Synthesis, reactivity, and NMR studies of dilithiated (E)-1,4-bis(trimethylsilyl)but-2-ene and (E)-1,4-bis(trimethylsilyl)-2,3-dimethylbut-2-ene

Leslie D. Field, Michael G. Gardiner, Colin H L Kennard, Barbara A. Messerle, Colin L. Raston*

*Corresponding author for this work

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

(Z)-1,4-Dilithio-1,4-bis(trimethylsilyl)but-2-ene and 1,4-dilithio-1,4-bis(trimethylsilyl)-2,3-dimethylbut-2-ene adducts of TMEDA (≡N,N,N′,N′-tetramethylethylenediamine), [{Li(TMEDA)}2{(Me3SiCHCH)2}] (3) and [{Li(TMEDA)}2{(Me3SiCHCMe)2}] (4), respectively, have been prepared by dimetalation of the corresponding (E)-but-2-ene using n-BuLi(TMEDA) in hexane. Assignment of the Z configuration of the dianions with Li atoms bridging the ipso carbons (C1,4) is based on NMR data: magnetically equivalent protons attached to the ipso carbons (C1,4) couple to 7Li (2JLi-H = ca. 1 Hz) in both compounds, lack of coupling of the protons attached to C2,3 with the lithiums in 3, and NOE enhancements for 1H-7Li HOESY experiments. The Z configuration is also consistent with the structures of two isolated silyl derivatives of 3; treatment with ClSiMe3 gives (Z)-1,1,4,4-tetrakis(trimethylsilyl)but-2-ene (5), and with Cl2SiMe2 it yields the (Z,Z)-16-disilacyclodeca-3,8-diene [{Me3SiCHC(H)=C(H)CH(SiMe3)SiMe2}2] (6). Compound 3 is a potent reducing agent, affording (E,E)-1,4-bis(trimethylsilyl)buta-1,3-diene (7) and metal when treated with HgCl2 (yield of 7 71%) or CaCl2. X-ray diffraction data for 5 revealed a distorted Z double bond, the C-C-C angles at the sp2 carbon centers being "opened up" to 130.2° (mean): crystals are monoclinic, space group P21/n, with a = 11.595 (4) Å, b = 12.205 (1) Å, c = 17.569 (6) Å, β = 107.33 (2)°, V = 2373 (1) Å3, and Z = 4.

Original languageEnglish
Pages (from-to)3167-3172
Number of pages6
JournalOrganometallics
Volume10
Issue number9
Publication statusPublished - 1991
Externally publishedYes

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