Schiff-Base Complexes and their Application to Styrene ...

1320 I. Kim, Y. S. Ha, D. F. Zhang, C. Ha, U. LeeExperimental PartGeneral Methods and MaterialsAll reactions were performed under a purified nitrogen atmosphereusing standard glove-box and Schlenk techniques. Styrene(from Aldrich) was washed twice with aqueous sodiumhydroxide (5 wt.-%) and twice with water, followed by dryingover MgSO 4 and distillation over CaH 2 under N 2 atmosphereat reduced pressure. Solvents were dried under nitrogen usingstandard reagents. MAO was obtained from Akzo Chemical asan 8.4 wt.-% total Al solution in toluene. The tetradentateligand salen [1a; N,N 0 -bis(salicylidene)ethylene-1,2-diamine]and its derivatives salen(tBu) [1b; N,N 0 -bis(3-tert-butyl-2-hydroxybenzylidene)ethylene-1,2-diamine], salen(di-Me) [1c;N,N 0 -bis(2-hydroxy-3,5-dimethylbenzylidene)ethylene-1,2-diamine], salen(di-tBu) [1d; N,N 0 -bis(3,5-di-tert-butyl-2-hydroxybenzylidene)ethylene-1,2-diamine], salen(Me) [1e;N,N 0 -bis(2-hydroxy-5-methylbenzylidene)ethylene-1,2-diamine]were prepared according to a literature procedure. [15]Polymerization of StyreneA Schlenk tube (30 mL) with a magnetic stirrer was attached toa high-vacuum line and then sealed under a nitrogen atmosphere.The required amounts of distilled toluene (5 mL),styrene (5 mL), MAO and precatalyst (25.6 mmol) werecharged into the dried Schlenk tube in this order under nitrogenflow. The polymerization was carried out at constant temperaturefor 5 h. The reaction was quenched with acidifiedmethanol (5 vol.-% HCl) and then precipitated with excessmethanol. The resulting mixture was filtered and dried undervacuum at 60 8C. The polymerization yield was determinedgravimetrically. The isolated samples comprised syndiotacticand atactic polymers, and the atactic part was extracted withrefluxing 2-butanone for 4 h. The atactic polymer was isolatedby vacuum removal of the solvent.Characterization1 H NMR spectra of salen and its derivatives were recorded on aVarian Unity Plus 300 spectrometer in CDCl 3 , using tetramethylsilaneas the internal reference. Elemental analysis wascarried out using a Vario EL analyser.The intrinsic viscosity was measured in o-dichlorobenzeneat 135 8C using a modified Ubbhelode viscometer. Theaverage molecular weight was calculated by the followingequation: [16]½ZŠ ¼1:38 10 4 M 0:7vThermal analysis of the hot 2-butanone insoluble polymerwas carried out with a differential scanning calorimeter (DSC,Perkin-Elmer DSC, model: Pyris1) at a heating rate of 10 8C/min under nitrogen atmosphere. Any thermal history differencein the polymers was eliminated by first heating the specimento above 280 8C, cooling at 10 8C/min to 90 8C, and thenrecording the second DSC scan.Syntheses of Titanium Complexes[TiCl 2 (salen)] (2a)Literature procedures were employed to synthesize titaniumsalen complexes. [17] As an example, [TiCl 2 (salen)] (2a)waspreparedas follows. H 2 salen (0.300 g, 1.12 mmol) in THF was treateddropwise with titanium(IV) chloride (0.212 g, 1.12 mmol)with vigorous stirring. Orange [TiCl 2 (salen)(THF)] precipitatedimmediately from solution. This mixture was thenrefluxed until all of the orange solid had been replaced by thedark red microcrystalline solid [TiCl 2 (salen)]. After removingthe solvent by filtration, the microcrystalline solid was washedwith an acetone/water mixture (50:50) and then with pureacetone. The resulting solid was dried in vacuo. Yield: 75.6%.1 H NMR (300 MHz, CDCl 3 , 293 K): d ¼ 4.26 (s, 4 H), 6.83–7.14 (m, 4 H), 7.46–7.66 (m, 4 H), 8.38 (s, 2 H) ppm.Anal. Calcd for C 16 H 14 Cl 2 N 2 O 2 Ti: C, 49.91; H, 3.66; N,7.27. Found: C, 50.02; H, 3.71; N, 7.24.[TiCl 2 {salen(tBu)}] (2b)Following the above procedures, the crude product was recrystallizedfrom p-xylene to yield red rectangular crystalssuitable for X-ray diffraction. Yield: 87.1%.1 H NMR (300 MHz, CDCl 3 , 293 K): d ¼ 1.45 (s, 9 H), 4.15(s, 4 H), 6.93 (t, J ¼ 7.5 Hz, 2 H), 7.30 (dd, J ¼ 7.65, 1.50 Hz,2 H), 7.53 (dd, J ¼ 7.95, 1.5 Hz, 2 H), 8.72 (s, 2 H) ppm.Anal. Calcd for C 24 H 30 Cl 2 N 2 O 2 Ti: C, 57.97; H, 6.08; N,5.63. Found: C, 58.02; H, 6.07; N, 5.61.[TiCl 2 {salen(di-Me)}] (2c)Following the above procedure, the crude product was recrystallizedfrom toluene. Yield: 90.3%.1 H NMR (300 MHz, CDCl 3 , 293 K): d ¼ 2.10 (s, 6 H), 2.34(s, 6 H), 3.89 (s, 4 H), 6.43 (s, 2 H), 6.93 (s, 2 H), 7.59 (s, 2 H)ppm.Anal. Calcd for C 20 H 22 Cl 2 N 2 O 2 Ti: C, 54.45; H, 5.03; N,6.35. Found: C, 54.47; H, 5.10; N, 6.37.[TiCl 2 {salen(di-tBu)}] (2d)Following the above procedures, the crude product was recrystallizedfrom toluene to yield red rectangular crystals suitablefor X-ray diffraction. Yield: 91.5%.1 H NMR (300 MHz, CDCl 3 , 293 K): d ¼ 1.26 (s, 18 H), 1.37(s, 18 H), 4.13 (s, 4 H), 7.19 (s, 2 H), 7.53 (s, 2 H), 8.26 (s, 2 H)ppm.Anal. Calcd. for C 32 H 46 Cl 2 N 2 O 2 Ti: C, 63.06; H, 7.61; N,4.60. Found: C, 62.98; H, 7.67; N, 4.62.[TiCl 2 {salen(Me)}] (2e)Following the above procedure, the crude product was recrystallizedfrom toluene. Yield: 83.6%.1 H NMR (300 MHz, CDCl 3 , 293 K): d ¼ 2.28 (s, 6 H), 4.15(s, 4 H), 6.93 (d, J ¼ 8.4 Hz, 2 H), 7.30 (dd, J ¼ 8.4, 2.1 Hz, 2 H),8.23 (s, 2 H) ppm.Anal. Calcd for C 18 H 18 Cl 2 N 2 O 2 Ti: C, 52.33; H, 4.39; N,6.78. Found: C, 52.32; H, 4.37; N, 6.69.Macromol. Rapid Commun. 2004, 25, 1319–1323 www.mrc-journal.de ß 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim