Polyelement substituted cyclopentadienes and indenes - Novel ligand precursors for organotransition metal chemistry

Article abstract of DOI:10.1016/S0022-328X(96)06757-5

A series of polyelement substituted cyclopentadienyl and indenyl boranes and arsanes containing Me₃Si-, Me₃Sn-was synthesised; (C₅H₄SiMe₃)BX₂ (2, X = Cl; 3, X = Br) and (C₉H₆SiMe₃)BX₂ (4, X = Cl; 5, X = Br) were obtained by Si/B exchange reaction in a low yield when X = Cl and in a moderate yield when X = Br, whereas Flu(SiMe₃)₂ does not react with BBr₃ at all. PhB(C₅H₄SiMe₃)₂ (6) and PhB[C₅H₃(SiMe₃)₂]₂ (7) were synthesised using appropriate thallium cyclopentadienides in high yields, 81% and 99% respectively. More bulky indenyl derivatives TrsB(C₉H₇)₂ (8, Trs = (Me₃Si)₃C-), PhB(C₉H₆SiMe₃)₂ (9), Ph₂B(C₉H₆SiMe₃) (10) were prepared by metathesis reactions of lithium indenides with boron halides in high yields. A subsequent transmetallation of C₉H₆(SnMe₃)₂ with PhBCl₂ followed by addition of ZrCl₄ gave (η-⁵-C₉H₆SnMe₂Cl)₂ZrCl₂ (11) in the form of one of two possible diastereomers in high yield. C₉H₆(SiMe₃)SnMe₃ reacts with BCl₃ to give the appropriate bis-indenyl derivative, that was easily converted to the ansa-zirconocene complex [MeB(η⁵-C₉H₆)₂]ZrCl₂ (12). The sterically demanding bis-indenyl ligand 8 underwent direct deprotonation by t-BuLi, affording [TrsB(η⁵-C₉H₆)₂]ZrCl₂ (13) by in situ reaction with Me₃SnCl and ZrCl₄. Indenylarsanes (C₉H₇)₃As (14), t-BuAs(C₉H₇)₂ (15), C₉H₇AsMe₂ (16) and (C₉H₆SiMe₃)AsMe₂ (17) were synthesised by reactions of lithium indenides with asenic halides in good to excellent yields. All these compounds were characterized by analytical and spectroscopic data (NMR, MS). 14 and 15 exist as complex isomeric mixtures with the arsenic atom in the allylic position of the indenyl ring; the crystal structure of a meso form of 15 was determined by X-ray diffraction methods. 17 consists of two isomers with a vinylic (17a) and an allylic (17b) Me₃Si substituent. Stannylation of 16 by Me₃SnNEt₂ led exclusively to the diallylic derivative (C₉H₆AsMe₂)SnMe₃ (18) in quantitative yield. The latter was readily converted to a polymeric, half-sandwich indenyl zirconocene [η⁵-(C₉H₆AsMe₂)ZrCl₃]_n (19) in high yield. Further reaction of 19 with Cp * Li resulted in the formation of a new arsano substituted bent metallocene complex [η⁵-(C₉H₆AsMe₂)-η⁵-(C₅Me₅)]ZrCl₂ (20) in good yield.