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Thursday Sep 02 12:31 PM StyleTag -- Journal: INOCHE (Inorganic Chemistry Communications) Article: 241

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Inorganic Chemistry Communications 2 (1999) 396–398

A novel route to titanium compounds containing cyclopentadienyl ligandswith bromoethyl substituents; molecular structure

of [(h5-C5H4CH2CH2Br)TiBr(m-O)]4

Zheng Li a, Jiling Huang a, Yanlong Qian a,*, Albert Sun-Chi Chan b, Kelvin Sze-Yin Leung b,Wing Tak Wong c

a Laboratory of Organometallic Chemistry, East China University of Science and Technology, Meilong Road 130, Shanghai 200237, PR Chinab Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, PR China

c Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong, PR China

Received 11 May 1999

Abstract

Compounds (h5-C5H4CH2CH2OCH3)TiCl3, (h5-C5H4CH2CH2OCH3)2TiCl2 and (h5-C5H4CH2CH2OCH3)(h5-C5H5)TiCl2 reactwith BBr3 to give a high yield of titanium compounds containing cyclopentadienyl ligands with bromoethyl substituents,(h5-C5H4CH2CH2Br)TiBr3 (1), (h5-C5H4CH2CH2Br)2TiBr2 (3) and (h5-C5H4CH2CH2Br)(h5-C5H5)TiBr2 (4), respectively. Hydrolysisof 1 in the presence of tert-butylamine affords cyclo-[(h5-C5H4CH2CH2Br)TiBr(m-O)]4 (2) in quantitative yield. The molecular structureof 2 was determined by X-ray diffraction. q 1999 Elsevier Science S.A. All rights reserved.

Keywords: Titanium; Bromoethyl; Cyclopentadienyl; Crystal structures

Scheme 1.

The cyclopentadienyl ligand is one of the most widely usedligands in organometallic chemistry. The application ofcyclopentadienyl complexes from Group IV transition metalsas homogeneous a-olefin polymerization catalysts has beenextensively studied [1]. Replacement of one or more cyclo-pentadienyl ring hydrogens has been shown to cause signif-icant changes in the steric and electronic effects of the metalcenter, as well as modify the catalytic activities and selectiv-ities of the complexes. Therefore, many substituted cyclo-pentadienyl titanium complexes have been synthesized [2–5]. However, only a few haloalkyl (especially bromoethyl)substituted cyclopentadienyl titanium compounds have beenreported [6] because general routes for preparing substitutedcyclopentadienyl titanium complexes are not available. Inthis report, we introduce a novel path which utilizes meth-oxyethyl substituted cyclopentadienyl titanium complexes asstarting materials along with boron tribromide as a bromi-nating agent, to prepare bromoethyl substituted cyclopenta-dienyl titanium complexes.

Treatment of a solution of (h5-C5H4CH2CH2OCH3)TiCl3in dichloromethane with 2 equiv. of boron tribromide at room

* Corresponding author. Tel.: q86 21 64253519; fax: q86 21 64702573

temperature gives (h5-C5H4CH2CH2Br)TiBr3 (1) as anorange crystal in an 81% yield (Scheme 1).

Two different kinds of reactions are taking place simulta-neously in Scheme 1: one is a reaction involved breaking theether bond CH2–O–CH2; the other is a halogen exchangingreaction between Cl and Br.

Compound 1 has been characterized by 1H NMR and IRspectroscopies, mass spectrometry and elemental analysis 1.

1 Characterization data for (h5-C5H4CH2CH2Br)TiBr3 (1): 1H NMR(CDCl3, 300 MHz): 3.40 (t, 2H, 3Js6.6 Hz, CH2), 3.63 (t, 2H, 3Js6.6Hz, CH2), 7.03 (m, 4H, C5H4). IR (KBr, cmy1): 3386s, 1631m, 1489w,1431w, 1273w, 1238w, 1039w, 796s, 599m. MS(EI) 379 (MyBr)q

(65%), 298 (My2Br)q (59%), 91 (C5H4CH2CH2)q (100%), 64

(C5H4)q (54%). Anal. Calc. for C7H8Br4Ti: C, 18.29; H, 1.75. Found:

C, 18.27; H, 1.72%.

Z. Li et al. / Inorganic Chemistry Communications 2 (1999) 396–398 397

Thursday Sep 02 12:31 PM StyleTag -- Journal: INOCHE (Inorganic Chemistry Communications) Article: 241

Scheme 2.

Fig. 1. The molecular structure of 2. Selected bond lengths (A) and angles(8): Ti(1)–O(1), 1.795(8), Ti(2)–O(1), 1.795(8), Ti(1)–O(4),1.793(8), Ti(2)–O(2), 1.811(8), Ti(1)–Br(1), 2.424(3), Ti(2)–Br(2),2.441(3), Ti(1)–C(1), 2.36(1), Ti(2)–C(8), 2.36(1), Ti(1)–C(2),2.34(1), Ti(2)–C(9), 2.39(2), Ti(1)–C(3), 2.36(1), Ti(2)–C(10),2.40(2), Ti(1)–C(4), 2.37(1), Ti(2)–C(11), 2.35(1), Ti(1)–C(5),2.38(1), Ti(2)–C(12), 2.32(1), Br(5)–C(7), 1.97(1), C(2)–C(6),1.51(2), C(6)–C(7), 1.50(2); O(1)–Ti(1)–O(4), 103.1(4), Ti(1)–O(1)–Ti(2), 168.8(6), O(1)–Ti(1)–Br(1), 103.0(3), Ti(1)–O(4)–Ti(4), 156.0(5), O(4)–Ti(1)–Br(1), 101.4(3), Ti(1)–C(2)–C(6),116.2(9), O(1)–Ti(1)–C(1), 85.7(5), Br(1)–Ti(1)–C(1), 119.6(4),O(1)–Ti(1)–C(2), 94.0(5), Br(1)–Ti(1)–C(2), 148.3(3), O(1)–Ti(1)–C(3), 128.3(5), Br(1)–Ti(1)–C(3), 125.8(4), O(1)–Ti(1)–C(4),143.5(5), Br(1)–Ti(1)–C(4), 95.1(4), O(1)–Ti(1)–C(5), 113.4(6),Br(1)–Ti(1)–C(5), 92.0(4).

It is sensitive to air and moisture, and shows excellent solu-bility in chlorinated solvents, tetrahydrofuran, toluene andbenzene, but only moderate solubility in hexane.

Refluxing of a solution of 1 in heptane with one equivalentof water in the presence of tert-butylamine gives [(h5-C5H4CH2CH2Br)TiBr(m-O)]4 (2) as a yellow crystal inquantitative yield (Scheme 2).

Compound 2 was also characterized by spectroscopic andelemental analyses 2. It is an air-, moisture and thermo-stablecrystal.

Crystallization of 2 from dichloromethane/hexane yieldssingle crystals suitable for X-ray structure determination 3.The molecular structure of 2 along with selected bond lengthsand bond angles is illustrated in Fig. 1. It consists of four (h5-C5H4CH2CH2Br)TiBr molecular units linked by four oxobridges forming an eight-membered ring with alternating Tiand O atoms. A cyclic structure similar to 2 was first reportedby Skapski and Troughton [7] for [(h5-C5H5)TiCl(m-O)]4,which was prepared similarly by the hydrolysis of (h5-C5H5)TiCl3 in methanol. Petersen [8] and Carlo and co-workers [9] have also characterized similar substitutedcyclopentadienyl [(h5-C5H4CH3)TiCl(m-O)]4 and [(h5-C5H4SiMe3)TiBr(m-O)]4.

Similarly, treatment of a solution of (h5-C5H4CH2-CH2OCH3)2TiCl2, and (h5-C5H4CH2CH2OCH3)(h5-C5H5)-TiCl2 with 3 equiv. of boron tribromide in dichloromethaneat room temperature gives (h5-C5H4CH2CH2Br)2TiBr2 (3)and (h5-C5H4CH2CH2Br)(h5-C5H5)TiBr2 (4), respec-tively, as brown crystals in 88% and 85% yields (Scheme 3).

2 Characterization data for [(h5-C5H4CH2CH2Br)TiBr(m-O)]4 (2): 1HNMR (CDCl3, 300 MHz): 3.49 (t, 2H, 3Js6.54 Hz, CH2), 3.71 (t, 2H,3Js6.54 Hz, CH2), 6.45 (t, 4H, 3Js2.50 Hz, C5H4), 6.65 (t, 4H, 3Js2.50Hz, C5H4). IR (KBr, cmy1): 3406w, 3097w, 1636w, 1437m, 1273m,1039m, 788s, 601m, 425m. MS(CI) 316 [(C5H4CH2CH2Br)TiBrO]q

(100%), 224 (C5H4TiBrO2)q (4%). Anal. Calc. for C28H32Br8O4Ti4: C,

26.62; H, 2.55. Found: C, 26.93; H, 2.61%.3 Enraf-Nonius diffractometer, solution with direct methods, refinement

with full-matrix least-squares. Crystal data for Ti4Br8C28H32O4, crystal sys-tem triclinic, space group P1 (No. 2), lattice parameters as10.042,bs13.800, cs15.435 A, as72.77, bs77.86, gs77.478, Vs1970.1 A3,Zs2, Dcalcs2.130 g cmy3, m(MoKa)s89.49 cmy1, 2umaxs488. Refine-ment converged at final Rs0.042, Rws0.045. The minimum and maximumfinal electron densities were y0.85 and 1.17 e Ay3. All calculations wereperformed using teXsan crystallographic software package of MolecularStructure Corporation on a Silicon Graphics workstation.

Z. Li et al. / Inorganic Chemistry Communications 2 (1999) 396–398398

Thursday Sep 02 12:31 PM StyleTag -- Journal: INOCHE (Inorganic Chemistry Communications) Article: 241

Scheme 3.

Compounds 3 and 4 have also been characterized by ele-mental and spectral analyses 4. They are both stable in air and

4 Characterization data for (h5-C5H4CH2CH2Br)2TiBr2 (3): 1H NMR(CDCl3, 300 MHz): 3.47 (t, 2H, 3Js6.58 Hz, CH2), 3.68 (t, 2H, 3Js6.58Hz, CH2), 6.43 (t, 4H, 3Js2.65 Hz, C5H4), 6.63 (t, 4H, 3Js2.65 Hz,C5H4). IR (KBr, cmy1): 3114m, 2962w, 2904w, 1493m, 1427s, 1388m,1370m, 1270m, 1238s, 1031s, 903m, 847s, 607m, 558s. MS(EI) 471(MyBr)q (44%), 378 (MyC5H4CH2CH2Br)q (46%), 299 (MyC5H4-CH2CH2BryBr)q (68%), 218 (MyC5H4CH2CH2Bry2Br)q (14%),91 (C5H4CH2CH2)

q (100%), 65 (C5H4)q (21%). Anal. Calc. for

C14H16Br4Ti: C, 30.47; H, 2.92. Found: C, 30.54; H, 2.76%. Characterizationdata for (h5-C5H4CH2CH2Br)(h5-C5H5)TiBr2 (4): 1H NMR (CDCl3, 300MHz): 3.48 (t, 2H, 3Js6.60 Hz, CH2), 3.69 (t, 2H, 3Js6.60 Hz, CH2),

moisture, and have excellent solubility in chlorinated sol-vents, tetrahydrofuran, toluene and benzene, but poor solu-bility in hexane.

Acknowledgements

This work was financially supported by the National Sci-ence Foundation of China (29734145 and 29871010).

References

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4140.[4] J.C. Leblanc, C. Moise, A. Maisonnat, R. Poilblanc, C. Charrier, F.

Mathey, J. Organomet. Chem. 231 (1982) C43.[5] S.C. Ciruelos, T. Cuenca, P. Gomez-sal, A. Manzanero, P. Royo,

Organometallics 14 (1995) 177.[6] C. Shoushan, L. Jinshan, W. Jitao, Acta Chim. Sin. 42 (1984) 163.[7] A.C. Skapski, P.G.H. Troughton, Acta Crystallogr., Sect. B 26 (1970)

716.[8] J.L. Petersen, Inorg. Chem. 19 (1980) 181.[9] C. Tommaso, F. Carlo, S. Antonio, R. Marzio, C.V. Angiola, R.

Corrado, J. Chem. Soc., Dalton Trans. (1992) 1081.

6.44 (t, 4H, 3Js2.68 Hz, C5H4), 6.63 (t, 4H, 3Js2.68 Hz, C5H4), 6.68 (s,5H, C5H5). IR (KBr, cmy1): 3105s, 2925w, 1492m, 1427s, 1210m, 1051s,852s, 830s, 596m. MS(EI): 380 (MyC5H5)

q (50%), 364 (MyBr)q

(3%), 298 (MyC5H5yBr)q (71%), 218 (MyC5H5y2Br)q (16%),91 (C5H4CH2CH2)

q (100%), 65 (C5H4)q (22%). Anal. Calc. for

C12H13Br3Ti: C, 32.40; H, 2.95. Found: C, 32.27; H, 3.04%.