Heteroatom-Substituted Constrained-Geometry Complexes. Dramatic Substituent Effect on Catalyst Efficiency and Polymer Molecular Weight Jerzy Klosin,* William J. Kruper, Jr., Peter N. Nickias, Gordon R. Roof, and Phillip De Waele The Dow Chemical Company, Catalysis Laboratory, 1776 Building, Midland, Michigan 48674 Khalil A. Abboud Department of Chemistry, University of Florida, Gainesville, Florida 32611 Received January 5, 2001 Summary: The new constrained-geometry complexes (CGC) [(η 5 -C 9 H 5 X)(SiMe 2 -t-Bu)TiR 2 (X ) 2-OEt (1a,b), 2-NMe 2 (2a,b) , 3-OMe (3a,b), 3-NC 4 H 4 (4a,b); R ) Cl, Me) have been synthesized with alkoxy and amino substituents attached to a second and third indenyl position. Four of the new complexes (1a-4a) have been characterized by single-crystal X-ray analysis. An eth- ylene/1-octene copolymerization study revealed an enor- mous substituent effect, both on the catalysts’ activity and the molecular weight of produced polymers. The 3-amino-substituted complex 4b exhibits the highest catalytic activity and forms the highest molecular weight ethylene/octene copolymers that have ever been reported for this class of catalysts. It is advantageous to conduct commercial solution polymerization reactions at very high temperatures (>130 °C). 1 Two major catalyst limitations often pre- venting access to such high reactor temperatures are the catalyst efficiency and the molecular weight of produced polymers, as both of these factors decrease as a function of rising temperature. Catalysts capable of producing high-molecular-weight polymers at high tem- perature with very high catalytic activities would be therefore greatly desired. In the last two decades there has been a considerable amount of research aimed at understanding the factors that govern fundamental metallocene properties in olefin polymerization reac- tions, such as efficiency, comonomer incorporation, tacticity, and polymer molecular weight. 2 Early studies on the constrained-geometry catalyst (CGC) systems suggest 3 that catalyst efficiency could be enhanced by an increase in electron density at the metal center. It was shown, for example, that the tetramethyl-substi- tuted CGC complex (η 5 -C 5 Me 4 )(SiMe 2 -N-t-Bu)TiCl 2 was 3 times more active than (η 5 -C 5 H 4 )(SiMe 2 -N-t-Bu)TiCl 2 in ethylene/octene polymerization when activated with MAO. 4,5 In looking for ways to further increase electron density at the metal center, we focused our attention on alkoxy and amino substituents, as they have been shown to be very effective electron-donating groups in electrophilic aromatic substitution reactions 6 as well as in substituted ferrocenes. 7 In this communication we wish to report 8 the synthesis and characterization of new alkoxy (1, 3) and amino (2, 4) substituted CGC complexes as well as the remarkable substituent effect on catalyst polymerization activity and polymer molec- ular weight. Complexes 1-4 (Chart 1) have been synthesized by previously described methods 3b,8b,c,9 and characterized by 1D and 2D (COSY, NOESY, HSQC, and gHMBC) NMR spectroscopy, elemental analysis, HRMS, and single-crystal X-ray analysis (1a-4a). 9,10 The complexes exhibit C 1 symmetry both in solution and in the solid state (vide infra). In addition to four multiplets (H4- H7) and a singlet (H2) observed in the aromatic region of 1 H NMR spectra of 1b-4b, there are two sets of singlets in the region 0-1 ppm corresponding to two diastereotopic silicon and titanium methyl groups. The chemical shifts of the two titanium methyl peaks differ substantially from one anothersCH 3 b (assigned on the basis of NOESY measurements) is shifted upfield by * To whom correspondence should be addressed. E-mail: klosin@ dow.com. (1) Albright, L. F. Polym. News 1997, 22, 281-284. (2) For recent reviews see: (a) Gladysz, J. A. Chem. Rev. 2000, 100, 1167-1682. (b) Marks, T. J.; Stevens, J. C. Top. Catal. 1999, 7,1-208. (c) Jordan, R. F. J. Mol. Catal. 1998, 128,1-337. (d) Piers, W. E. Chem. Eur. J. 1998, 4, 13-18. (e) Metallocenes; Togni, A., Halterman, R. L., Eds.; Wiley-VCH: Weinheim, Germany, 1998. (f) Kaminsky, W.; Arndt, M. Adv. Polym. Sci. 1997, 127, 144-187. (g) Bochmann, M. J. Chem. Soc., Dalton Trans. 1996, 255-270. (h) Brintzinger, H.-H.; Fischer, D.; Mu ¨ lhaupt, R.; Rieger, B.; Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143-1170. (3) (a) Stevens, J. C. Stud. Surf. Sci. Catal. 1994, 89, 277-284. (b) Stevens, J. C.; Timmers, F. J.; Wilson, D. R.; Schmidt, G. F.; Nickias, P. N.; Rosen, R. K.; Knight, G. W.; Lai, S. Eur. Patent Appl. EP-416- 815-A2, 1991. (4) For early work on constrained-geometry complexes see: (a) Shapiro, P. J.; Cotter, W. D.; Schaefer, W. P.; Labinger, J. A.; Bercaw, J. E. J. Am. Chem. Soc. 1994, 116, 4623-4640. (b) Piers, W. E.; Shapiro, P. J.; Bunel, E. E.; Bercaw, J. E. Synlett 1990, 2, 74-84. (c) Shapiro, P. J.; Bunel, E. E.; Schaefer, W. P.; Bercaw, J. E. Organo- metallics 1990, 9, 867-869. (d) Canich, J. M. U.S. Patent 5,026,798, 1991. (e) Okuda, J. Chem. Ber. 1990, 123, 1649-1651. (5) For reviews of constrained-geometry complexes see: (a) Mc- Knight, A. L.; Waymouth, R. M. Chem. Rev. 1998, 98, 2587-2598. (b) Okuda, J.; Eberle, T. In Metallocenes; Togni, A., Halterman, R. L., Eds.; Wiley-VCH: Weinheim, Germany, 1998; pp 415-453. (6) Pine, S. H. Organic Chemistry; McGraw-Hill: Englewood Cliffs, NJ, 1987; pp 609-638. (7) Stahl, K.; Boche, G.; Massa, W. J. J. Organomet. Chem. 1984, 277, 113-125. (8) Communicated in part: (a) Klosin, J.; Kruper, J. W.; Nickias, P. N.; Patton, J. T.; Abboud, K. A. Book of Abstracts, 217th National Meeting of the American Chemical Society, Anaheim, CA, 1999; American Chemical Society: Washington, DC, 1999; INOR-694. (b) Klosin, J.; Kruper, W. J.; Nickias, P. N.; Patton, J. T.; Wilson, D. R. WO 980672, 1998. (c) Klosin, J.; Kruper, W. J.; Nickias, P. N.; Patton, J. T.; Wilson, D. R. WO 9806728, 1998. (9) See Supporting Information for details. 2663 Organometallics 2001, 20, 2663-2665 10.1021/om010016d CCC: $20.00 © 2001 American Chemical Society Publication on Web 05/26/2001