Synthesis and characterization of trimethylsilylmethyl-, bis(trimethylsilyl)methyl- and silyl-substituted cyclopentadienes and their alkali metal complexes

A series of new Me3SiCH2-, (Me3Si)(2)CH-, (Me2BuSi)-Si-t- or Me3Si-substituted cyclopentadienes and some of their alkali metal complexes has been prepared. Alkylation or silylation of NaC5H5 with (Me3Si)(2)CHBr or (BuMe2SiCl)-Me-t in tetrahydrofuran yielded C5H5{CH(SiMe3)(2)} 1(=(CpH)-H-R) or C5H5(SiMe2But)2 (=(CpH)-H-t) and C5H4(SiMe2But), 3 (=(CpH)-H-tt), respectively. Metallation of 1, 2 or 3 with LiBun, NaNH2 or KH gave MCpR (M = Li 4, Na 5 or K 6), NaCpt 7 or MCptt (M = Li 8 or K 9). Treatment of 6 with (Me3Si)(2)CHBr produced C5H4[CH(SiMe3)(2)], 10 (=(CpH)-H-RR). Addition of Me2NCH2CH2NMe2 (TMEDA) to 4 or 8 afforded [LiCpR(TMEDA)] 11 or [LiCptt(TMEDA)] 12. From 6 and Me2SiCl2 Me2Si[C5H4CH(SiMe3)(2)](2) 13 [=Me2Si((CpH)-H-R)(2)] was obtained and converted into its potassium salt Me2Si((CpK)-K-R)(2) 14. Metallation of C5H3(SiMe3)(3) (=Cp'''H) with LiBun, NaNH2 or KH in tetrahydrofuran yielded [LiCp'''(THF)(3)] 15, NaCp''' 16 or KCp''' 17, respectively. Addition of MeN(CH2CH2NMe2)(2) (PMDETA) to 16 afforded [NaCp'''(PMDETA)] 18. Treatment of 6 with Me3SiCl gave C5H4(SiMe3)(CH(SiMe3)(2)) (=Cp'H-R) 19 which, with KK, underwent a dyotropic transformation in yielding [KC5H2(SiMe3)(2)-2,4-CH2SiMe3-1] 20. Each of the new compounds 1-20 was characterized by multinuclear NMR spectroscopy (H-1, C-13, Si-29 or Li-7) and C, H, N elemental analysis (not 1), and in the case of the neutral cyclopentadienes, by GC/MS. The molecular structure of the crystalline complex 18 was also established by X-ray crystallography, as was that of [Li C5H3Bu2t-1,3)(TMEDA)] 21. (C) 1998 Elsevier Science S.A.