Oligomerization of 2-chloroallyl alcohol by 2-pyridinecarboxylate complex of chromium(III) - new highly active and selective catalyst

Oligomerization of 2-chloroallyl alcohol by 2-pyridinecarboxylate complex of chromium(III) - new... www.nature.com/scientificreports OPEN Oligomerization of 2-chloroallyl alcohol by 2-pyridinecarboxylate complex of chromium(III) - new Received: 29 December 2017 highly active and selective catalyst Accepted: 23 May 2018 Published: xx xx xxxx Joanna Drzeżdżon, Artur Sikorski, Lech Chmurzyński & Dagmara Jacewicz The new 2-pyridinecarboxylate (2-pic) complex of chromium(III) has been designed and synthesized as a new highly active and selective oligomerization catalyst. The crystal structure of the new compound has been determined by X-ray diffraction. The composition and purity of [Cr(2-pic) (OH ) ]NO have been 2 2 2 3 confirmed by several spectroscopic methods and the elemental analysis. Furthermore, the new complex has been investigated towards its catalytic activity for the oligomerization of 2-chloro-2-propen-1-ol under the atmospheric pressure and at room temperature. It has turned out that the novel catalyst exhibits a very high catalytic activity. Consequently, [Cr(2-pic) (OH ) ]NO belongs to a new generation 2 2 2 3 of non-metallocene catalysts. The organometallic complexes of chromium(III) are known as catalysts for the olefin polymerization . The cat - alytic activity of the chromium(III) complexes is induced by the addition of methylaluminoxane (MAO) or its modified form (MMAO) . The metallocene chromium(III) complexes exhibit a very high catalytic activity but 3,4 unfortunately they are unstable under an industrial polymerization of olefins and their derivatives conditions . Additionally, the decomposition of the metallocene complexes of chromium(III) is observed aer t ft heir reaction with MAO. Owing to the interesting catalytic activity of the non-metallocene complexes of chromium(III), these com- plexes are considered as a new generation of catalysts for olefins and their derivatives polymerization . The exam- ple of the non-metallocene complex with a catalytic activity for ethylene polymerization is Cr[N(SiMe ) ] I 3 2 2 2 −1 −1 −1 6 (43 g∙mmol ∙h ∙bar ) . This chromium(III) complex containing neutral ligands exhibits low catalytic proper - ties. However, the non-metallocene catalysts include the chromium(III) complexes with monoanionic ligands a with moderate or high catalytic activity e.g. the bis(phosphino)amide complex of chromium(III) with the activ- −1 −1 −1 7,8 ity equal 500 g∙mmol ∙h ∙bar , the chromium(III) complex with triptycenyl and 2-pyridylmethyl exhibits −1 −1 −1 1 the 6970 g∙mmol ∙h ∙bar catalytic activity . The chromium(III) complexes with pyrrole–imino-amine/ether pro-ligands {ENN }H (E = NH, R = H, 1a; E = NH, R = tBu, 1b; E = O, R = H, 1c) have a very high catalytic activ- ity for the ethylene polymerization . Thus, the non-metallocene chromium(III) complexes with monoanionic 10,11 ligands are promising catalysts for the industrial olefin polymerization . Polyvinyl alcohol is used to produce hydrogels, to drugs production in the pharmaceutical industry and as a 12,13 stabilizer in emulsions . 2-Chloro-2-propen-1-ol is the derivative of vinyl alcohol (hydroxyethene). Thus, the product of the polymerization of this monomer (2-chloro-2-propen-1-ol) may exhibit similar properties and applications as polyvinyl alcohol. Therefore, 2-methyl-2-propen-1-ol as the derivative of 2-chloro-2-propen-1-ol was investigated as the substrate in production of renewable hydrogels by oligomerization . In the literature, there is lack of information about the polymerization of 2-chloro-2-propen-1-ol using complex compounds as the catalysts. Recently, the results of our studies on the new type of chromium(III) catalysts (dipicolinate complexes of Cr(III) with 2,2′-bipyridine and its derivative as ligands) containing both organic cations and anions designed for the polymerization of 2-chloro-2-propen-1-ol has been published . These new catalysts exhibit a very high catalytic activity. It has to be mentioned that the poly(2-chloroallyl alcohol) is prepared at the atmospheric pres- sure and the room temperature (21 °C) . This report is a continuation of our previous studies. We describe the structure of the new [Cr(2-pic) (OH ) ] 2 2 2 NO complex compound where 2-pic denotes the 2-pyridinecarboxylate anion. Moreover, the catalytic activity Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80–308, Gdańsk, Poland. Correspondence and requests for materials should be addressed to J.D. (email: joanna.drzezdzon@ug.edu.pl) Scientific REPO R ts | (2018) 8:8632 | DOI:10.1038/s41598-018-26973-6 1 www.nature.com/scientificreports/ Figure 1. e m Th olecular structure of [Cr(2-pic) (OH ) ]NO . Displacement ellipsoids are drawn at the 50% 2 2 2 3 probability level (Symmetry codes: (i) −x + 1, −y, −z + 1 (ii) −x + 1, y, −z + ½). Figure 2. e cr Th ystal packing of the title compound viewed along the b-axis (hydrogen bonds and halogen bonds are represented by dashed lines; symmetry codes (iii)) ½ + x, −½ + y, z. of the 2-pyridinecarboxylate complex of chromium(III) has been studied in the case of the 2-chloroallyl alcohol oligomerization. Furthermore, the catalytic activity of the novel catalyst has been compared with other known chromium(III)-based catalysts. Results The structure of the new complex. The crystal structure of the novel chromium(III) complex –[Cr(2- pic) (OH ) ]NO has been studied by the X-ray diffraction method. The molecular structure of the new com- 2 2 2 3 plex has been shown in Fig. 1. The crystallographic data for [Cr(2-pic) (OH ) ]NO have been collected in 2 2 2 3 Supplementary Information. In the crystal structure of the [Cr(2-pic) (OH ) ] a cation is arranged around a 2 2 2 center of a symmetry, and in NO anion N2 and O3 atoms lying on the rotational 2-fold axis (Fig. 1). The geometric parameters (bond lengths and angles) characterizing both [Cr(2-pic) (OH ) ] and in 2 2 2 NO are typical for these units (see Supplementary Information). In the crystal packing of tile compounds [Cr(2-pic) (OH ) ] cations are linked via O1W–H1WA···O2 hydrogen bonds to form tapes along the [110] 2 2 2 direction. The neighboring tapes are linked by O–H···O hydrogen bonds between water molecules and NO anion forming a three-dimensional framework structure (Fig. 2). e p Th urity and composition of [Cr(2-pic) (OH ) ]NO was confirmed by the elemental analysis. This test was 2 2 2 3 conducted on the CARBO ERBA - O 1108 automated analyzer. Anal. Calcd for [Cr(2-pic) (OH ) ]NO (%): C, 2 2 2 3 36.54, H, 3.07, N, 10.67. Found: C, 36.53, H, 3.07, N, 10.55. Additionally, the new complex has been studied using several spectroscopic methods, where the results are following: UV-Vis: The regions of the maximum absorption occur at 409 nm and 548 nm (in DMSO). MALDI-TOF-MS: m/z 394.0 (M) , m/z 358.1 (M minus 2 H O) Scientific REPO R ts | (2018) 8:8632 | DOI:10.1038/s41598-018-26973-6 2 www.nature.com/scientificreports/ Figure 3. e MS s Th pectrum for the oligomer consisting of 11 monomers (2-chloro-2-propen-1-ol). Figure 4. The H NMR spectrum for the system: the oligomer of 2-chloro-2-propen-1-ol (11 monomers), [Cr(2-pic) (OH ) ]NO and MMAO-12. 2 2 2 3 −1 −1 −1 IR: 3090.5 cm hydrogen bonds, 1660.8 cm C=O, 1476.6 cm C-C (aromatic) stretching vibrations, −1 −1 −1 822.4 cm C-N (aromatic), 1607.1 cm O-C=O, 769.7 cm Cr-O. 1 13 H NMR and C NMR spectra were not recorded due to the low solubility of [Cr(2-pic) (OH ) ]NO in deu- 2 2 2 3 terated solvents. The oligomerization of 2-chloro-2-propen-1-ol. e n Th ew complex compound has been investigated as catalyst in the case of the 2-chloro-2-propen-1-ol oligomerization. After mixing monomers and activated [Cr(2-pic) (OH ) ]NO (by MMAO-12) the oligomerization has been proceeded at the room temperature and at 2 2 2 3 the atmospheric pressure. The poly-2-chloroallyl alcohol has been obtained as the product of the reaction. The oligomer of 2-chloro-2-propen-1-ol contains 11 monomers. e Th composition of the obtained oligomer has been confirmed by the spectroscopic methods including NMR and MS (Figs  3–5). Moreover, the catalytic activity of Scientific REPO R ts | (2018) 8:8632 | DOI:10.1038/s41598-018-26973-6 3 www.nature.com/scientificreports/ Temperature Catalytic activity −1 −1 −1 Complex [°C] (g∙mmol ∙h ∙bar ) References [Cr{2-[2-(diphenylphosphino)-1-(N-methylimidazol-2-yl) ethyl]-N- 100 108 methy limidazole}Cl ] [Cr{tris(N-methylimidazol-2-yl)methoxymethane}Cl ] 100 208 [Cr(1,3,5-triazacyclohexane)]Cl 40 717 [(2,6-Me Ph) (nacnac)Cr (OEt )CH SiMe ] B(3,5-(CF ) C H ) 2 2 2 2 3 3 2 6 3 4 26 75 228 (nacnac = 2,4-pentane-N,N’-bis(aryl)ketiminato) CrMe[N(SiMe CH PPh ) 300 500 2 2 2 2 [2,6-bis(imino)pyridyl]CrCl 70 1000 Table 1. e co Th llection of catalytic activities of non-metallocene chromium(III) complexes for the ethylene polymerization. Figure 5. The C NMR spectrum for the system: the oligomer of 2-chloro-2-propen-1-ol (11monomers), [Cr(2-pic) (OH ) ]NO and MMAO-12. 2 2 2 3 − 1 − 1 [Cr(2-pic) ( OH ) ] NO has been calculated. It equals 1434.33 g∙mmol ∙h for the molar ratio 2 2 2 3 complex[Cr(2 − pic) (OH) ]NO : MMAO = 1: 1000. 22 23 Discussion The new complex - [Cr(2-pic) (OH ) ]NO exhibits a very high catalytic activity for the oligomerization of 2 2 2 3 −1 −1 2-chloro-2-propen-1-ol. The catalysts with an activity higher than 1000 g∙mmol ∙h are assumed to be the 3 −1 −1 very highly active catalysts . Thus, it has been concluded that [Cr(2-pic) (OH ) ]NO (1434.33 g∙mmol ∙h ) 2 2 2 3 is a remarkably active catalyst. The analysis of the poly(2-chloroallyl alcohol) by mass spectrometry shows that −1 the oligomer consisting of 11 monomers is formed. The molar mass of this oligomer is 1019.5 g∙mol (Fig. 3). The MS spectrum of the oligomer shows that the peak of the highest intensity occurs at 1019.5 m/z. This value responds to 11 linked monomers of 2-chloro-2-propen-1-ol. Moreover, the distribution of mass peaks shows that the peaks dier ff about 185 m/z and this difference in the m/z value responds to the molecular weight of two mono- mers of 2-chloro-2-propen-1-ol. e Th MS spectrum confirms that the distribution of the obtained oligomer occurs every two molecules of 2-chloro-2-propen-1-ol. Figure 3 shows three oligomers: the first contains 5 monomers (469.3 m/z), the second contains 7 monomers (665.3 m/z) and the third oligomer about 9 monomers (843.3 m/z). 1 13 Furthermore, H and C NMR methods reveal the isotactic molecular structure of the obtained oligomer. A small number of signals in range 20 ppm – 75 ppm in the C NMR spectrum of the system: the oligomer of Scientific REPO R ts | (2018) 8:8632 | DOI:10.1038/s41598-018-26973-6 4 www.nature.com/scientificreports/ 2-chloro-2-propen-1-ol (11 monomers), [Cr(2-pic) (OH ) ]NO and MMAO-12 confirms the isotactic structure 2 2 2 3 16,17 13 of the obtained oligomer (Fig. 5) . C NMR spectrum shows that there are three very high peaks at 74 ppm, 66 ppm and 22 ppm. Others peaks have a very low intensity. The configuration diversity visible on various carbon signals in C NMR makes it possible to propose the tacticity of the obtained oligomer. Recently, the first example of the poly(2-chloroallyl alcohol) preparation catalyzed by the complex compounds was reported in the literature . Two chromium(III) complex compounds containing both organic cations and anions, namely [Cr(dipic) ][Cr(bipy)(dipic)H O]∙2H O and [Cr(dipic) ]Hdmbipy∙2.5H O were reported to 2 2 2 2 2 exhibit a very high catalytic activity for the 2-chloro-2-propen-1-ol polymerization. These compounds have two times higher catalytic activity when compared to the catalyst described in this work - [Cr(2-pic) (OH ) ]NO 2 2 2 3. It may be explained by the fact that [Cr(dipic) ][Cr(bipy)(dipic)H O]∙2H O and [Cr(dipic) ]Hdmbipy∙2.5H O 2 2 2 2 2 complexes contain organic anions which may play an important role in interactions with MMAO in the polym- erization mechanism. In addition to the report referred above , so far in the literature there are no reports on the oligomerization or polymerization of 2-chloro-2-propen-1-ol catalyzed by any complex compound with MMAO. Thus, in order to compare the catalytic activity of the new catalyst - [Cr(2-pic) (OH ) ]NO with others catalysts known in the 2 2 2 3 literature, we have collected the polymerization data for the selected chromium(III) complexes in Table 1. These complexes were selected for non-metallocene structure that they are as close as possible to the catalyst described in this work. As seen, [Cr(2-pic) (OH ) ]NO as catalyst exhibits minimum about 1.4 and maximum 13.3 times 2 2 2 3 higher catalytic activity than the catalysts compiled in Table 1. Conclusions e co Th mposition and structure of the new complex catalyst- [Cr(2-pic) (OH ) ]NO has been confirmed by sev- 2 2 2 3 eral methods: NMR, MS, IR, UV-Vis, elemental analysis and the X-ray diffraction. The designed and synthesized [Cr(2-pic) (OH ) ]NO exhibit the very high catalytic activity in the case of the 2-chloroallyl alcohol oligomeriza- 2 2 2 3 tion. The oligomerization with the use of the new 2-pyridinecarboxylate complex of chromium(III) aer t ft he acti- vation by MMAO-12 undergoes very easily at the room temperature and at atmospheric pressure. The product of the oligomerization reaction with the use of [Cr(2-pic) (OH ) ]NO as catalyst is the poly(2-chloro-allyl alcohol) 2 2 2 3 consisting of 11 monomers The obtained oligomer has an isotactic structure. e r Th eported oligomerization results are promising. This means that the results described in this report give perspectives of the use of the new catalyst to the oligomerization of other beta-olefin derivatives. This kind of oligomers is used in the industrial production of elastomers and coatings. Methods Materials. e r Th eagents were purchased from Sigma-Aldrich: 2-pyridinecarboxylic acid (2-pic), 99% purity), chromium(III) nitrate hexahydrate (99% purity), lithium carbonate (99% purity), toluene (99% purity), modified methylaluminoxane (MMAO-12, 7 wt% aluminum in toluene), 2-chloro-2-propen-1-ol (90%), and from Stanlab - nitric acid (65%). Synthesis. 40 ml of the 0.7 M HNO solution has been mixed with Cr(NO ) ∙9H O (10 mmol, 4.0 g) and 3 3 3 2 2-pyridinecarboxylic acid (2-pic) (22 mmol, 2.7 g). e Th reaction mixture has been heated at reflux for 30 minutes. en t Th he solution obtained by dissolving (8 mmol, 0.59 g) of Li CO in 8 mL H O was added to the reaction mix- 2 3 2 ture. Aer t ft he addition of Li CO solution, the reaction mixture changed the color from green to purple. Then the 2 3 solution has been heated for 5 hours at reflux. In the next step the reaction mixture has been cooled in a refrigera- tor. Aer co ft oling, the obtained product was filtered off and washed with water cooled to about 2 °C. To obtain the crystals of [Cr(2-pic) (OH ) ]NO , the powder was again dissolved in 0.1 M HNO (preheated to 100 °C). Next, 2 2 2 3 3 the hot solution was filtered and left to cool. Then the red crystals of [Cr(2-pic) (OH ) ]NO were obtained. The 2 2 2 3 yield of the synthesis was 62%. X-Ray measurements. Good-quality single-crystal samples of [Cr(2-pic) (OH ) ]NO were selected for the 2 2 2 3 X-ray diffraction measurements (295(2) K) carried out on the Oxford Diffraction Gemini R ULTRA Ruby CCD diffractometer with the Mo K α (λ = 0.71073 Å) radiation. The structure of [Cr(2-pic) (OH ) ]NO was solved 2 2 2 3 with the SHELX package and the SHELXL-97 program. CrysAlis CCD has been used to determine the lattice 18,19 parameters . The standard geometrical calculations linked with the crystal structure of the new complex were made with the PLATON program . The following programs PLUTO-78, ORTEPII and Mercury were used to an 21–23 analysis and a presentation of molecular structures . Full crystallographic details of [Cr(2-pic) (OH ) ]NO have been deposited in the Cambridge Crystallographic 2 2 2 3 Data Center (deposition No. CCDC 1811764) and they may be obtained from www: http://www.ccdc.cam.ac.uk, e-mail: deposit@ccdc.cam.ac.uk or The Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK. −1 IR spectra. The IR spectrum (4000-650 cm range) were obtained using the BRUKER IFS 66 spectropho- tometer over the in a KBr pellet. UV-Vis spectra. e UV Th -Vis spectrum were registered on the Perkin-Elmer Lambda 650. The instrument is linked with the temperature control system (with a scan accuracy of 1 nm and a 1 nm slit width at a scanning rate −1 120.00 nm min (298 K) - Peltier System. The spectrum of [Cr(2-pic) (OH ) ]NO was recorded for the solution 2 2 2 3 of this complex in DMSO (C = 5 mM). complex MS spectra. e Th positive-ion mode MALDI-TOF mass spectrum were obtained using the Bruker Biflex III spectrometer. 2,5-Dihydroxybenzoic acid (DHB) was used as a matrix. Scientific REPO R ts | (2018) 8:8632 | DOI:10.1038/s41598-018-26973-6 5 www.nature.com/scientificreports/ 1 13 NMR spectra. The H and C NMR spectra of the system: the oligomer of 2-chloro-2-propen-1-ol (11mono- mers), [Cr(2-pic) (OH ) ]NO and MMAO-12 were recorded on the Bruker Avance III 500 (500.13/125.76 MHz) 2 2 2 3 instrument (300 K). The poly(2-chloroallyl alcohol) was dissolved in C D Cl . 2 2 4 The oligomerization process. e o Th ligomerization experiments were carried out at atmospheric pressure and at 21 °C under the nitrogen atmosphere. The red solution of [Cr(2-pic) (OH ) ]NO (3 μmol, 1.2 mg) in tol- 2 2 2 3 uene (2 mL) was placed using a glass syringe in the glass cell with a sealed stopper. The glass cell was placed on a magnetic stirrer throughout the duration of the experiments. In the next step, MMAO-12 solution (3 mL) was added to the toluenic solution of the new chromium(III) complex. Aer t ft he addition of the MMAO-12 solution the reaction mixture changed color to brown. 2-chloro-2-propen-1-ol as monomer (3 mL) was added to the glass cell with MMAO-12 and the solution of chromium(III) complex. The oligomerization reaction was carried out for 45 minutes. Aer t ft his time the sticky gel was obtained. The sample of the obtained oligomer, poly(2-chloroallyl alcohol), has been weighed. The product of the oligomerization has been characterized by the positive-ion mode MALDI-TOF mass spectrometry throughout selecting a matrix that facilitates its ionization (DHB). The MALDI-TOF was used to the direct molecular weight determination of the oligomeric poly(2-chloroallyl alco- hol). Moreover, the oligomer has been examined by the NMR spectroscopy. The sample of the oligomer in a small vial was dissolved in 1,1,2,2-tetrachloro( H )ethane. Next, it was transferred using a glass Pasteur pipette to the NMR tube. The analysis of the NMR spectra has been conducted on the ACD/NMR Processor Academic Edition computer program. References 1. Gibson, V. C. & Spitzmesser, S. K. Advances in non-metallocene olefin polymerization catalysis. Chem. Rev. 103, 283–316 (2003). 2. Tullo, A. H. Paying attention to activators. Chem. Eng. News 79(43), 38–38 (2001). 3. Britovsek, G. J., Gibson, V. C. & Wass, D. F. The search for new-generation olefin polymerization catalysts: life beyond metallocenes. Angew. Chem. Int. Edit. 38(4), 428–447 (1999). 4. Döhring, A. et al. Donor-ligand-substituted cyclopentadienylchromium (III) complexes: a new class of alkene polymerization catalyst. 1. Amino-substituted systems. Organometallics 19(4), 388–402 (2000). 5. Gibson, V. C. et al. Chromium(III) complexes bearing N, N-chelate ligands as ethene polymerization catalysts. Chem. Commun. 16, 1651–1652 (1998). 6. Ballem, K. H., Shetty, V., Etkin, N., Patrick, B. O. & Smith, K. M. Chromium(III) and chromium(IV) bis(trimethylsilyl) amido complexes as ethylene polymerisation catalysts. Dalton T. 21, 3431–3433 (2004). 7. Matsunaga, P. T. (Exxon Chemical Patents Inc., USA) PCT Int. Appl. WO9957159 (1999). 8. Fryzuk, M. D., Leznoff, D. B., Rettig, S. J. & Young, V. G. One-electron oxidation of paramagnetic chromium(II) alkyl complexes with alkyl halides: synthesis and structure of five-coordinate chromium(III) complexes. J. Chem. Soc. Dalton 2, 147–154 (1999). 9. Pinheiro, A. C., Roisnel, T., Kirillov, E., Carpentier, J. F. & Casagrande, O. L. Ethylene polymerization promoted by chromium complexes bearing pyrrolide–imine–amine/ether tridentate ligands. Dalton T. 44(36), 16073–16080 (2015). 10. Kirillov, E., Roisnel, T., Razavi, A. & Carpentier, J. F. Chromium(III) complexes of sterically crowded bidentante {ONR} and tridentate {ONNR} naphthoxy-imine ligands: syntheses, structures, and use in ethylene polymerization. Organometallics 28(8), 2401–2409 (2009). 11. McGuinness, D. S., Gibson, V. C., Wass, D. F. & Steed, J. W. Bis(carbene)pyridine complexes of Cr(III): exceptionally active catalysts for the polymerization of ethylene. J. the Am. Chem. Soc. 125(42), 12716–12717 (2003). 12. Millon, L. E. & Wan, W. K. The polyvinyl alcohol–bacterial cellulose system as a new nanocomposite for biomedical applications. J. Biomed. Mater. Res. B 79(2), 245–253 (2006). 13. Schmedlen, R. H., Masters, K. S. & West, J. L. Photocrosslinkable polyvinyl alcohol hydrogels that can be modified with cell adhesion peptides for use in tissue engineering. Biomaterials 23(22), 4325–4332 (2002). 14. Voepel, J., Edlund, U. & Albertsson, A. C. Alkenyl‐functionalized precursors for renewable hydrogels design. J. Polym. Sci. Part A 47(14), 3595–3606 (2009). 15. Drzeżdżon, J., Sikorski, A., Chmurzyński, L. & Jacewicz, D. New type of highly active chromium (III) catalysts containing both organic cations and anions designed for polymerization of beta-olefin derivatives. Sci. Rep. 8(1), 2315 (2018). 16. Kitayama, Y. & Hatada, K., NMR spectroscopy of polymers. Springer Science & Business Media, (Osaka 2013). 17. Cheng, H. N. English, A. D. (Eds) NMR Spectroscopy of Polymers in Solution and in the Solid State. (American Chemical Society 2002). 18. CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Yarnton, (England 2008). 19. Sheldrick, G. M. A short history of SHELX. Acta Cryst. A 64, 112–122 (2007). 20. Spek, A. L. Structure validation in chemical crystallography. Acta Cryst. D 65, 148–155 (2009). 21. Johnson, C. K. ORTEP II, Report ORNL-5138, Oak Ridge National Laboratory, Oak Ridge, TN, (USA 1976). 22. Mortherwell, S. & Clegg, S. PLUTO-78. Program for Drawing and Molecular Structure, University of Cambridge (England 1978). 23. Macrae, C. F. et al. Mercury: visualization and analysis of crystal structures. J. Appl. Cryst. 39, 453–457 (2006). 24. Rüther, T., Braussaud, N. & Cavell, K. J. Novel chromium(III) complexes containing imidazole-based chelate ligands with varying donor sets: synthesis and reactivity. Organometallics 20(6), 1247–1250 (2001). 25. Köhn, R. D. et al. Selective trimerization of α‐olefins with triazacyclohexane complexes of chromium as catalysts. Angew. Chem. Int. Edit. 39(23), 4337–4339 (2000). 26. MacAdams, L. A., Buffone, G. P., Incarvito, C. D., Rheingold, A. L. & Theopold, K. H. A chromium catalyst for the polymerization of ethylene as a homogeneous model for the phillips catalyst. J. Am. Chem. Soc. 127(4), 1082–1083 (2005). 27. Esteruelas, M. A., López, A. M., Méndez, L., Oliván, M. & Oñate, E. Preparation, structure, and ethylene polymerization behavior of bis(imino)pyridyl chromium(III) complexes. Organometallics 22(3), 395–406 (2003). Acknowledgements This work was supported by National Science Centre, Poland under Grant number 2015/19/N/ST5/00276. This publication is the subject filed with the Patent Office (application number P.423454). Author Contributions J.D. - designed the study, syntheses of the complex, oligomerization, data curation, formal analysis, writing of original draft; A.S. - X-Ray measurements, data analysis; L.C. - project administration, formal analysis; D.J. - supervising the work, project administration, formal analysis. Scientific REPO R ts | (2018) 8:8632 | DOI:10.1038/s41598-018-26973-6 6 www.nature.com/scientificreports/ Additional Information Supplementary information accompanies this paper at https://doi.org/10.1038/s41598-018-26973-6. Competing Interests: The authors declare no competing interests. Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Cre- ative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. 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Oligomerization of 2-chloroallyl alcohol by 2-pyridinecarboxylate complex of chromium(III) - new highly active and selective catalyst

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www.nature.com/scientificreports OPEN Oligomerization of 2-chloroallyl alcohol by 2-pyridinecarboxylate complex of chromium(III) - new Received: 29 December 2017 highly active and selective catalyst Accepted: 23 May 2018 Published: xx xx xxxx Joanna Drzeżdżon, Artur Sikorski, Lech Chmurzyński & Dagmara Jacewicz The new 2-pyridinecarboxylate (2-pic) complex of chromium(III) has been designed and synthesized as a new highly active and selective oligomerization catalyst. The crystal structure of the new compound has been determined by X-ray diffraction. The composition and purity of [Cr(2-pic) (OH ) ]NO have been 2 2 2 3 confirmed by several spectroscopic methods and the elemental analysis. Furthermore, the new complex has been investigated towards its catalytic activity for the oligomerization of 2-chloro-2-propen-1-ol under the atmospheric pressure and at room temperature. It has turned out that the novel catalyst exhibits a very high catalytic activity. Consequently, [Cr(2-pic) (OH ) ]NO belongs to a new generation 2 2 2 3 of non-metallocene catalysts. The organometallic complexes of chromium(III) are known as catalysts for the olefin polymerization . The cat - alytic activity of the chromium(III) complexes is induced by the addition of methylaluminoxane (MAO) or its modified form (MMAO) . The metallocene chromium(III) complexes exhibit a very high catalytic activity but 3,4 unfortunately they are unstable under an industrial polymerization of olefins and their derivatives conditions . Additionally, the decomposition of the metallocene complexes of chromium(III) is observed aer t ft heir reaction with MAO. Owing to the interesting catalytic activity of the non-metallocene complexes of chromium(III), these com- plexes are considered as a new generation of catalysts for olefins and their derivatives polymerization . The exam- ple of the non-metallocene complex with a catalytic activity for ethylene polymerization is Cr[N(SiMe ) ] I 3 2 2 2 −1 −1 −1 6 (43 g∙mmol ∙h ∙bar ) . This chromium(III) complex containing neutral ligands exhibits low catalytic proper - ties. However, the non-metallocene catalysts include the chromium(III) complexes with monoanionic ligands a with moderate or high catalytic activity e.g. the bis(phosphino)amide complex of chromium(III) with the activ- −1 −1 −1 7,8 ity equal 500 g∙mmol ∙h ∙bar , the chromium(III) complex with triptycenyl and 2-pyridylmethyl exhibits −1 −1 −1 1 the 6970 g∙mmol ∙h ∙bar catalytic activity . The chromium(III) complexes with pyrrole–imino-amine/ether pro-ligands {ENN }H (E = NH, R = H, 1a; E = NH, R = tBu, 1b; E = O, R = H, 1c) have a very high catalytic activ- ity for the ethylene polymerization . Thus, the non-metallocene chromium(III) complexes with monoanionic 10,11 ligands are promising catalysts for the industrial olefin polymerization . Polyvinyl alcohol is used to produce hydrogels, to drugs production in the pharmaceutical industry and as a 12,13 stabilizer in emulsions . 2-Chloro-2-propen-1-ol is the derivative of vinyl alcohol (hydroxyethene). Thus, the product of the polymerization of this monomer (2-chloro-2-propen-1-ol) may exhibit similar properties and applications as polyvinyl alcohol. Therefore, 2-methyl-2-propen-1-ol as the derivative of 2-chloro-2-propen-1-ol was investigated as the substrate in production of renewable hydrogels by oligomerization . In the literature, there is lack of information about the polymerization of 2-chloro-2-propen-1-ol using complex compounds as the catalysts. Recently, the results of our studies on the new type of chromium(III) catalysts (dipicolinate complexes of Cr(III) with 2,2′-bipyridine and its derivative as ligands) containing both organic cations and anions designed for the polymerization of 2-chloro-2-propen-1-ol has been published . These new catalysts exhibit a very high catalytic activity. It has to be mentioned that the poly(2-chloroallyl alcohol) is prepared at the atmospheric pres- sure and the room temperature (21 °C) . This report is a continuation of our previous studies. We describe the structure of the new [Cr(2-pic) (OH ) ] 2 2 2 NO complex compound where 2-pic denotes the 2-pyridinecarboxylate anion. Moreover, the catalytic activity Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80–308, Gdańsk, Poland. Correspondence and requests for materials should be addressed to J.D. (email: joanna.drzezdzon@ug.edu.pl) Scientific REPO R ts | (2018) 8:8632 | DOI:10.1038/s41598-018-26973-6 1 www.nature.com/scientificreports/ Figure 1. e m Th olecular structure of [Cr(2-pic) (OH ) ]NO . Displacement ellipsoids are drawn at the 50% 2 2 2 3 probability level (Symmetry codes: (i) −x + 1, −y, −z + 1 (ii) −x + 1, y, −z + ½). Figure 2. e cr Th ystal packing of the title compound viewed along the b-axis (hydrogen bonds and halogen bonds are represented by dashed lines; symmetry codes (iii)) ½ + x, −½ + y, z. of the 2-pyridinecarboxylate complex of chromium(III) has been studied in the case of the 2-chloroallyl alcohol oligomerization. Furthermore, the catalytic activity of the novel catalyst has been compared with other known chromium(III)-based catalysts. Results The structure of the new complex. The crystal structure of the novel chromium(III) complex –[Cr(2- pic) (OH ) ]NO has been studied by the X-ray diffraction method. The molecular structure of the new com- 2 2 2 3 plex has been shown in Fig. 1. The crystallographic data for [Cr(2-pic) (OH ) ]NO have been collected in 2 2 2 3 Supplementary Information. In the crystal structure of the [Cr(2-pic) (OH ) ] a cation is arranged around a 2 2 2 center of a symmetry, and in NO anion N2 and O3 atoms lying on the rotational 2-fold axis (Fig. 1). The geometric parameters (bond lengths and angles) characterizing both [Cr(2-pic) (OH ) ] and in 2 2 2 NO are typical for these units (see Supplementary Information). In the crystal packing of tile compounds [Cr(2-pic) (OH ) ] cations are linked via O1W–H1WA···O2 hydrogen bonds to form tapes along the [110] 2 2 2 direction. The neighboring tapes are linked by O–H···O hydrogen bonds between water molecules and NO anion forming a three-dimensional framework structure (Fig. 2). e p Th urity and composition of [Cr(2-pic) (OH ) ]NO was confirmed by the elemental analysis. This test was 2 2 2 3 conducted on the CARBO ERBA - O 1108 automated analyzer. Anal. Calcd for [Cr(2-pic) (OH ) ]NO (%): C, 2 2 2 3 36.54, H, 3.07, N, 10.67. Found: C, 36.53, H, 3.07, N, 10.55. Additionally, the new complex has been studied using several spectroscopic methods, where the results are following: UV-Vis: The regions of the maximum absorption occur at 409 nm and 548 nm (in DMSO). MALDI-TOF-MS: m/z 394.0 (M) , m/z 358.1 (M minus 2 H O) Scientific REPO R ts | (2018) 8:8632 | DOI:10.1038/s41598-018-26973-6 2 www.nature.com/scientificreports/ Figure 3. e MS s Th pectrum for the oligomer consisting of 11 monomers (2-chloro-2-propen-1-ol). Figure 4. The H NMR spectrum for the system: the oligomer of 2-chloro-2-propen-1-ol (11 monomers), [Cr(2-pic) (OH ) ]NO and MMAO-12. 2 2 2 3 −1 −1 −1 IR: 3090.5 cm hydrogen bonds, 1660.8 cm C=O, 1476.6 cm C-C (aromatic) stretching vibrations, −1 −1 −1 822.4 cm C-N (aromatic), 1607.1 cm O-C=O, 769.7 cm Cr-O. 1 13 H NMR and C NMR spectra were not recorded due to the low solubility of [Cr(2-pic) (OH ) ]NO in deu- 2 2 2 3 terated solvents. The oligomerization of 2-chloro-2-propen-1-ol. e n Th ew complex compound has been investigated as catalyst in the case of the 2-chloro-2-propen-1-ol oligomerization. After mixing monomers and activated [Cr(2-pic) (OH ) ]NO (by MMAO-12) the oligomerization has been proceeded at the room temperature and at 2 2 2 3 the atmospheric pressure. The poly-2-chloroallyl alcohol has been obtained as the product of the reaction. The oligomer of 2-chloro-2-propen-1-ol contains 11 monomers. e Th composition of the obtained oligomer has been confirmed by the spectroscopic methods including NMR and MS (Figs  3–5). Moreover, the catalytic activity of Scientific REPO R ts | (2018) 8:8632 | DOI:10.1038/s41598-018-26973-6 3 www.nature.com/scientificreports/ Temperature Catalytic activity −1 −1 −1 Complex [°C] (g∙mmol ∙h ∙bar ) References [Cr{2-[2-(diphenylphosphino)-1-(N-methylimidazol-2-yl) ethyl]-N- 100 108 methy limidazole}Cl ] [Cr{tris(N-methylimidazol-2-yl)methoxymethane}Cl ] 100 208 [Cr(1,3,5-triazacyclohexane)]Cl 40 717 [(2,6-Me Ph) (nacnac)Cr (OEt )CH SiMe ] B(3,5-(CF ) C H ) 2 2 2 2 3 3 2 6 3 4 26 75 228 (nacnac = 2,4-pentane-N,N’-bis(aryl)ketiminato) CrMe[N(SiMe CH PPh ) 300 500 2 2 2 2 [2,6-bis(imino)pyridyl]CrCl 70 1000 Table 1. e co Th llection of catalytic activities of non-metallocene chromium(III) complexes for the ethylene polymerization. Figure 5. The C NMR spectrum for the system: the oligomer of 2-chloro-2-propen-1-ol (11monomers), [Cr(2-pic) (OH ) ]NO and MMAO-12. 2 2 2 3 − 1 − 1 [Cr(2-pic) ( OH ) ] NO has been calculated. It equals 1434.33 g∙mmol ∙h for the molar ratio 2 2 2 3 complex[Cr(2 − pic) (OH) ]NO : MMAO = 1: 1000. 22 23 Discussion The new complex - [Cr(2-pic) (OH ) ]NO exhibits a very high catalytic activity for the oligomerization of 2 2 2 3 −1 −1 2-chloro-2-propen-1-ol. The catalysts with an activity higher than 1000 g∙mmol ∙h are assumed to be the 3 −1 −1 very highly active catalysts . Thus, it has been concluded that [Cr(2-pic) (OH ) ]NO (1434.33 g∙mmol ∙h ) 2 2 2 3 is a remarkably active catalyst. The analysis of the poly(2-chloroallyl alcohol) by mass spectrometry shows that −1 the oligomer consisting of 11 monomers is formed. The molar mass of this oligomer is 1019.5 g∙mol (Fig. 3). The MS spectrum of the oligomer shows that the peak of the highest intensity occurs at 1019.5 m/z. This value responds to 11 linked monomers of 2-chloro-2-propen-1-ol. Moreover, the distribution of mass peaks shows that the peaks dier ff about 185 m/z and this difference in the m/z value responds to the molecular weight of two mono- mers of 2-chloro-2-propen-1-ol. e Th MS spectrum confirms that the distribution of the obtained oligomer occurs every two molecules of 2-chloro-2-propen-1-ol. Figure 3 shows three oligomers: the first contains 5 monomers (469.3 m/z), the second contains 7 monomers (665.3 m/z) and the third oligomer about 9 monomers (843.3 m/z). 1 13 Furthermore, H and C NMR methods reveal the isotactic molecular structure of the obtained oligomer. A small number of signals in range 20 ppm – 75 ppm in the C NMR spectrum of the system: the oligomer of Scientific REPO R ts | (2018) 8:8632 | DOI:10.1038/s41598-018-26973-6 4 www.nature.com/scientificreports/ 2-chloro-2-propen-1-ol (11 monomers), [Cr(2-pic) (OH ) ]NO and MMAO-12 confirms the isotactic structure 2 2 2 3 16,17 13 of the obtained oligomer (Fig. 5) . C NMR spectrum shows that there are three very high peaks at 74 ppm, 66 ppm and 22 ppm. Others peaks have a very low intensity. The configuration diversity visible on various carbon signals in C NMR makes it possible to propose the tacticity of the obtained oligomer. Recently, the first example of the poly(2-chloroallyl alcohol) preparation catalyzed by the complex compounds was reported in the literature . Two chromium(III) complex compounds containing both organic cations and anions, namely [Cr(dipic) ][Cr(bipy)(dipic)H O]∙2H O and [Cr(dipic) ]Hdmbipy∙2.5H O were reported to 2 2 2 2 2 exhibit a very high catalytic activity for the 2-chloro-2-propen-1-ol polymerization. These compounds have two times higher catalytic activity when compared to the catalyst described in this work - [Cr(2-pic) (OH ) ]NO 2 2 2 3. It may be explained by the fact that [Cr(dipic) ][Cr(bipy)(dipic)H O]∙2H O and [Cr(dipic) ]Hdmbipy∙2.5H O 2 2 2 2 2 complexes contain organic anions which may play an important role in interactions with MMAO in the polym- erization mechanism. In addition to the report referred above , so far in the literature there are no reports on the oligomerization or polymerization of 2-chloro-2-propen-1-ol catalyzed by any complex compound with MMAO. Thus, in order to compare the catalytic activity of the new catalyst - [Cr(2-pic) (OH ) ]NO with others catalysts known in the 2 2 2 3 literature, we have collected the polymerization data for the selected chromium(III) complexes in Table 1. These complexes were selected for non-metallocene structure that they are as close as possible to the catalyst described in this work. As seen, [Cr(2-pic) (OH ) ]NO as catalyst exhibits minimum about 1.4 and maximum 13.3 times 2 2 2 3 higher catalytic activity than the catalysts compiled in Table 1. Conclusions e co Th mposition and structure of the new complex catalyst- [Cr(2-pic) (OH ) ]NO has been confirmed by sev- 2 2 2 3 eral methods: NMR, MS, IR, UV-Vis, elemental analysis and the X-ray diffraction. The designed and synthesized [Cr(2-pic) (OH ) ]NO exhibit the very high catalytic activity in the case of the 2-chloroallyl alcohol oligomeriza- 2 2 2 3 tion. The oligomerization with the use of the new 2-pyridinecarboxylate complex of chromium(III) aer t ft he acti- vation by MMAO-12 undergoes very easily at the room temperature and at atmospheric pressure. The product of the oligomerization reaction with the use of [Cr(2-pic) (OH ) ]NO as catalyst is the poly(2-chloro-allyl alcohol) 2 2 2 3 consisting of 11 monomers The obtained oligomer has an isotactic structure. e r Th eported oligomerization results are promising. This means that the results described in this report give perspectives of the use of the new catalyst to the oligomerization of other beta-olefin derivatives. This kind of oligomers is used in the industrial production of elastomers and coatings. Methods Materials. e r Th eagents were purchased from Sigma-Aldrich: 2-pyridinecarboxylic acid (2-pic), 99% purity), chromium(III) nitrate hexahydrate (99% purity), lithium carbonate (99% purity), toluene (99% purity), modified methylaluminoxane (MMAO-12, 7 wt% aluminum in toluene), 2-chloro-2-propen-1-ol (90%), and from Stanlab - nitric acid (65%). Synthesis. 40 ml of the 0.7 M HNO solution has been mixed with Cr(NO ) ∙9H O (10 mmol, 4.0 g) and 3 3 3 2 2-pyridinecarboxylic acid (2-pic) (22 mmol, 2.7 g). e Th reaction mixture has been heated at reflux for 30 minutes. en t Th he solution obtained by dissolving (8 mmol, 0.59 g) of Li CO in 8 mL H O was added to the reaction mix- 2 3 2 ture. Aer t ft he addition of Li CO solution, the reaction mixture changed the color from green to purple. Then the 2 3 solution has been heated for 5 hours at reflux. In the next step the reaction mixture has been cooled in a refrigera- tor. Aer co ft oling, the obtained product was filtered off and washed with water cooled to about 2 °C. To obtain the crystals of [Cr(2-pic) (OH ) ]NO , the powder was again dissolved in 0.1 M HNO (preheated to 100 °C). Next, 2 2 2 3 3 the hot solution was filtered and left to cool. Then the red crystals of [Cr(2-pic) (OH ) ]NO were obtained. The 2 2 2 3 yield of the synthesis was 62%. X-Ray measurements. Good-quality single-crystal samples of [Cr(2-pic) (OH ) ]NO were selected for the 2 2 2 3 X-ray diffraction measurements (295(2) K) carried out on the Oxford Diffraction Gemini R ULTRA Ruby CCD diffractometer with the Mo K α (λ = 0.71073 Å) radiation. The structure of [Cr(2-pic) (OH ) ]NO was solved 2 2 2 3 with the SHELX package and the SHELXL-97 program. CrysAlis CCD has been used to determine the lattice 18,19 parameters . The standard geometrical calculations linked with the crystal structure of the new complex were made with the PLATON program . The following programs PLUTO-78, ORTEPII and Mercury were used to an 21–23 analysis and a presentation of molecular structures . Full crystallographic details of [Cr(2-pic) (OH ) ]NO have been deposited in the Cambridge Crystallographic 2 2 2 3 Data Center (deposition No. CCDC 1811764) and they may be obtained from www: http://www.ccdc.cam.ac.uk, e-mail: deposit@ccdc.cam.ac.uk or The Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK. −1 IR spectra. The IR spectrum (4000-650 cm range) were obtained using the BRUKER IFS 66 spectropho- tometer over the in a KBr pellet. UV-Vis spectra. e UV Th -Vis spectrum were registered on the Perkin-Elmer Lambda 650. The instrument is linked with the temperature control system (with a scan accuracy of 1 nm and a 1 nm slit width at a scanning rate −1 120.00 nm min (298 K) - Peltier System. The spectrum of [Cr(2-pic) (OH ) ]NO was recorded for the solution 2 2 2 3 of this complex in DMSO (C = 5 mM). complex MS spectra. e Th positive-ion mode MALDI-TOF mass spectrum were obtained using the Bruker Biflex III spectrometer. 2,5-Dihydroxybenzoic acid (DHB) was used as a matrix. Scientific REPO R ts | (2018) 8:8632 | DOI:10.1038/s41598-018-26973-6 5 www.nature.com/scientificreports/ 1 13 NMR spectra. The H and C NMR spectra of the system: the oligomer of 2-chloro-2-propen-1-ol (11mono- mers), [Cr(2-pic) (OH ) ]NO and MMAO-12 were recorded on the Bruker Avance III 500 (500.13/125.76 MHz) 2 2 2 3 instrument (300 K). The poly(2-chloroallyl alcohol) was dissolved in C D Cl . 2 2 4 The oligomerization process. e o Th ligomerization experiments were carried out at atmospheric pressure and at 21 °C under the nitrogen atmosphere. The red solution of [Cr(2-pic) (OH ) ]NO (3 μmol, 1.2 mg) in tol- 2 2 2 3 uene (2 mL) was placed using a glass syringe in the glass cell with a sealed stopper. The glass cell was placed on a magnetic stirrer throughout the duration of the experiments. In the next step, MMAO-12 solution (3 mL) was added to the toluenic solution of the new chromium(III) complex. Aer t ft he addition of the MMAO-12 solution the reaction mixture changed color to brown. 2-chloro-2-propen-1-ol as monomer (3 mL) was added to the glass cell with MMAO-12 and the solution of chromium(III) complex. The oligomerization reaction was carried out for 45 minutes. Aer t ft his time the sticky gel was obtained. The sample of the obtained oligomer, poly(2-chloroallyl alcohol), has been weighed. The product of the oligomerization has been characterized by the positive-ion mode MALDI-TOF mass spectrometry throughout selecting a matrix that facilitates its ionization (DHB). The MALDI-TOF was used to the direct molecular weight determination of the oligomeric poly(2-chloroallyl alco- hol). Moreover, the oligomer has been examined by the NMR spectroscopy. The sample of the oligomer in a small vial was dissolved in 1,1,2,2-tetrachloro( H )ethane. Next, it was transferred using a glass Pasteur pipette to the NMR tube. The analysis of the NMR spectra has been conducted on the ACD/NMR Processor Academic Edition computer program. References 1. Gibson, V. C. & Spitzmesser, S. K. Advances in non-metallocene olefin polymerization catalysis. Chem. Rev. 103, 283–316 (2003). 2. Tullo, A. H. Paying attention to activators. Chem. Eng. News 79(43), 38–38 (2001). 3. Britovsek, G. J., Gibson, V. C. & Wass, D. F. The search for new-generation olefin polymerization catalysts: life beyond metallocenes. Angew. Chem. Int. Edit. 38(4), 428–447 (1999). 4. Döhring, A. et al. Donor-ligand-substituted cyclopentadienylchromium (III) complexes: a new class of alkene polymerization catalyst. 1. Amino-substituted systems. Organometallics 19(4), 388–402 (2000). 5. Gibson, V. C. et al. Chromium(III) complexes bearing N, N-chelate ligands as ethene polymerization catalysts. Chem. Commun. 16, 1651–1652 (1998). 6. Ballem, K. H., Shetty, V., Etkin, N., Patrick, B. O. & Smith, K. M. Chromium(III) and chromium(IV) bis(trimethylsilyl) amido complexes as ethylene polymerisation catalysts. Dalton T. 21, 3431–3433 (2004). 7. Matsunaga, P. T. (Exxon Chemical Patents Inc., USA) PCT Int. Appl. WO9957159 (1999). 8. Fryzuk, M. D., Leznoff, D. B., Rettig, S. J. & Young, V. G. One-electron oxidation of paramagnetic chromium(II) alkyl complexes with alkyl halides: synthesis and structure of five-coordinate chromium(III) complexes. J. Chem. Soc. Dalton 2, 147–154 (1999). 9. Pinheiro, A. C., Roisnel, T., Kirillov, E., Carpentier, J. F. & Casagrande, O. L. Ethylene polymerization promoted by chromium complexes bearing pyrrolide–imine–amine/ether tridentate ligands. Dalton T. 44(36), 16073–16080 (2015). 10. Kirillov, E., Roisnel, T., Razavi, A. & Carpentier, J. F. Chromium(III) complexes of sterically crowded bidentante {ONR} and tridentate {ONNR} naphthoxy-imine ligands: syntheses, structures, and use in ethylene polymerization. Organometallics 28(8), 2401–2409 (2009). 11. McGuinness, D. S., Gibson, V. C., Wass, D. F. & Steed, J. W. Bis(carbene)pyridine complexes of Cr(III): exceptionally active catalysts for the polymerization of ethylene. J. the Am. Chem. Soc. 125(42), 12716–12717 (2003). 12. Millon, L. E. & Wan, W. K. The polyvinyl alcohol–bacterial cellulose system as a new nanocomposite for biomedical applications. J. Biomed. Mater. Res. B 79(2), 245–253 (2006). 13. Schmedlen, R. H., Masters, K. S. & West, J. L. Photocrosslinkable polyvinyl alcohol hydrogels that can be modified with cell adhesion peptides for use in tissue engineering. Biomaterials 23(22), 4325–4332 (2002). 14. Voepel, J., Edlund, U. & Albertsson, A. C. Alkenyl‐functionalized precursors for renewable hydrogels design. J. Polym. Sci. Part A 47(14), 3595–3606 (2009). 15. Drzeżdżon, J., Sikorski, A., Chmurzyński, L. & Jacewicz, D. New type of highly active chromium (III) catalysts containing both organic cations and anions designed for polymerization of beta-olefin derivatives. Sci. Rep. 8(1), 2315 (2018). 16. Kitayama, Y. & Hatada, K., NMR spectroscopy of polymers. Springer Science & Business Media, (Osaka 2013). 17. Cheng, H. N. English, A. D. (Eds) NMR Spectroscopy of Polymers in Solution and in the Solid State. (American Chemical Society 2002). 18. CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Yarnton, (England 2008). 19. Sheldrick, G. M. A short history of SHELX. Acta Cryst. A 64, 112–122 (2007). 20. Spek, A. L. Structure validation in chemical crystallography. Acta Cryst. D 65, 148–155 (2009). 21. Johnson, C. K. ORTEP II, Report ORNL-5138, Oak Ridge National Laboratory, Oak Ridge, TN, (USA 1976). 22. Mortherwell, S. & Clegg, S. PLUTO-78. Program for Drawing and Molecular Structure, University of Cambridge (England 1978). 23. Macrae, C. F. et al. Mercury: visualization and analysis of crystal structures. J. Appl. Cryst. 39, 453–457 (2006). 24. Rüther, T., Braussaud, N. & Cavell, K. J. Novel chromium(III) complexes containing imidazole-based chelate ligands with varying donor sets: synthesis and reactivity. Organometallics 20(6), 1247–1250 (2001). 25. Köhn, R. D. et al. Selective trimerization of α‐olefins with triazacyclohexane complexes of chromium as catalysts. Angew. Chem. Int. Edit. 39(23), 4337–4339 (2000). 26. MacAdams, L. A., Buffone, G. P., Incarvito, C. D., Rheingold, A. L. & Theopold, K. H. A chromium catalyst for the polymerization of ethylene as a homogeneous model for the phillips catalyst. J. Am. Chem. Soc. 127(4), 1082–1083 (2005). 27. Esteruelas, M. A., López, A. M., Méndez, L., Oliván, M. & Oñate, E. Preparation, structure, and ethylene polymerization behavior of bis(imino)pyridyl chromium(III) complexes. Organometallics 22(3), 395–406 (2003). Acknowledgements This work was supported by National Science Centre, Poland under Grant number 2015/19/N/ST5/00276. This publication is the subject filed with the Patent Office (application number P.423454). Author Contributions J.D. - designed the study, syntheses of the complex, oligomerization, data curation, formal analysis, writing of original draft; A.S. - X-Ray measurements, data analysis; L.C. - project administration, formal analysis; D.J. - supervising the work, project administration, formal analysis. Scientific REPO R ts | (2018) 8:8632 | DOI:10.1038/s41598-018-26973-6 6 www.nature.com/scientificreports/ Additional Information Supplementary information accompanies this paper at https://doi.org/10.1038/s41598-018-26973-6. Competing Interests: The authors declare no competing interests. Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Cre- ative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not per- mitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. © The Author(s) 2018 Scientific REPO R ts | (2018) 8:8632 | DOI:10.1038/s41598-018-26973-6 7

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