Anionic ansa-zirconocenes with pentafluorophenyl-substituted borato bridges

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The ansa-borane complex (Me2S)(C6H5)B(C5H4)2ZrCl2 (1) reacts selectively with 2 equiv of LiC6F5 to give (Me2S)(C6H5)B(C5H4)2Zr(C6F5)2 (2) and with 3 equiv LiC6F5 to form the borato-bridged complex [Li(Et2O)3][(C6F5)(C6H5)B(C5H4)2Zr(C6F5)2] (3a). The C6F5 groups are exchanged for Me by reaction with AlMe3 to form [Li(Et2O)x][(C6F5)(C6H5)B(C5H4)2ZrMe2] (4). Treatment of BCl3 with (SiMe3)(SnMe3)C5H4 affords BCl(C5H4SiMe3)2 (5), which undergoes a dehalosilylation reaction with ZrCl4(Me2S)2 to give Cl(Me2S)B(C5H4)ZrCl2 (6). The reaction of 6 with LiC6F5 proceeds in a fashion similar to that of 2, leading first to (Et2O)ClB(C5H4)2Zr(C6F5)2 (7) and with 5 equiv of LiC6F5 to [Li(Et2O)4][(C6F5)2B(C5H4)2Zr(C6F5)2] (9a) in 28% yield. The yield is improved through the use of C6F5MgBr at 60 °C. The C6F5 groups are readily exchanged for Me through reaction with LiMe to give [Li(Et2O)4][(C6F5)2B(C5H4)2ZrMe2] (10a). Complexes 3, 9, and 10 are catalysts for ethene polymerization when activated with MAO or AlBui3/[CPh3][B(C6F5)4].
Original languageEnglish
Pages (from-to)2093-2101
Number of pages9
Issue number10
Publication statusPublished - 19 Apr 2001

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