Synthesis and characterization of 2-(2-benzhydrylnaphthyliminomethyl) pyridylnickel halides: formation of branched polyethylene

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1 Journl me Dynmic Article Links Cite this: DOI:.39/c0xx00000x ARTICLE TYPE Synthesis nd chrcteriztion of 2-(2-benzhydrylnphthyliminomethyl) pyridylnickel hlides: formtion of brnched polyethylene Erlin Yue,, Qifeng Xing, Liping Zhng, Xio-Ping Co, *, Qisong Shi, Lin Wng, Crl Redshw, *, nd Wen-u Sun, *,, Received (in XXX, XXX) Xth XXXXXXXXX XX, Accepted Xth XXXXXXXXX XX DOI:.39/b000000x Abstrct: A series of 2-(2-benzhydrylnphthyliminomethyl)pyridine derivtives (L1 L3) ws prepred nd used to synthesize the corresponding bis-ligted nickel(ii) hlide complexes (i1 i6) in good yield. The moleculr structures of representtive complexes, nmely the bromide i3 nd the chloride complex i6, were confirmed by single crystl X ry diffrction, nd reveled distorted octhedrl geometry t nickel. Upon ctivtion with either methylluminoxne (MAO) or modified methylluminoxne (MMAO), ll nickel complex pre-ctlysts exhibited high ctivities (up to g(pe) mol 1 (i) h 1 ) towrds ethylene polymeriztion, producing brnched polyethylene of low moleculr weight nd nrrow polydispersity. The influence of the rection prmeters nd the nture of 1 the lignds on the ctlytic behvior of the title nickel complexes were investigted Introduction Polyolefin mterils re extensively used in our dily life nd the nnully consumption mounts to over 1 million tonnes. In order to produce dvnced polyolefins using new ctlytic systems, ttention hs switched to lte-trnsition metl complex pre-ctlysts in both the industril nd cdemic rens. 1,2 Since the discovery of the α-diiminometl (i or Pd) complexes 3 nd bis(imino)pyridylmetl (Fe or Co) complexes, 4 the chrcteristic fetures of the polyethylene obtined hve been shown to rely on metl employed: highly liner polyethylene ws generlly produced from either iron or coblt complex pre-ctlysts, 1,2 wheres brnched polyethylene ws commonly observed from ctlytic systems bsed on nickel complex pre-ctlysts. 1,2b The polymeriztion mechnism operting within nickel systems is n illustrtion of how hydrogen-elimintion fcilittes chin-trnsfer to produce brnched polymers. Currently, industril processes for ccessing brnched polyethylenes mostly rely on the copolymeriztion of ethylene with α-olefins. ickel pre-ctlysts re providing new pproches to highly brnched polyethylene, nd the resulting new polymers cn potentilly exhibit new properties nd my yield new fmily of dvnced polyethylenes. 2b Therefore, the syntheses of nickel complexes hve extensively been conducted through designing new lignds with modifiction vi the use of different substituents. 6 As n exmple, the 2-iminopyridylnickel complex pre-ctlysts (A, Scheme 1) exhibited high ctivities towrds ethylene polymeriztion or oligomeriztion, 7 whilst the methyl-bridged binucler complex pre-ctlysts (B, Scheme 1) performed ethylene oligomeriztion nd polymeriztion. 8,9 Recently, progress hs been mde through the use of benzhydryl-substituted nilines, 12 nd the 2-iminopyridylnickel complex model (C, Scheme 1) ws revisited to revel high ctivities solely for 0 ethylene polymeriztion. 13 R R i i X Ar X Br Br 2 A B i X X D CPh 2 R i X X Ph 2 C C CPh 2 X i X Ph 2 C Scheme 1 Models of,-bidentte mono- nd bi-metllic nickel complexes Subsequently, new benzhydryl-substituted nphthylmines were designed nd were used to prepre 2-(1-(2-benzhydrylnphthylimino)ethyl)pyridylnickel complexes (D, Scheme 1), which reveled high ctivities of up to g(pe) mol 1 (i) h 1 towrds ethylene polymeriztion. 14 Given this, the 2-(2-benzhydrylnphthyliminomethyl)pyridine derivtives re lso of interest, prticulrly in terms of their nickel complexes nd the polymeriztion ctlysis thereof. Interestingly, such 2-(2-benzhydrylnphthyliminomethyl)pyridyl nickel hlide complexes re bis-ligted complexes (E, Scheme 1), which ccording to literture would be expected to be inctive in E

2 1 ctlysis polymeriztion. 1 owever, the title nickel complexes were found to exhibit even higher ctivities towrd ethylene polymeriztion thn did their 2-(1-(2-benzhydrylnphthylimino) ethyl)pyridyl-nickel nlogues. 14 erein, the synthesis nd chrcteriztion of the 2-(2-benzhydrylnphthyliminomethyl) pyridine derivtives nd their nickel complexes re reported, nd the ctlytic performnces of these nickel complexes, s well s the properties of the resulting polyethylene, re investigted. Results nd discussion Synthesis nd chrcteriztion The series of 2-(2-benzhydrylnphthyliminomethyl)pyridine derivtives (L1 L3, Scheme 2) ws redily synthesized by the condenstion rection of picolinldehyde with benzhydrylsubstituted nphthylmines in moderte yields following the reported procedure. 14 All orgnic compounds were chrcterized by FT IR, 1 nd 13 C MR spectroscopy s well s by elementl nlysis. 4 moleculr structures of i3 nd i6 re shown in Fig. 1 nd 2, respectively, nd their selected bond lengths nd ngels re tbulted in Tble 1. Fig. 1 ORTEP drwing of i3. Therml ellipsoids re shown t % probbility level. ydrogen toms hve been omitted for clrity. O + 2 Ar s: Ph 2 C Ar p-tso toluene (DME)iBr 2 or icl O Ar L1 - L3 C 2 Cl 2 EtO 2 3 X = Br X = Cl L1 i1 i4 L2 i2 i Ph 2 C L3 i3 i6 Ph 2 C Ph 2 C Ar X i X Ar i1 - i6 Scheme 2 Synthetic procedure for the orgnic nd nickel complexes Trils of the rection of the 2-(2-benzhydrylnphthyliminomethyl)pyridine in dichloromethne solution with different molr rtios of icl2 62O or (DME)iBr2 in ethnol were conducted, nd the bis-ligted nickel hlide (chloride or bromide) complexes (i1 i6) were best isolted when using two equivlents of orgnic compound to nickel hlide (Scheme 2). According to the FT IR spectr, the C= stretching vibrtions in complexes i1 i6 were shifted to lower frequencies in the region cm -1 with weker intensity compred to the peks t cm -1 for the free orgnic compounds, indicting the effective coordintion between the imino-group nd the ctionic nickel center. Elementl nlysis dt ws consistent with these nickel complexes hving the formul L2iX2 (X = Br, Cl). Crystl structures of representtive bromide (i3) nd chloride (i6) complexes were determined. Single-crystl X ry diffrction studies Single crystls of i3 nd i6 suitble for X ry diffrction nlysis were obtined by lying diethyl ether onto their dichloromethne solutions t room temperture. Both complexes i3 nd i6 re bis-ligted mononickel(ii) complexes possessing distorted octhedrl geometry t the nickel center. The 0 Fig. 2 ORTEP drwing of i6. Therml ellipsoids re shown t % probbility level. ydrogen toms hve been omitted for clrity. Tble1 Selected bond lengths (Å) nd ngles ( ) for i3 nd i6 i3 i6 Bond lengths (Å) i(1) (1) 2.068(3) i(1) (1) 2.086(3) i(1) (2) 2.27(3) i(1) (2) 2.234(3) i(1) (1 i ) 2.068(3) i(1) (1 i ) 2.086(3) i(1) (2 i ) 2.27(3) i(1) (2 i ) 2.234(3) i(1) Br(1) 2.41(6) i(1) Cl(1) 2.24(9) Bond ngles ( ) (1) i(1) (2) 78.08() (1) i(1) (2) 78.13() (1) i(1) (1 i ) (17) (1) i(1) (1 i ) (18) (1 i ) i(1) (2) 1.92(1) (1 i ) i(1) (2) 1.87() (1) i(1) (2 i ) 1.92(1) (1) i(1) (2 i ) 1.87() (1 i ) i(1) (2 i ) 78.08() (1 i ) i(1) (2 i ) 78.13() (2) i(1) (2 i ) 180.0(3) (2) i(1) (2 i ) (13) (1) i(1) Br(1) 87.98(8) (1) i(1) Cl(1) 91.33(8) (1 i ) i(1) Br(1) 92.02(8) (1 i ) i(1) Cl (1) 88.67(8) (2) i(1) Br(1) 96.26(7) (2) i(1) Cl (1) 83.32(7) (2 i ) i(1) Br(1) 83.74(7) (2 i ) i(1) Cl (1) 96.68(7) As shown in Fig. 1, the nickel center is coordinted by four nitrogens (1, 2, 1 i nd 2 i ) of the two chelte lignds nd two bromides (Br1 nd Br1 i ), which is similr to the nilinebsed bis(iminopyridyl)nickel dibromide. 13,16 There is fivemembered hetero-nickel plne with 1, i1, 2, C1 nd C6

3 toms, nd the bond length of i1 1pyridine (3) Å is shorter thn tht of i1 2imino 2.27 (3) Å, reflecting the stronger bonding between the imino nd ctionic nickel center. The dihedrl ngle between the pyridyl nd imino-nphthyl plnes is 9.87, which is similr to tht within the nickel nlogues bering (1-ryliminoethyl)pyridines. 13 A closely similr structure ws observed for the chloride nlogue i6 (Fig. 2 nd Tble 1). Ctlytic Behvior towrd Ethylene Polymeriztion Vrious co-ctlysts such s MAO, MMAO nd Et2AlCl were used to ctivte the nickel pre-ctlyst i2 for ethylene polymeriztion (runs 1 3 in Tble 2), which indicted tht higher ctlytic ctivities in ethylene polymeriztion were chievble when employing either MAO or MMAO. ctlytic system with the Al/i rtio of 00 (run 6, Tble 3) reveled higher ctivity thn did the system with the Al/i rtio of 170 (run, Tble 3). Therefore there re two mximum ctivities for such ctlytic systems t different Al/i rtio rtios of 0 nd 00. of MAO, indicting potentilly two kinds of ctive species. As seen in the GPC curve (Fig. 3), ll ctlytic systems generlly exhibited single-site ctlysis with nrrow polydispersity for ll the obtined polyethylene. 1 Tble 2 Ethylene polymeriztion by i2 using vrious co-ctlysts Run Coctlyst Al/i Yield/g Activity b M w/gmol - M w/m c n T m/ o C d 1c 1 MAO MMAO Et 2AlCl Generl conditions: 2 μmol of i; min; o C; 0 ml of toluene for tm of ethylene. b 6 g(pe) mol 1 (i) h 1. c Determined by GPC. d Determined by DSC. Ethylene polymeriztion in the presence of MAO In the presence of the co-ctlyst MAO, complex i2 ws evluted to optimize the polymeriztion conditions including the molr rtio of Al/i nd the rection temperture, nd the results re collected in Tble 3, which lso includes some of the 2 properties of the obtined polyethylene. Tble 3 Ethylene polymeriztion by i1 i6/mao Run Prect. Al/i T/ o C Yield/g Activity b c M w /gmol -1 M w/m c n T d m / o C 1 i i i i i i i i i i i i i i i i Fig. 3 GPC trces for the polyethylene by i2/mao system with vrious Al/i rtios (runs 1 7 in Tble 3). On fixing the Al/i molr rtio t 0, the rection temperture ws chnged from to C (runs 4, nd 8 11, Tble 3); the highest ctivity observed, nmely g (PE) mol 1 (i) h 1, ws t C (run 4 in Tble 3). The GPC dt indicted tht higher moleculr weight polyethylene ws obtined t lower tempertures, nd the GPC curves re shown in Fig. 4. These phenomen were consistent to previous observtions for 2-iminopyridylnickel pre-ctlysts, 6,,13,14 nd re scribed to incresed chin-trnsfer nd termintion t higher temperture. As well s the GPC mesurements, the melting points of resultnt polyethylenes were mesured by differentil scnning clorimetry (DSC). The Tm vlues of the polyethylene drmticlly decresed on elevting the rection temperture (runs 4, nd 8 11, Tble 3), nd re slightly higher thn those of their nlogs bering 2-(1-(2-benzhydrylnphthylimino)ethyl) pyridines, probbly reflecting less brnches in the current systems. Generl conditions: 2 μmol of i; min; 0 ml of toluene. b 6 g(pe) mol 1 (i) h 1. c Determined by GPC. d Determined by DSC. 3 At C nd tm of ethylene, the Al/i rtio ws chnged from 70 to 2 (runs 1 7, Tble 3), nd the highest ctivity ws observed with the Al/i rtio 0 (run 4, Tble 3) t g(pe) mol 1 (i) h 1. In generl, the moleculr weights of the resultnt polyethylene slightly decresed on incresing the Al/i rtio (runs 1, Tble 3), which ws scribed to fster chin trnsfer on incresing the Al concentrtion. 12b owever, the 6 70 Fig. 4 GPC curves for the polyethylene obtined using the i2/ MAO system t different tempertures (runs 4, 8 11 in Tble 3) On the bsis of bove results, the optimum conditions with n Al/i rtio of 0 t C were utilized to explore the ctlytic behvior of ll the other nickel pre-ctlysts i1 nd i3 i6 (runs 12 16, Tble 3). All nickel pre-ctlysts exhibited high ctivities towrds ethylene polymeriztion, which differs from

4 reported bis-ligted nickel pre-ctlysts which usully possess low ctlytic ctivities. 1 In ddition, the two hlides re locted in trns positions, which is not fvorbly for coordintion insertion; the trnsformtion of these bis-ligted nickel species into mono-ligted ctive species is ssumed to occur during the ethylene polymeriztion. 17 It is noteworthy tht the nickel prectlysts (i3 nd i6) bering more benzhydryl substituents exhibited reltively higher ctivities thn did their nlogues, which is different to the ctlytic performnces by the nlogues ligted by 2-(1-(2-benzhydrylnphthylimino)ethyl) pyridines in the presence of Et2AlCl. 14 The 13 C MR spectrum for the polyethylene obtined from the i2/mao t C (run 11 in Tble 3) is shown in Fig.. Interpreted ccording to the literture, 18 there re 182 brnches 1 per 00 crbons, nd the signls re presented in Tble 4, which indictes tht the min brnches include methyl (26.88 %), some long chins (3.18 %) nd myl chins (17.00 %), which is consistent to the observtions for the nlogue system comprising the 2-(1-(2-benzhydrylnphthylimino)ethyl)pyridylnickel hlide complexes Al/i rtio of 170 t C (run 4 in Tble ). On comprison with the system using MAO, the system with MMAO is less thermlly stble, whilst the resultnt polyethylene exhibited reltively lower moleculr weights nd nrrower PDIs, but slightly higher melting points suggestive of less brnching. Tble Ethylene polymeriztion by i1 i6/ MMAO Run Prect. Al/i T/ t/ Yield/ Act. b M c w / M w/m c n T d m / C min g gmol -1 C 1 i i i i i i i i i i i i i i i i i Generl conditions: 2 μmol of i; 0 ml of toluene for tm of ethylene. b 6 g(pe) mol 1 (i) h 1. c Determined by GPC. d Determined by DSC. 2 Fig. 13 C MR spectrum of the polyethylene by i2/ MAO t C (run 11 in Tble 3) Tble 4 Percentge of brnches for the polyethylene (run 11 in Tble 3) 18 Pek no. Chem. Shifts /ppm Integrl exp. Brnch content Percentge over totl brnching m m(1,4) m(1,) m(1,6) e p b l l(1,4) δδc [E] [R] Totl brnching = 182 Brnches/00C Methyl brnches % Ethyl brnches 1.09 % Propyl brnches % Butyl brnches 7.16 % Amyl brnches % Long brnches 3.18 % Ethylene polymeriztion in the presence of MMAO In similr mnner, the pre-ctlyst i2 in the presence of MMAO ws explored (runs 1 9, Tble ), nd the highest ctivity of g(pe) mol 1 (i) h 1 ws obtined with the 4 0 Regrding the lifetime of the ctive species, the polymeriztion ws conducted over different periods from to min (runs 4, nd 12, Tble ). On prolonging the rection time, the ctlytic ctivities slightly decresed, whilst the obtined polyethylene reveled higher moleculr weight nd wider polydispersity (Fig. 6). These results re consistent to the observtions for the reported nickel nlogues bering the 2- iminopyridine lignd system., Fig. 6 GPC curves of polyethylene obtined using the i2/ MMAO system over different times (runs 4, 12 in Tble ) All the other nickel pre-ctlysts were investigted in the presence of MMAO, nd were found to perform with good ctivities in ethylene polymeriztion under the optimum conditions of Al/i molr rtio 170 t C (runs 13 17, Tble ). Regrding to the influences of rection prmeters nd the nture of lignds, the tendency of ctlytic performnce of the i/mmao systems is highly similr to the observtion of the i/mao; however, the system with MMAO exhibited slightly

5 lower ctivity nd produced lower moleculr weight polyethylene thn did the system using MAO. Conclusion The series of 2-(2-benzhydrylnphthyliminomethyl)pyridine derivtives nd their nickel hlide complexes were synthesized nd fully chrcterized, nd single crystl X ry diffrction reveled the complexes i3 nd i6 to contin bis-ligted mononickel with distorted octhedrl geometry t the metl. All the nickel complex pre-ctlysts, ctivted by either MAO or MMAO, exhibited high ctivities (up to g(pe) mol 1 (i) h 1 ) towrds ethylene polymeriztion, nd produced polyethylene of lower moleculr weight nd nrrow moleculr polydispersity. This is rre exmple of bis-ligted nickel hlides performing with high ctivities towrds ethylene polymeriztion, especilly given tht the two hlides re trns. The nickel complexes bering 2-(ryliminomethyl)pyridines showed slightly higher ctivity thn their nlogues bering 2-(1- (rylimino)ethyl)pyridine derivtives. 14 Experimentl Section Generl considertion. All mnipultions involving ir- nd moisture-sensitive compounds were crried out under nitrogen tmosphere using stndrd Schlenk techniques. Toluene ws refluxed over sodium nd distilled under nitrogen prior to use. Methylluminoxne (MAO, 1.46 M solution in toluene) nd modified methylluminoxne (MMAO, 1.93 M in heptne) were purchsed from Akzo obel Corp. Diethylluminium chloride (Et2AlCl, 0. M in toluene) ws purchsed from Acros Chemicls. igh-purity ethylene ws purchsed from Beijing Ynsn Petrochemicl Co. nd used s received. Other regents were purchsed from Aldrich, Acros, or locl suppliers. MR spectr were recorded on Bruker DMX 0 Mz instrument t mbient temperture using TMS s n internl stndrd; IR spectr were recorded on Perkin Elmer System 00 FT IR spectrometer. Elementl nlysis ws crried out using Flsh EA 1112 micro-nlyzer. Moleculr weights nd moleculr weight distribution (MWD) of polyethylene were determined by PL GPC2 t C, with 1,2,4-trichlorobenzene s the solvent. The melting points of polyethylene were mesured from the second scnning run on Perkin Elmer TA Q00 differentil scnning clorimetry (DSC) nlyzer under nitrogen tmosphere. In the procedure, smple of bout 4.0 mg ws heted to 1 C rte of C /min nd kept for 2 min t 1 C to remove the therml history nd then cooled t rte of C /min to - C. 13 C MR spectr of the polyethylenes were recorded on Bruker DMX 0 Mz instrument t 13 C in deuterted 1,2-dichlorobenzene with TMS s n internl stndrd. Synthesis of lignds 2-(2-Benzhydrylnphthyliminomethyl)pyridine (L1). A solution of picolinldehyde (0.221 g, 2.06 mmol), 2- benzhydrylnphylmine (0.670 g, 2.17 mmol) nd ctlytic mount of p-toluenesulfonic cid (0.079 g, 0.41 mmol) in toluene (80 ml) ws refluxed for 8 h. The solvent ws evported under reduced pressure, nd then the residue ws purified by column chromtogrphy on bsic lumin with the eluent of petroleum ether ethyl cette (v : v = : 1) to fford yellow solid in 76 % isolted yield. Mp: 8 9 C. 1 MR (0 Mz, CDCl3, TMS): δ 8.71 (d, 1, J = 4.8 z, Py ), 8.19 (d, 1, J = 8.0 z, Py ), 8.0 (s, 1, C=), (m, 2, Py ), 7.76 (d, 1, J = 8.4 z, Ar ), 7.9 (d, 1, J = 8.4 z, Ar ), (m, 3, Ar ), (m, 11, Ar ),.84 (s, 1, CPh2). 13 C MR (0 Mz, CDCl3, TMS): 16.7, 14.2 ( C=), 149.9, 146.9, 143.9, 136.8, 133.1, 129.8, 128.7, 128.4, 128.0, 127.6, 126.4, 126.1, 12.9, 12.7, 12.6, 124.1, 123., 122.0, 1.8 ( CPh2). FT IR (KBr, disk, cm -1 ): 2, 24, 1642 (νc=), 176, 1466, 12, 127, 98, 8, 748, 736, 698. Anl. Clcd for C29222 (398.18): C, 87.41;,.6;, 7.03 %; Found: C, 87.26;,.79;, 6.93 %. 2-(2,4-dibenzhydrylnphthyliminomethyl)pyridine (L2). Using the sme procedure s for the synthesis of L1, L2 ws prepred s yellow solid in 72 % yield. Mp: C. 1 MR (0 Mz, CDCl3, TMS): δ 8.70 (d, 1, J = 4.8 z, Py ), 8. (d, 1, J = 8.0 z, Py ), 8.09 (s, 1, C=), 7.96 (d, 1, J = 8.4 z, Py ), (m, 2, Py nd Ar ), (m, 23, Ar ), 6.68 (s, 1, Ar ), 6.17 (s, 1, CPh2),.71 (s, 1, CPh2),. 13 C MR (0 Mz, CDCl3, TMS): 16.6, 14.2 ( C=), 149.9, 14.7, 143.8, 143.7, 136.8, 13.7, 131.2, 1.3, 129.6, 129., 129.4, 128.6, 128.4, 128.2, 127., 126.3, 126.2, 126.1, 12., 124.3, 124.2, 121.9, 3.0 ( CPh2), 1.7 ( CPh2). FT IR (KBr, disk, cm -1 ): 3, 24, 1643 (νc=), 178, 1491, 14, 1384, 1342, 122, 11, 7,, 991, 948, 91, 73, 736, 698. Anl. Clcd for C42322 (64.26) C, 89.33;,.71;, 4.96 %; Found: C, 89.09;,.74;, 4.90 %. 2-(2,4,7-tribenzhydrylnphthyliminomethyl)pyridine (L3). Using the sme procedure s for the synthesis of L1, L3 ws prepred s yellow solid in 64 % yield. Mp: C. 1 MR (0 Mz, CDCl3, TMS): δ 8.68 (d, 1, J = 4.4 z, Py ), 8.00 (d, 1, J = 7.6 z, Py ), 7.9 (s, 1, C=), 7.87 (d, 1, J = 8.8 z, Py ), 7.78 (t, 1, J = 7.6 z, Py ), (m, 33, Ar ), 6.64 (s, 1, Ar ), 6.12 (s, 1, CPh2),.6 (s, 1, CPh2),.7 (s, 1, CPh2),. 13 C MR (0 Mz, CDCl3, TMS): 16.6, 14.1 ( C=), 149.7, 14.6, 143.9, 143.8, 143.7, 1.9, 136.8, 136.6, 13.6, 1.2, 1.0, 129.6, 129., 129.4, 128.6, 128.4, 128.3, 128.2, 128.1, 127.7, 126.3, 126.2, 12.4, 124., 124.3, 121.9, 6.9 ( CPh2), 3.0 ( CPh2), 1.7 ( CPh2). FT IR (KBr, disk, cm -1 ): 6, 24, 1642 (νc=), 197, 1493, 1446, 137, 1336, 1182, 74, 32, 9, 779, 746, 700. Anl. Clcd for C422 (7.33) C, 90.38;,.79;, 3.83 %; Found: C, 89.90;,.89;, 3.70 %. Synthesis of nickel Complexes Generl procedure. icl2 62O (0.2 mmol) or (DME)iBr2 (0.2 mmol) ws dissolved in ml ethnol nd dded to the solution of the lignds (0. mmol) in ml C2Cl2. The mixture ws stirred for 12 h, nd then diethyl ether ws poured into the mixture to precipitte the complex. The precipitnt ws collected by filtrtion, wshed with diethyl ether (3 ml), nd dried under vcuum t C. Bis(2-(2-benzhydrylnphthyliminomethyl)pyridyl)nickel bromide (i1) (, yellow, 92 % yield): FT IR (KBr, disk, cm -1 ):, 24, 1622 (νc=), 196, 1493, 1446, 137, 1322, 1261, 76, 27, 782, 741, 700. Anl. Clcd for C844Br24i (12.13): C, 68.;, 4.37;,.2 %. Found: C, 68.36;,

6 4.48;,.46 %. Bis(2-(2,4-dibenzhydrylnphthyliminomethyl)pyridyl)nickel bromide (i2) (, yellow, 9 % yield): FT IR (KBr, disk, cm -1 ): 9, 24, 1633 (νc=), 197, 171, 1493, 1446, 13, 17, 1224, 116, 17, 72, 29, 94, 764, 742, 700. Anl. Clcd for C8464Br24i ( ): C, 74.8;, 4.79;, 4.16 %. Found: C, 74.9;, 4.96;, 4.02 %. Bis(2-(2,4,7-tribenzhydrylnphthyliminomethyl)pyridyl)nickel bromide (i3) (, yellow, 84 % yield): FT IR (KBr, disk, cm - 1 ):, 2, 1628 (νc=), 197, 1493, 1447, 1376, 132, 1264, 76, 28, 782, 748, 698. Anl. Clcd for C184Br24i ( ): C, 78.62;,.04;, 3.33 %. Found: C, 78.36;,.28;, 3.26 %. Bis(2-(2-benzhydrylnphthyliminomethyl)pyridyl)nickel 1 chloride (i4) (, yellow, 91 % yield): FT IR (KBr, disk, cm -1 ): 61, 2973, 1633 (νc=), 196, 173, 4, 1382, 14, 1227, 11, 18, 67, 43, 8, 780, 71, 70. Anl. Clcd for C844Cl24i (924.23): C, 7.18;, 4.79;, 6.0 %. Found: C, 7.02;, 4.86;,.98 %. Bis(2-(2,4-dibenzhydrylnphthyliminomethyl)pyridyl)nickel chloride (i) (, yellow, 83 % yield): FT IR (KBr, disk, cm -1 ):, 23, 1634 (νc=), 198, 173, 1491, 1447, 1377, 18, 1224, 117, 18, 74, 948, 76, 743, 700. Anl. Clcd for C8464Cl24i (126.39): C, 80.13;,.12;, 4.4 %. Found: 2 C, 79.98;,.26;, 4.38 %. Bis(2-(2,4,7-tribenzhydrylnphthyliminomethyl)pyridyl)nickel chloride (i6) (, yellow, 84 % yield): FT IR (KBr, disk, cm -1 ): 8, 2, 1629 (νc=), 197, 1492, 1448, 133, 16, 116, 1111, 76, 28, 894, 742, 701. Anl. Clcd for C184Cl24i (188.4): C, 83.02;,.32;, 3.2 %. Found: C, 82.98;,.48;, 3.46 % X-ry crystllogrphic studies Single crystls of i3 nd i6 suitble for X ry diffrction nlyses were obtined by slow diffusion of diethyl ether onto the respective dichloromethne solution t room temperture. X ry studies were crried out on Rigku Sturn CCD with grphite-monochromtic Mo-Kα rdition (λ = Å) t 173(2) K (i3) nd 0(2) K (i6), cell prmeters were obtined by globl refinement of the positions of ll collected reflections. Intensities were corrected for Lorentz nd polriztion effects nd empiricl bsorption. The structures were solved by direct methods nd refined by full-mtrix lest squres on F 2. All hydrogen toms were plced in clculted positions. Structure solution nd refinement were performed by using the SELXL 97 pckge. 19 Within structure refinement of i3 nd i6, there were free solvent molecules which hve no influence on the geometry of the min compounds. Therefore, the SQUEEZE option of the crystllogrphic progrm PLATO ws used to remove these free solvents from the structure. Detils of the X ry structure determintions nd refinements re provided in Tble 6. Generl procedure for ethylene polymeriztion A ml stinless steel utoclve equipped with mechnicl stirrer nd temperture controller ws used to perform ethylene polymeriztion. The utoclve ws evcuted by vcuum pump nd bck-filled twice with 2 nd once with ethylene. When the desired rection temperture ws reched, ml toluene ws 6 dded under ethylene tmosphere, nd the nickel pre-ctlyst in ml toluene ws injected. The required mount of co-ctlysts (MAO, MMAO or Et2AlCl) nd dditionl toluene (mintining totl volume s 0 ml in rector) were dded by syringe. The rection mixture ws intensively stirred for the desired time under tm of ethylene nd mintined t this level by constnt feeding of ethylene. The rection ws quenched by ddition of cidic ethnol. The precipitted polymer ws wshed with ethnol severl times nd dried in vcuo. Tble 6 Crystl dt nd structure refinement for i3 nd i6 identifiction code i3 i6 Crystl color red red Empiricl formul C 1 84Br 2 4i C 1 84Cl 2 4i Formul weight Temperture/K 173 (2) 0 (2) Wvelength/Å Crystl system Monoclinic Monoclinic Spce group P2(1)/c P2(1)/n /Å 17.08(3) (4) b/å 1.393(3) 1.219(3) c/å (8) 18.7(4) Alph/ Bet/ 1.83(18) 9.81(3) Gmm/ Volume/Å (2) (17) Z 2 2 D clcd/(g cm -3 ) µ/mm F(000) Crystl size/mm θ rnge ( o C) Limiting indices -1 h -18 k l h k l 23 o. of rflns collected o. unique rflns R(int) o. of prms 29 Completeness to θ 99.9 % 99.6 % Goodness of fit on F Finl R indices [I > 2 ( I )] = w = = 0.08 w = R indices (ll dt) = w = = 0.1 w = 0.20 Lrgest diff. pek, nd hole/(e.å -3 ) 0.64 nd nd Acknowledgements This work is supported by SFC o nd U The EPSRC is thnked for the wrded of trvel grnt (to CR). otes nd references Stte Key Lbortory of Applied Orgnic Chemistry, College of Chemistry nd Chemicl Engineering, Lnzhou University, Lnzhou 7000, Chin. Fx: ; Tel: ; E- 7 mil: coxplzu@163.com. b Key Lbortory of Engineering Plstics nd Beijing tionl Lbortory for Moleculr Sciences, Institute of Chemistry, Chinese Acdemy of Sciences, Beijing 0190, Chin. Fx: ; Tel: ; E-mil: whsun@iccs.c.cn. c 80 Deprtment of Chemistry, University of ull, ull, U6 7RX, UK. Fx: ; Tel: ; Emil: c.redshw@hull.c.uk. Appendix A. Supplementry mteril: CCDC nd contin the supplementry crystllogrphic dt for i3 nd i6. These

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