This article is published as part of the Dalton Transactions themed issue entitled:

d0

organometallics in catalysis

Guest Editors John Arnold (UC Berkeley) and Peter Scott (University of Warwick)

Published in issue 30, 2011 of Dalton Transactions

Image reproduced with permission of Guo-Xin Jin

Articles in the issue include: PERSPECTIVES:

Half-titanocenes for precise olefin polymerisation: effects of ligand substituents and some mechanistic aspects Kotohiro Nomura and Jingyu Liu Dalton Trans., 2011, DOI: 10.1039/C1DT10086F

ARTICLES:

Stoichiometric reactivity of dialkylamine boranes with alkaline earth silylamides Michael S. Hill, Marina Hodgson, David J. Liptrot and Mary F. Mahon Dalton Trans., 2011, DOI: 10.1039/C1DT10171D Synthesis and reactivity of cationic niobium and tantalum methyl complexes supported by imido and β-diketiminato ligands Neil C. Tomson, John Arnold and Robert G. Bergman Dalton Trans., 2011, DOI: 10.1039/ C1DT10202H

Visit the Dalton Transactions website for more cutting-edge inorganic and organometallic research

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Selected examples concerning eff ects of both cyclopenta-

dienyl fragment (Cp’) and anionic donor ligand (Y) in non-

bridged modifi ed half-titanocenes of the type, Cp’TiX2(Y)

(X = halogen, alkyl), which display unique characteristics as

new olefi n polymerisation catalysts, have been reviewed;

a precise fi ne tuning of the ligand substituents plays an

important role for the successful (co)polymerisation.

Title: Half-titanocenes for precise olefi n polymerisation: eff ects of

ligand substituents and some mechanistic aspects (Perspective)

Showcasing research from the Organic Chemistry Laboratory (Prof. Dr. Kotohiro Nomura) at the Chemistry Department, Tokyo Metropolitan University (TMU), in collaboration with former/present group members (in TMU and Nara Institute of Science and Technology), partly funded by the Japan Society for the Promotion of Science (JSPS). The image describes four major catalytically-active species, and the background is the picture in the Nara Park, Japan (National Park).

As featured in:

See Nomura et al., Dalton Trans., 2011, 40, 7666.

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COVER ARTICLEJin et al.Syntheses, reactions, and ethylene polymerization of titanium complexes with [N,N,S] ligands

Themed issue: d0 organometallics in catalysis

dt040030_cover_PRINT_LITHO.indd 1-3dt040030_cover_PRINT_LITHO.indd 1-3 7/11/11 5:23:35 PM7/11/11 5:23:35 PM

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Syntheses, reactions, and ethylene polymerization of titanium complexes with[N,N,S] ligands†

Ai-Quan Jia,a Jian-Qiang Wang,b Ping Hua and Guo-Xin Jin*a

Received 20th December 2010, Accepted 18th February 2011DOI: 10.1039/c0dt01800g

Tridentate dianionic arylsulfide free ligands [ArNHCH2C6H4NHC6H4-2-SPh] (Ar = Ph (3a); Ar =2,4,6-trimethylphenyl (3b); Ar = 2,6-diisopropylphenyl (3c)) have been prepared by reduction of thecorresponding imine compounds [ArN CHC6H4NHC6H4-2-SPh] (Ar = Ph (2a); Ar =2,4,6-trimethylphenyl (2b); Ar = 2,6-diisopropylphenyl (2c)) with LiAlH4 in high yields. Reactions ofTiCl4 with the tridentate dianionic arylsulfide free ligands (3a–3c) afford five-coordinate andfour-coordinate titanium complexes [kS, k2N-(ArNHCH2C6H4NHC6H4-2-SPh)TiCl2] (Ar = Ph (4a);Ar = 2,4,6-trimethylphenyl (4b)] and [k2N-(ArNHCH2C6H4NHC6H4-2-SPh)TiCl2] (Ar =2,6-diisopropylphenyl (4c)], respectively. The molecular structures of compounds 2b, 2c, 3b and 3c·HClhave been characterized by single crystal X-ray diffraction analyses. Complexes 2a–4c are characterizedby IR,1H-NMR spectra, and elemental analysis. EXAFS spectroscopy performed on complexes 4b and4c reveals the expected different coordination geometry due to steric hindrance effect. When activatedby excess methylaluminoxane (MAO), 4a–4c can be used as catalysts for ethylene polymerization andexhibit moderate to good activities.

Introduction

Ever since the discovery of Ziegler–Natta catalysis,1 non-metallocene molecular catalysts, including both early and latetransition metal complexes, have attracted great attention.2–4

Complexes containing chelating anilido-imine ligands are amongthe typical examples due to their readily preparation as well asversatile modification of the steric and electronic demands.5 Ithas been widely known that zirconium complexes bearing b-diketiminate ligands with electron-withdrawing groups displayedhigh catalytic activities for ethylene polymerization (1.1 ¥ 107

gPE·mol-1Zr·h-1) and produced polyethylene with narrow molec-ular weight distribution (PDI ~ 2.7).6 Wu and Huang reportedgroup 4 complexes with bis(b-diketiminate) ligands for ethylenepolymerization and copolymerization with norbornene.7

In 2004, Gibson reported that group 4 metal complexescontaining phenoxy-amide ligands bearing soft pendant donorsare shown to give more highly active ethylene polymerizationcatalysts than the counterparts containing hard donors or systemswithout a pendant donor (1.95 ¥ 107 gPE·mol-1Ti·h-1 vs. 9.6 ¥

aShanghai Key Laboratory of Molecular Catalysis and Innovative Ma-terials, Department of Chemistry, and Key Lab of Molecular Engi-neering of Polymers of Chinese Ministry of Education, Department ofMacromolecular Science, Fudan University, Shanghai, 200 433, China.E-mail: gxjin@fudan.edu.cn; Fax: +86-21- 65641740; Tel: +86-21-65643776bShanghai Synchrotron Radiation Facility, Shanghai Institute of AppliedPhysics, Chinese Academy of Sciences, Shanghai, 201204, P. R. China† CCDC reference numbers 805154–805157. For crystallographic data inCIF or other electronic format see DOI: 10.1039/c0dt01800g

104 gPE·mol-1Ti·h-1).8 The soft pendant donors in his paper arephosphorous and sulfur atoms, while the hard donors are nitrogenand oxygen atoms. Wu reported the nickel complexes with sulfur-containing tridentate monoanionic ligand have higher catalyticactivity than [N,N] bidentate anilido–imino nickel complexes to-wards norbornene polymerization.9 Additionally, Okuda reportedthat group 4 complexes with tetra-dentate ligand [SO-O-S] showedgood selectivity and activity towards polymerization of styrene.10

However, despite the extensive investigations of organometalliccomplexes of chelating anilido-imine ligands and the utility ofmonoanionic tridentate [N-NS] nickel and palladium complexesin norbornene polymerization,9 few dianionic tridentate [N-N-S]ligands of titanium(IV) complexes have been described and theirreaction chemistry is rarely developed. Previously, Our group havereported Ni, Cu, Ir catalysts containing [NN-] ligands for ethyleneand norbornene polymerization.11 Furthermore, heterogeneousTi, Zr and Hf catalysts,12 as well as homogeneous Ti, Zrcatalysts containing [O-NO-] and [O-NS-] ligands,13 have alsobeen studied in our group. Herein, we describe the syntheses,X-ray crystallographic characterizations, EXAFS spectroscopyexperiment, and ethylene polymerization chemistry of dianionictridentate arylsulfide [N-N-S] titanium(IV) complexes (Scheme 1).

Results and discussion

Syntheses and characterizations of the titanium complexes

Three [N,N,S] tridentate dianionic free ligands with varioussterically hindered substituents were synthesized. The synthetic

7730 | Dalton Trans., 2011, 40, 7730–7736 This journal is © The Royal Society of Chemistry 2011

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Scheme 1 Synthesis of titanium complexes 4a–4c.

route for these tridentate free ligands is shown in Scheme 2. Con-densation of 2-fluorobenzaldehyde with various anilines affordedimines 1a–1c in high yields. The reactions of 1a–1c with PhS-2-C6H4NHLi proceeded completely under 40 ◦C. Pure products of2a–2c were obtained as yellow crystals by initial chromatographyand then crystallization from ethanol, in about 50% yields. Theaniline–arylamido derivatives 3a–3c were readily prepared in highyields by reduction of the corresponding aniline–arylimine 2a–2cwith excess LiAlH4 in cool diethyl ether. 3a and 3b were lightyellow powder, while 3c was somewhat oily. However, it is worthnoting that excess HCl in the workup would lead to acidificationof compouns 3a–3c. For example, when compound 3c combinedwith one molecule of HCl, it became to be 3c·HCl (Scheme 3).All of these free ligands were proved by 1H NMR and comparedwith known compounds. The chemical shift of CH N protonsin compounds 2a–2c are 8.54, 8.22, and 8.27 ppm, respectively.The signals disappeared in 1H NMR spectra of compounds 3a–3c, while new signals appeared and identified as NH (3.51, 2.75,2.90 ppm) and CH2 (4.08, 3.88, 4.19 ppm) protons, indicating theCH N (imine) has been transformed to CH2NH (amine). TheIR spectra also verified the transformation of imine to amine,for example, in the spectrum of 3a, there were two absorptionpeaks at 3359 cm-1 and 3217 cm-1, indicating the existence oftwo secondary amines. The structures of 2b, 2c, 3b and 3c·HCl

Scheme 3 Acidification of free ligand 3c.

were further confirmed by single-crystal X-ray diffraction analysis(Fig. 1–4). In 2b, the C(7)–N(2) bond length is 1.259(3) A, for 3b,the C(7)–N(1) bond length is 1.471(3) A, which is typical of acarbon-nitrogen single bond. For 2c, the C(7)–N(2) bond distanceis 1.262(3) A, similar to that in 2b. In 3c·HCl, the C(19)–N(2)bond length is 1.517(4) A, longer than that in 3b, and much longerthan the corresponding C(7)–N(2) bond in 2c (1.262(3) A). TheC(6)–C(7)–N(2) bond angle in 2b is 125.9 (3)◦, which is similarto that in 2c (126.1(3)◦). In 3b, the C(1)–C(7)–N(1) bond angle is111.2(2)◦, smaller than that in 2b, and similar to the bond angle ofC(14)–C(19)–N(2) in 3c·HCl (114.8(3)◦). In addition, the chlorideanion in 3c·HCl is nearer to N(2), as the Cl ◊ ◊ ◊ N(2) and Cl ◊ ◊ ◊ N(1)distance are 3.081(4) and 3.230(3) A, respectively.

Fig. 1 Molecular structure of 2b with thermal ellipsoids drawn at the30% level.

Scheme 2 Synthetic routes to free ligands 3a–3c.

This journal is © The Royal Society of Chemistry 2011 Dalton Trans., 2011, 40, 7730–7736 | 7731

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Fig. 2 Molecular structure of 2c with thermal ellipsoids drawn at the 30%level.

Fig. 3 Molecular structure of 3b with thermal ellipsoids drawn at the30% level.

The first attempt to synthesize complexes 4a–4c involved twosteps: (1) deprotonation of the free ligands with 2 equiv. nBuLi; (2)reaction of the lithium salts with TiCl4 in toluene. However, thereactions seemed to be more complicated than they were expected,and the desired products were not isolated successfully. We tried toprepare complexes 4a–4c based on our group’s previous work,13f bythe reaction of TiCl4 with 1 equiv. free ligand without any base intoluene at low temperature for more than 12 h. Attempts to applythe method to the preparation of 4a–4c proved to be accessible(Scheme 1). The yellow solution turned to be red immediately,when the reaction was complete, the suspension was filtered andthe precipitate was washed with toluene and hexane for threetimes, sequentially. The complexes were fully characterized by1H NMR and elemental analyses (see Experimental Section).The two NH signals in 1H NMR spectra of 3a–3c (3.51 and7.61 ppm for 3a; 2.75 and 8.02 ppm for 3b; 2.90 and 7.70 ppmfor 3c) disappeared in the 1H NMR spetra of 4a–4c, indicating

Fig. 4 Molecular structure of 3c·HCl with thermal ellipsoids drawn atthe 30% level.

obvious coordination of the two nitrogen atoms to the titaniummetal. Chemical shift of protons (NCH2) in complexes 4a–4cwere shifted downfield 0.11, 0.98, and 0.70 ppm compared to freeligands, respectively. The absorption peaks of secondary amine inIR spectra of 3a–3c were no longer observed for complexes 4a–4c.The local atomic environment and charge state of Ti in compounds4b and 4c were investigated by X-ray absorption spectroscopy,including extended X-ray absorption fine structure (EXAFS) andX-ray absorption near edge structure (XANES) (Fig. 5, 6). Thepre-edge at about 4970 eV in XANES spectra can be assignedto 1s→3d electron transition. The observed differences in theintensity of pre-edge peaks are consistent with the difference inthe coordinated model.14 The EXAFS spectra allows us to getinformation on the environment around the metal center, whichhas already been used for the characterization of Ti complexes forethylene polymerization.15 The fitting of the Ti–K-edge EXAFSspectra (Table 1) of both investigated complexes was performedusing a two shell model, in which the first coordination shellat about 1.8 A consists of the two coordinating nitrogen atomsof the diimine ligand group, the second shell of the chlorineand sulfur backscatterer at about 2.3–2.5 A. With the help of

Fig. 5 Ti K-edge XANES spectra of sample for 4b. Inset: Fouriertransform of experimental data and fit for 4b.

7732 | Dalton Trans., 2011, 40, 7730–7736 This journal is © The Royal Society of Chemistry 2011

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Table 1 Fit parameters of Ti EXAFS spectra for sample 4b and 4c

Shell N R s2 (10-3 A2) DE0 (eV)

4b Ti–N 1.7 ± 0.2 1.84 ± 0.02 8.1 ± 1.8 -14.3 ± 2.9Ti–Cl 1.8 ± 0.3 2.32 ± 0.02 3.7 ± 0.7 4.2 ± 0.6Ti–S 0.9 ± 0.1 2.46 ± 0.02 15.0 ± 3.5 12.4 ± 3.1

4c Ti–N 2.1 ± 0.3 1.84 ± 0.02 4.1 ± 0.6 -4.2 ± 0.7Ti–Cl 2.3 ± 0.2 2.32 ± 0.02 9.3 ± 0.9 7.1 ± 2.0

Fig. 6 Ti K-edge XANES spectrum of sample for 4c. Inset: Fouriertransform of experimental data and fit for 4c.

EXAFS analysis, the solid state structure of 4b and 4c werefound to be five coordinate and four coordinate titanium com-plexes as [kS, k2N-(ArNHCH2C6H4NHC6H4-2-SPh)TiCl2] (Ar =2,4,6-trimethylphenyl (4b)] and [k2N-(ArNHCH2C6H4NHC6H4-2-SPh)TiCl2] (Ar = 2,6-diisopropylphenyl (4c)] (Fig. 5–6). It isassumed that the iso-propyl was too crowded to form four-coordinate complex 4c, as a result, we proposed 4a was afive-coordinate complex as [kS, k2N-(PhNHCH2C6H4NHC6H4-2-SPh)TiCl2].

Ethylene polymerization. The prepared complexes were brieflyinvestigated in ethylene polymerization. Titanium complexes 4a–4c showed moderate to good activities under the initiation ofMAO. The results are summarized in Table 2.

In the 4a–4c/MAO systems, the red mixture turned intotransparent yellow immediately as MAO was charged, indicatingthe active species had better solubility in toluene. Ethylene con-sumption continued during 30 min of polymerization. Complex 4c

Table 2 Ethylene polymerization results with titanium complexes 4a–4ca

Entry Catalyst Al/Ti ratio T/◦C Time/min Activityb Mvc ¥ 10-4

1 4a 1000 20 30 250 1922 4b 1000 20 30 600 2623 4c 500 20 30 700 964 4c 1000 20 30 1250 1945 4c 1500 20 30 1100 3616 4c 2000 20 30 700 3647 4c 1000 40 30 1500 1248 4c 1000 60 60 1300 153

a Conditions: [Ti] 10 mmol, toluene = 50 mL, ethylene pressure = 1 atm. b 103

gPE·molTi-1·h-1. c Mv measured by the Ubbelohde calibrated viscosimetertechnique.

exhibited the highest activity about 1.5 ¥ 106 gPE·molTi-1·h-1. Theinfluence of polymerization temperature has also been studied.As it demonstrates in Table 2, when the temperature goes upfrom 20 to 60 ◦C, the activity of 4c firstly obviously increasesand then decreases a little. The highest activity appears at 40 ◦C.Different ratio of Al/Ti also influences the catalytic behavior ofthe catalysts, for example, in 4c/MAO system, the activity goesup with the increased amount of MAO and achieves the highestactivity when the ratio of Al/Ti is 1000, but it decreases whenmore MAO is added. The activity of complex 4c, having a bulkyiso-propyl group, is somewhat higher than that of complexes 4aand 4b.

The polymerization temperature and the ratio of Al/Ti haslittle influence on the molecular weight of polyethylene, the Mv ofpolymer was about 105–106 gmol-1.

Conclusions

A series of titanium complexes with tridentate dianionic arylsul-fide ligands [NNSR]2- have been prepared. The routes employedproved to be effective with preparation of both compounds 3a–3c and complexes 4a–4c. The molecular structures of compounds2b, 2c, 3b and 3c·HCl have been characterized by single X-raydiffraction analysis. Under the guidance of EXAFS spectroscopyanalysis, it is found that when the substituent R1 is varied from Hto iPr, both five-coordinate [kS, k2N-(ArNHCH2C6H4NHC6H4-2-SPh)TiCl2] (Ar = Ph (4a); Ar = 2,4,6-trimethylphenyl(4b)] and four-coordinate and [k2N-(ArNHCH2C6H4NHC6H4-2-SPh)TiCl2] (Ar = 2,6-diisopropylphenyl (4c)] titanium complexeswere synthesized, reflecting that the steric hindrance plays asignificant role on the geometry of complexes. When activated byexcess methylaluminoxane (MAO), these complexes can be used ascatalysts for ethylene polymerization. The activities of complexes4a–4c increase as the R1 group is replaced from H to iPr. Thehighest activity can reach ca.106 gPE·molTi-1·h-1.

Experimental

General considerations

All the operations were carried out under pure argon atmosphereusing standard Schlenk techniques. Tetrahydrofuran (THF),hexane, and toluene were distilled from sodium-benzophenone.Dichloromethane was distilled from calcium hydride. Com-mercial reagents, namely, TiCl4, methylaluminoxane (MAO),LiAlH4, nBuLi, 2-fluorobenzaldehyde, aniline, 2,4,6- trimethylben-zenamine and 2,6-diisopropylbenzenamine were purchased fromACROS Co. The free ligands 3a–3c were prepared according tothe modified literature.9

1H (400 MHz) NMR measurements were obtained on a BrukerAC400 spectrometer in CDCl3 solution. Elemental analyses for Cand H were carried out on an Elementar III Vario EI analyzer.

2a–2c. A solution of n-butyllithium (12.5 mL, 20.0 mmol) wasadded slowly to a solution of 2-(phenylthio)aniline (4.02 g, 20.0mmol) in THF (40 mL) at - 78 ◦C, and the reaction mixturewas warmed to room temperature and stirred overnight. This palesuspension was added to a solution of 1a–1c (20.0 mmol) in THF(20 mL) at room temperature. After stirring for 12 h at 40 ◦C,the red transparent solution was quenched with H2O (20 mL)

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and extracted with n-hexane. The organic phase was combinedand evaporated to dryness in vacuo to give the crude productas yellow oil. Pure product was obtained as yellow crystals byrecrystallization from ethanol in about 50% yield.

2a. 1H NMR (CDCl3, 400 MHz): d 6.83 (t, 1H, Ar–H), 6.98–7.43 (m, 16H, Ar–H), 7.61 (d, 1H, Ar–H), 8.54 (s, 1H, CH N),11.45 (s, 1H, NH).

2b. 1H NMR (CDCl3, 400 MHz): d 2.05 (s, 6H, o-Me), 2.28 (s,3H, p-Me), 6.84 (m, 3H, Ar–H), 6.98–7.09 (m, 6H, Ar–H), 7.28–7.38 (m, 5H, Ar–H), 7.62 (d, 1H, Ar–H), 8.22 (s, 1H, CH N),11.19 (s, 1H, NH).

2c. 1H NMR (CDCl3, 400 MHz): d 1.12 (d, 12H, CH(CH3)2),3.06 (hept, 2H, CH(CH3)2), 6.82–6.88 (m, 1H, Ar–H), 6.98–7.29(m, 13H, Ar–H) 7.36 (d, 1H, Ar–H), 7.58 (d, 1H, Ar–H), 8.27 (s,1H, CH N), 11.09 (brs, 1H, NH).

3a–3c. To a suspension of LiAlH4 (0.76 g, 20.0 mmol) in ether(20 mL) was slowly added a solution of ligand 2a–2c (5.0 mmol) inethyl ether (30 mL). After the mixture was stirred for 2 h at roomtemperature, water (13 mL) and HCl (20%; 20 mL) aqueous wereadded sequentially at 0 ◦C. The organic phase was separated andwashed with water (15 mL ¥ 3). The organic layers were dried withanhydrous MgSO4. The solvent was removed under vacuum, andthe pure product 3a–3c was obtained as yellow solid in about 90%yield.

3a. 1H NMR (CDCl3, 400 MHz): d 3.51 (s, 1H, NH), 4.08 (s,2H, CH2), 6.55 (d, 2H, Ar–H), 6.75 (t, 1H, Ar–H), 6.82–6.86 (m,1H, Ar–H), 6.96–7.05 (m, 4H, Ar–H), 7.09–7.16 (m, 4H, Ar–H),7.22–7.32 (m, 4H, Ar–H), 7.39 (d, 1H, Ar–H), 7.53–7.55 (m, 1H,Ar–H), 7.61 (s, 1H, NH).

3b. 1H NMR (CDCl3, 400 MHz): d 2.16 (s, 6H, o-Me), 2.23(s, 3H, p-Me), 2.75 (brs, 1H, NH), 3.88 (s, 2H, CH2), 6.81 (s, 2H,Ar–H), 6.85–6.95 (m, 2H, Ar–H), 7.03–7.10 (m, 5H, Ar–H), 7.21(d, 2H, Ar–H), 7.27 (m, 2H, Ar–H), 7.34 (d, 1H, Ar–H), 7.51 (d,1H, Ar–H), 8.02 (s, 1H, NH).

3c. 1H NMR (CDCl3, 400 MHz): d 1.15 (d, 12H, CH(CH3)2),2.90 (brs, 1H, NH), 3.21 (hept, 2H, CH(CH3)2), 3.86 (s, 2H, CH2),6.85–6.88 (m, 1H, Ar–H), 6.96–7.04 (m, 2H, Ar–H), 7.07–7.29 (m,12H, Ar–H), 7.52 (d, 1H, Ar–H), 7.70 (brs, 1H, NH).

4a. To a stirred suspension of TiCl4 (1.0 mL, 1.0 mmol) in10 mL of toluene was added 3a (0.38 g, 1.0 mmol) in 20 mLtoluene dropwise at - 78 ◦C. Stirring was maintained for 12 hat room temperature, and the precipitate was filtered and washedby toluene and hexane sequentially, affording 4a (0.40 g, 80%) asbrown red powder. 4a 1H NMR (CDCl3, 400 MHz): d 4.19 (s, 2H,CH2), 6.31 (d, 1H, Ar–H), 6.79 (t, 1H, Ar–H), 6.96 (d, 1H, Ar–H), 7.09–7.18 (m, 13H, Ar–H), 7.47 (d, 1H, Ar–H), 7.85 (d, 1H,Ar–H). IR (KBr): n = 2851, 1714, 1578, 1464, 1376, 1303, 1262,1157, 726 cm-1. Anal. Calc. for C25H20N2SCl2Ti: C, 60.14; H, 4.04;N, 5.61; Found: C, 60.23; H, 4.09; N, 5.54.

4b. This complex was prepared as described above for 4a,starting from 3b (0.21 g, 0.5 mmol), and TiCl4 (0.5 mL, 0.5 mmol).Workup afforded 4b (0.21 g, 78%) as orange red powder. 1H NMR(CDCl3, 400 MHz): d 2.01 (s, 6H, o-Me), 2.18 (s, 3H, p-Me), 4.86(s, 2H, CH2), 6.48 (s, 1H, Ar–H), 6.70 (s, 2H, Ar–H), 6.86–7.23 (m,

6H, Ar–H), 7.36–7.45 (m, 3H, Ar–H), 7.78 (d, 1H, Ar–H), 8.66(d, 2H, Ar–H). IR (KBr): n = 2917, 1716, 1624, 1583, 1460, 1377,1300, 1153, 723 cm-1. Anal. Calc. for C28H26N2SCl2Ti: C, 62.12;H, 4.84; N, 5.17; Found: C, 62.23; H, 4.89; N, 5.14.

4c. This complex was prepared as described above for 4a,starting from 3c (0.47 g, 1.0 mmol), and TiCl4 (1.0 mL, 1.0 mmol).Workup afforded 4c (0.21 g, 78%) as purple red powder. 4c 1HNMR (CDCl3, 400 MHz): d 1.08 (d, 12H, CH(CH3)2), 2.78 (hept,2H, CH(CH3)2),, 4.56 (s, 2H, CH2), 6.10 (s, 1H, Ar–H), 6.38 (d,1H, Ar–H), 6.80 (d, 1H, Ar–H), 6.90 (t, 1H, Ar–H), 7.15–7.55 (m,10H, Ar–H), 8.90 (s, 2H, Ar–H). IR (KBr): n = 2857, 1716, 1460,1376, 1301, 1254, 1112, 726 cm-1. Anal. Calc. for C31H34N2SCl2Ti:C, 63.82; H, 5.53; N, 4.80; Found: C, 63.85; H, 5.59; N, 4.75.

Single-crystal X-ray structure determination of compounds 2b,2c, 3b and 3c·HCl. For compounds 2b, 2c, 3b and 3c·HCl, asingle crystal suitable for X-ray analysis was sealed into a glasscapillary, all the intensity data of the single crystal were collectedon the CCD-Bruker Smart APEX system. All determinations ofthe unit cell and intensity data were performed with graphite-monochromated Mo-Ka radiation (l = 0.71073 A). All data werecollected at room temperature using the w-scan technique. Thesestructures were solved by direct methods, using Fourier techniques,and refined on F 2 by a full-matrix least-squares method. Allthe non-hydrogen atoms were refined anisotropically, and all thehydrogen atoms were included but not refined. Crystallographicdata are summarized in Table 3.

Crystallography data (excluding structure factors) for thestructures reported in this paper have been deposited with theCambridge Crystallographic Data Centre, CCDC 805154 (2a),CCDC 805155 (2b), 805156 (3b) and 805157 (3c·HCl).† Copiesof these data can be obtained free of charge on applicationto the Director, CCDC, 12 Union Road, Cambridge CB2IEZ, UK (fax: +44-1223-336033; e-mail: deposit@ccdc.ac.uk orhttp://www.ccdc.cam.ac.hk).

XAFS data collection. The X-ray absorption data at the TiK-edge of the sample were measured in the fluorescent mode withLytle fluorescence detector on beam line BL14W1 of the ShanghaiSynchrotron Radiation Facility (SSRF), China. The station wasoperated with a double crystal monochromator, Si(111), detunedto 40% intensity to minimize the presence of higher harmonics.All measurements were done in transmission or fluorescent modeusing ion chambers filled with a mixture of He and N2 to havean X-ray absorbance of 20% in the first and 80% in the secondchamber. Data processing and analysis were performed using theprogram ATHENA.16 All fits to the EXAFS data were performedusing the program ARTEMIS.16

Ethylene polymerization. A 100 mL flask was equipped withan ethylene inlet, a magnetic stirrer, and a vacuum line. Theflask was filled with 30 mL of freshly distilled toluene, MAO(10 wt% in toluene) was added, and the flask was placed in abath at the desired polymerization temperature for 10 min. Thepolymerization reaction was started by adding a toluene solutionof the catalyst precursor (0.010 mmol) with a syringe. Then thesolvent toluene was added to make the total volume of the solution50 mL. The polymerization was carried out for the desired time andthen quenched with 3% HCl in ethanol (250 mL). The precipitated

7734 | Dalton Trans., 2011, 40, 7730–7736 This journal is © The Royal Society of Chemistry 2011

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Table 3 Summary of crystallographic data for 2b, 2c, 3b, 3c·HCl

2b 2c 3b 3c·HCl

Formula C28H26N2S C31H32N2S C28H28N2S C31H35ClN2Sfw 422.57 464.65 424.58 503.12T/K 293(2) 293(2) 293(2) 293(2)Cryst syst Monoclinic Monoclinic Monoclinic MonoclinicSpace group C2/c P21/c P21/n P21/na/A 35.541(8) 14.352(6) 15.068(6) 11.802(5)b/A 8.540(2) 38.303(15 7.717(3) 10.335(5)c/A 16.126(4) 10.056(4) 20.796(9) 23.884(11)a (◦) 90 90 90 90b (◦) 108.397(4) 107.106(6) 99.169(6) 103.704(7)g (◦) 90 90 90 90V/A3 4644.6(19) 5284(34) 2387.3(17) 2830(2)Z 8 8 4 4Dcalc/Mg m-3 1.209 1.168 1.181 1.181m/mm-1 0.157 0.143 0.153 0.230F(000) 1792 1984 904 1072Cryst size/mm 0.15 ¥ 0.12 ¥ 0.10 0.20 ¥ 0.10 ¥ 0.10 0.20 ¥ 0.18 ¥ 0.16 0.16 ¥ 0.12 ¥ 0.082q range (◦) 2.42–25.01 1.48–27.01 1.56–26.99 1.76–26.01no. of reflns collected/unique 9343/4089 25507/11211 11132/5115 12465/5508

[R(int) = 0.0984] [R(int) = 0.0828] [R(int) = 0.0648] [R(int) = 0.0836]no. of data/restraints/params 4089/0/287 11211/0/629 5115/0/291 5508/0/332goodness of fit on F 2 0.752 0.753 0.967 0.872Final R indices [I > 2s(I)]a R1 = 0.1565 R1 = 0.1767 R1 = 0.0914 R1 = 0.1496

wR2 = 0.0794 wR2 = 0.1310 wR2 = 0.1740 wR2 = 0.1650lgst diff peak and hole/e A-3 0.144 and -0.169 0.315 and -0.254 0.558 and -0.337 0.467 and -0.245

a R1 = ‖F o| - |F c‖/∑

|F o|; wR2 = [∑

w(|F o2| - |F c

2|)2/∑

w|F o2|2]1/2.

polymer was filtered and then dried overnight in a vacuum ovenat 80 ◦C.

Acknowledgements

This work was supported by the Shanghai Science and TechnologyCommittee (08DZ2270500, 08DJ1400103), Shanghai LeadingAcademic Discipline Project (B108), the National Basic ResearchProgram of China (2009CB825300, 2010DFA41160), and theNational Science Foundation of China (21001112). The authorsthank beamline BL14W1 (Shanghai Synchrotron Radiation Fa-cility) for providing the beam time.

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