgCl2 surfaces. The preparation method presented in this article allows control over the structure and morphology of the MgCl2/THF complexes.

■

RESULTS AND DISCUSSION Morphology of the Complexes. The synthesized MgCl2/ THF complexes with THF/Mg molar ratio 0.063−2.0, and their analyzed molar ratio, are presented in Table 1. The Table 1. Synthesized MgCl2/THF Complexes and Their Analyzed THF/Mg Molar Ratios MgCl2/THF sample

added THF/Mg

1 2 3 4 5 6

0.063 0.13 0.25 0.50 1.0 2.0

determined THF/Mga 0.044 0.072 0.28 0.50 1.07 1.21

± ± ± ± ± ±

0.002 0.007 0.02 0.02 0.05 0.12

a The amount of THF was determined from 1H NMR analysis, and the amount of Mg was determined by titration with EDTA. The standard deviation for the determined THF/Mg ratios is presented after the ratio.

morphology of the MgCl2 complexes was studied by scanning electron microscopy (SEM). The images (Figure 1) show the change from an amorphous type to crystalline morphology as the amount of THF is increased in the complex. The amorphous and agglomerated particles of sample 3 seem to

Figure 2. Structure of [Mg3Cl5(THF)4Bu]2 (MgCl2/THF complex 6).

Figure 1. SEM images of the MgCl2/THF complexes: (a) sample 3; (b) sample 4; (c) sample 5; (d) sample 6.

X-ray diffraction measurement from a single crystal. Complex 6 has an open dicubane-like structure, [Mg3Cl5(THF)4Bu]2 (Bu = n-butyl). It contains three different types of Mg atoms: two 6coordinated octahedral MgCl4O2 units, two 6-coordinated octahedral MgCl5O units, and two 4-coordinated tetrahedral MgCl2BuO units. The present structure is similar to the proposed structure of [MgCl2(THF)1.5],27 and it can be considered to be extended from the dicubane structure of [MgCl2(THF)1.5] with two BuMgCl(THF) units. The BuMgCl group originates from the chemical reaction that takes place in the formation of MgCl2 through Grignard−Wurtz coupling reaction. A Grignard compound containing similar structural units, PrMgCl2(THF)2 (Pr = propenyl), is found in the literature.28 Compounds having the open dicubane-like structure have been reported previously in the literature.29−32 These previously reported structures differ from the present stoichiometric complex, as they contain only four Mg atoms instead of six Mg atoms in [Mg3Cl5(THF)4Bu]2. The theoretical THF/Mg molar ratio in [Mg3Cl5(THF)4Bu]2 is 4209

dx.doi.org/10.1021/om400407p | Organometallics 2013, 32, 4208−4213

Organometallics

Article

solvates and be responsible for the nanoporosity of the δMgCl2. According to the SEM and PXRD measurements of the MgCl2/THF complexes, sample 4 with a three-dimensional network morphology could be an intermediate between the crystals of samples 5 and 6 and the amorphous MgCl2 particles of samples 1−3. In conclusion, our results from the synthesis series indicate that the proposed polynuclear (MgCl2)x species can be present in the structural transition from more crystalline toward structurally disordered complexes. The open dicubanelike structure, as in [Mg3Cl5(THF)4Bu]2, has a high similarity with the theoretical models of MgCl2,35−37 where the (110) surface has been described as an open polycubane-like structure.38 This structure can be considered as a building block of the Cl−Mg−Cl layer. Bonding of THF. A clear shift in the asymmetric and symmetric C−O−C stretching vibration of THF toward lower wavenumber was observed in the infrared spectra of MgCl2/ THF complexes (1−6) in comparison to that of free THF. For free THF the νas(C−O−C) and νs(C−O−C) bands are at 1070 and 913 cm−1 (the νas(C−O−C) region is shown in Figure 4). For MgCl2/THF complexes the maxima of the

1.33, while the analyzed THF/Mg ratio in sample 6 was 1.21. This small difference can be explained with the presence of some amorphous particles in sample 6, as evidenced from the SEM images. Samples 5 and 6 containing the organometallic complex appeared to be more sensitive to ambient moisture than samples 1−4. Powder X-ray diffraction (PXRD) results clearly indicate a structural transition from a partially crystalline to fully crystalline material as a function of the increasing THF/Mg ratio in the samples. PXRD patterns for the synthesized MgCl2/ THF complexes and MgCl2 synthesized in the absence of THF are presented in Figure 3. The MgCl2 material synthesized

Figure 3. PXRD patterns of the MgCl2 and the MgCl2/THF complexes. Reflections arising from the sample holder are denoted by asterisks.

without THF is structurally disordered, as can be concluded from the broad reflection at 2θ = 14.9° corresponding to the (003) surface and from the emergeing reflections arising from (006), (10−2), and (104) planes in the area 2θ = 28−38°.7 As the amount of THF is increased from sample 1 to sample 3, the reflections become weaker and the stacks of Cl−Mg−Cl layers become smaller, as indicated by the diminishing (003) reflection. A clear difference can be seen in the X-ray pattern of sample 4 in comparison to those of samples 1−3. The PXRD pattern of sample 4 has multiple reflections, the strongest ones being located at 2θ = 7.2 and 11.5°. In addition to the appearance of the new reflections, a small proportion of the structure type observed in samples 1−3 is still present in sample 4. The PXRD patterns of samples 5 and 6 show a great number of sharp reflections. Although the reflection intensities in the PXRD patterns of samples 5 and 6 do not completely match, the 2θ positions of the reflections are the same. This result indicates that samples 5 and 6 mainly consist of the same type of crystalline structure. The reflection at 2θ = 7.2° in the PXRD pattern of sample 4 is observed also in the PXRD pattern of sample 5 but not in the case of sample 6. This probably indicates that the reflection at 2θ = 7.2° arises from the fiberlike material that was observed in the SEM images of samples 4 and 5. The PXRD measurements show the same result as the SEM images; sample 4 with a THF/Mg molar ratio of 0.500 has features from both crystalline and structurally disordered MgCl2/THF complexes. The theoretical study by Auriemma et al.33,34 suggested that a three-dimensional network structure made up of long chains of (MgCl2)x polynuclear species can play a key role in the formation of δ-MgCl2 from solid complex

Figure 4. IR spectrum of THF and DRIFT spectra of the MgCl2/THF complexes in the νas(C−O−C) region.

νas(C−O−C) and νs(C−O−C) bands are in the ranges of 1027−1020 and 877−873 cm−1, respectively. The shift in the stretching frequencies clearly indicates the binding of THF through oxygen to Mg. In addition to the absorption band at 1020−1021 cm−1 for samples 2−4, a second band as a shoulder is clearly observed at 1038−1040 cm−1. The presence of the second band indicates that THF is bound to two different types of Mg sites. These different Mg sites could be located on the (104) and (110) surfaces of MgCl2, from which the 4coordinated (110) is more Lewis acidic than the 5-coordinated (104) face. The theoretical study of Grau et al.39 suggested that THF will be more strongly bound on the (110) face than on the (104) face. The νas(C−O−C) band of THF bound on the more Lewis acidic (110) surface should be at lower wavenumber (stronger binding of THF) than the νas(C−O− C) band of THF bound on the less Lewis acidic (104) surface. This would, according to the IR spectra, indicate a higher proportion of THF donors bound on the (110) surface than on the (104) face, at least in the case of samples 2−4. For samples 5 and 6, these surfaces do not exist in the same manner as in other samples, because samples 5 and 6 are mostly stoichiometric complexes and thus the IR spectra in the νas(C−O−C) region contain only one broad band, differing from those of the other samples. However, the IR spectra of the samples seem to indicate that THF is more strongly bound on amorphous MgCl2 particles than on the single crystals (the 4210

dx.doi.org/10.1021/om400407p | Organometallics 2013, 32, 4208−4213

Organometallics

Article

Figure 5. 13C CP/MAS NMR spectra of MgCl2/THF complexes: (a) sample 3; (b) sample 4; (c) sample 5; (d) sample 6.

Figure 6. Deconvoluted 13C CP/MAS NMR spectra of MgCl2/THF complexes: (a) sample 5; (b) sample 6. The resonances (O1, O2,3, and O4) displayed are from α-carbons bonded to oxygen of the THF molecules in the crystalline MgCl2/THF structure. Black curves are measured spectra, blue curves are fitted signals, and red curves are the sums of the fitted signals.

νas(C−O−C) absorption band maxima for samples 5 and 6 are in the range 1025−1027 cm−1). The 13C cross-polarization/magic angle spinning nuclear magnetic resonance spectra of samples 3−6 are presented in Figure 5. The α-carbon resonances of THF have shifted downfield to 69.6−70.4 ppm with respect to free THF (signal for the α-carbons at 68.0 ppm). The downfield shift indicates that THF is bound to Mg.39 For samples 3 and 4 (Figure 5a,b), only one narrow symmetric signal at 70.4 ppm is observed. The νas(C−O−C) region in the IR spectra of these samples indicated at least two different coordination sites for THF. The absence of multiple signals in the 13C NMR spectra could be due to a dynamic disorder of THF molecules on the NMR time scale.40 For samples 5 and 6, at least three α-carbon signals are observed in the area of 69.6−70.4 ppm (see insets in Figure 5c,d). These resonances correspond to THF bound to different Mg sites. The signal on the downfield side at 70.4 ppm corresponds to THF bound on the MgCl2 surface of the structurally disordered complexes such as found for samples 3 and 4. In sample 5 this signal at 70.4 ppm clearly has a higher intensity than in sample 6, indicating a larger proportion of the

structurally disordered type material in sample 5 than in sample 6. This is in good agreement with the SEM images showing a larger amount of amorphous type material present in sample 5. The other signals in the area 69.6−70.4 ppm come from THF ligands bound to Mg in the stoichiometric complex. Deconvolution of the chemical shift range 69.6−70.4 ppm by Lorentzian line shapes reveals three nonequivalent THF species present in [Mg3Cl5(THF)4Bu]2 (Figure 6). The ratio of the relative areas of the fitted signals obtained from the deconvolution is approximately 1:1:2. Fitted signals could be assigned to α-carbons belonging to THF ligands O1, O2, O3, and O4 with Mg−O bond lengths of 2.030(2), 2.073(2), 2.072(2), and 2.058(2) Å, respectively (see Figure 2 and Table S2 (Supporting Information)). The assignment is based on the assumption that a THF molecule with a shorter Mg−O bond (O1) is bound more strongly and the 13C signal of the corresponding α-carbons shifts more downfield than do those of the THF molecules with longer Mg−O bonds (O2,3,4). Signals in the range 25.7−25.1 ppm (Figure 5) come from the β-carbons in THF and show a slight high-field shift39 or have no shift at all with respect to free THF (signal for the βcarbons at 25.7 ppm). The rest of the three resonances in 4211

dx.doi.org/10.1021/om400407p | Organometallics 2013, 32, 4208−4213

Organometallics

Article

Figure 5c,d (−CH2−Mg at 6.4 ppm, CH3− at 13.6 ppm, and −CH2−CH2− at 32.1 ppm) come from the butyl group bound to the Mg atom. These three signals are not clearly observed in the NMR spectra of samples 3 and 4, indicating that those samples contain mainly MgCl2 and THF.

direct methods using the SHELXS-9742 programs with the WinGX43 graphical user interface. A semiempirical absorption correction (SADABS)44 was applied to all data. Structural refinements were carried out using SHELXL-97. 42 All hydrogen atoms in [Mg3Cl5(THF)4Bu]2 were positioned geometrically and were constrained to ride on their parent atoms, with C−H = 0.98−0.99 Å and Uiso = 1.2−1.5 times the Ueq value of the parent atom. The crystallographic details are summarized in Table S1 (Supporting Information), and selected structural parameters are given in Table S2 (Supporting Information). For the powder X-ray diffraction measurements samples of the MgCl2/THF complexes were placed in a selfmade sample holder where the sample was protected from contact with air by a Mylar film. The step size was 0.05°, and the time per step was 8 s.

■

CONCLUSIONS The synthesis of MgCl2 in the presence of THF gives rise to crystalline stoichiometric or structurally disordered complexes, depending on the molar ratio of THF/Mg used in the synthesis. The structural transition of the MgCl2/THF particles from crystals toward amorphous particles appears to take place via an intermediate type morphology that has a threedimensional network formed from fiberlike MgCl2/THF structures. The presence of THF donors bound to different Mg sites is evidenced from IR and NMR data. The open dicubane-like structure of the MgCl2/THF crystals can serve as a structural model for the building block of layered MgCl2 and give information about the possible coordination sites of Mg. The present synthesis series forms a useful platform for the development of activated MgCl2 supports by giving a method to control the formation of the MgCl2/THF complexes that can be used as supports for Ziegler−Natta catalysts for ethylene polymerization.

■

■

ASSOCIATED CONTENT

S Supporting Information *

Tables and a CIF file giving X-ray crystallographic data for [Mg3Cl5(THF)4Bu]2 and a figure giving SEM images of samples 1 and 2. This material is available free of charge via the Internet at http://pubs.acs.org.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail for T.T.P.: tuula.pakkanen@uef.fi. Notes

EXPERIMENTAL SECTION

The authors declare no competing financial interest.

■

General Data. All synthesis and characterizations were performed under inert gas using glovebox and Schlenk line techniques unless otherwise mentioned. Solvents were dried over activated 3 Å molecular sieves. Solution-state 1H NMR samples were recorded with a Bruker Avance-400 NMR spectrometer using 32 scans and a relaxation delay of 10 s. A Bruker AMX-400 NMR spectrometer was used to obtain a 13C CP/MAS NMR spectrum of the samples. Glycine was used as an external reference; the spin rate was 4500 Hz, the relaxation delay was 4 s, and the contact time was 3 ms. The number of scans was 2000. The SEM samples were measured with a Hitachi S4800 scanning electron microscope and were protected from air before they were quickly placed on a sample holder and immediately moved to the loading chamber. The voltage used in the imaging was 3 kV. Infrared spectra of the samples were measured with a Nicolet Impact 400 D infrared spectrometer mounted inside a glovebox. In the diffuse reflectance infrared Fourier transform (DRIFT) method the number of scans was 32 and the resolution was 2 cm−1. Synthesis of MgCl2/Tetrahydrofuran Complexes. Mg dried in an oven at 110 °C overnight (0.5 g, 0.021 mol), a few small crystals of iodine, octane (20 mL), 1-chlorobutane (4.6 mL, 0.044 mol), and tetrahydrofuran (with THF/Mg molar ratio varying from 0.063 to 2.0) were packed in an autoclave inside a nitrogen-filled glovebox. The autoclave was closed tightly and moved to a heating unit, where it was heated to 130 °C for 2 h with mixing. The solid that formed was separated from the solution in the glovebox and washed three times with octane. The solid was dried under vacuum at room temperature. The final product was a white powder. In order to determine the amount of THF in the MgCl2/THF complexes, a known amount of sample and the internal reference sodium acetate were dissolved in 10% (v/v) D2SO4/D2O and a 1H NMR spectrum was recorded. The area of the CH3− signal of the sodium acetate and the area of the CH2−O signal of THF were compared to calculate the amount of THF. Mg was determined by titration with the disodium salt of ethylenediaminetetraacetic acid. Both THF and Mg were determined as an average of three measurements. X-ray Measurements. For single-crystal X-ray measurements the highly hygroscopic crystals of [Mg3Cl5(THF)4Bu]2 were immersed in cryo-oil, mounted in a nylon loop, and measured at a temperature of 120 K. The X-ray diffraction data were collected using Mo Kα radiation (λ = 0.71073 Å). The APEX241 program package was used for cell refinements and data reductions. The structure was solved by

ACKNOWLEDGMENTS We gratefully acknowledge financial support from the Finnish Funding Agency for Technology and Innovation and European Union/European Regional Development Fund (grant 70054/ 09).

■

REFERENCES

(1) Albizzati, E.; Cecchin, G.; Chadwick, J. C.; Collina, G.; Giannini, U.; Morini, G.; Noristi, L. In Polypropylene Handbook, 2nd ed.; Pasquini, N., Ed.; Hanser: Munich, 2005; Chapter 2. (2) Credendino, R.; Pater, J. T. M.; Correa, A.; Morini, G.; Cavallo, L. J. Phys. Chem. C 2011, 115, 13322−13328. (3) Makwana, U.; Naik, D. G.; Singh, G.; Patel, V.; Patil, H. R.; Gupta, V. K. Catal. Lett. 2009, 131, 624−631. (4) Rö nkkö , H.-L.; Knuuttila, H.; Denifl, P.; Leinonen, T.; Venäläinen, T. J. Mol. Catal. A: Chem. 2007, 278, 127−134. (5) Di Noto, V.; Bresadola, S. Macromol. Chem. Phys. 1996, 197, 3827−3835. (6) Di Noto, V.; Fregonese, D.; Marigo, A.; Bresadola, S. Macromol. Chem. Phys. 1998, 199, 633−640. (7) Bart, J. C. J. J. Mater. Sci. 1993, 28, 278−284. (8) Giunchi, G.; Allegra, G. J. Appl. Crystallogr. 1984, 17, 172−178. (9) Kashiwa, N. Polym. J. 1980, 12, 603−608. (10) Bart, J. C. J.; Roovers, W. J. Mater. Sci. 1995, 30, 2809−2820. (11) Forte, M. C.; Coutinho, F. M. B. Eur. Polym. J. 1996, 32, 223− 231. (12) Buchacher, P.; Fischer, W.; Aichholzer, K. D.; Stelzer, F. J. Mol. Catal. A: Chem. 1997, 115, 163−171. (13) Huang, R.; Malizia, F.; Pennini, G.; Koning, C. E.; Chadwick, J. C. Macromol. Rapid Commun. 2008, 29, 1732−1738. (14) Stukalov, D. V.; Zakharov, V. A.; Potapov, A. G.; Bukatov, G. D. J. Catal. 2009, 266, 39−49. (15) Brambilla, L.; Zerbi, G.; Piemontesi, F.; Nascetti, S.; Morini, G. J. Mol. Catal. A: Chem. 2007, 263, 103−111. (16) Brambilla, L.; Zerbi, G.; Piemontesi, F.; Nascetti, S.; Morini, G. J. Phys. Chem. C 2010, 114, 11475−11484. (17) Cheruvathur, A. V.; Langner, E. H. G.; Niemantsverdriet, H. J. W.; Thüne, P. C. Langmuir 2012, 28, 2643−2651. 4212

dx.doi.org/10.1021/om400407p | Organometallics 2013, 32, 4208−4213

Organometallics

Article

(18) Singh, G.; Kaur, S.; Makwana, U.; Patankar, R. B.; Gupta, V. K. Macromol. Chem. Phys. 2009, 210, 69−76. (19) Andoni, A.; Chadwick, J. C.; Niemantsverdriet, H. J. W.; Thüne, P. C. J. Catal. 2008, 257, 81−86. (20) Correa, A.; Piemontesi, F.; Morini, G.; Cavallo, L. Macromolecules 2007, 40, 9181−9189. (21) Brun, C.; Brusson, J.-M.; Duranel, L.; Spitz, R. U.S. Patent 5,599,760, February 4, 1997. (22) Spitz, R.; Soto, T.; Brun, C.; Duranel, L. U.S. Patent 6,232,422, May 15, 2001. (23) Sobota, P. Chem. Eur. J. 2003, 9, 4854−4860. (24) Sobota, P. Coord. Chem. Rev. 2004, 248, 1047−1060. (25) Nowlin, T. E.; Mink, R. I.; Kissin, Y. V. In Handbook of Transition Metal Polymerization Catalysts; Hoff, R., Mathers, R. T., Ed.; Wiley: Hoboken, NJ, 2010; Chapter 6. (26) Bialek, M.; Czaja, K. Polymer 2000, 41, 7899−7904. (27) Seenivasan, K.; Sommazzi, A.; Bonino, F.; Bordiga, S.; Groppo, E. Chem. Eur. J. 2011, 17, 8648−8656. (28) Layfield, R. A.; Bullock, T. H.; Carcía, F.; Humphrey, S. M.; Schüler, P. Chem. Commun. 2006, 2039−2041. (29) Toney, J.; Stucky, G. D. J. Organomet. Chem. 1971, 28, 5−20. (30) Casellato, U.; Ossola, F. Organometallics 1994, 13, 4105−4108. (31) Day, B. M.; Coles, M. P. Eur. J. Inorg. Chem. 2010, 5471−5477. (32) Blasberg, F.; Bolte, M.; Wagner, M.; Lerner, H.-W. Organometallics 2012, 31, 1001−1005. (33) Auriemma, F.; De Rosa, C. Chem. Mater. 2007, 19, 5803−5805. (34) Auriemma, F.; De Rosa, C. J. Appl. Crystallogr. 2008, 41, 68−82. (35) Toto, M.; Morini, G.; Guerra, G.; Corradini, P.; Cavallo, L. Macromolecules 2000, 33, 1134−1140. (36) Stukalov, D. V.; Zakharov, V. A.; Zilberberg, I. L. J. Phys. Chem. C 2010, 114, 429−435. (37) D’amore, M.; Credendino, R.; Budzelaar, P. H. M.; Causá, M.; Busico, V. J. Catal. 2012, 286, 103−110. (38) Sobota, P.; Szafert, S. Dalton Trans. 2001, 1379−1386. (39) Grau, E.; Lesage, A.; Norsic, S.; Copéret, C.; Monteil, V.; Sautet, P. ACS Catal. 2013, 3, 52−56. (40) Sozzani, P.; Bracco, S.; Comotti, A.; Simonutti, R.; Camurati, I. J. Am. Chem. Soc. 2003, 125, 12881−12893. (41) APEX2 - Software Suite for Crystallographic Programs; Bruker AXS, Madison, WI, 2009. (42) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, A64, 112−122. (43) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837−838. (44) Sheldrick, G. M. SADABS-2008/1 - Bruker AXS area detector scaling and absorption correction; Bruker AXS, Madison, WI, 2008.

4213

dx.doi.org/10.1021/om400407p | Organometallics 2013, 32, 4208−4213