[(Allylsilyl)(η-amidosilyl)-η5-cyclopentadienyl] Group 4 Metal

Organometallics 2007, 26, 445-454

445

[(Allylsilyl)(η-amidosilyl)-η5-cyclopentadienyl] Group 4 Metal Complexes: Synthesis, Reactivity, and Olefin Polymerization Cristina Ramos,† Pascual Royo,*,† Maurizio Lanfranchi,‡ Maria A. Pellinghelli,‡ and Antonio Tiripicchio‡ Departamento de Quı´mica Inorga´ nica, UniVersidad de Alcala´ , Campus UniVersitario, E-28871 Alcala´ de Henares, Spain, and Dipartamento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, UniVersita` di Parma, Viale G.P. Usberti 17/A, I-43100 Parma, Italy ReceiVed October 2, 2006

Reaction of the dilithium salts Li2{C5H3[1-SiMe2(NR)][3-SiMe2(CH2CHdCH2)]} with TiCl3(THF)3 and further oxidation with PbCl2 gave the allylsilyl-substituted η1-amidosilyl-η5-cyclopentadienyltitanium(IV) complexes [Ti{η5-C5H3(SiMe2-η1-NR)[SiMe2(CH2CHdCH2)]}Cl2] (R ) tBu, 1; 2,6-Me2C6H3, 2). Complex 1 was reacted with MeMgCl and (CH2Ph)MgCl to give the dialkyl complexes [Ti{η5-C5H3(SiMe2-η1-NtBu)[SiMe2(CH2CHdCH2)]}R2] (R ) Me, 3; CH2Ph, 4). Reaction of 1 and related monocyclopentadienyl zirconium and hafnium complexes with Na(C5H5) gave the η-amidosilyl metallocene derivatives [M(η5-C5H5){η5-C5H3(SiMe2-η1-NtBu)[SiMe2(CH2CHdCH2)]}Cl] (M ) Ti, 5; Zr, 6; Hf, 7), which were further methylated with MeMgCl and MeLi to give the methyl derivatives [M(η5-C5H5){η5-C5H3(SiMe2-η1-NtBu)[SiMe2(CH2CHdCH2)]}Me] (M ) Ti, 8; Zr, 9). Insertion of CN(2,6-Me2C6H3) into the Zr-Me bond of complex 9 afforded the iminoacyl derivative [Zr(η5-C5H5){η5-C5H3(SiMe2-η1NtBu)[SiMe2(CH2CHdCH2)]}{η1-CMe[N(2,6-Me2C6H3)]}], 10. Methyl abstraction by reaction of the amidosilyl-metallocene compounds 8 and 9 with B(C6F5)3 gave the ionic species [M(η5-C5H5){η5-C5H3(SiMe2-η1-NtBu)[SiMe2(CH2-η2-CHdCH2)]}]+[MeB(C6F5)3]- (M ) Ti, 11; Zr, 12) stabilized by coordination of the allyl olefinic moiety, whereas similar benzyl abstraction reactions from the dibenzylamidosilyl-monocyclopentadienyl compounds produced further benzyl-migratory insertion of the η2coordinated olefinic moiety to give the cyclic alkyl complexes [M{η5-C5H3(SiMe2-η1-NtBu)[SiMe2CH2-CH(CH2Ph)-CH2]}]+[(CH2Ph)B(C6F5)3]- (M ) Zr, 13; Hf, 14). The new compounds were characterized by elemental analysis and NMR spectroscopy, and the molecular structures of complexes 2, 6, and 7 were determined by X-ray diffraction methods. The chloro complexes 1 and 5-7 were studied as catalyst precursors in the polymerization of different olefins and the copolymerization of ethylene/ 1-hexene, after activation with MAO. Introduction Many studies related to single-site metallocene catalysts have reported1,2 the structure, dynamic behavior, and reactivity of the active cationic species in olefin polymerization processes, providing insights that facilitate catalyst and cocatalyst modifications designed to control the tacticity, molecular weight, chain branching, and other desirable properties in the derived polymeric materials. * To whom correspondence should be addressed. E-mail: pascual.royo@ uah.es. Tel: 34 91 8854765. Fax: 34 91 8854683. † Universidad de Alcala ´. ‡ Universita ` di Parma. (1) (a) Beck, S.; Lieber, S.; Schaper, F.; Geyer, A.; Brintzinger, H. H. J. Am. Chem. Soc. 2001, 123, 1483-1489. (b) Bochmann, M. J. Chem. Soc., Dalton Trans. 1996, 255-270. (c) Brandow, C. G.; Mendiratta, A.; Bercaw, J. E. Organometallics 2001, 20, 4253-4261. (d) Carpentier, J. F.; Wu, Z.; Lee, C. W.; Stromberg, S.; Christopher, J. N.; Jordan, R. F. J. Am. Chem. Soc. 2000, 122, 7750-7767. (e) Mo¨hring, P. C.; Coville, N. J. J. Organomet. Chem. 1994, 479, 1-29. (f) Mo¨hring, P. C.; Vlachakis, N.; Grimmer, N. E.; Coville, N. J. J. Organomet. Chem. 1994, 483, 159-166. (g) Schaper, F.; Geyer, A.; Brintzinger, H. H. Organometallics 2002, 21, 473-483. (h) Wu, Z.; Jordan, R. F.; Petersen, J. L. J. Am. Chem. Soc. 1995, 117, 58675868. (i) Erker, G. Chem. Commun. 2003, 1469-1476. (2) (a) Brintzinger, H. H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.; Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143-1170. (b) Erker, G. Acc. Chem. Res. 2001, 34, 309-317. (c) Jordan, R. F. AdV. Organomet. Chem. 1991, 32, 325-387. (d) Marks, T. J. Acc. Chem. Res. 1992, 25, 57-65. (e) Resconi, L.; Cavallo, L.; Fait, A.; Piemontesi, F. Chem. ReV. 2000, 100, 1253-1345.

Substitution of one cyclopentadienyl ring in silyl-bridged ansa-metallocenes by an alkylamido ligand provided new types of coordinatively unsaturated and sterically open “constrained geometry (CGC) catalysts” that can polymerize long-chain R-olefins and produce long-chain branching and ethylene copolymers with a high content of different R-olefins.3-7 Further studies were extended to related compounds obtained by changing the bridging silyl groups for different methylene8 and boron bridges9 and the amido group by other ligands with different O- (phenolate)10 and P-donor atoms.8d,h,11 The active species in all of these homogeneous Ziegler-Natta catalysts is (3) (a) Piers, W. E.; Shapiro, P. J.; Bunel, E. E.; Bercaw, J. E. Synlett 1990, 74-84. (b) Okuda, J. Chem. Ber. 1990, 123, 1649-1651. (c) Shapiro, P. J.; Bunel, E.; Schaefer, W. P.; Bercaw, J. E. Organometallics 1990, 9, 867-869. (d) Hughes, A. K.; Meetsma, A.; Teuben, J. H. Organometallics 1993, 12, 1936-1945. (e) Shapiro, P. J.; Cotter, W. D.; Schaefer, W. P.; Labinger, J. A.; Bercaw, J. E. J. Am. Chem. Soc. 1994, 116, 4623-4640. (f) Herrmann, W. A.; Morawietz, M. J. A. J. Organomet. Chem. 1994, 482, 169-181. (g) Spence, R.; Piers, W. E. Organometallics 1995, 14, 46174624. (h) Okuda, J.; Schattenmann, F. J.; Wocadlo, S.; Massa, W. Organometallics 1995, 14, 789-795. (i) du Plooy, K. E.; Moll, U.; Wocadlo, S.; Massa, W.; Okuda, J. Organometallics 1995, 14, 3129-3131. (j) Amor, F.; Okuda, J. J. Organomet. Chem. 1996, 520, 245-248. (4) (a) Okuda, J.; Eberle, T. In Half-Sandwich Complexes as Metallocene Analogues, Metallocenes Synthesis, ReactiVity, Applications; Togni, A., Halterman, R. L., Eds.; Wiley-VCH: Weinheim, Germany, 1998; Vol. 1, pp 415-453. (b) McKnight, A. L.; Waymouth, R. M. Chem. ReV. 1998, 98, 2587-2598. (c) Braunschweig, H.; Breitling, F. M. Coord. Chem. ReV. 2006, 250, 2691.

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446 Organometallics, Vol. 26, No. 2, 2007

Ramos et al.

a cationic coordinatively unsaturated 12-electron d0 alkyl compound.5h,12 Coordination of the olefin to this unsaturated metal cation followed by migratory insertion of the alkyl group is assumed to be the initiation step of the polymerization process. We reported13 that the doubly silylamido-bridged cyclopentadienyl zirconium cation [Zr{(η5-C5H3(SiMe2-η1-NtBu)2}]+ polymerizes ethene despite being free from the alkyl group required for insertion. Similar results were also reported14 for silylamido-zirconocenium cations [Zr{(η5-C5Me4(SiMe2-η1-

Scheme 1

(5) (a) Mu, Y.; Piers, W. E.; MacQuarrie, D. C.; Zaworotko, M. J.; Young, V. G. Organometallics 1996, 15, 2720-2726. (b) Dias, H. V. R.; Wang, Z. Y.; Bott, S. G. J. Organomet. Chem. 1996, 508, 91-99. (c) Ciruelos, S.; Cuenca, T.; Gomez, R.; GomezSal, P.; Manzanero, A.; Royo, P. Organometallics 1996, 15, 5577-5585. (d) Carpenetti, D. W.; Kloppenburg, L.; Kupec, J. T.; Petersen, J. L. Organometallics 1996, 15, 15721581. (e) Okuda, J.; Eberle, T.; Spaniol, T. P. Chem. Ber.-Recl. 1997, 130, 209-215. (f) McKnight, A. L.; Masood, M. A.; Waymouth, R. M.; Straus, D. A. Organometallics 1997, 16, 2879-2885. (g) Hughes, A. K.; Marsh, S. M. B.; Howard, J. A. K.; Ford, P. S. J. Organomet. Chem. 1997, 528, 195-198. (h) Chen, Y. X.; Marks, T. J. Organometallics 1997, 16, 36493657. (i) Sinnema, P. J.; Liekelema, K.; Staal, O. K. B.; Hessen, B.; Teuben, J. H. J. Mol. Catal. A: Chem. 1998, 128, 143-153. (j) Royo, B.; Royo, P.; Cadenas, L. M. J. Organomet. Chem. 1998, 551, 293-297. (k) Go´mez, R.; Go´mez-Sal, P.; Martı´n, A.; Nu´n˜ez, A.; del Real, P. A.; Royo, P. J. Organomet. Chem. 1998, 564, 93-100. (l) Eberle, T.; Spaniol, T. P.; Okuda, J. Eur. J. Inorg. Chem. 1998, 237-244. (m) Amor, F.; du Plooy, K. E.; Spaniol, T. P.; Okuda, J. J. Organomet. Chem. 1998, 558, 139-146. (6) (a) Li, L. T.; Metz, M. V.; Li, H. B.; Chen, M. C.; Marks, T. J.; Liable-Sands, L.; Rheingold, A. L. J. Am. Chem. Soc. 2002, 124, 1272512741. (b) Klosin, J.; Kruper, W. J.; Nickias, P. N.; Roof, G. R.; De, Waele, P.; Abboud, K. A. Organometallics 2001, 20, 2663-2665. (c) Park, J. T.; Yoon, S. C.; Bae, B. J.; Seo, W. S.; Suh, I. H.; Han, T. K.; Park, J. R. Organometallics 2000, 19, 1269-1276. (d) Juvaste, H.; Pakkanen, T. T.; Iiskola, E. I. J. Organomet. Chem. 2000, 606, 169-175. (e) Doufou, P.; Abboud, K. A.; Boncella, J. M. J. Organomet. Chem. 2000, 603, 213219. (f) Ciruelos, S.; Sebastia´n, A.; Cuenca, T.; Go´mez-Sal, P.; Manzanero, A.; Royo, P. J. Organomet. Chem. 2000, 604, 103-115. (g) Okuda, J.; Eberle, T.; Spaniol, T. P.; Piquet-Faure, V. J. Organomet. Chem. 1999, 591, 127-137. (h) Galan-Fereres, M.; Koch, T.; Hey-Hawkins, E.; Eisen, M. S. J. Organomet. Chem. 1999, 580, 145-155. (7) (a) Va´zquez, A. B.; Royo, P.; Herdtweck, E. J. Organomet. Chem. 2003, 683, 155-164. (b) Va´zquez, A. B.; Royo, P. J. Organomet. Chem. 2003, 671, 172-178. (c) Cano, J.; Sudupe, M.; Royo, P.; Mosquera, M. E. G. Organometallics 2005, 24, 2424-2432. (d) Wang, J. X.; Li, H. B.; Guo, N.; Li, L. T.; Stern, C. L.; Marks, T. J. Organometallics 2004, 23, 51125114. (e) Braun, L. F.; Dreier, T.; Christy, M.; Petersen, J. L. Inorg. Chem. 2004, 43, 3976-3987. (f) McKittrick, M. W.; Jones, C. W. J. Am. Chem. Soc. 2004, 126, 3052-3053. (8) (a) Konemann, M.; Erker, G.; Fro¨hlich, R.; Wurthwein, E. U. J. Am. Chem. Soc. 1997, 119, 11155-11164. (b) Duda, L.; Erker, G.; Fro¨hlich, R.; Zippel, F. Eur. J. Inorg. Chem. 1998, 1153-1162. (c) Kunz, D.; Erker, G.; Fro¨hlich, R.; Kehr, G. Eur. J. Inorg. Chem. 2000, 409-416. (d) Kunz, K.; Erker, G.; Do¨ring, S.; Fro¨hlich, R.; Kehr, G. J. Am. Chem. Soc. 2001, 123, 6181-6182. (e) Kunz, M.; Erker, G.; Do¨ring, S.; Bredeau, S.; Kehr, G.; Fro¨hlich, R. Organometallics 2002, 21, 1031-1041. (f) Kunz, K.; Erker, G.; Kehr, G.; Fro¨hlich, R. Organometallics 2001, 20, 392-400. (g) Bertuleit, A.; Konemann, M.; Duda, L.; Erker, G.; Fro¨hlich, R. Top. Catal. 1999, 7, 37-44. (h) Bredeau, S.; Altenhoff, G.; Kunz, K.; Do¨ring, S.; Grimme, S.; Kehr, G.; Erker, G. Organometallics 2004, 23, 1836-1844. (9) (a) Braunschweig, H.; Breitling, F. M.; von Koblinski, C.; White, A. J. P.; Williams, D. J. Dalton Trans. 2004, 938-943. (b) Braunschweig, H.; von Koblinski, C.; Englert, U. Chem. Commun. 2000, 1049. (10) Chen, Y. X.; Fu, P. F.; Stern, C. L.; Marks, T. J. Organometallics 1997, 16, 5958-5963. (11) (a) Altenhoff, G.; Bredeau, S.; Erker, G.; Kehr, G.; Kataeva, O.; Fro¨hlich, R. Organometallics 2002, 21, 4084-4089. (b) Kotov, V. V.; Avtomonov, E. V.; Sundermeyer, J.; Harms, K.; Lemenovskii, D. A. Eur. J. Inorg. Chem. 2002, 678-691. (c) Tardif, O.; Hou, Z. M.; Nishiura, M.; Koizumi, T.; Wakatsuki, Y. Organometallics 2001, 20, 4565-4573. (12) (a) Lanza, G.; Fragala, I. L.; Marks, T. J. J. Am. Chem. Soc. 1998, 120, 8257-8258. (b) Amor, F. B., A.; du Plooy, K. E.; Spaniol, T. P.; Okuda, J. Organometallics 1998, 17, 5836-5849. (c) Go´mez, R.; Go´mezSal, P.; del Real, P. A.; Royo, P. J. Organomet. Chem. 1999, 588, 22-27. (d) Carpentier, J. F.; Maryin, V. P.; Luci, J.; Jordan, R. F. J. Am. Chem. Soc. 2001, 123, 898-909. (e) Keaton, R. J.; Jayaratne, K. C.; Fettinger, J. C.; Sita, L. R. J. Am. Chem. Soc. 2000, 122, 12909-12910. (13) Cano, J.; Royo, P.; Lanfranchi, M.; Pellinghelli, M. A.; Tiripicchio, A. Angew. Chem., Int. Ed. 2001, 40, 2495-2497. (14) Jin, J. Z.; Wilson, D. R.; Chen, E. Y. X. Chem. Commun. 2002, 708-709.

Scheme 2

NtBu)}(η5-C5H5)] and for imino cobalt(I) [Co{2,6-(CR′d NAr)2C5H3N}R]+ compounds,15 for which different activation mechanisms, involving coordination of the olefin and nucleophilic attack by the alkyl group abstracted by the Lewis acid cocatalyst, through formation of a bimetallic complex16 and activation by Li+ 17 have been proposed. We were interested in studying the formation of catalytically active group 4 metal cationic species stabilized by coordination of the ring-tethered silylallyl olefinic moiety of η-amidosilylcyclopentadienyl and -metallocene compounds. We have recently reported18 the synthesis of dialkyl zirconium and hafnium compounds of the type represented in Scheme 1 (A) as precursors of the η-amidosilyl-cyclopentadienyl cations. In this paper we report the synthesis of the related titanium compounds, new η-amidosilyl-metallocene derivatives of the type represented in Scheme 1 (B) and the behavior of both types of compound in reactions with B(C6F5)3 and as catalysts for olefin polymerization processes following activation with MAO.

Results and Discussion The method based on the reaction of the metal(IV) chlorides with the dilithium salt of the disilylated cyclopentadienyl ring was initially used to transfer this ligand in order to synthesize the zirconium and hafnium derivatives reported recently.18 However similar reaction with TiCl4 led to a mixture containing reduction products from which the desired compound could be isolated only in very low yields. As shown in Scheme 2, the most convenient method was direct access to the titanium(III) complex by reaction of the dilithium salt Li2{C5H3[1-SiMe2(NR)][3-SiMe2(CH2CHdCH2)]} (R ) tBu) with [TiCl3(THF)3] and further oxidation with PbCl2 to give the η-amidosilyl complex [Ti{η5-C5H3(SiMe2-η1-NtBu)[SiMe2(CH2CHdCH2)]}Cl2], 1, in high yield. Complex 1 is highly soluble in hexane and could not be recrystallized and (15) (a) Humphries, M. J.; Tellmann, K. P.; Gibson, V. C.; White, A. J. P.; Williams, D. J. Organometallics 2005, 24, 2039-2050. (b) Steffen, W.; Blomker, T.; Kleigrewe, N.; Kehr, G.; Fro¨hlich, R.; Erker, G. Chem. Commun. 2004, 1188-1189. (c) Kooistra, T. M.; Knijnenburg, Q.; Smits, J. M. M.; Horton, A. D.; Budzelaar, P. H. M.; Gal, A. W. Angew. Chem., Int. Ed. 2001, 40, 4719-4722. (16) Natta, G.; Mazzanti, G. Tetrahedron 1960, 8, 86-100. (17) Kleigrewe, N.; Steffen, W.; Blomker, T.; Kehr, G.; Fro¨hlich, R.; Wibbeling, B.; Erker, G.; Wasilke, J. C.; Wu, G.; Bazan, G. C. J. Am. Chem. Soc. 2005, 127, 13955-13968. (18) Ramos, C.; Royo, P.; Lanfranchi, M.; Pellinghelli, M. A.; Tiripicchio, A. Eur. J. Inorg. Chem 2005, 3962-3970.

Amidosilyl Group 4 Metallocene Complexes

Organometallics, Vol. 26, No. 2, 2007 447 Table 1. Selected Bond Lengths [Å] and Angles [deg] for Compounds 2, 6, and 7a M-Cl(1) M-Cl(2) M-CE(1) M-CE(2) M-N C(1)-C(2) C(2)-C(3) C(3)-C4) C(4)-C(5) C(1)-C(5) Si(1)-C(1) Si(1)-N Si(1)-C(6) Si(1)-C(7) N-C(8) Si(2)-C(4)

Figure 1. ORTEP drawing of the molecular structure of 2 in the solid state. Thermal ellipsoids are drawn at the 30% probability level. Only one of the two disordered allyl groups is represented.

was isolated as a dark oily product characterized by elemental analysis and NMR spectroscopy. We reported18 that the X-ray diffraction analysis of the related zirconium complex showed a dinuclear structure with two bridging chloro ligands that alleviate the electron deficiency of the otherwise monomeric 14-electron compound, which would be the more favorable disposition expected for the smaller titanium atom. Nevertheless the spectroscopic data for this type of asymmetric molecule did not allow the two structural assignments to be distinguished. For this reason, in the hope of obtaining improved crystallinity19 we decided to prepare the analogous (2,6-dimethylphenyl)amido compound using the same method with the appropriate dilithium salt (R ) 2,6-Me2C6H3). The new silylamido complex [Ti{(η5C5H3[SiMe 2-η1-N(2,6-Me 2C6H3)][SiMe 2(CH 2CHdCH2)]}Cl2], 2, was isolated as a solid characterized by elemental analysis and NMR spectroscopy and was recrystallized from a hexane solution cooled to -35 °C to give yellow crystals appropriate for X-ray diffraction studies. As expected, the molecular structure of 2 corresponds to a monomeric complex where the titanium atom is in a pseudotetrahedral environment defined by two chlorine atoms, the centroid of the cyclopentadienyl ring, and the nitrogen atom of the silylamido group (Figure 1). From a comparison of 13 structures20 of TiCl2 complexes containing a linked amidosilylcyclopentadienyl ligand, all the metrical parameters of 2 are within the expected range (Table 1). The complex shows a chirality plane (the disubstituted Cp ring), and in the structure both the M and P isomers are present. As shown in Scheme 2, the synthesis of the alkyl titanium derivatives was carried out by the reaction of 1 with 2 equiv of alkylating agents such as MeLi, MeMgCl, (CH2Ph)MgCl, and (CH2Ph)2Mg(THF)2. The dialkyl complexes [Ti{η5-C5H3(SiMe2η1-NtBu)[SiMe2(CH2CHdCH2)]}R2] (R ) Me, 3; CH2Ph, 4) are highly soluble in hexanes and were isolated as black or red, oily products in 60% yield after purification and characterized by elemental analyses and NMR spectroscopy. Several features of the 1H and 13C NMR spectra of the dichloro and dialkyl complexes 1-4 are worthy of note. The enantiotopic faces of the 1,3-disilylated cyclopentadienyl ligand with two different silyl groups are responsible for the asymmetry in these molecules, all of which probably show the same (19) Humphries, M. J.; Green, M. L. H.; Douthwaite, R. E.; Rees, L. H. J. Chem. Soc., Dalton Trans. 2000, 4555-4562. (20) Retrieved from CCDC data bank (ConQuest 1.8, 2006).

Cl(1)-M-Cl(2) Cl(1)-M-CE(2) Cl(1)-M-CE(1) Cl(2)-M-CE(1) CE(2)-M-CE(1) Cl(1)-M-N N-M-CE(1) N-M-CE(2) Cl(2)-M-N Si(1)-N-M Si(1)-N-C(8) C(8)-N-M

M ) Ti

M ) Zr

M ) Hf

2.2620(14) 2.2552(16) 2.026(4)

2.4628(14)

2.433(2)

2.208(3) 2.256(4) 2.116(2) 1.413(3) 1.409(3) 1.414(3) 1.416(3) 1.418(3) 1.863(3) 1.736(2) 1.866(3) 1.856(3) 1.500(3) 1.874(2)

2.199(10) 2.241(16) 2.099(6) 1.433(12) 1.396(11) 1.414(12) 1.457(11) 1.427(11) 1.858(9) 1.732(6) 1.866(10) 1.858(11) 1.527(11) 1.876(8)

106.07(9) 107.81(7)

106.0(3) 107.9(2)

125.45(14) 100.25(7) 100.12(9) 114.33(11)

125.2(5) 99.6(2) 100.7(3) 114.6(3)

105.12(10) 121.79(15) 132.90(15)

104.9(3) 122.1(5) 132.8(5)

1.912(3) 1.426(5) 1.406(5) 1.410(5) 1.428(4) 1.405(5) 1.864(4) 1.760(3) 1.852(4) 1.848(4) 1.434(4) 1.867(4) 101.49(5) 117.85(10) 117.01(11) 106.12(8) 105.46(14) 108.23(9) 107.34(14) 126.3(2) 126.29(19)

a CE(1) and CE(2) are the centroids of the Cp rings C(1),C(2),C(3),C(4), C(5) and C(17),C(18),C(19),C(20),C(21), respectively.

molecular structure found for complex 2 by X-ray diffraction studies. Therefore four occasionally overlapped methyl signals (1H and 13C) attributed to the bridging η-amidosilyl and to the allylsilyl groups are observed, together with an ABC spin system for the cyclopentadienyl ring protons and five 13C resonances for the ring carbon atoms (see Experimental Section). In addition, all of the complexes show the signals typical of the allyl moiety and the N-bonded tBu or 2,6-Me2C6H3 groups. The 13C resonance due to the bridge-bonded ring Cipso is shifted highfield (δ 110.2-112.6), as reported5c for chelate “constrained geometry” compounds. The π-bonding contribution of the bridging tert-butylamido ligand measured by the ∆δ ) (δ Ctert-CMe) values21 is higher in the more acidic titanium complexes 1-4 (32.0-24.7) than in related zirconium and hafnium compounds (24.7-19.9), which are in the known range for this type of cyclopentadienylsilyl-η1-amido complex, ranging from 24.7 (R ) CH2Ph) for the more donating to 32.0 (R ) Cl) for the less donating substituents. As illustrated in Scheme 2 the dialkyl complexes 3 and 4 show two nonequivalent alkyl groups, one of which is located under the allylsilyl ring substituent. The two 1H NMR singlets observed for the titanium-bonded methyl groups of 3 are shifted lowfield (δ 0.68, 0.74) with respect to the values observed for related zirconium and hafnium compounds ( 2σ(I)] (R1, wR2)a R indices (all data) (R1, wR2)a largest diff peak and hole (e Å-3)

2

6

7

C20H29Cl2NSi2Ti 458.42 293(2) 0.71073 monoclinic, P21/c 13.118(6) 12.472(5) 15.820(8) 90 111.22(2) 90 2412.8(19) 4, 1.262 0.680 960 0.30 × 0.25 × 0.20 3.00 to 25.00 -15 e h e 14, 0 e k e 14, 0 e l e 18 4317/4186 [R(int) ) 0.0895] 4186/6/269 0.981 0.0572, 0.1497 0.0818, 0.1650 0.470 and -0.693

C21H34ClNSi2Zr 483.34 293(2) 0.71073 monoclinic, C2/c 25.800(12) 11.597(8) 20.893(10) 90 128.79(2) 90 4873(5) 8, 1.318 0.665 2016 0.45 × 0.35 × 0.25 3.00 to 30.00 -36 e h e 28, 0 e k e 16, 0 e l e 29 7294/7123 [R(int) ) 0.0236] 7123/0/242 0.913 0.0334, 0.0707 0.0770, 0.0807 0.580 and -0.462

C21H34ClNSi2Hf 570.61 293(2) 0.71073 monoclinic, C2/c 25.784(12) 11.589(6) 20.647(10) 90 127.95(2) 90 4865(4) 8, 1.558 4.502 2272 0.30 × 0.27 × 0.25 3.00 to 24.00 -29 e h e 23, 0 e k e 13, 0 e l e 23 3735/3623 [R(int) ) 0.0314] 3623/0/242 1.015 0.0351, 0.0767 0.0542, 0.0858 1.308 and -0.806

a GOF ) [∑[w(F 2 - F 2)2]/(n - p)]1/2, R ) ∑||F | - |F ||/∑|F |, wR ) [∑[w(F 2 - F 2)2]/∑[w(F 2)2]]1/2, w ) 1/[σ2(F 2) + (aP)2 + bP], where P ) o c 1 o c o 2 o c o o [max(Fo2,0) + 2Fc2]/3.

(20.00 mg, 0.035 mmol) and B(C6F5)3 (18.00 mg, 0.035 mmol) in C7D8 to give an orange solution, in which the presence of complex 13 was confirmed by the following NMR data. Data for 13: 1H NMR (C7D8): -0.03 (s, 3H, SiMe2), 0.04 (s, 3H, SiMe2), 0.07 (s, 3H, SiMe2), 0.14 (s, 3H, SiMe2), 0.16 (m, 1H, SiCH2), 0.47 (m, 1H, ZrCH2), 0.58 (s, 9H, tBu), 0.63 (m, 1H, ZrCH2), 0.79 (m, 1H, SiCH2), 1.80 (m, 1H, CH), 2.16 (m, 1H, CH2Ph), 2.54 (m, 1H, CH2Ph), 3.20 (br, 1H, BCH2Ph), 3.34 (br, 1H, BCH2Ph), 5.36 (m, 1H, C5H3), 5.69 (m, 1H, C5H3), 6.03 (m, 1H, C5H3), 5.87 (m, 1H, p-BCH2Ph), 6.09 (m, 1H, m-BCH2Ph), 6.18 (m, 1H, m-BCH2Ph), 6.71 (m, 1H, o-BCH2Ph), 6.89 (m, 1H, o-BCH2Ph), 6.96-7.14 (m, 5H, C6H5). 13C{1H} NMR (C7D8): -1.7 (SiMe2), -0.1 (SiMe2), 1.0 (SiMe2), 4.1 (SiMe2), 24.3 (SiCH2), 33.8 (CMe3), 35.0 (BCH2Ph), 41.4 (CH), 51.6 (CH2Ph), 59.2 (CMe3), 63.5 (ZrCH2), 117.6 (C5H3), 118.0 (Cipso, C5H3), 120.3, 121.8 (C5H3), 124.5-131.1 (C6H5), 134.9, 139.6, 146.3, 150.9 (C6F5), 141.4 (Cipso, CH2Ph), 158.8 (Cipso, BCH2Ph). 19F NMR (C7D8): -131.1 (o-C6F5), -161.0 (p-C6F5), -165.2 (m-C6F5). [Hf{η5-C5H3(SiMe2-η1-NtBu)[SiMe2-CH2-CH(CH2Ph)-η1CH2]}][(CH2Ph)B(C6F5)3] (14). The same procedure described for 11 was followed using [Hf(η5-C5Me4SiMe2-η1-NtBu)(CH2Ph)2] (80.00 mg, 0.120 mmol) and B(C6F5)3 (60.00 mg, 0.120 mmol) in C7D8 to give an orange solution, in which the presence of complex 14 was confirmed by the following NMR data. Data for 14: 1H NMR (C7D8): -0.03 (s, 3H, SiMe2), 0.02 (s, 3H, SiMe2), 0.10 (s, 3H, SiMe2), 0.16 (s, 3H, SiMe2), 0.17 (m, 1H, SiCH2), 0.24 (m, 1H, HfCH2), 0.36 (m, 1H, HfCH2), 0.58 (s, 9H, tBu), 0.82 (m, 1H, SiCH2), 1.90 (m, 1H, CH), 2.23 (m, 1H, CH2Ph), 2.55 (m, 1H, CH2Ph), 3.20 (br, 1H, BCH2Ph), 3.35 (br, 1H, BCH2Ph), 5.30 (m, 1H, C5H3), 5.71 (m, 1H, C5H3), 5.91 (m, 1H, p-BCH2Ph), 5.99 (m, 1H, C5H3), 6.16 (m, 2H, m-BCH2Ph), 6.75 (m, 1H, o-BCH2Ph), 6.83 (m, 1H, o-BCH2Ph), 6.92-7.16 (m, 5H, C6H5). 13C{1H} NMR (C7D8): -1.7 (SiMe2), -0.1 (SiMe2), 1.1 (SiMe2), 4.2 (SiMe2), 24.2 (SiCH2), 34.1 (CMe3), 35.0 (BCH2Ph), 41.3 (CH), 53.0 (CH2Ph), 58.5 (CMe3), 64.8 (HfCH2), 117.0 (C5H3), 117.5 (Cipso, C5H3), 119.9, 121.9 (C5H3), 124.8-131.2 (C6H5), 135.8, 139.2, 147.0, 150.1 (C6F5), 141.6 (Cipso, CH2Ph), 159.4 (Cipso, BCH2Ph). 19F NMR (C7D8): -131.0 (o-C6F5), -161.1 (p-C6F5), -165.2 (m-C6F5).

X-ray Structure Determination for Complexes [Ti{η5-C5H3[SiMe2-η1-N(2,6-Me2C6H3)][SiMe2(CH2CHdCH2)]}Cl2] (2), [Zr(η5-C5H5){η5-C5H3(SiMe2-η1-NtBu)[SiMe2 (CH2CHdCH2)]}Cl] (6), and [Hf(η5-C5H5){η5-C5H3(SiMe2-η1-NtBu)[SiMe2 (CH2CHd CH2)]}Cl] (7). Crystals of compounds 2, 6, and 7 were obtained by crystallization from hexane, and suitable sized crystals in a Lindemann tube were mounted on a Philips PW 1100 diffractometer with graphite-monochromated Mo KR radiation (λ ) 0.71073 Å). Crystallographic and experimental details are summarized in Table 2. Compound 7, which is isostructural with 6, underwent partial decomposition during data collection. The structures were solved by direct methods (SIR92)29 and refined by least-squares against Fo2 (SHELXL-97).30 All the non-hydrogen atoms for the three compounds were refined anisotropically. For 2 the allyl group (C(18)-C(19)-C(20)) was found to be disordered in two positions and refined with GOF of 0.53 and 0.47, respectively. All the hydrogen atoms were introduced from geometrical calculations and refined using a riding model. The programs PARST31 ad ORTEP32 were also used. Polymerization Procedures. A Bu¨chi glass reactor was employed for the polymerization of ethylene and propylene and for the copolymerization of ethylene/1-hexene (5 mL). In a typical example, dry toluene (50 mL) was added to a 500 mL glass reactor, which was then pressurized with the olefins (at 3 atm). The solution was maintained with stirring and a thermostat used to determine the polymerization temperature (30 °C). The required amount of MAO (Witco, 10% solution in toluene) was added. Polymerization was started by adding a toluene solution of the required amount of catalyst. After a determined time (2-30 min) acidified methanol was added to terminate the polymerization and the olefin feed was stopped. The resulting polymer was collected by filtration, washed with methanol, and dried in vacuo at 50 °C for 10 h. (29) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Gualiardi, A.; Burla, M. C.; Polidori, G.; Camalli, M. J. Appl. Crystallogr. 1994, 27, 435. (30) Sheldrick, G. M. SHELXL-97, Program for the Refinement of Crystal Structures; Universita¨t Go¨ttingen, Go¨ttingen, Germany, 1997. (31) Nardelli, M. Comput. Chem. 1983, 7, 95. (32) Zsolnai, L.; Pritzkow, H. ZORTEP. ORTEP original program modified for PC; Universita¨t Heidelberg: Heidelberg, Germany, 1994.

454 Organometallics, Vol. 26, No. 2, 2007 A small reactor of 100 mL was used for the polymerization of styrene. In a typical example, toluene (40 mL) was added to a 100 mL argon-purged glass reactor equipped with a stirrer, and then styrene (5 mL) was added at 1 atm. This solution was maintained at a determined polymerization temperature (30 °C) using a thermostat, and the required amount of MAO (Witco, 10% solution in toluene) was added. Polymerization was started by adding a toluene solution of the required amount of catalyst. After a determined time, acidified methanol was added to terminate the polymerization. The resulting polymer was collected by filtration, washed with methanol, and dried in vacuo at 50 °C for 10 h.

Ramos et al.

Acknowledgment. We gratefully acknowledge Ministerio de Educacio´n y Ciencia (project MAT2004-02614) and DGUIComunidad de Madrid (programme S-0505/PPQ-0328) (Spain) for financial support. Supporting Information Available: Crystallographic data for 2, 6, and 7 in .cif format. This material is available free of charge via the Internet at http://pubs.acs.org. OM060900+