Hydrosilylation in the Design and Functionalization of ansa-Metallocene Complexes

Synthesis, structural characterization, and reactivity of Group 4 metallacarboranes bearing the ligand [H2C(C5Me4)(C2B9H10)]3-

A new organic-inorganic hybrid ligand H(2)C(C(5)Me(4)H)(C(2)B(10)H(11)) (2) has been prepared. A selective deboration reaction with piperidine in ethanol resulted in the isolation of [Me(3)NH][H(2)C(C(5)Me(4)H)(C(2)B(9)H(11))] (3). An amine-elimination reaction of 3 with [Zr(NMe(2))(4)] produced a neutral metal-amide complex [η(5):η(5)-H(2)C(C(5)Me(4))(C(2)B(9)H(10))]Zr(NMe(2))(NHMe(2)) (4). The double-ring-opening reaction of 4 with tetrahydrofuran (THF) afforded [η(5):η(5)-H(2)C(C(5)Me(4))(C(2)B(9)H(10))]Zr (OCH(2)CH(2)CH(2)CH(2))(2)N(CH(3))(2) (5). Treatment of the trianionic salt of 3 with [MCl(4)(thf)(2)] gave complexes [{η(5):η(5)-H(2)C(C(5)Me(4))(C(2)B(9)H(10))}M(μ-Cl)(2)][Li(thf)(2)] (M=Zr (6), Hf (7)). Reaction of 6 with LiCH(2)TMS generated the ionic species [{η(5):η(5)-H(2)C(C(5)Me(4))(C(2)B(9)H(10))}Zr(CH(2)TMS)(2)][Li(thf)(3)] (9). Interaction of complex 6 with KCH(2)(NMe(2))-o-C(6)H(4) led to the formation of the neutral metal alkyl complex [η(5):η(5)-H(2)C(C(5)Me(4))(C(2)B(9)H(10))]Zr[σ:σ-CH(2)(NMe(2))-o-C(6)H(4)] (10). All complexes have been fully characterized by various spectroscopic techniques and elemental analyses. Some were further confirmed by single-crystal X-ray analyses.

Synthesis of Bulky Zirconocene Dichloride Compounds and Their Applications in Olefin Polymerization

The bulky substituted cyclopentadienyllithium derivatives, LiC5H4(CHMeR) (R = C6H5 (1), 1-naphthyl (2), 9-anthryl (3)), were synthesized from the reaction of 6-phenylfulvene, 6-(1-naphthyl)fulvene or 6-(9-anthryl)fulvene with LiMe. The ansa-bis(cyclopentadiene) ligands Me2Si(C5HMe4){C5H4(CHMeR)} (R = C6H5 (4), 1-naphthyl (5), 9-anthryl (6)), and their lithium derivatives Li2(Me2Si(C5Me4){C5H3(CHMeR)}) (R = C6H5 (7), 1-naphthyl (8), 9-anthryl (9)) have been prepared. The zirconocene complexes, [Zr(η5-C5H5){η5-C5H4- (CHMeR)}Cl2] (R = C6H5 (10), 1-naphthyl (11), 9-anthryl (12)) and [Zr{η5-C5H4(CHMeR)}2Cl2] (R = C6H5 (13), 1-naphthyl (14), 9-anthryl (15)), were synthesized by the reaction of lithium derivatives 1-3 and [Zr(η5-C5H5)Cl3] or ZrCl4, respectively. The reaction of the lithium ansa-derivatives 7-9 and zirconium tetrachloride yielded the ansa-zirconocene complexes, [Zr(Me2Si(η5-C5Me4){η5-C5H3(CHMeR)})Cl2] (R = C6H5 (16), 1-naphthyl (17), 9-anthryl (18)). The zirconocene complexes have been tested in the polymerization of ethene and propene. The polymerization of propene with the ansa-zirconocene catalysts 16-18 gave polypropylene with 70% mmmm pentads and the symmetric zirconocene catalysts 13-15 30-60% mmmm pentads.

Ansa-metallocene polymerization catalysts derived from [2+2]cycloaddition reactions of bis(1-methylethenyl-cyclopentadienyl)zirconium systems

Bis(1-methylethenyl-cyclopentadienyl)zirconium dichloride (7a) was prepared by a fulvene route. Photolysis at 0 degrees C with Pyrex-filtered UV light resulted in a rapid and complete intramolecular [2+2]cycloaddition reaction to yield the corresponding cyclobutylene-bridged ansa-zirconocene dichloride isomer (8a). This is one of the rare examples of an organic functional group chemistry that leads to carbon-carbon coupling at the framework of an intact sensitive group 4 bent metallocene complex. More sterically hindered open metallocenes that bear bulky isopropyl or tert-butyl substituents at their Cp rings in addition to the active 1-methylethenyl functional group undergo the photochemical ansa-metallocene ring closure reaction equally facile. The metallocene systems used and obtained in this study have served as transition metal components for the generation of active metallocene propene polymerization catalysts.